Bioanalytical chromatographic method validation according to current regulations, with a special focus on the non-well defined parameters limit of quantification, robustness and matrix effect

Enhancing breast cancer screening with urinary biomarkers and Random Forest supervised classification: A comprehensive investigation

OBJECTIVES

Urinary sex hormones are investigated as potential biomarkers for the early detection of breast cancer, aiming to evaluate their relevance and applicability, in combination with supervised machine-learning data analysis, toward the ultimate goal of extensive screening.

METHODS

Sex hormones were determined on urine samples collected from 250 post-menopausal women (65 healthy - 185 with breast cancer, recruited among the clinical patients of Candiolo Cancer Institute FPO-IRCCS (Torino, Italy). Two analytical procedures based on UHPLC-MS/HRMS were developed and comprehensively validated to quantify 20 free and conjugated sex hormones from urine samples. The quantitative data were processed by seven machine learning algorithms. The efficiency of the resulting models was compared.

RESULTS

Among the tested models aimed to relate urinary estrogen and androgen levels and the occurrence of breast cancer, Random Forest (RF) proved to underscore all the other supervised classification approaches, including Partial Least Squares - Discriminant Analysis (PLS-DA), in terms of effectiveness and robustness. The final optimized model built on only five biomarkers (testosterone-sulphate, alpha-estradiol, 4-methoxyestradiol, DHEA-sulphate, and epitestosterone-sulphate) achieved an approximate 98% diagnostic accuracy on replicated validation sets. To balance the less-represented population of healthy women, a Synthetic Minority Oversampling TEchnique (SMOTE) data oversampling approach was applied.

CONCLUSIONS

By means of tunable hyperparameters optimization, the RF algorithm showed great potential for early breast cancer detection, as it provides clear biomarkers ranking and their relative efficiency, allowing to ground the final diagnostic model on a restricted selection five steroid biomarkers only, as desirable for noninvasive tests with wide screening purposes.

Evaluating the Role of N-Acetyl-L-Tryptophan in the Aβ 1-42-Induced Neuroinflammation and Cognitive Decline in Alzheimer's Disease

Alzheimer's disease (AD), a neurodegenerative condition previously known to affect the older population, is also now seen in younger individuals. AD is often associated with cognitive decline and neuroinflammation elevation primarily due to amyloid β (Aβ) accumulation. Multiple pathological complications in AD call for therapies with a wide range of neuroprotection. Our study aims to evaluate the effect of N-acetyl-L-tryptophan (NAT) in ameliorating the cognitive decline and neuroinflammation induced by Aβ 1-42 oligomers and to determine the therapeutic concentration of NAT in the brain. We administered Aβ 1-42 oligomers in rats via intracerebroventricular (i.c.v.) injection to induce AD-like conditions. The NAT-treated animals lowered the cognitive decline in the Morris water maze characterized by shorter escape latency and increased path efficiency and platform entries. Interestingly, the hippocampus and frontal cortex showed downregulation of tumor necrosis factor, interleukin-6, and substance P levels. NAT treatment also reduced acetylcholinesterase activity and total and phosphorylated nuclear factor kappa B and Tau levels. Lastly, we observed upregulation of cAMP response element-binding protein 1 (CREB1) signaling. Surprisingly, our HPLC method was not sensitive enough to detect the therapeutic levels of NAT in the brain, possibly due to NAT concentrations being below the lowest limit of quantification of our validated method. To summarize, the administration of NAT significantly lowered cognitive decline, neuroinflammatory pathways, and Tau protein and triggered the upregulation of CREB1 signaling, suggesting its neuroprotective role in AD-like conditions.

Population pharmacokinetics of ramipril in patients with chronic heart failure: A real-world longitudinal study

In patients with chronic heart failure (CHF), the use of angiotensin-converting enzyme inhibitors, including ramipril, is recommended to reduce the risk of heart failure worsening, hospitalisation, and death. Our aim was to investigate the influence of body composition on the pharmacokinetics of ramipril and its active metabolite ramiprilat and to evaluate the changes in pharmacokinetics after prolonged therapy. Twenty-three patients with CHF who were on regular therapy with ramipril participated at the first study visit ( median age 77 years, 65 % male, and 70 % New York Heart Association Class II); 19 patients attended the second study visit and the median time between the two visits was 8 months. Pharmacokinetics were assessed using a nonlinear mixed-effects parent-metabolite model comprising two compartments for ramipril and one compartment for ramiprilat. The influence of body size and composition was best described by an allometric relationship with fat-free mass. In addition, ramipril clearance was related to patient age and daily ramipril dose, while clearance of ramiprilat was influenced by glome rular filtration rate and daily ramipril dose. There were no clinically relevant changes in the pharmacokinetics of ramipril and ramiprilat between the study visits. Due to the relatively stable pharmacokinetics of ramipril, regular outpatient visits at 6-month intervals seem appropriate to evaluate ramipril therapy.

Advanced quality assessment of Sanshishi (Gardenia jasminoides Ellis) and Kampo medicines using a monoclonal antibody against geniposide

Gardenia jasminoides Ellis, a plant widely used in traditional medicine, is known for its array of biological activities. A key bioactive compound, geniposide (GE), an iridoid glycoside, significantly contributes to the medicinal properties of the plant, with potential side effects. Thus, a reliable and efficient method for GE detection is required to ensure the quality of medicinal-grade G. jasminoides Ellis. This study developed such a method by first synthesizing GE-bovine serum albumin conjugates to function as immunizing agents in mice. This led to the production of a monoclonal antibody (mAb 3A6) against GE from the fusion of splenocytes from immunized mice with myeloma cells (P3U1), resulting in a hybridoma that produces mAb 3A6. Thereafter, we developed a mAb 3A6-based indirect competitive enzyme-linked immunosorbent assay (icELISA). The icELISA exhibited satisfactory sensitivity (0.391-12.5 μg/ml) and repeatability (coefficients of variation <10%). The accuracy of this method was validated through a spike-recovery assay (recovery of 101-112%). Furthermore, the icELISA was employed to determine the GE content in plant and Kampo medicine samples. The GE content positively correlated with those determined by high-performance liquid chromatography-ultraviolet. The proposed icELISA is rapid, cost-effective, and reliable for high-throughput GE detection in G. jasminoides Ellis, thereby contributing to the improved quality control and standardization of this valuable medicinal plant.

Development of an Untargeted LC-MS Metabolomics Method with Postcolumn Infusion for Matrix Effect Monitoring in Plasma and Feces

Untargeted metabolomics based on reverse phase LC-MS (RPLC-MS) plays a crucial role in biomarker discovery across physiological and disease states. Standardizing the development process of untargeted methods requires paying attention to critical factors that are under discussed or easily overlooked, such as injection parameters, performance assessment, and matrix effect evaluation. In this study, we developed an untargeted metabolomics method for plasma and fecal samples with the optimization and evaluation of these factors. Our results showed that optimizing the reconstitution solvent and sample injection amount was critical for achieving the balance between metabolites coverage and signal linearity. Method validation with representative stable isotopically labeled standards (SILs) provided insights into the analytical performance evaluation of our method. To tackle the issue of the matrix effect, we implemented a postcolumn infusion (PCI) approach to monitor the overall absolute matrix effect (AME) and relative matrix effect (RME). The monitoring revealed distinct AME and RME profiles in plasma and feces. Comparing RME data obtained for SILs through postextraction spiking with those monitored using PCI compounds demonstrated the comparability of these two methods for RME assessment. Therefore, we applied the PCI approach to predict the RME of 305 target compounds covered in our in-house library and found that targets detected in the negative polarity were more vulnerable to the RME, regardless of the sample matrix. Given the value of this PCI approach in identifying the strengths and weaknesses of our method in terms of the matrix effect, we recommend implementing a PCI approach during method development and applying it routinely in untargeted metabolomics.

Development and evaluation of a comprehensive workflow for suspect screening of exposome-related xenobiotics and phase II metabolites in diverse human biofluids

Suspect and non-target screening (SNTS) methods are being promoted in order to decode the human exposome since a wide chemical space can be analysed in a diversity of human biofluids. However, SNTS approaches in the exposomics field are infra-studied in comparison to environmental or food monitoring studies. In this work, a comprehensive suspect screening workflow was developed to annotate exposome-related xenobiotics and phase II metabolites in diverse human biofluids. Precisely, human urine, breast milk, saliva and ovarian follicular fluid were employed as samples and analysed by means of ultra-high performance liquid chromatography coupled with high resolution tandem mass spectrometry (UHPLC-HRMS/MS). To automate the workflow, the "peak rating" parameter implemented in Compound Discoverer 3.3.2 was optimized to avoid time-consuming manual revision of chromatographic peaks. In addition, the presence of endogenous molecules that might interfere with the annotation of xenobiotics was carefully studied as the employment of inclusion and exclusion suspect lists. To evaluate the workflow, limits of identification (LOIs) and type I and II errors (i.e., false positives and negatives, respectively) were calculated in both standard solutions and spiked biofluids using 161 xenobiotics and 22 metabolites. For 80.3 % of the suspects, LOIs below 15 ng/mL were achieved. In terms of type I errors, only two cases were identified in standards and spiked samples. Regarding type II errors, the 7.7 % errors accounted in standards increased to 17.4 % in real samples. Lastly, the use of an inclusion list for endogens was favoured since it avoided 18.7 % of potential type I errors, while the exclusion list caused 7.2 % of type II errors despite making the annotation workflow less time-consuming.

A novel and sensitive method for simultaneous determination of 6 low-calorie bulk sweeteners by HPLC-ELSD

A novel and sensitive method for the simultaneous analysis of six low-calorie bulk sweeteners (D-allulose, D-tagatose, D-mannitol, mycose, palatinose, and erythritol) without derivatisation was developed using high-performance liquid chromatography-evaporative light scattering detector (HPLC-ELSD). Chromatographic separations were carried out on a Zorbax Original NH2 (5 μm particle size, 250 mm×4.60 mm id, 70 Å) column with flow rate gradient elution with acetonitrile: water (80:20, v/v). Drift tube temperature was set at 50 ℃, the nebuliser carrier gas flow rate was 1.0 mL·min-1, and nitrogen pressure was regulated to 276 kPa with gain:3. The regression equation showed good linearity (R2 = 0.9985-0.9998) for all six low-calorie bulk sweeteners in the tested range (0.060-0.60 mg·mL-1). The limits of detection (LOD) for the six low-calorie bulk sweeteners ranged from 0.02 to 0.06 mg·mL-1. The proposed HPLC-ELSD method was validated for the quantification of the low-calorie bulk sweeteners in 14 types of foods, and the results were satisfactory. In addition, the results showed that the number of sweeteners in each food product varied. The presence of multiple low-calorie bulk sweeteners in certain foods is interesting. This method is successful in monitoring low-calorie bulk sweeteners in food.

Development of simultaneous quantitative analytical method for three active components of Korean mint (Agastache rugosa (Fisch. & C.A.Mey.) Kuntze) extract in human plasma using ultra-high-performance liquid chromatography-tandem mass spectrometry

Agastache rugosa contains phenolic compounds and flavonoids, and has been extensively used as a traditional herbal medicine. The major components in Agastache rugosa extract (ARE) are rosmarinic acid, tilianin, and acacetin, for which several analytical techniques have been reported. However, these substances have yet to be simultaneously quantified in human plasma. In this study, we aimed to simultaneously determine the three active components of ARE in human plasma by developing a reliable quantitative analytical method using ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Chromatographic separation of the plasma samples was achieved using an ACQUITY UPLC® BEH C18 column with a gradient mobile phase of water and acetonitrile containing 0.1 % formic acid. Mass spectrometric detection was performed using a triple quadrupole tandem mass spectrometer in negative electrospray ionization (ESI-) and multiple reaction monitoring (MRM) modes. The developed quantitative method was validated for the three active components. All three analytes exhibited a linear response over the ranges of 0.5-50 ng/mL for rosmarinic acid, 0.1-20 ng/mL for acacetin, and 0.5-20 ng/mL for tilianin with a weighting factor of 1/x (where x is the concentration). At three quality control (QC) concentration levels (low, medium, and high), including the lower limit of quantitation (LLOQ), acceptable accuracy (±15 %) was achieved in the intra- and interday validations. The concentration of rosmarinic acid was highest in plasma. Tilianin and acacetin appeared and were eliminated earlier in the plasma than rosmarinic acid. This study provides a successfully validated method that can be used in further clinical applications of Agastache rugosa extracts.

Preparation of restricted-access boronate affinity adsorbent with excellent anti-protein adsorption property for directly extracting small cis-diol molecules from biological matrices

Boronate affinity adsorbents are of great promise in the enrichment of small cis-diol-containing molecules (cis-diols) from biological matrices. This work develops a restricted-access boronate affinity mesoporous adsorbent, in which boronate sites are only distributed on the internal surface of mesopores and the external surface is a strongly hydrophilic layer. The adsorbent has high binding capacities (30.3 mg g-1, 22.9 mg g-1 and 14.9 mg g-1 for dopamine, catechol and adenosine, respectively) in spite of removal of the boronate sites on the external surface of adsorbent. The adsorption specific of adsorbent towards cis-diols was assessed by dispersive solid-phase extraction (d-SPE) method, and the results show that the adsorbent can selectively extract small cis-diols in the biosamples while exclude proteins completely. Under the optimal d-SPE, the nucleosides and cis-diol drugs in human serum were successfully analyzed by coupling d-SPE with high-performance liquid chromatography. Where, the detection limits are between 6.1 and 13.4 ng mL-1 for four nucleosides, and 24.9 and 34.3 ng mL-1 for two cis-diol drugs; the relative recoveries of all the analytes vary from 84.1% to 110.1% (RSDs <13.4%, n = 6). The results indicate that the adsorbent can directly treat the real biosamples without the necessary protein precipitation steps in advance, thus simplifying the analysis process.

Simultaneous analysis of avatrombopag, eltrombopag, and hetrombopag in human plasma by UPLC-MS/MS for therapeutic drug monitoring

Avatrombopag, eltrombopag, and hetrombopag are three oral thrombopoietin receptor agonists used to treat thrombocytopenia. To investigate the pharmacokinetic properties, a fast and robust UPLC-MS/MS method was developed and validated for simultaneous determination of avatrombopag, eltrombopag, and hetrombopag in human plasma. Chromatographically separation was achieved on an Acquity BEH C18 column using a gradient elution of methanol-water (20:80, v/v) and acetonitrile containing 0.1% formic acid at a flow rate of 0.4 mL/min within 4.5 min. The linearity was assessed over the range of 7.5-1500 ng/mL for avatrombopag, 50-10,000 ng/mL for eltrombopag, and 5-1000 ng/mL for hetrombopag. This method was validated with adequate results in terms of selectivity, precision (intra- and inter-day CV from 4.2% to 12.2%), accuracy (RE from -6.6% to 7.5%), dilution integrity, carryover, recovery, matrix effects, as well as stability of the analytes under various conditions. The developed approach has been successfully applied to the therapeutic drug monitoring of avatrombopag, eltrombopag, and hetrombopag in patients with immune thrombocytopenia.

Theoretical charge plots as a tool for targeted and accelerated ion exchange chromatography method development of NANOBODYⓇ molecules

NANOBODYⓇ molecules are an innovative class of biotherapeutics based on heavy chain only VHH immunoglobulins. Much like canonical antibodies, they are prone to the formation of charge variants and other post-translational modifications, which can potentially impact their critical quality attributes. Therefore, establishing high-resolution product-specific methods, such as IEX chromatography, is essential for evaluating the purity of these molecules. However, due to the lower surface charge of NANOBODYⓇ molecules, their charge-based elution behavior can differ considerably from that of classical antibodies, resulting in a more extensive method development set-up for these smaller molecules. Using an initial pH screening gradient based on theoretical protein charge plots, we investigated the IEX retention behavior of eight NANOBODYⓇ molecules with a wide range of pI values (pI 5.0 to 10.0). Our findings reveal that the charge-based chromatographic behavior of NANOBODYⓇ molecules cannot be solely attributed to the isoelectric point (pI) of the protein. Rather, a molecule-specific charge threshold was identified as a critical parameter for NANOBODYⓇ molecule retention. Furthermore, the protein charge plot also showed that NANOBODYⓇ molecule elution can be characterized by a charge plateau where the net charge of the protein remains constant over a certain pH range (∼ pH 5.5 to pH 8.0), further challenging the paradigm that elution pH and pI are fixed values. The application of this theoretical approach using protein charge plots to define NANOBODYⓇ molecule charge threshold and charge plateau parameters, can reduce overall IEX method development turnaround time by at least 2-fold.

Triblock copolymer–grafted restricted access materials with zwitterionic polymer outer layers for highly efficient extraction of fluoroquinolones and exclusion of proteins

High-selectivity and high-exclusion restricted access materials (RAMs) benefit the analysis of biological samples. Herein, triblock copolymer-functionalized poly(4-vinylbenzyl chloride-co-divinylbenzene) (P_VBC/DVB) microspheres were prepared via the sequential surface-initiated atom radical polymerization of hydrophobic styrene (St), ionic vinylimidazole (VIm), and zwitterionic sulfobetaine methacrylate (SBMA), affording RAMs with multiple interaction-adsorption sites and zwitterionic polymer exclusion sites on the internal and external surfaces of P_VBC/DVB. The preferential extraction of fluoroquinolones (FQs) is realized based on the hydrophobic/π-π/ion exchange interactions due to the grafted poly-St-VIm, and the zwitterionic poly-SBMA block in the triblock copolymers can efficiently exclude various proteins. A sensitive detection method for FQs in chicken was established by solid phase extraction with RAMs as adsorbent combined with UPLC-MS/MS, achieving wide linearity (2.0-200.0 ng mL^-1), low limit of detection (0.5 μg kg^-1) and limit of quantification (1.5 μg kg^-1), and good inter- and intraday precision with satisfactory recoveries (104.1%-117.7% and 115.3%-121.2% with RSDs < 12%).

Chromatographic method development using multivariate approaches for organic solvents optimized analysis in [18F]fluorocholine

A fast and simple method using Gas Chromatography combined with Flame Ionization Detection (GC-FID) was developed for the determination of ethanol, acetonitrile, dibromomethane, dimethylaminoethanol, and dimethyl sulfoxide in [¹⁸F]fluorocholine. The combination of fractional factorial design, Doehlert design, and Desirability function was used to evaluate the operational parameters and to establish the best working condition. The validation results revealed that the proposed method has good recovery (85.1-104.1%) and repeatability (RSD ≤8.1%). Correlation coefficients (R ≥ 0.983) indicated good linearity over a wide range. The limit of detection (≤2.5 ppm) and the limit of quantification (≤7.5 ppm) were satisfactory. The proposed method is based on minimum manual operation, sample preparation free, direct injection technique, and short chromatographic separation time. This method is useful for routine analysis of organic solvents in [¹⁸F]fluorocholine, feasible for the modernization of specific monograph, and was therefore successfully implemented to assess samples manufactured by Nuclear Technology Development Center (CDTN).

A Liquid Chromatography Tandem Mass Spectrometry Method for the Simultaneous Estimation of the Dopamine Receptor Antagonist LE300 and Its N-methyl Metabolite in Plasma: Application to a Pharmacokinetic Study

LE300 is a novel dopamine receptor antagonist used to treat cocaine addiction. In the current study, a sensitive and fast liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been established and validated for the simultaneous analysis of LE300 and its N-methyl metabolite, MLE300, in rat plasma with an application in a pharmacokinetic study. The chromatographic elution of LE300, MLE300, and Ponatinib (IS, internal standard), was carried out on a 50 mm C₁₈ analytical column (ID: 2.1 mm and particle size: 1.8 μm) maintained at 22 ± 2 °C. The run time was 5 min at a flow rate of 0.3 mL/min. The mobile phase consisted of 42% aqueous solvent (10 mM ammonium formate, pH: 4.2 with formic acid) and 58% organic solvent (acetonitrile). Plasma samples were pretreated using protein precipitation with acetonitrile. The electrospray ionization (ESI) source was used to generate an ion-utilizing positive mode. A multiple reaction monitoring mass analyzer mode was utilized for the quantification of analytes. The linearity of the calibration curves in rat plasma ranged from 1 to 200 ng/mL (r² = 0.9997) and from 2 to 200 ng/mL (r² = 0.9984) for LE300 and MLE300, respectively. The lower limits of detection (LLOD) were 0.3 ng/mL and 0.7 ng/mL in rat plasma for LE300 and MLE300, respectively. Accuracy (RE%) ranged from -1.71% to -0.07% and -4.18% to -1.48% (inter-day), and from -3.3% to -1.47% and -4.89% to -2.15% (intra-day) for LE300 and MLE300, respectively. The precision (RSD%) was less than 2.43% and 1.77% for the inter-day, and 2.77% and 1.73% for intra-day of LE300 and MLE300, respectively. These results are in agreement with FDA guidelines. The developed LC-MS/MS method was applied in a pharmacokinetic study in Wistar rats. T_max and C_max were 2 h and 151.12 ± 12.5 ng/mL for LE300, and 3 h and 170.4 ± 23.3 ng/mL for MLE300.

Fluorescence-Coupled Techniques for Determining Rose Bengal in Dermatological Formulations and Their Application to Ex Vivo Skin Deposition Studies

Rose Bengal (RB) is a fluorescent dye with several potential biomedical applications, particularly in dermatology. Due to RB's poor physicochemical properties, several advanced delivery systems have been developed as a potential tool to promote its permeation across the skin. Nevertheless, no validated quantitative method to analyse RB within the skin is described in the literature. Considering RB exhibits a conjugated ring system, the current investigation proposes fluorescence-based techniques beneficial for qualitatively and quantitatively determining RB delivered to the skin. Notably, the development and validation of a fluorescence-coupled HPLC method to quantify RB within the skin matrix are herein described for the first time. The method was validated based on the ICH, FDA and EMA guidelines, and the validated parameters included specificity, linearity, LOD, LLOQ, accuracy and precision, and carry-over and dilution integrity. Finally, the method was applied to evaluate RB's ex vivo permeation and deposition profiles when loaded into dermatological formulations. Concerning qualitative determination, multiphoton microscopy was used to track the RB distribution within the skin strata, and fluorescence emission spectra were investigated to evaluate RB's behaviour when interacting with different environments. The analytical method proved specific, precise, accurate and sensitive to analyse RB in the skin. In addition, qualitative side-analytical techniques were revealed to play an essential role in evaluating the performance of RB's dermatological formulation.

Discovery and validation of bladder cancer related excreted nucleosides biomarkers by dilution approach in cell culture supernatant and urine using UHPLC-MS/MS

The exploration of nucleoside changes in human biofluids has profound potential for cancer diagnosis. Herein, we developed a rapid methodology to quantify 17 nucleosides by UHPLC-MS/MS. Five pairs of isomers were successfully separated within 8 min. The ME was mostly eliminated by sample dilution folds of 1000 for urine and 40 for CCS. The optimized method was firstly applied to screen potential nucleoside biomarkers in CCS by comprising bladder cancer cell lines (5637 and T24) and normal human bladder cell line SV-HUC-1 together with student's t-test and OPLS-DA. Nucleosides with significant differences in the supernatant of urine samples were also uncovered comparing BCa with the non-tumor group, as well as a comparison of BCa recurrence group with the non-recurrence group. By intersecting the differential nucleosides in CCS and urine supernatant, and then further confirmed using validation sets, the combination of m³C and m¹A with AUC of 0.775 was considered as a potential biomarker for bladder cancer diagnosis. A panel of m³C, m¹A, m¹G, and m²₂G was defined as potential biomarkers for bladder cancer prognosis with an AUC of 0.819. Above all, this method provided a new perspective for diagnosis and recurrence monitoring of bladder cancer. SIGNIFICANCE: The exploration of nucleoside changes in body fluids has profound potential for the diagnosis and elucidation of the pathogenesis of cancer. In this study, we developed a rapid methodology for the simultaneous quantitative determination of 17 nucleosides in the supernatant of cells and urine samples using UHPLC-MS/MS to discover and validate bladder cancer related excreted nucleoside biomarkers. The results of this paper provide a new strategy for diagnosis and postoperative recurrence monitoring of bladder cancer and provide theoretical support for the exploration of its pathogenesis.

In vitro evaluation of NA1-115-7-loaded nanoemulsions, an MCL-1-specific inhibitor of natural origin, intended to treat B-cell lymphoproliferative disorders after oral administration

MCL-1, an anti-apoptotic member of the BCL-2 protein family, is overexpressed in many types of cancer and contributes to chemotherapy resistance. The drimane derivative NA1-115-7 is a natural compound isolated from Zygogynum pancheri that can be considered as a very promising lead for treating MCL-1-dependent hematological malignancies. As this drug suffers from low stability in acidic conditions and poor aqueous solubility, we evaluated the potential oral use of NA1-115-7 by encapsulating it in lipid nanoemulsions (NA-NEs) prepared by spontaneous emulsification. NA-NEs showed a particle size of 41.9 ± 2.2 nm, PDI of 0.131 ± 0.016, zeta potential of -5.8 ± 3.4 mV, encapsulation efficiency of approximately 100 % at a concentration of 24 mM. The stability of NA-1-115-7 was sixfold higher than that of the unencapsulated drug in simulated gastric fluid. NA-NEs significantly restored apoptosis and halved the effective doses of NA1-115-7 on BL2, a Burkitt lymphoma cell line, without toxicity in normal cells. Such a drug-delivery system appears to be particularly interesting for the oral administration of NA1-115-7, as it improves its solubility and stability, as well as efficacy, by reducing the therapeutic dose, making it possible to further consider in-vivo studies of this promising drug in BL2 xenografted mice.

Quantification of Endocannabinoids in Human Plasma

The determination of the concentration of endocannabinoids and related compounds in human plasma has become a matter of interest due to their implication in physiological processes and, thus, their possible relation with physiological conditions or illnesses. The analysis of these compounds though has to be carefully designed as they are found in very low concentrations, and some of them degrade easily once blood is collected. In this chapter, a simple method based on a liquid-liquid extraction and analysis by liquid chromatography tandem mass spectrometry (LC-MS/MS) is described to determine the concentration of eight of the most relevant endocannabinoids in plasma.

In Vitro Permeation Studies on Carvedilol Containing Dissolving Microarray Patches Quantified Using a Rapid and Simple HPLC-UV Analytical Method

Analytical method validation is a vital element of drug formulation and delivery studies. Here, high-performance liquid chromatography in conjunction with UV detection (HPLC-UV) has been used to produce a straightforward, quick, yet sensitive analytical approach to quantify carvedilol (CAR). A C18 column was used to isolate the analyte from the mixture by isocratic elution with a mobile phase comprising a mixture of 0.1% v/v trifluoroacetic acid in water and acetonitrile in a ratio of 65:35 v/v at a flow rate of 0.6 mL min^-1. Linearity was observed for CAR concentrations within the range of 1.5-50 μg mL^-1 (R² = 0.999) in phosphate buffer saline and within the range of 0.2-6.2 μg mL^-1 (R² = 0.9999) in methanol. The International Council on Harmonization (ICH) requirements were followed throughout the validation of the isocratic approach, rendering it specific, accurate, and precise. Moreover, robustness tests indicated that the method remained selective and specific despite small deliberate changes to environmental and operational factors. An efficient extraction procedure was also developed to extract and quantify CAR from excised neonatal porcine skin, resulting in recovery rates ranging from 95 to 97%. The methods reported here have been successfully utilised to evaluate CAR permeation, both transdermally and intradermally following application of a dissolving microarray patch (MAP) to excised neonatal porcine skin.

Analysis of Total-Forms of Cyanotoxins Microcystins in Biological Matrices: A Methodological Review

Microcystins (MCs) are cyclic heptapeptidic toxins produced by many cyanobacteria. Microcystins can be accumulated in various matrices in two forms: a free cellular fraction and a covalently protein-bound form. To detect and quantify the concentration of microcystins, a panel of techniques on various matrices (water, sediments, and animal tissues) is available. The analysis of MCs can concern the free or the total (free plus covalently bound) fractions. Free-form analyses of MCs are the most common and easiest to detect, whereas total-form analyses are much less frequent and more complex to achieve. The objective of this review is to summarize the different methods of extraction and analysis that have been developed for total forms. Four extraction methods were identified: MMPB (2-methyl-3-methoxy-4-phenylbutyric acid) method, deconjugation at basic pH, ozonolysis, and laser irradiation desorption. The study of the bibliography on the methods of extraction and analysis of the total forms of MCs showed that the reference method for the subject remains the MMPB method even if alternative methods and, in particular, deconjugation at basic pH, showed results encouraging the continuation of the methodological development on different matrices and on naturally-contaminated samples.

From target analysis to suspect and non-target screening of endocrine-disrupting compounds in human urine

In the present work, a target analysis method for simultaneously determining 24 diverse endocrine-disrupting compounds (EDCs) in urine (benzophenones, bisphenols, parabens, phthalates and antibacterials) was developed. The target analysis approach (including enzymatic hydrolysis, clean-up by solid-phase extraction and analysis by liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS)) was optimized, validated and applied to volunteers’ samples, in which 67% of the target EDCs were quantified. For instance, benzophenone-3 (0.2–13 ng g⁻¹), bisphenol A (7.7–13.7 ng g⁻¹), methyl 3,5-dihydroxybenzoate (8–254 ng g⁻¹), mono butyl phthalate (2–17 ng g⁻¹) and triclosan (0.3–9 ng g⁻¹) were found at the highest concentrations, but the presence of other analogues was detected as well. The developed target method was further extended to suspect and non-target screening (SNTS) by means of LC coupled to high-resolution MS/MS. First, well-defined workflows for SNTS were validated by applying the previously developed method to an extended list of compounds (83), and then, to the same real urine samples. From a list of approximately 4000 suspects, 33 were annotated at levels from 1 to 3, with food additives/ingredients and personal care products being the most abundant ones. In the non-target approach, the search was limited to molecules containing S, Cl and/or Br atoms, annotating 4 pharmaceuticals. The results from this study showed that the combination of the lower limits of detection of MS/MS and the identification power of high-resolution MS/MS is still compulsory for a more accurate definition of human exposome in urine samples.

Creatine@SiO2 @Fe3 O4 nanocomposite as an efficient sorbent for magnetic solid-phase extraction of escitalopram and chlordiazepoxide from urine samples through quantitation via HPLC-UV

An efficient, cost-effective, and fast-synthesis method is presented in the current study to prepare magnetic nanoparticles covered by cheap and nitrogen-rich creatine. The hydrothermal method was used for the synthesis of the magnetic core. The prepared magnetic core was then covered by SiO₂ and subsequently functionalized using creatine. The prepared creatine@SiO₂ @Fe₃ O₄ was utilized as a sorbent in the magnetic solid-phase extraction of the selected antidepressants including escitalopram and chlordiazepoxide as the model drugs. The extracted drugs were desorbed by a suitable organic solvent and analyzed by high-performance liquid chromatography equipped with an ultraviolet detection system. The influence of different variables on the magnetic solid-phase extraction method was examined by the Plackett-Burman and Box-Behnken designs for screening and optimization, respectively. Under the obtained optimum conditions, the linear ranges of the method were found to be in the range of 1-500 µg L^-1 . The limits of detection and limits of quantification were in the range of 0.27-0.63 µg L^-1 and 0.89-1.93 µg L^-1 for the selected analytes, respectively. Furthermore, the enrichment factors were found to be 79.8 and 92.7 for chlordiazepoxide and escitalopram, respectively. The method was successfully employed for the analysis of selected drugs in urine samples.

Simultaneous determination of four cobalamins in rat plasma using online solid phase extraction coupled to high performance liquid chromatography-tandem mass spectrometry: Application to pentylenetetrazole-induced seizures in Sprague-Dawley rats

A high throughput and high sensitive online solid phase extraction coupled to high performance liquid chromatography-tandem mass spectrometry method was established and validated for simultaneous quantification of four cobalamins including OHCbl, CNCbl, AdoCbl and MeCbl in rat plasma. Analytes were first enriched on an online SPE Shim-pack MAYI-ODS column and then separated using a Poroshell 120 EC C18 analytical column. The linear range was from 0.05 to 5 ng/ml and the LLOQ was 0.05 ng/ml for all four cobalamins. In addition, this method was applied to determine the cobalamins levels in pentylenetetrazole-induced kindling rat model for the first time.

Postcolumn Infusion as a Quality Control Tool for LC-MS-Based Analysis

Postcolumn infusion has been widely used to study the matrix effect of analytical methods based on liquid chromatography coupled to mass spectrometry (LC-MS). Nevertheless, this methodology is usually only applied during a method development or validation. With this application note, we aim to demonstrate that the continuous use of postcolumn infusion can be also a very useful tool to monitor the quality of LC-MS analyses and easily detect flaws in the analytical method performance. Here we propose a protocol that can be transferred to other LC-MS platforms, and we show some real situations in bioanalysis in which postcolumn infusion proved to be extremely helpful in, for example, the evaluation of a sample treatment or the detection of unexpected sources of the matrix effect.

Evaluation of three methods for betanin quantification in fruits from cacti

In México, production of cacti fruits has increased. These fruits have high concentration of betalains (pigments), and market has increased interest in food with natural ingredients. In the near future, a sustainable method for betanin quantification in cacti fruits for rural communities will be necessary. Betanin in pulp of garambullo (Myrtillocactus geometrizan), chico fruit (Pachycereus weber), jiotilla (Escontria chiotilla) and pitaya de mayo (Stenocereus pruinosus) were quantified using three different analytical methods. The techniques were of Spectrophotometry UV-Vis (SCC), High-Performance Liquid Chromatography (HPLC) and Spectrophotometry technique using Molar Extinction Coefficient (SEC). The accuracy and intermediate precision were evaluated in SEC, SCC, and HPLC with the four cacti´s fruit. The means betanin concentration in the pulps were 0.68±0.05 (mg/g dry weight) garambullo, 1.28±0.06 (mg/g dry weight) chico fruit, 1.84±0.34 jiotilla and 2.0±0.25 pitaya de mayo (mg/g dry weight). The concentration of betanin in garambullo pulp measured by the three methods did not differ significantly (P >0.05). In this case, SEC method represents the best option to reduce costs, time and solvents in this way this method is aligned with green chemistry. In the three methods, coefficient of variation between measurements obtained are below 15%.•Robust method to quantify betanin and evaluate intermediate precision•Validation parameters such as LOD, LOQ, accuracy, intermediate precision, and HorRat were considered•The developed method enriches the valorization of underutilized national agricultural sources of Mexico.

A New and Sensitive HPLC-UV Method for Rapid and Simultaneous Quantification of Curcumin and D-Panthenol: Application to In Vitro Release Studies of Wound Dressings

Curcumin (CUR) and D-panthenol (DPA) have been widely investigated for wound-healing treatment. In order to analyse these two compounds from a dosage form, such as polymer-based wound dressings or creams, an analytical method that allows the quantification of both drugs simultaneously should be developed. Here, we report for the first time a validated high-performance liquid chromatographic (HPLC) method coupled with UV detection to quantify CUR and DPA based on the standards set by the International Council on Harmonization (ICH) guidelines. The separation of the analytes was performed using a C₁₈ column that utilised a mobile phase consisting of 0.001% v/v phosphoric acid and methanol using a gradient method with a run time of 15 min. The method is linear for drug concentrations within the range of 0.39–12.5 μg mL⁻¹ (R² = 0.9999) for CUR and 0.39–25 μg mL⁻¹ for DPA (R² = 1). The validated method was found to be precise and accurate. Moreover, the CUR and DPA solution was found to be stable under specific storage conditions. We, therefore, suggest that the HPLC-UV method developed in this study may be very useful in screening formulations for CUR and DPA within a preclinical setting through in vitro release studies.

Development and characterization of a dry reservoir-hydrogel-forming microneedles composite for minimally invasive delivery of cefazolin

Cefazolin (CFZ) is one of the most extensively used cephalosporins. This antibiotic exerts its bactericidal activity by interfering with bacterial cell wall formation, leading to bacteriolysis. CFZ is highly polar, resulting in the drug having poor oral bioavailability. Accordingly, the antibiotic is administered via intramuscular or intravenous injections, which are both painful and invasive. Due to these limitations, there is an impetus to explore alternative drug delivery platforms which offer a minimally invasive approach to delivery CFZ into and across the skin. The current work presents the development of a composite pharmaceutical system composed of hydrogel-forming microneedles (MNs) in tandem with CFZ dry reservoirs. The hydrogel system was fabricated from Gantrez® S-97 and Carbopol® 974P NF crosslinked with PEG 10,000. Swelling kinetic studies showed that the hydrogel system developed was capable of achieving 4000% swelling in PBS pH 7.4. In addition, results from a solute diffusion study showed that CFZ was able to achieve ≈100% cumulative permeation across the swollen hydrogel film. When formulated into MNs, the hydrogel system was capable of breaching the stratum corneum, resulting in intradermal insertion of the hydrogel forming MNs into ex vivo neonatal porcine skin, as evidenced from optical coherence tomography. In addition, two different CFZ loaded dry reservoirs consisting of directly compressed tablets (DCT) and lyophilised (LYO) wafers were formulated and characterised. These dry reservoir systems showed fast dissolution, dissolving in phosphate buffer saline pH 7.4 in less than one minute. In vitro permeation studies, using full thickness ex vivo neonatal porcine skin were conducted. HPLC analysis demonstrated the dry reservoir combination consisting of DCT with hydrogel-forming MNs was capable of achieving up to 80 µg CFZ delivery into the epidermis within 2 hours of application. In addition, DCT reservoir coupled with hydrogel-forming MNs were able to deliver CFZ up to 1.8 mg into and across the skin at 24 hours. Should this system be translated into clinical practice, it may provide a minimally invasive strategy to administer CFZ for the treatment of infections such as septic arthritis, osteomyelitis and cellulitis.

Development and validation of simple and sensitive HPLC-UV method for ethambutol hydrochloride detection following transdermal application

A new high-performance liquid chromatographic method coupled with UV detection (HPLC-UV) to quantify ethambutol (ETH) post permeation studies following microneedle administration has been developed. This method involves the derivatization of ETH with phenethyl isocyanate (PEIC) at room temperature for 90 min. The separation of the derivative was performed using a C18 column that utilised a mobile phase consisting of 25 mM sodium dihydrogen phosphate buffer (with 1% v/v triethylamine, pH 3.0 adjusted using orthophosphoric acid) and methanol (25 : 75 v/v). The developed analytical method was validated according to the standards set by the International Council on Harmonization (ICH) guidelines. The method is linear for drug concentrations within the range of 0.39-12.5 μg mL^-1 (R² = 0.9999). The validated method was found to be specific, precise, and accurate. Moreover, the ETH derivative was found to be stable under specific storage conditions. In addition, a simple and straightforward extraction procedure for extracting and quantifying ETH from the skin was developed and evaluated. The extraction procedure displayed recovery rates that range from 101.77 ± 7.10% to 102.33 ± 8.69% indicating high extraction efficiency. The developed method was utilised in assessing the permeation of ETH across dermatomed neonatal porcine skin following microneedle application. Collectively, the simple and stable HPLC method developed in this study may be of great utility in screening formulations for ethambutol within a preclinical setting through in vitro permeation studies.

Validation Study on the Simultaneous Quantitation of Multiple Wine Aroma Compounds with Static Headspace-Gas Chromatography-Ion Mobility Spectrometry

A new quantitative method based on static headspace-gas chromatography-ion mobility spectrometry (SHS-GC-IMS) is proposed, which enables the simultaneous quantitation of multiple aroma compounds in wine. The method was first evaluated for its stability and the necessity of using internal standards as a quality control measure. The two major hurdles in applying GC-IMS in quantitation studies, namely, nonlinearity and multiple ion species, were also investigated using the Boltzmann function and generalized additive model (GAM) as potential solutions. Metrics characterizing the model performance, including root mean squared error, bias, limit of detection, limit of quantitation, repeatability, reproducibility, and recovery, were investigated. Both nonlinear fitting methods, Boltzmann function and GAM, were able to return desirable analytical outcomes with an acceptable range of error. Potential pitfalls that would cause inaccurate quantitation, that is, effects of ethanol content and competitive ionization, were also discussed. The performance of the SHS-GC-IMS method was subsequently compared against that of a currently established method, namely, GC-MS, using commercial wine samples. These findings provide an initial validation of a GC-IMS-based quantitation method, as well as a starting point for further enhancing the analytical scope of GC-IMS.

A validated method for the analysis and profiling of ‘nyaope’ using gas chromatography – mass spectrometry

Nyaope, a Tswana word for a mixture or ‘mish-mash’, describes a drug cocktail consisting of heroin, cannabis, and on occasion other controlled substances and warfarin. It is highly addictive with extremely unpleasant side effects caused by withdrawal from the drug. It is a problem drug especially in townships in South Africa. However, its prevalence in neighbouring southern African states and further afield is not yet known. There is currently no validated method for the analysis and comparison of nyaope. We describe a validated method for the gas chromatography – mass spectrometry analysis of nyaope so that within-batch and between-batch comparisons of nyaope can successfully be made for the first time. The validated method managed an accuracy within the range 80–120%, the precision was less than 20% for all analytes and managed linearity with R2≥0.99. The detection limits for diamorphine, efavirenz, nevirapine and Δ9-tetrahydrocannabinol were 14.2, 18.6, 18.7 and 9.94 pg on column, respectively, and the limits of quantitation were 43.1, 56.3, 56.6 and 30.1 pg on column, respectively. The simulated and casework samples were successfully discriminated into original batches using the identified nyaope components, the unsupervised chemometric methods principal component analysis and hierarchical clustering, as well as chromatographic profiles.

Clinical Pharmacokinetics and Safety of a 10% Aminolevulinic Acid Hydrochloride Nanoemulsion Gel (BF-200 ALA) in Photodynamic Therapy of Patients Extensively Affected With Actinic Keratosis: Results of 2 Maximal Usage Pharmacokinetic Trials

The nanoemulsion‐based 10% aminolevulinic acid (ALA) hydrochloride gel BF‐200 ALA optimizes epidermal penetration of its active ingredient and is approved for topical photodynamic therapy (PDT) for the treatment of actinic keratosis in the United States and Europe. To characterize systemic absorption from dermal application during PDT, ALA and its key active metabolite protoporphyrin IX (PpIX) were analyzed in 2 maximal usage pharmacokinetic trials (MUsT) in patients severely affected with actinic keratosis. The primary objective of both MUsTs was to assess baseline‐adjusted plasma concentration–time curves for ALA and PpIX after a single PDT treatment applying either 2 g (1 tube) of BF‐200 ALA on the face (MUsT‐1) or applying 6 g (3 tubes) of BF‐200 ALA on the face/scalp or body periphery (MUsT‐2), to 20 or 60 cm², respectively. All PDTs were performed using red light at around 635 nm wavelength. Safety and tolerability were documented along with pharmacokinetics. In both MUsTs, ALA plasma concentrations were transiently increased to a maximum concentration at about 2.5 to 3.3 times above endogenous baseline with time to maximum concentration at ≈3 hours after dosing. Plasma levels subsequently returned to baseline within 10 hours after dosing. Overall baseline‐adjusted mean area under the baseline‐adjusted plasma concentration‐time curve from time zero to the last sampling time point at which the concentration was at or above the lower limit of quantification ranged from 142.8 to 146.2, indicating that a similar, minor fraction of topical ALA is systemically absorbed under both dosing regimens. Systemic PpIX exposure after administration of either dose of BF‐200 ALA was equally minimal. Application site skin reactions were treatment area size‐related, albeit transient and consistent with the known safety profile of BF‐200 ALA.

Removal of adsorption sites on the external surface of mesoporous adsorbent for eliminating the interference of proteins in enrichment of phosphopeptides/nucleotides

Various mesoporous adsorbents are of great promise for enriching small molecules from biological samples based on the size-exclusion effect. At present, the mesoporous adsorbents have adsorption sites distributed uniformly on the internal and external surfaces of mesopores. However, the adsorption sites on the external surface can adsorb proteins, interfering with the enrichment of small molecules. Herein, a novel immobilized-Ti⁴⁺ magnetic mesoporous adsorbent removing the adsorption sites on the external surface was facile prepared via the coupling chemistry of isocyanate with amine and consequent hydrolysis of urea linkage by urease. The adsorbent enables fast and selective enrichment of phosphopeptides and nucleotides from biological samples. In addition, sensitive detection methods for phosphopeptides and nucleotides in human serum are developed by coupling the magnetic solid-phase extraction with matrix-assisted laser desorption/ionization time of flight mass spectrometry and liquid chromatography-mass spectrometer, respectively. Under optimal conditions, response is linear (R² ≥ 0.9923), limits of detection are low (0.41-9.48 ng mL^-1), and reproducibility is acceptable (inter- and intra-day assay RSDs of≤15.0%) for six nucleotides. The developed strategy offers an effective method to eliminate the interference of proteins in the enrichment of small molecules from real biological samples.

Fast and reliable analysis of veterinary metomidate and etomidate in human blood samples by liquid chromatography-tandem mass spectrometry (LC-MS/MS) in a postmortem case

Metomidate and etomidate belong to the non-barbiturate imidazole family of sedative-hypnotics and elicit little analgesic action when used alone. Metomidate, in particular, has little analgesic activity in humans and is, therefore, used for veterinary purposes. In 2019, a Korean woman in her twenties was found unconscious in a motel bath and eventually died. Etomidate, alprazolam, escitalopram, and metomidate were detected in the postmortem specimens. To our knowledge, this is the first case of human metomidate abuse reported in the Republic of Korea. In this research, a simple and reliable method was developed for the analysis of metomidate and etomidate in human blood samples using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Blood samples were deproteinized with acetonitrile, filtered, and analyzed by LC-MS/MS. Linear calibration curves were obtained with six concentrations ranging from 1 to 50 ng/ml for metomidate and 10 to 500 ng/ml for etomidate. The method was validated by assessing the selectivity, linearity, limit of detection (LOD), limit of quantitation (LOQ), intra- and inter-day precision and accuracy, matrix effect, and stability and successfully applied to the analysis of metomidate and etomidate in human blood samples. In a postmortem case, the concentrations of metomidate and etomidate were found to be 8 and 110 ng/ml in femoral blood and 6 and 210 ng/ml in cardiac blood, respectively.

A liquid chromatography-tandem mass spectrometry method for the analysis of primary aromatic amines in human urine

Aromatic amines are widely used in personal care products and human exposure to this class of chemicals is widespread. Bioanalytical methods to determine trace levels of aromatic amines in human urine are scarce. In this study, a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed to determine 39 primary aromatic amines (AAs) along with nicotine and cotinine in human urine. Chromatographic separation of the 41 analytes was achieved on an Ultra Biphenyl (100 mm × 2.1 mm, 5 µm) column. Mass spectrometry was operated in electrospray ionization positive ion multiple reaction monitoring (MRM) mode. The method exhibited excellent linear dynamic range (0.1-50 ng/mL) with correlation coefficients (r) > 0.999 for all analytes. Urine samples (2 mL) were hydrolyzed using 10 M NaOH at 95 °C for 15 h and target analytes were extracted using methyl-tert-butyl ether (MTBE). Addition of 15 µL of 0.25 M HCl to the sample extracts improved the recoveries of several target analytes. The method was validated through the analysis of fortified quality control (QC) samples and a certified standard reference material (SRM). Relative recoveries (%) of target analytes fortified in QC samples were in the range of 75-114% for 37 of the 41 analytes while the other analytes exhibited lower recoveries (16-74%). The limits of detection (LOD) and limits of quantification (LOQ) of target analytes were in the range of 0.025-0.20 ng/mL and 0.1-1.0 ng/mL, respectively. Intra-day and inter-day precision of the method assessed through the analysis of fortified urine QC samples at three different concentrations were < 11.7% and < 15.9% (measured as RSD), respectively. The method was applied in the analysis of urine samples from the general population and known smokers; aniline, para-anisidine, para-toluidine, ortho/meta-toluidine, 3-chloroaniline, 4-chloroaniline, 3,4-dichloroaniline, and 4,4'-methylenedianiline were found in all smoker's urine at sum concentrations ranging from 0.04 to 9.16 ng/mL.

Lipemia in the Plasma Sample Affects Fentanyl Measurements by Means of HPLC-MS2 after Liquid-Liquid Extraction

Examination of fentanyl levels is frequently performed in certain scientific evaluations and forensic toxicology. It often involves the collection of very variable blood samples, including lipemic plasma or serum. To date, many works have reported the methods for fentanyl detection, but none of them have provided information about the impact on the assay performance caused by an excessive amount of lipids. This aspect may be, however, very important for highly lipophilic drugs like fentanyl. To address this issue, we developed the liquid chromatography method with mass spectrometry detection and utilized it to investigate the impact of lipids presence in rabbit plasma on the analytical method performance and validation. The validation procedure, conducted for normal plasma and lipemic plasma separately, resulted in good selectivity, sensitivity and linearity. The limits of detection and quantification were comparable between the two matrices, being slightly lower in normal plasma (0.005 and 0.015 µg/L) than in lipemic plasma (0.008 and 0.020 µg/L). Liquid–liquid extraction provided a low matrix effect regardless of the lipid levels in the samples (<10%), but pronounced differences were found in the recovery and accuracy. In the normal plasma, this parameter was stable and high (around 100%), but in the lipemic matrix, much more variable and less efficient results were obtained. Nevertheless, this difference had no impact on repeatability and reproducibility. In the present work, we provided reliable, convenient and sensitive method for fentanyl detection in the normal and lipemic rabbit plasma. However, construction of two separate validation curves was necessary to provide adequate results since the liquid-liquid extraction was utilized. Therefore, special attention should be paid during fentanyl quantification that involves lipemic plasma samples purified by this technique.

Expediting Disulfiram Assays through a Systematic Analytical Quality by Design Approach

An Analytical Quality by Design (AQbD) approach is presented, aiming at the development and validation of an HPLC method for the quantification of disulfiram and copper diethyldithiocarbamate in lipid nanoparticles. Following the definition of the analytical target profile (ATP), encompassing the critical analytical attributes (CAA), a two-level risk assessment strategy (Ishikawa diagram—failure mode and effect analysis (FMEA)) was employed to identify the critical method parameters (CMPs) with an extensive impact on method performance. The behavior of the CMPs (flow rate and mobile phase composition) was further characterized by experimental design, resorting to a face-centered central composite design (FcCCD). Statistical modeling, response surface analysis, and Monte Carlo simulations led to the definition of the Method Operable Design Region (MODR), associated with a negligible risk of failing the predefined CAA specifications. The optimal method was validated according to international regulatory recommendations. Apart from guaranteeing linearity, accuracy, precision, specificity, robustness, and stability, these conditions were found to be suitable for analysis using a different HPLC column and equipment. In a nutshell, the development and optimization strategies, under the comprehensive framework of AQbD, provided an effective, simple, rapid, reliable, and flexible method for routine analysis of the compounds in research or industrial environments.

HPLC method for levothyroxine quantification in long-acting drug delivery systems. Validation and evaluation of bovine serum albumin as levothyroxine stabilizer

Deficiency of thyroid hormones (hypothyroidism) is treated with oral levothyroxine (LEVO). However, the effectiveness of oral administration is highly dependent on the co-administration of food and other drugs. This factor, in combination with the chronic nature of this condition, mean that there are concerns with patient compliance. Development of long acting formulations to treat hypothyroidism could potentially solve this problem. However, LEVO instability in solution could be problematic. In order to develop long acting LEVO delivery systems in vitro drug release experiments should be carried out. However, short term LEVO stability in aqueous solution will prevent this. BSA was used as a stabiliser for LEVO; extending the stability of the drug in aqueous solutions from a few hours to 2 weeks. In order to achieve this, the required concentration of the protein was 0.1% w/v. Subsequently, an HPLC method capable of separating LEVO from the protein was developed and validated following ICH guidelines. The analysis was carried out using a reverse phase HPLC method on an Agilent 1220 Infinity II LC system. The column used to achieve separation was a Zorbax Eclipse plus C18 (95 Å pore size, 250 mm length x 4.6 mm internal diameter; 5 μm particle size). The mobile phase used was composed of acetonitrile and 0.1% trifluoroacetic acid at a ratio of 50:50% v/v. UV detection of LEVO sodium was carried out at 225 nm. The retention time for the drug was 6.6 minutes. The method showed a limit of detection of 0.03 μg/mL and a limit of quantification of 0.09 μg/mL. Finally, this method was used to evaluate the release from implants containing 20% w/w of LEVO. These devices were prepared using a solvent casting method with poly(caprolactone) and LEVO. These devices showed an initial burst release over the first 3 days. Subsequently, they were capable of providing a linear release rate over the following 25 days.

A normalized signal calibration with a long-term reference improves the robustness of RPLC-MRM/MS lipidomics in plasma

Improving the reliability of quantification in lipidomic analyses is crucial for its successful application in the discovery of new biomarkers or in clinical practice. In this study, we propose a workflow to improve the accuracy and precision of lipidomic results issued by the laboratory. Lipid species from 11 classes were analyzed by a targeted RPLC-MRM/MS method. The peak areas of species were used to estimate concentrations by an internal standard calibration approach (IS-calibration) and by an alternative normalization signal calibration schema (NS-calibration). The latter uses a long-term reference plasma material as a matrix-matched external calibrator whose accuracy was compared to the NIST SRM-1950 mean consensus values reported by the Interlaboratory Lipidomics Comparison Exercise. The bias of lipid concentrations showed a good accuracy for 69 of 89 quantified lipids. The quantitation of species by the NS-calibration schema improved the within- and between-batch reproducibility in quality control samples, in comparison to the usual IS-calibration approach. Moreover, the NS-calibration workflow improved the robustness of the lipidomics measurements reducing the between-batch variability (relative standard deviation <10% for 95% of lipid species) in real conditions tested throughout the analysis of 120 plasma samples. In addition, we provide a free access web tool to obtain the concentration of lipid species by the two previously mentioned quantitative approaches, providing an easy follow-up of quality control tasks related to lipidomics.

Simultaneous measurement of free and conjugated estrogens in surface water using capillary liquid chromatography tandem mass spectrometry

Given detrimental impacts induced by estrogens at trace level, determination of them is significant but challenging due to their low content in environmental samples and inherent weak ionisation. A modified derivatisation-based methodology was applied for the first time to detect estrogen in free and conjugated forms including some isomers simultaneously using liquid chromatography tandem mass spectrometry (LC-MSn). Derivatisation reaction with previously used 1,2-dimethyl-1H-imidazole-5-sulphonyl chloride allowed significant increase of mass spectrometric signal of analytes and also provided distinctive fragmentation for their confirmation even in complicated matrix. Then satisfactory recovery (>75%) for the majority of analytes was achieved following optimisation of solid phase extraction (SPE) factors. The linearity was validated over a wide concentration with the correlation coefficient around 0.995. The repeatability of this methodology was also confirmed via the intra-day and inter-day precision and was less than 11.73%. Validation of method quantification limits (MQLs) for all chosen estrogens was conducted using 1000 mL surface water, ranging from 7.0 to 132.3 pg L-1. The established methodology was applied to profile presence of targeted estrogens in natural surface water samples. Out of the ten compounds of interest, three free estrogens (E1, E2, E3) and two sulphate estrogens (E1-3S and E2-3S) were found over their MQLs, being in the range of 0.05-0.32 ng L-1.

Development and optimization of a quantitative analysis of main odorants causing off flavours in cork stoppers using headspace solid-phase microextraction gas chromatography tandem mass spectrometry

A simple and sensitive method was developed and validated to simultaneously separate and determine the 2-Methoxy-3,5-dimethylpyrazine, 2-Isopropyl-3-methoxypyrazine, guaiacol, 2-Isobutyl-3-methoxypyrazine, 2-Methylisoborneol, geosmin, 2,4,6-Trichloroanisole, 2,3,4,6-Tetrachloroanisole, 2,4,6-Tribromoanisole and Pentachloroanisole in cork stoppers via headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography tandem mass spectrometry (GC-MS/MS). The influence of the fibre coating used, the extraction times and temperatures, the sodium chloride additions and the desorption temperatures were investigated. Once done, the optimial HS-SPME conditions established were divinylbenzene/carboxenpolydimethylsiloxane/polydimethylsiloxane (DVB/CAR/PDMS) fibres, a 50°C extraction temperature, 60-min extraction time, an ionic strength of 3-g sodium chlorid and a 290°C desorption temperature. The method showed a good linearity (R2  ≥ 0.994) within the tested range (from 0.1 to 50 ng L-1 ) for all the compounds. Using TCA-d10 and MIB-d3 as internal standards the precision, expressed as repeatability and reproducibility RSD, was <10% in both. Note that the limits of quantifications (LOQs) are below the sensory threshold levels for such compounds in water and wine. Good recoveries were obtained for cork macerates (from 100.4% to 126%) and when compared with other reported methods using HS-SPME in water and cork stopper samples, the present method had more analytes with the lowest limit of detection for most of the targeted compounds, along with good precision and recovery.

Fast fabric phase sorptive extraction of selected β-blockers from human serum and urine followed by UHPLC-ESI-MS/MS analysis

A fast fabric phase sorptive extraction method is presented herein for the rapid isolation of selected beta-blocker drugs from human serum and urine. Among many high efficiency sol-gel sorbent coated FPSE membranes, sol-gel CW20 M coated FPSE membrane was identified as the best FPSE membrane for the target beta-blocker drugs possessing logP values ranging from 0.1 (highly polar) to 3.1 (moderately polar). Due to the engineered affinity towards the analytes via complementary intermolecular interactions and high mass transfer rate of the analytes from the bulk sample solution to the FPSE membrane, the extraction is accomplished in relatively short time (15 min) while its high permeability permits the direct extraction of biological samples without any other pretreatment. The advantages of the fabricated extraction membrane were exploited for the determination of six beta-blockers (namely atenolol, nadolol, metoprolol, oxprenolol, labetalol and propranolol) in biological matrices in combination with UHPLC-ESI-MS/MS. Important parameters including extraction time, sample volume, sorbent size, elution solvent, etc. affecting the performance of the extraction were systematically investigated. The linearity of the method was evaluated in the range of 50-5000 ng mL^-1 by constructing weighted (1/X) matrix-matched calibration curves. The intra-day and inter-day trueness were ranged between - 17.2 to 13.3% and - 10.8 to 12.6%, respectively. The intra-day and inter-day precision were less than 11.5 and 14.5 %, respectively. The proposed analytical scheme was successfully applied to the determination of the target drugs in human serum and urine.

Cyanogenic Glycoside Analysis in American Elderberry

Cyanogenic glycosides (CNGs) are naturally occurring plant molecules (nitrogenous plant secondary metabolites) which consist of an aglycone and a sugar moiety. Hydrogen cyanide (HCN) is released from these compounds following enzymatic hydrolysis causing potential toxicity issues. The presence of CNGs in American elderberry (AE) fruit, Sambucus nigra (subsp. canadensis), is uncertain. A sensitive, reproducible and robust LC-MS/MS method was developed and optimized for accurate identification and quantification of the intact glycoside. A complimentary picrate paper test method was modified to determine the total cyanogenic potential (TCP). TCP analysis was performed using a camera-phone and UV-Vis spectrophotometry. A method validation was conducted and the developed methods were successfully applied to the assessment of TCP and quantification of intact CNGs in different tissues of AE samples. Results showed no quantifiable trace of CNGs in commercial AE juice. Levels of CNGs found in various fruit tissues of AE cultivars studied ranged from between 0.12 and 6.38 µg/g. In pressed juice samples, the concentration range measured was 0.29-2.36 µg/mL and in seeds the levels were 0.12-2.38 µg/g. TCP was highest in the stems and green berries. Concentration levels in all tissues were generally low and at a level that poses no threat to consumers of fresh and processed AE products.

In-situ synthesis of nanocubic cobalt oxide @ graphene oxide nanocomposite reinforced hollow fiber-solid phase microextraction for enrichment of non-steroidal anti-inflammatory drugs from human urine prior to their quantification via high-performance liquid chromatography-ultraviolet detection

The in-situ synthesis and application of nanocubic Co₃O₄-coated graphene oxide (Co₃O₄@ GO) was introduced for the first time to present a cost-effective, stable and convenient operation and a simple device for hollow fiber solid-phase microextraction (HF-SPME) of four selected nonsteroidal anti-inflammatory drugs (NSAIDs) including diclofenac, mefenamic acid, ibuprofen and indomethacin. The extracted analytes were desorbed by an appropriate organic solvent and analyzed via high-performance liquid chromatography-ultraviolet detection (HPLC-UV). The prepared sorbent was approved using different characterization methods such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The variables effective on the Co₃O₄@GO-HF-SPME method including extraction time, desorption time, desorption solvent volume, sample pH, stirring rate and ionic strength were screened via Plackett-Burman design and then optimized by Box-Behnken design. Under optimal condition, the calibration curves were linear within the range of 1.0-200.0 µg L^-1 of analyte concentration with detection limits of 0.18-1.1 µg L^-1 and the relative standard deviations less than 10.1%. The limits of quantification (LOQs) were in the range of 0.60-3.67 µg L^-1. Matrix effect was not observed with this method; therefore, standard addition is not necessary for quantification of target compounds. The enrichment factors were obtained in the range of 49-68. The relative recoveries of the urine sample analysis were calculated in the range of 93-102%. Finally, the presented method exhibited good sensitivity, excellent repeatability, high reusability and acceptable precision, which will be a promising method to analyze various nonsteroidal anti-inflammatory drugs in urine samples.