Dispersive liquid-liquid microextraction: trends in the analysis of biological samples

Ionic-liquid/Carbowax 20 M functionalized capsule phase microextraction platform for the extraction of phosphodiesterase-5 inhibitors from human serum and urine prior to their determination by LC-MS

Capsule phase microextraction (CPME) is an efficient bioanalytical technique that streamlines the sample preparation by integrating the filtration and stirring mechanism directly into the device. A novel composite sorbent designed to be selective towards the target analytes consisting of mixed-mode sorbent chemistry synthesized by sol-gel technology is found promising and superior to the conventional C18 sorbents. Herein we describe the encapsulation of an ionic liquid (IL)/Carbowax 20M-functionalized sol-gel sorbent (sol-gel IL/Carbowax 20 M) in the lumen of porous polypropylene tubes for the capsule phase microextraction of three phosphodiesterase-5 inhibitors namely avanafil, sildenafil, and tadalafil in human serum and urine samples. The CPME device was characterized by Scanning Electron Microscopy (SEM) and Fourier-Transform Infrared Spectroscopy (FT-IR). The experimental parameters of CPME procedure (e.g. sample pH and ionic strength, extraction time, stirring rate, elution solvent and volume) were carefully optimized to achieve the highest possible extraction efficiency for the analytes. Method validation was conducted in terms of precision, linearity, accuracy, matrix effect, lower limits of quantification, and limits of detection (LOD). The method linearity was investigated in the range of 50-1000 ng mL-1 for all analytes while the precision was less than 11.8 % in all cases. For all analytes, the LOD values were 17 ng mL-1. The IL/CW 20M-functionalized microextraction capsules could be reused at least 25 times both for urine and serum samples. The green character and the applicability of the proposed method were evaluated using the ComplexGAPI and BAGI indexes. The optimized CPME protocol exhibited reduced consumption of organic solvent and generation of waste, cost-effectiveness, and simplicity. Finally, the proposed method was successfully applied to the analysis of sildenafil in human urine after administration of drug-containing formulation.

Deep eutectic solvents for the determination of endocrine disrupting chemicals

The harmful effects of endocrine disrupting chemicals (EDCs) to humans and other organisms in the environment have been well established over the years, and more studies are ongoing to classify other chemicals that have the potential to alter or disrupt the regular function of the endocrine system. In addition to toxicological studies, analytical detection systems are progressively being improved to facilitate accurate determination of EDCs in biological, environmental and food samples. Recent microextraction methods have focused on the use of green chemicals that are safe for analytical applications, and present very low or no toxicity upon disposal. Deep eutectic solvents (DESs) have emerged as one of the viable alternatives to the conventional hazardous solvents, and their unique properties make them very useful in different applications. Notably, the use of renewable sources to prepare DESs leads to highly biodegradable products that mitigate negative ecological impacts. This review presents an overview of both organic and inorganic EDCs and their ramifications on human health. It also presents the fundamental principles of liquid phase and solid phase microextraction methods, and gives a comprehensive account of the use of DESs for the determination of EDCs in various samples.

Development of an analytical method for the determination of pesticides in tropical fruits by LC-QTOF-MS/MS after QuEChERS extraction sample cleanup and DLLME preconcentration

In this study, QuEChERS extraction was combined with dispersive liquid-liquid microextraction (DLLME) to extract pesticides from tropical fruits for determination by a highly accurate and sensitive liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QTOF-MS/MS) system. The QuEChERS method served as a matrix clean-up tool and the DLLME method preconcentrated the analytes for their determination at trace levels. All parameter variables of the DLLME method were optimized to improve the extraction output and lower the limits of detection and quantification (LOD and LOQ) for all the analytes. Under the optimum experimental conditions, the LOD and LOQ values were found in the range of 0.004-0.013 and 0.27-0.61μg l-1, respectively. The detection limits achieved by direct LC-QTOF-MS/MS analysis were increased by about 10-260 folds using the optimized DLLME method. To assess the accuracy and applicability of the developed method, spike recovery experiments on tropical fruits were carried out. The matrix matching calibration method was used to enhance the quantification accuracy of the analytes in kiwi, pineapple, and mango matrices, with percent recoveries ranging between 89 and 117%.

Chemometric assisted natural DES based VA-DLLME-LC-MS/MS method for the quantitative determination of Garcinol in biofluids/tissues: A practical application to pharmacokinetics and biodistribution studies

Garcinol (GAR) is a polyisoprenylated benzophenone obtained from Garcinia indica used as anti-oxidant and anti-inflammatory in traditional medicine and due to these activities, it possesses anticancer properties. It is considered to be a next generation epigenetic drug. A green solvent based analytical method which is efficient, sophisticated, and highly enriched has been developed for the quantitative analysis of GAR in biological samples (plasma, liver, kidney and spleen) with the use of deep eutectic solvent (DES) for its extraction. A series of 23 DESs were synthesized and out of which, Thymol (Th)-Terpeniol (T), 2:1 molar ratio with a more hydrophobic environment and high interaction efficiency between GAR and DES was identified for the better extraction from mice plasma and tissue samples. The Design of Experiment approaches like placket-burmann design and central composite design were used to optimize the method conditions. The method validation characteristics, such as limit of detection (0.193-0.237 ng/mL), limit of quantification (0.644-0.697 ng/mL), lower limit of quantification (0.5 ng/mL), broad range of linearity with R2 (0.9994-0.9997) with a percent recovery not less than 87% was observed, which are well within the acceptance criteria for a bioanalytical method. The enrichment factor is upto 53-60 folds, with high extraction efficiency (89-97%). The measurement uncertainty was estimated with an expanded uncertainty ranged between 10.9%-19.0%. The method developed and validated was effectively applied to examine the pharmacokinetic and biodistribution patterns for GAR in mice.

Advancements in Preprocessing and Analysis of Nitrite and Nitrate since 2010 in Biological Samples: A Review

As a substance present in organisms, nitrite is a metabolite of nitric oxide and can also be ingested. Nitrate is the metabolite of nitrite. Therefore, it is necessary to measure it quickly, easily and accurately to evaluate the health status of humans. Although there have been several reviews on analytical methods for non-biological samples, there have been no reviews focused on both sample preparation and analytical methods for biological samples. First, rapid and accurate nitrite measurement has significant effects on human health. Second, the detection of nitrite in biological samples is problematic due to its very low concentration and matrix interferences. Therefore, the pretreatment plus measuring methods for nitrite and nitrate obtained from biological samples since 2010 are summarized in the present review, and their prospects for the future are proposed. The treatment methods include liquid-liquid microextraction, various derivatization reactions, liquid-liquid extraction, protein precipitation, solid phase extraction, and cloud point extraction. Analytical methods include spectroscopic methods, paper-based analytical devices, ion chromatography, liquid chromatography, gas chromatography-mass spectrometry, electrochemical methods, liquid chromatography-mass spectrometry and capillary electrophoresis. Derivatization reagents with rapid quantitative reactions and advanced extraction methods with high enrichment efficiency are also included. Nitrate and nitrate should be determined at the same time by the same analytical method. In addition, much exploration has been performed on formulating fast testing through microfluidic technology. In this review, the newest developments in nitrite and nitrate processing are a focus in addition to novel techniques employed in such analyses.

A review of bioanalytical applications of microextraction techniques combined with derivatization

Microextraction techniques have attracted the attention of many researchers working in the field of bioanalysis due to their unique advantages, mainly in downsizing the scale of sample preparation steps. In parallel, analytical derivatization offers a powerful combination in terms of additional sensitivity, selectivity and compatibility with modern separation techniques. The aim of this review is to discuss the most recent advances in bioanalytical sample preparation based on the combination of microextraction and analytical derivatization. Both innovative fundamental reports and analyte-targeted applications are included and discussed. Dispersive liquid-liquid extraction and solid-phase microextraction are the most common techniques that typically combined with derivatization, while the development of novel and greener protocols is receiving substantial consideration in the field of analytical chemistry.

Profiling Docetaxel in Plasma and Urine Samples from a Pediatric Cancer Patient Using Ultrasound-Assisted Dispersive Liquid-Liquid Microextraction Combined with LC-MS/MS

In recent years, therapeutic drug monitoring (TDM) has been applied in docetaxel (DOC)-based anticancer therapy to precisely control various pharmacokinetic parameters, including the concentration of DOC in biofluids (e.g., plasma or urine), its clearance, and its area under the curve (AUC). The ability to determine these values and to monitor DOC levels in biological samples depends on the availability of precise and accurate analytical methods that both enable fast and sensitive analysis and can be implemented in routine clinical practice. This paper presents a new method for isolating DOC from plasma and urine samples based on the coupling of microextraction and advanced liquid chromatography with tandem mass spectrometry (LC-MS/MS). In the proposed method, biological samples are prepared via ultrasound-assisted dispersive liquid-liquid microextraction (UA-DLLME) using ethanol (EtOH) and chloroform (Chl) as the desorption and extraction solvents, respectively. The proposed protocol was fully validated according to the Food and Drug Administration (FDA) and the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH) requirements. The developed method was then applied to monitor the DOC profile in plasma and urine samples collected from a pediatric patient suffering from cardiac angiosarcoma (AS) with metastasis to lungs and mediastinal lymph nodes, who was receiving treatment with DOC at a dose of 30 mg/m² body surface area. Due to the rarity of this disease, TDM was carried out to determine the exact levels of DOC at particular time points to ascertain which levels were conducive to maximizing the treatment's effectiveness while minimizing the drug's toxicity. To this end, the concentration-time profiles of DOC in the plasma and urine samples were determined, and the levels of DOC at specific time intervals up to 3 days after administration were measured. The results showed that DOC was present at higher concentrations in the plasma than in the urine samples, which is due to the fact that this drug is primarily metabolized in the liver and then eliminated with the bile. The obtained data provided information about the pharmacokinetic profile of DOC in pediatric patients with cardiac AS, which enabled the dose to be adjusted to achieve the optimal therapeutic regimen. The findings of this work demonstrate that the optimized method can be applied for the routine monitoring of DOC levels in plasma and urine samples as a part of pharmacotherapy in oncological patients.

Synergistic Combination of Facile Thiol-Maleimide Derivatization and Supramolecular Solvent-Based Microextraction for UHPLC-HRMS Analysis of Glutathione in Biofluids

Glutathione (GSH) is the most abundant non-protein thiol in biofluids, enabling diverse physiological functions. Among the proposed methods for GSH detection, ultra-high-performance liquid chromatography (UHPLC) coupled with high-resolution mass spectrometry (HRMS) has the advantages of high sensitivity and efficiency. In this study, a novel analytical method was developed for the determination of GSH using supramolecular solvent (SUPRAS)-based dispersive liquid–liquid microextraction (DLLME) and UHPLC–HRMS. N-Laurylmaleimide was dissolved in tetrahydrofuran, which served three functions: 1) precipitate the proteins present in the biofluid sample, 2) provide a reaction environment for derivatization, and 3) enable the use of SUPRAS as the dispersing agent. Critical parameters were optimized based on single factor testing and response surface methodology. The established method was validated in terms of linearity, accuracy, precision, and successful quantitative analysis of GSH in saliva, urine, and plasma samples. Experimental results showed that SUPRAS as an extraction solvent was particularly suitable for the extraction of GSH from complex matrices. The current study provides a useful tool for accurate measurements of GSH concentrations, which could potentially be used for clinical diagnostics.

The occurrence of selected endocrine-disrupting chemicals in water and sediments from an urban lagoon in Southern Italy

Endocrine-disrupting chemicals (EDCs) are agents able to exert perturbation toward the endocrine system via a broad array of signalling pathways. Some EDCs are released into the environment as a result of antropogenic activities. Analytical surveillance plays a critical role in investigating the prevalence of such chemicals in environmental samples. A study was carried out in a lagoon in Southern Italy, a water basin relates to the sea through a mouth channel, making this water body a "dynamic environment". The screening of fourteen EDCs in surface waters and sediments, includes a fast and cost-effective sample preparation, based on a solid-liquid (sediments) and liquid-liquid (surface waters) extraction and a chromatographic analysis by liquid chromatography tandem UV and fluorescence detection. Only four chemicals out the fourteen investigated EDCs were detected in both matrices with a frequency higher than 60%. The average concentrations of the single EDC were higher in sediments (730-155.000 ng kg^-1  dw) than in surface waters (132-28.000 ng L^-1 ). Limited to the assayed EDCs, the ecosystem has a low risk regarding to the conservation of biodiversity of the animal species living thereby, since the total estrogenic activity does not exceed 1 ng L^-1 . PRACTITIONER POINTS: Occurrence of selected EDCs was investigated in an Italian lagoon in Southern Italy. BPAF, BADGE, and BPA were the most frequently and highly detected compounds in both waters and sediments. Concentration levels were greater in the sediment than in water samples. Low risk for the ecosystem biodiversity concerning investigated EDCs.

Bioanalytical strategies in drug discovery and development

A reliable, rapid, and effective bioanalytical method is essential for the determination of the pharmacokinetic, pharmacodynamic, and toxicokinetic parameters that inform the safety and efficacy profile of investigational drugs. The overall goal of bioanalytical method development is to elucidate the procedure and operating conditions under which a method can sufficiently extract, qualify, and/or quantify the analyte(s) of interest and/or their metabolites for the intended purpose. Given the difference in the physicochemical properties of small and large molecule drugs, different strategies need to be adopted for the development of an effective and efficient bioanalytical method. Herein, we provide an overview of different sample preparation strategies, analytical platforms, as well as procedures for achieving high throughput for bioanalysis of small and large molecule drugs.

Metabolic Profiling and Quantitative Analysis of Cerebrospinal Fluid Using Gas Chromatography-Mass Spectrometry: Current Methods and Future Perspectives

Cerebrospinal fluid is a key biological fluid for the investigation of new potential biomarkers of central nervous system diseases. Gas chromatography coupled to mass-selective detectors can be used for this investigation at the stages of metabolic profiling and method development. Different sample preparation conditions, including extraction and derivatization, can be applied for the analysis of the most of low-molecular-weight compounds of the cerebrospinal fluid, including metabolites of tryptophan, arachidonic acid, glucose; amino, polyunsaturated fatty and other organic acids; neuroactive steroids; drugs; and toxic metabolites. The literature data analysis revealed the absence of fully validated methods for cerebrospinal fluid analysis, and it presents opportunities for scientists to develop and validate analytical protocols using modern sample preparation techniques, such as microextraction by packed sorbent, dispersive liquid-liquid microextraction, and other potentially applicable techniques.

Modern microextraction techniques for natural products

Natural product analysis has gained wide attention in recent years, especially for herbal medicines, which contain complex ingredients and play a significant clinical role in the therapy of numerous diseases. The constituents of natural products are usually found at low concentrations, and the matrices are complex. Thus, the extraction of target compounds from natural products before analysis by analytical instruments is very significant for human health and its wide application. The commonly used traditional extraction methods are time-consuming, using large amounts of sample and organic solvents, as well as expensive and inefficient. Recently, microextraction techniques have been used for natural product extraction to overcome the disadvantages of conventional extraction methods. In this paper, the successful applications of and recent developments in microextraction techniques including solvent-based and sorbent-based microextraction methods, in natural product analysis in recent years, especially in the last 5 years, are reviewed for the first time. Their features, advantages, disadvantages, and future development trends are also discussed.

DLLME-SFO-GC-MS procedure for the determination of 10 organochlorine pesticides in water and remediation using magnetite nanoparticles

There exists a high demand for fast, simple, and reliable methodologies for determining the presence of organochlorine pesticides (OCPs) on environmental samples. Moreover, the toxicity and accumulation of potential OCPs in several environments have led to the development of technologies that achieve their removal from contaminated waters. In this study, a novel method combining a dispersive liquid-liquid microextraction procedure based on the solidification of floating organic drop is developed and validated for the extraction, preconcentration, and determination of 10 OCPs: α-BHC, p,p'-DDE, δ-BHC, dieldrin, p,p'-DDT, endosulfan I, endosulfan sulfate, heptachlor, heptachlor epoxide (isomer B), and methoxychlor in water samples. The results show that the calibration curves were linear for all the studied compounds, and the coefficients of correlation higher than 0.99. The variation coefficient for precision and accuracy was lower than 10%, and the accuracy ranged from 93 to 105%. Low limit of detection and limit of quantification values ranging from 0.06-3.00 ng mL^-1 and 0.20-10 ng mL^-1 were obtained, respectively. The capability of the proposed method was confirmed using an analysis of the water samples before and after the degradation process; this was achieved by employing nanomaterials, while performing an analysis of 160 real samples that were sourced from a Brazilian river. A cobalt-doped magnetite was applied for the environmental remediation of the studied compounds, and it was verified that the novel material has the potential to be used in environmental remediation with a degradation efficiency exceeding 80% for the majority of the studied compounds.

Chromatographic methods development for clinical practice: requirements and limitations

Development of a chromatographic method in bioanalysis is a challenging and complex procedure with many pitfalls and often unexpected reversals that can require several months to accomplish. Even an experienced analytical team must contend many limitations mainly in connection with the strict requirements imposed on current clinical research. These restrictions typically persist throughout the whole development process, from clinical trial assignment, across optimization of extraction of biological materials and chromatographic separation, to validation and data interpretation. This paper describes questions and their possible answers raised during the pre-analytical phase such as use of modern sample preparation techniques in clinical methods, application of internal standards, as well as selection of stationary phases and detection techniques in the analytical phase. Validation problems and interpretation of results are demonstrated with three typical examples of characteristics to be considered, i.e. recovery, matrix effect, and limit of detection vs. lower limit of quantification.

Innovative Configurations of Sample Preparation Techniques Applied in Bioanalytical Chemistry: A Review

Background:

Recently, in all fields of analytical chemistry, increased attention has been paid to extraction procedures and instrumental methods, which are easily scalable and are able to automate in order to improve the “high-throughput” capability.

Introduction:

The main goal of these applications relates to an improvement of the precision in the quantitative analysis, reduction of different sources of errors, decrease the analysis time and, in general, improve the analytical performances. Often these points can be in contrast to each other, not allowing to achieve the expected result but forcing a compromise between the objectives of the method and the analytical performance.

Methods:

In this review, following the evolution of the (micro)extraction procedures and instrument configurations, the recent procedures used in bioanalytical chemistry are critically evaluated. The aim of this paper is providing an overview of the approaches available in order to perform on-line coupling of various extraction techniques with chromatographic methods for the analysis of different compounds in various samples. Furthermore, a comparison between off-line and on-line systems, advantages of on-line systems applied on major extractive techniques and future perspectives are described.

Result:

The extraction methods suitable for on-line coupling covered in this review are: liquid-liquid extraction (LLE), solid phase extraction (SPE), solid phase microextraction (SPME), dispersive liquid- liquid microextraction (DLLME), microextraction by packed sorbent (MEPS), supercritical fluid extraction (SFE) and fabric phase sorptive extraction (FPSE).

Conclusion:

An overview of the micro-extraction techniques mentioned above was provided, making a comparison between them and focusing attention on future perspectives.

Determination of valproic acid and 3-heptanone in plasma using air-assisted liquid-liquid microextraction with the assistance of vortex: Application in the real samples

Introduction: Valproic acid (VPA) is an antiepileptic drug used to treat epilepsy and bipolar disorder. Adverse effects of VPA were studied in many reports, however, a dose-response relationship between VPA and its metabolites in epilepsy patients are extremely limited. In this paper, a high efficient method was developed for the preconcentration and determination of VPA and its main metabolite in plasma. Methods: For the extraction and preconcentration of the selected analytes, a volume of an extractant was placed at the bottom of the microtube containing pretreated plasma. The mixture was repeatedly withdrawn from the microtube and pushed-out into it using a 1.0-mL glass syringe and resulted in a cloudy mixture. For further turbidity, the mixture was shaken on a vortex agitator. This procedure was used to analyze the plasma samples of patients with epilepsy (n = 70). Results: The results revealed that in most patients with a low level of VPA relative to its expected level, 3-heptanone concentrations were high. The limits of quantification of 3-heptanone and VPA were 0.04 mg L-1 and 0.2 mg L-1, respectively. A suitable precision at a concentration of 2 mg L-1 for each analyte was obtained (relative standard deviation ≤ 9%). Conclusion: The obtained results indicated that this procedure is easy, sensitive, and reliable, and can be used for the analysis of the selected analytes in the plasma samples of patients with epilepsy.

Sample preparation for polar metabolites in bioanalysis

Sample preparation is a primary step of any bioanalytical workflow, especially in metabolomics where maximum information has to be obtained without spoiling the analytical instrument. The sample extraction of polar metabolites is still challenging but strategies exist to enable the phase transfer of hydrophilic metabolites from the biological phase to a clean interference-free phase.

Advances in bioanalytical techniques to measure steroid hormones in serum

Steroid hormones are measured clinically to determine if a patient has a pathological process occurring in the adrenal gland, or other hormone responsive organs. They are very similar in structure making them analytically challenging to measure. Additionally, these hormones have vast concentration differences in human serum adding to the measurement complexity. GC–MS was the gold standard methodology used to measure steroid hormones clinically, followed by radioimmunoassay, but that was replaced by immunoassay due to ease of use. LC–MS/MS has now become a popular alternative owing to simplified sample preparation than for GC–MS and increased specificity and sensitivity over immunoassay. This review will discuss these methodologies and some new developments that could simplify and improve steroid hormone analysis in serum.