In Silico and Chromatographic Methods for Analysis of Biotransformation of Prospective Neuroprotective Pyrrole-Based Hydrazone in Isolated Rat Hepatocytes

In the current study, chromatographic and in silico techniques were applied to investigate the biotransformation of ethyl 5-(4-bromophenyl)-1-(2-(2-(2-hydroxybenzylidene) hydrazinyl)-2-oxoethyl)-2-methyl-1H-pyrrole-3-carboxylate (11b) in hepatocytic media. The initial chromatographic procedure was based on the employment of the conventional octadecyl stationary phase method for estimation of the chemical stability. Subsequently, a novel and rapid chromatographic approach based on a phenyl-hexyl column was developed, aiming to separate the possible metabolites. Both methods were performed on a Dionex 3000 ThermoScientific (ACM 2, Sofia, Bulgaria) device equipped with a diode array detector set up at 272 and 279 nm for analytes detection. An acetonitrile: phosphate buffer of pH 3.5: methanol (17:30:53 v/v/v) was eluted isocratically as a mobile phase with a 1 mL/min flow rate. A preliminary purification from the biological media was achieved by protein precipitation with methanol. A validation procedure was carried out, where the method was found to correspond to all ICH (Q2) and M10 set criteria. Additionally, an in silico-based approach with the online server BioTransformer 3.0 was applied in an attempt to predict the possible metabolites of the title compound 11b. It was hypothesized that four CYP450 isoforms (1A2, 2C9, 3A4, and 2C8) were involved in the phase I metabolism, resulting in the formation of 12 metabolites. Moreover, docking studies were conducted to evaluate the formation of stable complexes between 11b and the aforementioned isoforms. The obtained data indicated three metabolites as the most probable products, two of which (M9_11b and M10_11b) were synthesized by a classical approach for verification. Finally, liquid chromatography with a mass detector was implemented for comprehensive and summarized analysis, and the obtained results revealed that the metabolism of the 11b proceeds possibly with the formation of glucuronide and glycine conjugate of M11_11b.

Polar licit and illicit ingredients in dietary supplements: chemometric optimization of extraction and HILIC-MS/MS analysis

Many dietary supplements claim the ability to enhance sports performance and to improve the fitness of the consumers. Occasionally, along with legal ingredients, illicit compounds may be added without being labelled, leading to unintended doping. Hence, the aim of this study was to develop an analytical method to determine a set of 12 polar (logDpH=7 from -2.0 to +0.3) compounds including diuretics, stimulants, β2-agonists, methylxanthines, and sweeteners. Hydrophilic interaction liquid chromatography was chosen as separation strategy, coupled with tandem mass spectrometry. The instrumental method was optimized using a two-step design of experiments (DoE). Firstly, a Plackett-Burman (PB) DoE was performed to identify the more influencing variables affecting peak areas and chromatographic resolution among temperature, water percentage in the mobile phase, and flow rate, as well as type and concentration of buffers. Secondly, a D-optimal DoE was set, considering only the most significant variables from the PB-DoE results, achieving a deeper understanding of the retention mechanism. Sample processing by salt-assisted liquid-liquid extraction was studied through DoE as well, and the whole method showed recoveries in the range 40-107% and procedural precision ≤11% for all analytes. Finally, it was applied to real samples, in which the four methylxanthines and two artificial sweeteners were detected and quantified in the range of 0.02-192 mg g-1. These values were compared to the quantities declared on the DS labels, when possible. Furthermore, a sequence of MS/MS scans allowed detection of a signal in one of the samples, structurally similar to the β2-agonist clenbuterol.

Rapid determination of chromium species in environmental waters using a diol-bonded polymer-stationary column under water-rich conditions coupled with ICPMS

Chromium speciation analysis in environmental water is of great significance for the monitoring of water pollution and assessing its influences on human health. This study proposes a rapid analytical approach for the simultaneous determination of Cr(VI) and Cr(III) in environmental waters by hydrophilic interaction chromatography (HILIC) coupled with ICPMS under a water-rich condition. 2,6-Pyridinedicarboxylic acid (PDCA) was used to unify Cr(III) species in various chemical forms into a stable Cr(III)-PDCA anion complex and then separated from Cr(VI) oxyanion on a diol-bonded polymer-based HILIC column. An aqueous mobile phase containing 50 mmol L-1 ammonium acetate (pH 7.0), 2 mmol L-1 PDCA, and 4% acetonitrile successfully separates chromium species as well as chloride ions. In addition, our method elutes Cr(VI) preferentially over Cr(III)-PDCA, enabling rapid determination of Cr(VI), and both chromium species were analyzed within 6.2 min. The detection limits of 0.19 μg L-1 for Cr(VI) and 0.35 μg L-1 for Cr(III) at m/z 52 under He collision mode are comparable to or better than the conventional ion exchange chromatography-ICPMS methods, and quantitative recovery was obtained from spike-recovery tests on river water samples containing various levels of matrix. Optimization experiments of the HPLC conditions indicate that the retentions of Cr(VI) and Cr(III)-PDCA are characterized by electrostatic and nonpolar interactions, respectively. The retention behavior of inorganic anions and cations in water-rich conditions observed in this study will provide new insights into the separation mechanism in polymer-based HILIC columns, which has been poorly understood.

A Predictive Model to Correlate Amino Acids and Aromatic Compounds in Calabrian Honeys

To better understand the biochemistry of the organoleptic properties of honey influencing its commercial value, a predictive model for correlating amino acid profiles to aromatic compounds was built. Because the amino acid composition of different varieties of honey plays a key role as a precursor of specific aroma bouquets, it is necessary to relate the amino acid typesetting to aromatic molecules. A selection of unifloral honeys produced in Calabria, South Italy, were used, and a new methodology based on the use of HILIC-UHPLC-ESI-MS/MS and HS-SPME-GC-MS combined with multivariate processing has been developed. This study, carried out for the first time on honey, shows its excellent potential as a modern analytical tool for a rapid multicomponent analysis of food-quality indicators. Data obtained showed strong positive linear correlations between aldehydes and isoleucine, valine, leucine, and phenylalanine. Furans are correlated with isoleucine, leucine, and phenylalanine; hydrocarbons with serine, glutamic acid, and aspartic acid; and ketones with serine, alanine, glutamine, histidine, asparagine, and lysine. Alcohols were more associated with tyrosine than esters with arginine. Proline, tryptophan, and threonine showed poor correlations with all the classes of aroma compounds.

Improved analysis ZIC-HILIC-HCD-Orbitrap method for mapping the glycopeptide by mass spectrometry

Glycosylation is one of the most common post-translational modifications (PTMs). Protein glycosylation analysis is the bottleneck to deeply understand their functions. At present, the LC-MS analysis of glycosylated post-translational modification is mainly focused on the analysis of glycopeptides. However, the factors affecting the identification of glycopeptides were not fully elucidated. In the paper, we have carefully studied the factors, e.g., HILIC materials, search engines, protein amount, gradient duration, extraction solution, etc. According to the results, HILIC materials were the most important factors affecting the glycopeptides identification, and the amphoteric sulfoalkyl betaine stationary phase enriched glycopeptides 6-fold more compared to the amphiphilic ion-bonded fully porous spherical silica stationary phase. We explored the influence of the extraction solutions on glycan identification. Comparing sodium dodecyl sulfate (SDS) and urea (UA), the results showed that N-glycolylneuraminic acid (NeuGc) type of glycan content was found to be increased 1.4-fold in the SDS compared to UA. Besides, we explored the influence of the search engine on glycopeptide identification. Comparing pGlyco3.0 and MSFragger-Glyco, it was observed that pGlyco3.0 outperformed MSFragger-Glyco in identifying glycopeptides. Then, using our optimized method we found that there was a significant difference in the distribution of monosaccharide types in plasma and brain tissue, e.g., the content of NeuAc in brain was 5-fold higher than that in plasma. To importantly, two glycoproteins (Neurexin-2 and SUN domain-containing protein 2) were also found for the first time by our method. In summary, we have comprehensively studied the factors influencing glycopeptide identification than any previous research, and the optimized method could be widely used for identifying the glycoproteins or glycolpeptides biomarkers for disease detection and therapeutic targets.

Exploration of the effects of chloride ions on the analysis of polar compounds at low concentrations by hydrophilic interaction liquid chromatography coupled to a charged aerosol detector: Application to tromethamine

In this study, we discuss the origin of the slightly increased response of the charged aerosol detector when low-concentration polar drugs formulated with sodium chloride are analyzed by hydrophilic interaction liquid chromatography coupled to the charged aerosol detector. In the case of tromethamine mixed with saline solutions, we investigated several levels including the mobile phase, sample matrix, and detection. We show that the analysis of the rich-salted sample results in both interactions with the mobile phase modifiers and the stationary phase during the run time. With 150 mM NaCl as a compounding solution, a slight increase in the tromethamine peak area was observed (<5.5%). Our study suggests that chloride ions in excess sequentially interact firstly with the counterions from the organic modifiers and secondly with the analyte via the stationary phase and the contribution of hydrophilic interaction liquid chromatography retention mechanisms. Because of these effects, the hydrophilic interaction liquid chromatography-charged aerosol detector analysis of drugs in saline solutions requires particular attention, and a correction factor for quantitative purposes that accounts for formulation ions remains appropriate.

Quantitative analysis of 20 purine and pyrimidine metabolites by HILIC-MS/MS in the serum and hippocampus of depressed mice

Purine and pyrimidine metabolism are vital metabolic pathways in the development, proliferation or repairment of cells or tissues associated with various diseases. Here, a simple, all-in-one injection hydrophilic interaction liquid chromatography-tandem mass spectrometry method was developed for simultaneous determination of 20 metabolites: adenine, adenosine, deoxyadenosine, adenosine 5'-monophosphate, cyclic adenosine monophosphate, hypoxanthine, xanthine, inosine, deoxyinosine, xanthosine, xanthosine 5'-monophosphate and uric acid, which are products of purine metabolism; uridine, deoxyuridine, uridine 5'-monophosphate and uracil, are products of pyrimidine metabolism; and corticosterone, methionine, acetylcholine and serotonin. To minimize interference of endogenous molecules in sample matrixes, a combination of activated carbon adsorption and a serum substitute matrix (5% bovine serum albumin in phosphate buffered saline) was utilized and jointly applied. The sensitivity, linearity, stability, precision, accuracy and extraction recovery were evaluated, and the method was demonstrated to be accurate, sensitive and reliable. An analytical strategy was successfully applied to quantitatively determine 20 metabolite levels in the serum and hippocampus of mice with chronic social defeat stress-induced depression. The results showed greatly perturbed purine metabolism in the depressed mice, which was primarily characterized by dramatic increases in hypoxanthine, xanthine and inosine in serum and reduced levels of adenine, adenosine and adenosine 5'-monophosphate in the hippocampus. These findings suggest that this novel strategy can facilitate the quantitative analysis of adenine and other purine and pyrimidine metabolites in tissue and serum and exhibits great potential in the exploration of metabolism-related mechanisms of relevant diseases.

LC-MS/MS methods to quantify HCP002 in human plasma and urine: applications in a pharmacokinetic study

Aim: HCP002, a phosphate-modified derivative of voriconazole, can improve solubility without using the nephrotoxic solubilizer, sulfobutylether-β-cyclodextrin. To study pharmacokinetics in humans, LC-MS/MS methods to quantify HCP002 in human plasma and urine were developed and validated. Method: After protein precipitation by acetonitrile containing voriconazole-d₃, HCP002 was separated on a ZORBAX SB-Aq column, and LCMS/MS analysis was performed in multi-response monitoring mode. Results: The analytical run time was 3 min. Linearity was observed over the ranges of 0.100-40.0 and 0.400-200 μg/ml in plasma and urine, respectively. Precision and accuracy were within acceptable limits. Sample stability was confirmed. Conclusion: Rapid and reproducible methods quantified HCP002 in urine, and plasma samples were established.

Development and validation of a hydrophilic interaction liquid chromatography-tandem mass spectrometry method for the quantification of regadenoson in human plasma and its pharmacokinetic application

Regadenoson, the first selective adenosine A_2A receptor agonist, is used to perform exercise stress test during radionuclide myocardial perfusion imaging. To detect the concentration of regadenoson in human plasma, a simple, fast, and sensitive tandem mass spectrometry method was established herein. Acetonitrile was used as a protein precipitation agent. Chromatographic separation was completed in 6.5 min using a BEH HILIC column (50 × 2.1 mm, 1.7 μm). The mobile phase consisted of 10 mmol/L ammonium acetate/acetonitrile (gradient elution). To quantify regadenoson and regadenoson-d3, an API 4000 mass spectrometry in multiple reaction monitoring mode with transitions of 391.3→259.2 and 394.3→262.2, respectively, was utilized. The calibration curve was linear in the range of 0.100-50.0 μg/L, and the intrabatch and interbatch precisions were <9.7% and <13.0%, respectively, and the accuracy was 2.0-6.9%. There was no apparent matrix effect for regadenoson or regadenoson-d3. The developed method was used to study the pharmacokinetic characteristics of regadenoson in healthy Chinese subjects.

Characterization and Analysis of Food-Sourced Carbohydrates

Food carbohydrates are macronutrients that are found in fruits, grains, vegetables, and milk products. These organic compounds are present in foods in the form of sugars, starches, and fibers and are composed of carbon, hydrogen, and oxygen. These wide ranging macromolecules can be classified according to their chemical structure into three major groups: low molecular weight mono- and disaccharides, intermediate molecular weight oligosaccharides, and high molecular weight polysaccharides. Notably, the digestibility of specific carbohydrate components differ and nondigestible carbohydrates can reach the large intestine intact where they act as food sources for beneficial bacteria. In this review, we give an overview of advances made in food carbohydrate analysis. Overall, this review indicates the importance of carbohydrate analytical techniques in the quest to identify and isolate health-promoting carbohydrates to be used as additives in the functional foods industry.

Recent progress of microfluidic technology for pharmaceutical analysis

In recent years, the progress of microfluidic technology has provided new tools for pharmaceutical analysis and the proposal of pharm-lab-on-a-chip is appealing for its great potential to integrate pharmaceutical test and pharmacological test in a single chip system. Here, we summarize and highlight recent advances of chip-based principles, techniques and devices for pharmaceutical test and pharmacological/toxicological test focusing on the separation and analysis of drug molecules on a chip and the construction of pharmacological models on a chip as well as their demonstrative applications in quality control, drug screening and precision medicine. The trend and challenge of microfluidic technology for pharmaceutical analysis are also discussed and prospected. We hope this review would update the insight and development of pharm-lab-on-a-chip.

Performance of ion pairing chromatography and hydrophilic interaction liquid chromatography coupled to charged aerosol detection for the analysis of underivatized amino acids

The charged aerosol detector (CAD) is frequently employed in liquid chromatography for the analysis of small polar and ionizable compounds such as amino acids and amino sugars, which provide a weak chromophore only. Separation of these compounds is achieved by means of ion pair chromatography (IPC), and, more recently, hydrophilic interaction chromatography (HILIC) techniques. However, as the CAD's response is highly dependent on the mobile phase composition, the substantial differences in the mobile phase composition of IPC and HILIC have a distinct impact on the detector's performance. This study was aimed at systematically comparing the performance of IPC and HILIC when coupled to the CAD. Therefore, the separation techniques characterized by their specific mobile phase compositions were evaluated for their influence on the CAD response and the signal-to-noise ratio (S/N) of the amino acids L-alanine, L-leucine, and L-phenylalanine applying the response surface methodology (RSM). The RSM results derived from flow injection analysis (FIA) indicated that the CAD response and thus the obtainable S/N are significantly higher in HILIC compared to IPC where the S/N decreased with the chain length of the applied ion-pairing reagent. In addition, an IPC and a HILIC method, respectively, were developed for the impurity profiling of the branched-chain amino acids (BCAAs) L-leucine, L-isoleucine, and L-valine. The beneficial effects of the HILIC conditions on the S/N observed under FIA conditions were partly offset by moderate column bleed effects when using an amide functionalized column, which facilitates the separation in the HILIC method. Satisfactory LOQs (3-10 ng on column) were obtained with both methods; however, the HILIC method was found to be slightly superior in terms of sensitivity and separation efficiency.

Quantitative Determination of Fosfomycin in 10 μL of Plasma and Dialysate by Hydrophilic Interaction Liquid Chromatography Electrospray Ionization Mass Spectrometry

Fosfomycin is an antibiotic with a broad spectrum of activity against many multidrug-resistant bacterial strains. It is mainly excreted unchanged by the kidneys, and its half-life therefore depends on kidney function which varies considerably among individuals, and within individuals over time. Proper fosfomycin dosing thus depends on assaying blood concentration of the drug. We developed and validated a simple, sensitive and specific chromatography assay, which was coupled to electrospray ionization mass spectrometry for determination of fosfomycin. Separation of fosfomycin was based on the method of the hydrophilic interaction liquid chromatography; specifically, plasma and dialysate samples were acidified and the protein precipitated with acetonitrile. The calibration curves showed excellent coefficients of determination (R2 > 0.999) over the relevant concentration range of 25-700 μg/mL. Intraday precision was 1.1-1.2% and accuracy was -5.9% to 0.9% for quality control samples. Interday precision was 2.9-3.4% and accuracy was -3.7% to 5.5%. Extraction recovery was ≥87% and matrix effects ranged from 2.2% to 4.3%. After laboratory validation, the method was successfully applied to clinical samples.

Influence of the mobile phase composition on hyphenated ultraviolet and charged aerosol detection for the impurity profiling of vigabatrin

Recently, charged aerosol detection (CAD), a universal detection technique in liquid chromatography, has been introduced into monographs of the European Pharmacopoeia (Ph. Eur.), which now employs HPLC-UV-CAD for assessing the impurities of the drug vigabatrin. The separation of vigabatrin and its impurities is facilitated by ion pair chromatography (IPC) in the compendial method using tridecafluoroheptanoic acid (TDFHA) as ion-pairing reagent. However, the subsequent detection of the impurities by UV-CAD is considerably impaired due to the substantial amount of ion-pairing reagent applied in the method generating high levels of background noise. In this study, the influence of the mobile phase composition on the background noise of the CAD was evaluated applying response surface methodology. The model's results indicated that the chain length of the ion-pairing reagent is a predominant factor for noise generation. Thus, an alternative method for the impurity analysis of vigabatrin using mixed-mode chromatography (MMC) instead of IPC was developed. The dual separation mechanism of the MMC column enabled the choice of a mobile phase better suited for the individual requirements of the UV-CAD detectors, while maintaining excellent selectivity. The MMC method does not require the addition of a post-column solution to reduce the TDFHA concentration in the mobile phase, and, therefore, needs less instrumentation. Moreover, the sample concentration could be halved due to the improved LOQs of the impurities (<50 ng on column) and the analysis time could be shortened (30 to 20 min) due to improved separation efficiency. The MMC method was validated with respect to ICH guideline Q2(R1).

Analysis of adsorption energy distribution in selected hydrophilic-interaction chromatography systems with amide, amine, and zwitterionic stationary phases

Adsorption mechanisms of caffeine, quercetin, and phenol as test substances in various chromatographic systems have been analyzed. The investigations were conducted using three different chromatographic columns packed with polar bonded stationary phases, that is, amide, amine, and zwitterionic. Methanol-water and acetonitrile-water systems with different organic solvent contents have been used as mobile phases. On the basis of adsorption isotherms obtained for the tested systems, Scatchard plots and adsorption energy distributions have been determined. The most likely retention mechanisms have been discussed. The results of investigations indicate that (i) the surfaces of tested adsorbents are energetically heterogeneous, and (ii) the main role in sorption mechanism is played by low-energy sites.

Hydrophilic Interaction Liquid Chromatography (HILIC): Latest Applications in the Pharmaceutical Researches

Background:

Significant advances have been occurred in analytical research since the 1970s by Liquid Chromatography (LC) as the separation method. Reverse Phase Liquid Chromatography (RPLC) method, using hydrophobic stationary phases and polar mobile phases, is the most commonly used chromatographic method. However, it is difficult to analyze some polar compounds with this method. Another separation method is the Normal Phase Liquid Chromatography (NPLC), which involves polar stationary phases with organic eluents. NPLC presents low-efficiency separations and asymmetric chromatographic peak shapes when analyzing polar compounds. Hydrophilic Interaction Liquid Chromatography (HILIC) is an interesting and promising alternative method for the analysis of polar compounds. HILIC is defined as a separation method that combines stationary phases used in the NPLC method and mobile phases used in the RPLC method. HILIC can be successfully applied to all types of liquid chromatographic separations such as pharmaceutical compounds, small molecules, metabolites, drugs of abuse, carbohydrates, toxins, oligosaccharides, peptides, amino acids and proteins.

Objective:

This paper provides a general overview of the recent application of HILIC in the pharmaceutical research in the different sample matrices such as pharmaceutical dosage form, plasma, serum, environmental samples, animal origin samples, plant origin samples, etc. Also, this review focuses on the most recent and selected papers in the drug research from 2009 to the submission date in 2020, dealing with the analysis of different components using HILIC.

Results and Conclusion:

The literature survey showed that HILIC applications are increasing every year in pharmaceutical research. It was found that HILIC allows simultaneous analysis of many compounds using different detectors.

In depth investigation of the retention behavior of structurally related β-blockers on RP-HPLC column: Quality by design and quantitative structure-property relationship complementary approaches for optimization and validation

The persistent introduction of new β-blockers motivates the demand for optimizing RP-HPLC well-designed analytical procedures that could be applied to this structurally related and commonly prescribed pharmacological group in order to reduce time and chemicals consumption in quality control units. Betoxolol HCl (BEX) and Carvidolol (CAR) were selected as representative examples to conduct predictive studies based on two complementary approaches, Quality by design (QBD) and Quantitative structure property relationship (QSPR). In concern QBD, a Box-Behnken design was adopted at variable chromatographic parameters to achieve the most proper conditions that might be applied for efficient analysis of the majority of group members. On the other hand, the retention time was chosen as the target property in the QSPR study that was conducted onto seven β. blockers (the two investigated drugs in addition to five other β. blockers) to find the best correlated molecular descriptors to the retention behavior. Both external and internal validation studies have comparable quality with training levels. Hence a simple selection algorithm of conventional features provides robust confirmatory predictive QBD and QSPR models. Derringer's desirability function as as a multi-criteria approach was applied for getting the optimum chromatographic analysis conditions. Efficient analysis of BET and CAR was achieved at column temperatures of 26.00 and 27.50 °C, respectively using acetonitrile and phosphate buffer (pH 4.55) 70:30 v/v as a mobile phase with a flow rate of 1.00 mL/min, and UV detection at 220 nm. The method was validated in accordance to ICH guidelines, and had exhibited acceptable precision, accuracy, linearity, and robustness.

Preparation and chromatographic evaluation of the hydrophilic interaction chromatography stationary phase based on nucleosides or nucleotides

In this work, a series of novel hydrophilic interaction chromatography (HILIC) stationary phases were prepared by grafting nucleosides or nucleotides on the surface of silica gel. Firstly, the silica was modified with 3-glycidoxypropyltrimethoxysilane (GPTMS). And then nucleosides or nucleotides were bonded on the surface of GPTMS-modified silica through the epoxy-amine ring-opening reaction to provide four HILIC materials. These obtained stationary phases were successfully characterized by Fourier transform-infrared spectroscopy (FT-IR) and elemental analysis (EA), respectively. Effects of column temperature, water content of the mobile phase, pH and buffer concentration on the retention behavior of these HILIC materials and the corresponding separation mechanism were evaluated using various nucleosides and nucleobases, respectively. In addition, polar and hydrophilic compounds such as amino acids and water-soluble vitamins were successfully separated using the corresponding columns, showing application potential for the separation of bioactive substances.

Characterization of synthetic dyes for environmental and forensic assessments: A chromatography and mass spectrometry approach

Dyes have become common substances since they are employed in mostly all objects surrounding our daily activities such as clothing and upholstery. Based on the usage and disposal of these objects, the transfer of the dyes to other media such as soil and water increases their prevalence in our environment. However, this prevalence could help to solve crimes and pollution problems if detection techniques are proper. For that reason, the detection and characterization of dyes in complex matrices is important to determine the possible events leading to their deposition (natural degradation, attempts of removal, possible match with evidence, among others). Currently, there are several chromatographic and mass spectrometric approaches used for the identification of these organic molecules and their derivatives with high specificity and accuracy. This review presents current chromatographic and mass spectrometric methods that are used for the detection and characterization of disperse, acid, basic, and reactive dyes, and their derivatives.

Simultaneous determination of three iridoid glycosides of Rehmannia glutinosa in rat biological samples using a validated hydrophilic interaction-UHPLC-MS/MS method in pharmacokinetic and in vitro studies

The purpose of this study was to develop a method for simultaneous analysis of aucubin, catalpol, and geniposide, which are representative iridoid glycoside constituents of Rehmannia glutinosa, in rat plasma, urine, and feces using hydrophilic interaction ultra high-performance liquid chromatography with tandem mass spectrometry. The three components were separated using 10 mmol/L aqueous ammonium formate containing 0.01% (v/v) formic acid and acetonitrile as a mobile phase by gradient elution at a flow rate of 0.2 mL/min, equipped with a Kinetex^® HILIC column (50 × 2.1 mm, 2.6 μm). Quantitation of this analysis was performed on a triple quadrupole mass spectrometer employing electrospray ionization and operated in multiple reaction monitoring mode. The chromatograms showed high resolution, sensitivity, and selectivity with no interference with plasma constituents. In all three iridoid glycosides, both the intra- and interbatch precisions (coefficient of variation %) were less than 4.81%. The accuracy was 96.56-103.55% for aucubin, 95.23-106.21% for catalpol, and 94.50-104.16% for geniposide. The developed analytical method satisfied the criteria of international guidance and was successfully applied to pharmacokinetic studies including oral bioavailability of aucubin, catalpol, and geniposide, and their urinary and fecal excretion ratios after oral or intravenous administration to rats. The new method was also applied to measure plasma protein binding ratios in vitro.

The separation and identification of synthetic cathinones by portable low microflow liquid chromatography with dual capillary columns in series and dual wavelength ultraviolet detection

This study ascertained the viability of a portable liquid chromatograph, operating at low microliter per minute flow, for the analysis of seized drugs at remote sites as well as in laboratory settings. Synthetic cathinones were screened using dual capillary columns in series, C8 and biphenyl, with on-column ultraviolet detection at 255 and 275 nm. The relative retention times of the two columns in series and their peak area absorbance ratio were used to determine if the 16 synthetic cathinones investigated could be uniquely identified in these conditions. Based on these parameters all of the analytes could be distinguished. Representative mixtures of synthetic cathinones were used to determine the repeatability, linearity, and limits of detection of the method. This cost effective and green instrumentation has the potential to satisfy minimum international guidelines for the analysis of seized drugs.

A simple, versatile, and automated pulse-diffusion-focusing strategy for sensitive milliliter-level-injection HILIC-MS/MS analysis of hydrophilic toxins

The measurement of trace hydrophilic toxins in complex aqueous-rich matrices is a daunting challenge. To address this analytical bottleneck, pulse diffusion focusing (PDF), a novel sample injection technique for hydrophilic interaction chromatography-tandem mass spectrometry (HILIC-MS/MS), was developed. Theoretical and experimental investigations of the mechanism and key parameters revealed that the pulse-injection approach, assisted by solvent diffusion, efficiently solved the volume overload problem. This milliliter-level-injection HILIC-MS/MS technique was reported for the first time herein, and provided a significant enhancement in sensitivity compared to the conventional injection method, in addition to being an efficient approach to address the solvent incompatibility of off-line sample preparation and HILIC. The automated PDF-HILIC-MS/MS system was obtained by slightly modifying a commercial LC-MS/MS instrument in an easy and economical manner. The efficiency of the system was demonstrated through the detection of trace tetrodotoxin contents in plasma and urine samples. Low limits of detection (i.e., 0.65 and 2.2 ng·mL^-1) were obtained using the simplified sample preparation method. The recoveries were in the range 91-113.3 % with intra-day and inter-day precisions of ≤9.6 %. Further experimental results proved the method to be versatile for various hydrophilic toxins.

Rapid and cost-effective LC-MS/MS method for determination of hydroxycitric acid in plasma: Application in the determination of pharmacokinetics in commercial Garcinia preparations

Garcinia cambogia is one of the most commonly used anti-obesity dietary supplements, and hydroxycitric acid (HCA) is a major constituent in the commercial preparations of Garcinia. High doses of HCA are often consumed without much awareness of its pharmacokinetic and toxicokinetic parameters, and therefore, a complete understanding of its effects is lacking. The first step in understanding these parameters is the availability of a reliable bioanalytical method. Here, we present the first report on a UPLC-MS/MS method for analysis of HCA in rat plasma after a simplified and cost-effective protein precipitation. Chromatographic separation of the analytes in the supernatant was achieved using hydrophilic interaction liquid chromatography, where mass parameters were optimized and a rapid 5-min quantitative assay was developed. The method was highly sensitive, accurate, precise and linear in the concentration range of 10.5-5000 ng/mL (validated according to the United States Food and Drug Administration guidelines). Further, the method was successfully used to describe the pharmacokinetic profile of HCA in rat plasma after the administration of pure HCA and commercial Garcinia preparations.

The Emergence of Universal Chromatographic Methods in the Research and Development of New Drug Substances

Manufacturing process development of new drug substances in the pharmaceutical industry combines numerous chemical challenges beyond the efficient synthesis of complex molecules. Optimization of a synthetic route involves the screening of multiple reaction variables with a desired outcome that not only depends on an increased product yield but is also highly influenced by the removal efficacy of residual chemicals and reaction byproducts during the subsequent synthetic route. Consequently, organic chemists must survey a wide array of synthetic variables to develop a highly productive, green, and cost-effective manufacturing process. The time constraints of developing robust quantitative methods prior to each processing step can easily lead to sample analysis becoming a bottleneck in synthetic route development. In this regard, conventional "on demand" analytical method development and optimization approaches, traditionally used for guiding synthetic chemistry efforts, become unsustainable. This Account introduces recent efforts to address the aforementioned challenges through the development and implementation of generic or more universal chromatographic methods that can cover a broad spectrum of targeted compound classes. Such generic methods require significant resolving power to enable baseline resolution of multicomponent mixtures in a single experimental run without additional method customization but must be simple enough to allow for routine use by chemists, chemical engineers and other researchers with little experience in chromatographic method development. These powerful analytical methodologies are often employed to minimize the time spent developing new analytical assays, while also facilitating method transfer to manufacturing facilities and application in regulatory settings. Diverse examples of universal and fit-for-purpose analytical procedures are presented herein, illustrating the power of modern readily available analytical technology for streamlining the development of new drug substances in organic chemistry laboratories across both academic and industrial sectors. With recent advances in analytical instrumentation and column technologies, universal chromatographic methods are quickly becoming a proactive and effective strategy to accelerate the discovery and implementation of new synthetic methodologies, especially but not limited to laboratories where the synthetic process route is undergoing rapid change and optimization. Targets of these generic methods include analysis of organic solvents, acid and basic additives, nucleotide species, palladium scavengers, impurity mapping, enantiopurity, synthetic intermediates, active pharmaceutical ingredients and their counterions, dehalogenation byproducts, and mixtures of organohalogenated pharmaceuticals, among other chemicals used or formed in process chemistry reactions.

HPLC Enantioseparations with Polysaccharide-Based Chiral Stationary Phases in HILIC Conditions

In contrast to achiral hydrophilic interaction liquid chromatography (HILIC), which is a popular and largely applied technique to analyze polar compounds such as pharmaceuticals, metabolites, proteins, peptides, amino acids, oligonucleotides, and carbohydrates, the introduction of the HILIC concept in enantioselective chromatography has been relatively recent and scarcely debated. In this chapter, the HILIC enantioseparations carried out on polysaccharide-based chiral stationary phases are grouped and discussed. Another objective of this chapter is to provide a comprehensive overview and insight into the experimental conditions needed to operate under HILIC mode. Finally, to stimulate and facilitate the application of this chromatographic technique, a detailed experimental protocol of a chiral resolution on a chlorinated cellulose-based chiral stationary phase under HILIC conditions is described.

Sample as solid support in MSPD: A new possibility for determination of pharmaceuticals, personal care and degradation products in sewage sludge

A method based on matrix-solid phase dispersion (MSPD), focused on the principles of green analytical chemistry, aimed at the use of alternative solid supports and less toxic solvents, was developed for the simultaneous determination of 19 pharmaceuticals, 4 personal care products (PPCPs) and 4 degradation products in sewage sludge samples. Higher recoveries were achieved when 2 g sample was macerated for 5 min in a glass mortar, transferred to a centrifuge tube, and 1 min vortex agitation with 5 mL methanol. The performance of the method was evaluated through linearity, recovery, precision (intra-day), method detection and quantification limits (MDL and MQL) and matrix effect. The calibration curves prepared in methanol and in the matrix extract showed a correlation coefficient ranging from 0.98 to 0.99. MQL values ranged from 1.25 to 1250 ng g^-1. Recoveries between 50 and 120% were reached with RSDs lower than 20% for most compounds. The method presented low and medium matrix effects for most analytes. This method was successfully applied to real samples and of the 27 compounds determined, amitriptyline, carbamazepine, diclofenac, haloperidol, ketoconazole, miconazole, albendazole, mebendazole, thiabendazole, triclosan and triclocarban were detected in concentrations between 2.5 and 5400 ng g^-1.

Determination of glucosamine and monitoring of its mutarotation by hydrophilic interaction liquid chromatography with evaporative light scattering detector

Saccharides and their derivatives are typical polar analytes without a suitable UV-chromophore that are nowadays analyzed by HPLC (high-performance liquid chromatography) under HILIC (hydrophilic interaction liquid chromatography) mode. Usually an evaporative light scattering detector (ELSD) is utilized which, however, gives a nonlinear response. A procedure to overcome the problem of mutarotating (time-varying) analytes recorded with such a nonlinear response detector is described. The procedure was applied for determination of glucosamine in two commercially available pharmaceutical formulations containing the common inorganic ions that the detector gives a response to. Under optimized conditions, both the anomers of glucosamine were separated and could be determined separately. Owing to the short retention time of the analyte (a run time <4 min) and relatively slow kinetics of the anomeric conversion (equilibration time 2.5 h), mutarotation could be monitored and corresponding rate constants calculated.

Chemical, computational and functional insights into the chemical stability of the Hedgehog pathway inhibitor GANT61

This work aims at elucidating the mechanism and kinetics of hydrolysis of GANT61, the first and most-widely used inhibitor of the Hedgehog (Hh) signalling pathway that targets Glioma-associated oncogene homologue (Gli) proteins, and at confirming the chemical nature of its bioactive form. GANT61 is poorly stable under physiological conditions and rapidly hydrolyses into an aldehyde species (GANT61-A), which is devoid of the biological activity against Hh signalling, and a diamine derivative (GANT61-D), which has shown inhibition of Gli-mediated transcription. Here, we combined chemical synthesis, NMR spectroscopy, analytical studies, molecular modelling and functional cell assays to characterise the GANT61 hydrolysis pathway. Our results show that GANT61-D is the bioactive form of GANT61 in NIH3T3 Shh-Light II cells and SuFu^−/− mouse embryonic fibroblasts, and clarify the structural requirements for GANT61-D binding to Gli1. This study paves the way to the design of GANT61 derivatives with improved potency and chemical stability.

Impurity profiling of drug candidates: Analytical strategies using reversed-phase and mixed-mode high-performance liquid chromatography methods

The development of new active pharmaceutical ingredients (API) requires accurate impurity profiling. Nowadays, reversed-phase HPLC (RPLC) on C18 stationary phase is the method of first choice for this task and usually employed in generic screening methods. However, this method sometimes fails, especially when the target analyte is not sufficiently retained, making impurity analysis difficult or even impossible. In such cases, a second method must be available. In the present paper, we compare the merits of RPLC on C18 phase to those of previously optimized alternative methods, based on the analysis of a large and diverse set of small-molecule drug candidates. Various strategies are considered: RPLC on C18 phase but with different mobile phase composition (acidic or basic), RPLC with a pentafluorophenyl stationary phase, or mixed-mode HPLC with both bimodal and trimodal stationary phases. First, method performances were compared in terms of response rate (proportion of compounds eluted) and peak shapes for a large set of synthetic drugs (140) with structural diversity and their orthogonality was evaluated. Then a subset of compounds (25) containing varied impurity profiles was used to compare the methods based on the capability to detect impurities and evaluate the relative purity of the API.

Determination of olopatadine in human tears by hydrophilic interaction liquid chromatography–MS/MS method

Aim: The objective of the study was development of hydrophilic interaction liquid chromatography–ESI/MS/MS method for the determination of olopatadine in tear matrix. Materials & methods: Separation was performed on Acquity BEH amide column (2.1 × 100 mm, 1.7 μm). The mobile phase was consisted of 0.1% formic acid in water and acetonitrile. Mianserin hydrochloride was implemented as an internal standard. The artificial tear fluid was used as matrix. The tear samples were collected using Schirmer test strips. For the optimization of ultra pressure liquid chromatography conditions, Box–Benhken design was utilized. Results: The optimal values of the ion source and collision cell parameters were found. Quantification was performed in multiple reaction monitoring mode. The optimized method was fully validated. Conclusion: The proposed method was utilized for monitoring of olopatadine in human tear.

Chemometric-assisted method development in hydrophilic interaction liquid chromatography: A review

With an enormous growth in the application of hydrophilic interaction liquid chromatography (HILIC), there has also been significant progress in HILIC method development. HILIC is a chromatographic method that utilises hydro-organic mobile phases with a high organic content, and a hydrophilic stationary phase. It has been applied predominantly in the determination of small polar compounds. Theoretical studies in computer-aided modelling tools, most importantly the predictive, quantitative structure retention relationship (QSRR) modelling methods, have attracted the attention of researchers and these approaches greatly assist the method development process. This review focuses on the application of computer-aided modelling tools in understanding the retention mechanism, the classification of HILIC stationary phases, prediction of retention times in HILIC systems, optimisation of chromatographic conditions, and description of the interaction effects of the chromatographic factors in HILIC separations. Additionally, what has been achieved in the potential application of QSRR methodology in combination with experimental design philosophy in the optimisation of chromatographic separation conditions in the HILIC method development process is communicated. Developing robust predictive QSRR models will undoubtedly facilitate more application of this chromatographic mode in a broader variety of research areas, significantly minimising cost and time of the experimental work.