Chiral separation of cathinone derivatives used as recreational drugs by cyclodextrin-modified capillary electrophoresis

Enantiomeric separation of nefopam and cathinone derivatives using a supramolecular deep eutectic solvent as a chiral selector in capillary electrophoresis

The present study investigates the utilization of a supramolecular deep eutectic solvent (SUPRADES), consisting of sulfated-β-cyclodextrin (S-β-CD) and citric acid (CA), as a chiral selector (CS) in capillary electrophoresis for the enantiomeric separation of nefopam (NEF) and five cathinone derivatives (3-methylmethcathinone [3-MMC], 4-methylmethcathinone [4-MMC], 3,4-dimethylmethcathinone [3,4-DMMC], 4-methylethcathinone [4-MEC], and 3,4-methylendioxycathinone [MDMC]). A significant improvement in enantiomeric separation of the target analytes was observed upon the addition of S-β-CD-CA to the background electrolyte (BGE), leading to a baseline separation of all analytes. In particular, the optimum percentage of S-β-CD-CA, added to the BGE, was determined to be 0.075% v/v for NEF (Rs = 1.5) and 0.050% v/v for three out of five cathinone derivatives (Rs = 1.5, 1.6, and 2.4 for 3-MMC, 4-MEC, and 3,4-DMMC, respectively). In the case of 4-MMC and MDMC, a higher percentage of the CS, equal to 0.075% and 0.10% v/v, respectively, was required to achieve baseline separation (Rs = 1.5, 1.9 for MDMC and 4-MMC, respectively). The outcomes of the present study highlight the potential effectiveness of using SUPRADES as a CS in electrophoretic enantioseparations.

Cyclodextrin-Enabled Enantioselective Complexation Study of Cathinone Analogs

The characteristic alkaloid component of the leaves of the catnip shrub (Catha edulis) is cathinone, and its synthetic analogs form a major group of recreational drugs. Cathinone derivatives are chiral compounds. In the literature, several chiral methods using cyclodextrins (CDs) have been achieved so far for diverse sets of analogs; however, a comprehensive investigation of the stability of their CD complexes has not been performed yet. To characterize the enantioselective complex formation, a systematic experimental design was developed in which a total number of 40 neutral, positively, and negatively charged CD derivatives were screened by affinity capillary electrophoresis and compared according to their cavity size, substituent type, and location. The functional groups responsible for the favorable interactions were identified in the case of para-substituted cathinone analog mephedrone, flephedrone, and 4-methylethcathinone (4-MEC) and in the case of 3,4-methylendioxy derivative butylone and methylenedioxypyrovalerone (MDPV). The succinylated-β-CD and subetadex exhibited the highest complex stabilities among the studied drugs. The complex stoichiometry was determined using the Job's plot method, and the complex structures were further studied using ROESY NMR measurements. The results of our enantioselective complex formation study can facilitate chiral method development and may lead to evaluate potential CD-based antidotes for cathinone analogs.

Stereoselective separation of psychoactive substances: Multivariate optimization and validation of a capillary electrophoresis method using carboxymethyl-β-CD/deep eutectic solvent dual system

A comprehensive study was performed to determine an optimum enantioseparation method for fluorine-substituted amphetamine and cathinone derivatives (fluor-amphetamine and fluor-cathinone derivatives), using a binary system consisting of carboxymethyl-β-CD (CM-β-CD) and a deep eutectic solvent (DES), namely choline chloride-ethylene glycol (ChCl-EG). Under this framework, the optimization and modeling of the separation conditions in a binary system were performed with the objective of maximizing resolution and minimizing analysis time. This was achieved through the application of response surface methodology. In particular, the effect of chiral selector concentration and percentage of DES on resolution and analysis time were investigated and optimized using a complete experimental design. The optimum enantioseparation conditions were determined to be 13.84 mM CM-β-CD and 0.15% v/v ChCl-EG for fluorine-substituted amphetamine derivatives and 14.36 mM and 0.75% v/v ChCl-EG for fluorine-substituted cathinone derivatives, respectively. This combination resulted in a baseline separation for eight out of the nine analytes studied. Overall, the results demonstrated the synergistic effect of the CM-β-CD/DES dual system and highlighted the significance of DESs as additives in capillary electrophoresis.

The potential of the use of deep eutectic solvents and amino acid-based ionic liquids to enhance the chiral discrimination ability of different chiral selectors in capillary electrophoresis

The effect of the combined use of amino acid-based ionic liquids (AAILs) and deep eutectic solvents (DESs) with either cyclodextrin- (CD) or cyclofructan- (CF) based chiral selectors for the chiral separation of amphetamine derivatives was investigated in the present study. A non-significant improvement in enantiomeric separation of target analytes was observed when AAILs were combined with either CF or CD. On the other side, a markedly improved chiral separation of enantiomers was obtained using the dual carboxymethyl-β-cyclodextrin/DES system, highlighting the existence of a synergistic effect. After the addition of 0.5% v/v of choline chloride-ethylene glycol, the resolution of the enantiomers of amphetamine, methamphetamine and 3-fluorethamphetamine, increased from 1.4, 1.1, 1.0 to 1.8, 1.8, and 1.5 min, and the analysis times increased from 19.54, 20.48, 18.71 to 35.71, 35.78 and 32.90 min, respectively. This was not the case for the CF/DES dual system, in which the separation of amphetamines worsened, indicating an antagonistic effect. In conclusion, DESs are a very promising additive in capillary electrophoresis that can improve the separation of chiral molecules in combination with CDs but not CFs.

Enantioseparation and a comprehensive spectroscopic analysis of novel synthetic cathinones laterally substituted with a trifluoromethyl group

Recently, the number of structural modifications of synthetic cathinones has been growing making them the second largest group of new psychoactive substances in Europe. Although they are abused because of their various psychoactive effects, some compounds from this group also serve as pharmaceuticals. Since synthetic cathinones are chiral molecules with one chiral center, their biological, toxicological, and pharmacological properties may significantly differ according to their absolute configuration and enantiomeric excess. In this study, we have synthesized two substances bearing a pharmacologically interesting trifluoromethyl group and developed a chiral liquid chromatography method using a polysaccharide chiral stationary phase to separate the corresponding enantiomers of both these drugs. Subsequently, we utilized molecular spectroscopic methods including chiroptical (electronic circular dichroism and vibrational circular dichroism) and non-polarizable (infrared and ultraviolet absorption) spectroscopies. In combination with density functional theory calculations, we have obtained stable conformers of selected enantiomers in solution and their relative abundances, which we used to simulate their spectra. The experimental and calculated data have been used to elucidate the 3D structure of the enantiomerically pure compounds and assign the absolute configuration of all prepared compounds.

Evaluation of cyclodextrin- and cyclofructan-based chiral selectors for the enantioseparation of psychoactive substances in capillary electrophoresis

During this study, a simple and easy-to-prepare electrophoretic method was developed for the enantioseparation of amphetamine and cathinone derivatives. Different types of β-cyclodextrin and cyclofructan-based chiral selectors (CSs), both native and derivatized, were utilized, and the most effective ones, in terms of resolution and analysis time, were identified. In addition, several electrophoretic parameters, such as background electrolyte concentration and pH, and CS concentration, were examined to optimize the separation conditions. Under the optimal electrophoretic conditions, 10 psychoactive substances were enantiomerically separated using 1 mM sulfated cyclofructan-6 (SCF-6) for the amphetamine derivatives and 1 mM sulfated cyclofructan-7 (SCF-7) for the cathinone derivatives dissolved in an aqueous solution of 20-mM monobasic sodium phosphate at pH 2.5, a temperature of 25°C, and an applied voltage of 25 kV. In addition, the method was validated by estimating the intra- and interday precision.

Development of a sensitive MEKC-LIF method for synthetic cathinones analysis

Synthetic cathinones are phenylalkylamine compounds related to natural cathinone from Catha edulis leaves. Due to their sympathomimetic effects comparable to common illicit drugs, these substances are mainly drugs of abuse and constitute the second most frequently seized group of new psychoactive substances. In order to ensure their regulation and to promote public health, reliable analytical tools are required to track these substances. In the present study, we developed a CE hyphenated to laser-induced fluorescence detection method to demonstrate its suitability to perform fast and cost-effective synthetic cathinones analysis. Fourteen compounds including isobaric compounds and position isomers were selected to encompass the large panel of chemical structures. To separate the FITC-labeled analytes (presenting the same negative charge and close mass to charge ratios), MEKC separation mode was selected. Method selectivity was not suitable using common surfactants. In this context, alkyl polyethylene glycol ether surfactants were successfully used as neutral surfactant to overcome this analytical challenge. The effect of surfactant nature on separation performances and migration behaviors of the analytes was also studied. Optimal BGE composition included 75 mM borate buffer at pH 9.3 and 0.4 mM of C12E10 surfactant. Final MEKC separation conditions were proposed to analyze a large panel of synthetic cathinones. This method helped to reach a sensitivity with LOD from 0.1 to 0.4 nM (pg/mL order).

Enantioseparation performance of superficially porous particle vancomycin-based chiral stationary phases in supercritical fluid chromatography and high performance liquid chromatography; applicability for psychoactive substances

Novel psychoactive substances (NPS) are synthetic compounds that have been designed to produce the physiological and psychological effects of known recreational drugs, while circumventing current drug control laws and scheduling guidelines. Such "designer drugs" pose problems in detection and prevention of use, and they are no less dangerous than known controlled substances. Among the various classes of NPS, many are chiral. As they are synthetic products, most are racemates. Not unexpectedly, there is limited information about different the pharmacological and toxicological properties of their pure enantiomers. Hence, fast and reliable enantioselective methods are of great interest. In this work, superficially porous particle (SPP) vancomycin-based chiral stationary phases were used for development of fast enantioselective separation methods for various classes of NPS in supercritical fluid chromatography and liquid chromatography. The NPS tested included pyrovalerones, benzofurans, phenidines and phenidates. The effect of mobile phase composition on the retention and resolution of NPS in supercritical fluid chromatography was examined. The amount as well as the ratios of additives used is crucial for enantioseparation efficiency. Results showed the high enantioselective potential of vancomycin-based columns in both chromatographic techniques; 88% of NPS tested were enantioseparated in supercritical fluid chromatography and 69% of NPS tested were enantioseparated in liquid chromatography. Moreover, under optimized conditions, simultaneous enantioseparations of some NPS were achieved, which indicates great suitability of vancomycin-based columns for this purpose. The proposed methods can serve as guides for method development and for enantioseparation of further upcoming NPS.

Determination of the chiral status of different novel psychoactive substance classes by capillary electrophoresis and β-cyclodextrin derivatives

Besides the abuse of well‐known illicit drugs, consumers discovered new synthetic compounds with similar effects but minor alterations in their chemical structure. Originally, these so‐called novel psychoactive substances (NPS) have been created to circumvent law of prosecution because of illicit drug abuse. During the past decade, such compounds came up in generations, the most popular compound was a synthetic cathinone derivative named mephedrone. Cathinones are structurally related to amphetamines; to date, more than 120 completely new derivatives have been synthesized and are traded via the Internet. Cathinones possess a chiral center; however, only little is known about the pharmacology of their enantiomers. However, NPS comprise further chiral compound classes such as amphetamine derivatives, ketamines, 2‐(aminopropyl)benzofurans, and phenidines. In continuation of our project, a cheap and easy‐to‐perform chiral capillary zone electrophoresis method for enantioseparation of cathinones presented previously was extended to the aforementioned compound classes. Enantioresolution was achieved by simply adding native β‐cyclodextrin, acetyl‐β‐cyclodextrin, 2‐hydroxypropyl‐β‐cyclodextrin, or carboxymethyl‐β‐cyclodextrin as chiral selector additives to the background electrolyte. Fifty‐one chiral NPS served as analytes mainly purchased from online vendors via the Internet. Using 10 mM of the aforementioned β‐cyclodextrins in a 10 mM sodium phosphate buffer (pH 2.5), overall, 50 of 51 NPS were resolved. However, chiral separation ability of the selectors differed depending on the analyte. Additionally, simultaneous enantioseparations, the determination of enantiomeric migration orders of selected analytes, and a repeatability study were performed successfully. It was proven that all separated NPS were traded as racemic mixtures.

Enantioseparation and Determination of Mephedrone and Its Metabolites by Capillary Electrophoresis Using Cyclodextrins as Chiral Selectors

Mephedrone, a psychoactive compound derived from cathinone, is widely used as a designer drug. The determination of mephedrone and its metabolites is important for understanding its possible use in medicine. In this work, a method of capillary electrophoresis for the chiral separation of mephedrone and its metabolites was developed. Carboxymethylated β-cyclodextrin was selected as the most effective chiral selector from seven tested cyclodextrin derivates. Based on the simplex method, the optimal composition of the background electrolyte was determined: at pH 2.75 and 7.5 mmol·L^-1 carboxymethylated β-cyclodextrin the highest total resolution of a mixture of analytes was achieved. For mephedrone and its metabolites, calibration curves were constructed in a calibration range from 0.2 to 5 mmol·L^-1; limits of detection, limits of quantification, precision, and repeatability were calculated, and according to Mandel's fitting test, the linear calibration ranges were determined.

A Simple HPLC–UV Approach for Rapid Enantioseparation of Cathinones, Pyrovalerones and Other Novel Psychoactive Substances on a 2.5-µm Cellulose Tris-(3,5-dimethylphenyl-carbamate) Column

The misuse of so called novel psychoactive substances is still a challenging problem worldwide. A special attribute of a lot of these compounds is a chiral centre enabling two possible enantiomers probably related to different pharmacological and toxicological properties. The goal of the present study was to present a simple and isocratic HPLC–UV method for enantioseparation of mainly cathinone and pyrovalerone derivatives as well as selected representatives of amphetamines, ketamines, benzofuries, phenidines, phenidates, morpholines and thiophenes. A Waters Acquity UPC2® Trefoil™ CEL1 2.5 µm, 3.0 × 150 mm column served as chiral stationary phase by means of cellulose tris-(3,5-dimethylphenylcarbamate) as chiral selector. Mobile phases consisted either of n-hexane/n-butanol/diethylamine (100:0.3:0.2) or n-hexane/diethylamine (100:0.2). The method was found to be applicable for rapid simultaneous chiral separations of cathinone derivatives, to determine enantiomeric elution orders, to detect positional isomers and to identify real-life samples. Also, a repeatability study was performed successfully. 78 out of 95 compounds were separated in their enantiomers successfully, 51 of them within 6 min. It was shown that all NPS bought from online vendors or seized by police were traded as racemic mixtures.

Successful use of a novel lux® i-Amylose-1 chiral column for enantioseparation of "legal highs" by HPLC

Bath salts, fumigations, cleaners and air fresheners, behind these terms substances are hidden, which count as "Legal Highs". These fancy names are used to pretend Legal Highs as harmless compounds, to circumvent legal regulations for marketing as well as to increase the sales. Besides classic illicit drugs of synthetic origin such as amphetamines, cocaine and MDMA, the trade of these compounds, also known as new psychoactive substances (NPS), is not uncommon today. In many countries, NPS are still not subject to drug control. Among them, there are stimulants such as new amphetamine derivatives or cathinones, which possess a chiral centre. Little is known about the fact that the two possible enantiomers may differ in their pharmacological effect. The aim of this study was to test a novel HPLC column for the enantioseparation of a set of 112 NPS coming from different chemical groups and collected by internet purchases during the years 2010-2018. The CSP, namely Lux® 5 μm i-Amylose-1, LC Column 250 x 4.6 mm, was run in normal phase mode under isocratic conditions, UV detection was performed at 245 nm and 230 nm, injection volume was 10 μl and flow rate was 1 ml/min. With a mobile phase consisting of n-hexane/isopropanol/diethylamine (90:10:0.1), herein, 79 NPS were resolved into their enantiomers successfully, for 37 of them baseline resolution was achieved. After increase of lipophily of the mobile phase to 99:1:0.1, another 27 compounds were baseline separated. It was found that all separated NPS are traded as racemic compounds.

Chiral separation of cathinone derivatives using β-cyclodextrin-assisted capillary electrophoresis-Comparison of four different β-cyclodextrin derivatives used as chiral selectors

In the past decade, more than 100 different cathinone derivatives slopped over entire Europe due to their enormous popularity. Generally, these novel psychoactive substances are easily available via the internet. This fact leads to various social problems, since cathinones are substances with consciousness-changing effects and are mainly misused for recreational matters by their consumers. Cathinones possess a chiral center including two enantiomeric forms with potentially different pharmacological behavior. This fact makes analytical method development regarding their chiral separation indispensable. In this study, a chiral capillary zone electrophoresis method for the enantioseparation of 61 cathinone and pyrovalerone derivatives was developed by means of four different β-cyclodextrin derivatives. As chiral selectors, native β-cyclodextrin as well as three of its derivatives namely acetyl-β-cyclodextrin, 2-hydroxypropyl-β-cyclodextrin, and carboxymethyl-β-cyclodextrin were used. The cathinone and pyrovalerone derivatives were either purchased in internet stores or seized by police. As a result, overall 58 of 61 studied substances were partially or baseline separated by at least one of the four chiral selectors using 10 mM of β-cyclodextrin derivative in a 10 mM sodium phosphate buffer (pH 2.5). Furthermore, the method was found to be suitable for simultaneous enantioseparations, for enantiomeric purity checks and to differentiate between positional isomers. Moreover, an intra- and an interday validation was performed successfully for each chiral selector to prove the robustness of the method.

Enantiomeric separation of Novel Psychoactive Substances by capillary electrophoresis using (+)-18-crown-6-tetracarboxylic acid as chiral selector

In the recent years, hundreds of Novel Psychoactive Substances (NPS) have entered both the European and the global drug market. These drugs, which are mainly used for recreational matters, have caused serious social problems. Every year, the spectrum of these misused drugs is enlarged by new derivatives, which are produced by modifications of basic structures of already well-known substances. Additionally, a lot of them possess a stereogenic center which leads to 2 enantiomeric forms. The fact that the pharmacological effects and potencies of the enantiomers of these chiral NPS may differ can be assumed from a broad spectrum of active pharmaceutical ingredients. For this reason, analytical method development regarding enantiomeric separation for these classes of substances is of great pharmaceutical and medical interest. The aim of this work was to create an easy-to-prepare chiral capillary electrophoresis method for the enantioseparation of NPS which contains a primary amino group by means of (+)-18-crown-6-tetracarboxylic acid as chiral selector. Novel Psychoactive Substances were purchased at various Internet stores or represent samples seized by Austrian police. The effects of selector concentration, the electrolyte composition, and the addition of organic modifiers to the background electrolyte on enantioseparation were investigated. Under optimized conditions, the use of 20-mM (+)-18-crown-6-tetracarboxylic acid, 10-mM Tris, and 30-mM citric acid buffer at pH 2.10 turned out to be effective. Fifteen of 24 tested NPS were resolved in their enantiomers within 15 minutes. It was found that all NPS were traded as racemic mixtures.

Simultaneous Quantitative Determination of Synthetic Cathinone Enantiomers in Urine and Plasma Using GC-NCI-MS

Development and validation of sensitive and selective method for enantioseparation and quantitation of synthetic cathinones is reported using GC-MS triple quadrupole mass spectrometry with negative chemical ionization (NCI) mode. Indirect chiral separation of thirty-six synthetic cathinone compounds has been achieved by using an optically pure chiral derivatizing agent (CDA) called (S)-(-)-N-(trifluoroacetyl)pyrrolidine-2-carbonyl chloride (L-TPC), which converts cathinone enantiomers into diastereoisomers that can be separated on achiral columns. As a result of using Ultra Inert 60 m column and performing slow heating rate (2°C/min) on the GC oven, an observed enhancement in enantiomer peak resolution has been achieved. An internal standard, (+)-cathinone, was used for quantitation of synthetic cathinones. Method validation in terms of linearities and sensitivity in terms of limits of detection (LODs), limits of quantitation (LOQs), recoveries, and reproducibilities has been obtained for fourteen selected compounds that examined simultaneously as a mixture after being spiked in urine and plasma. It was found that the LOD of the fourteen synthetic cathinones in urine was in the range of 0.26-0.76 µg/L, and in plasma, it was in the range of 0.26-0.34 µg/L. While the LOQ of the mixture in urine was in the range of 0.86-2.34 µg/L, and in plasma, it was in the range of 0.89-1.12 µg/L. Unlike the electron impact (EI) ion source, NCI showed better sensitivity by two orders of magnitude by comparing the obtained results with the recently published reports for quantitative analysis and enantioseparation of synthetic cathinones.

Toward Confirmatory On-Site Real-Time Detection of Emerging Drugs Using Portable Ultrafast Capillary Electrophoresis Mass Spectrometry

Currently, law enforcement agencies rely upon presumptive tests such as color tests (or spot tests) for on-site, real-time identification of forensic evidence, such as controlled substances. These tests are simple and easy to use and require no instrumentation. However, they are unreliable and have a large false positive rate. On the other hand, confirmatory tests are done in analytical laboratories using sophisticated instrumentation by expert analysts, and have lower false positive rates. However, they are bulky and impractical for on-site real-time analysis. To provide more accurate identification of forensic evidence on-site, in real-time, it is important to develop portable confirmatory instrumentation using information-rich technologies. Moreover, because the analysis of controlled substances could be complicated by the existence of various isomers (including optical isomers) it is desirable that the portable instruments have the capability to separate structural and optical isomers of the controlled substances, because scheduling is some times dependent upon which isomer is present. To this end, we have developed a portable ultrafast capillary electrophoresis (UFCE) system for the separation of controlled substances and their structural and optical isomers. The UFCE instrument has an integrated porous tip for facile interfacing with electrospray ionization mass spectrometry. The technique has been successfully applied to the analysis of mixtures of several controlled substances such as amphetamines, cathinones, nor-mephedrone, and pregabalin and their optical isomers in about a minute.

Enantioselective determination of cathinone derivatives in human hair by capillary electrophoresis combined in-line with solid-phase extraction

A suitable method has been developed and validated for the chiral separation and determination of R,S-mephedrone and one of its metabolites, R,S-4-methylephedrine, and R,S-methylenedioxypyrovalerone (R,S-MDPV) in human hair samples by the in-line coupling between SPE and CD-assisted CE with a previous sample pretreatment procedure based on pressurized liquid extraction. Optimum separation was achieved on a fused silica-capillary of 50 μm id and 80 cm total length using 12 mg/mL β-CD in an aqueous solution of 80 mM disodium phosphate at pH 2.5 as the BGE and an applied voltage of 30 kV. The SPE-CE device consists of a short length of a capillary of 2 mm packed with Oasis HLB sorbent, which was inserted near to the inlet end of the CE capillary. Several parameters affecting the in-line preconcentration were evaluated. The LOQs reached for hair samples were 0.05 ng/mg for the enantiomers of mephedrone and its metabolite, and 0.40 ng/mg for the enantiomers of MDPV. The RSDs (%) obtained in intra- and interday studies were less than 10% and the relative recoveries were greater than 80%. The method established in this paper is advantageous for its simplicity, overall analysis time and ability to provide information of both enantiomers of a chiral drug in hair samples.

Chiral enantioresolution of cathinone derivatives present in "legal highs", and enantioselectivity evaluation on cytotoxicity of 3,4-methylenedioxypyrovalerone (MDPV)

Recently, great interest has been focused on synthetic cathinones since their consumption has increased exponentially. All synthetic cathinones exist as chiral molecules; the biological and/or toxicological properties of cathinones generally differ according to the enantiomers in human body. In this study, a chiral liquid chromatography method was developed to separate and determine the enantiomeric ratio of synthetic cathinones present in "legal highs" acquired in old smart shops or over the Internet. All the synthetic cathinones were efficiently enantio-separated with α and Rs ranging from 1.24 to 3.62 and from 1.24 to 10.52, respectively, using polysaccharide-based chiral stationary phases. All synthetic cathinones, with the exception of 4-methylethcathinone (4-MEC), were present in the commercialized "legal highs" in an enantiomeric proportion of 50:50. One of the studied chiral compounds was 3,4-methylenedioxypyrovalerone (MDPV), one of the most consumed cathinone derivative worldwide. Our research group has recently reported its hepatotoxicity in the racemic form. Thus, the analytical enantioresolution of the MDPV was scaled up to multi-milligram using a semi-preparative amylose tris-3,5-dimethylphenylcarbamate column (20 cm × 7.0 mm ID, 7 µm particle size). Both enantiomers were isolated with high enantiomeric purity (enantiomeric excess > 99 %). The toxicity of S-(-)-MDPV and R-(+)-MDPV was evaluated, for the first time, using primary cultures of rat hepatocytes. It was also possible to verify that MDPV enantiomers showed hepatotoxicity in a concentration-dependent manner, but displayed no enantioselective toxicity in this cell culture model.

One-step preparation and application of mussel-inspired poly(norepinephrine)-coated polydimethylsiloxane microchip for separation of chiral compounds

In this paper, using the self-polymerization of norepinephrine (NE) and its favorable film-forming property, a simple and green preparation approach was developed to modify a PDMS channel for enantioseparation of chiral compounds. After the PDMS microchip was filled with NE solution, poly(norepinephrine) (PNE) film was gradually formed and deposited on the inner wall of microchannel as permanent coating via the oxidation of NE by the oxygen dissolved in the solution. Due to possessing plentiful catechol and amine functional groups, the PNE-coated PDMS microchip exhibited much better wettability, more stable and suppressed EOF, and less nonspecific adsorption. The water contact angle and EOF of PNE-coated PDMS substrate were measured to be 13° and 1.68 × 10(-4) cm(2) V(-1) s(-1) , compared to those of 108° and 2.24 × 10(-4) cm(2) V(-1) s(-1) from the untreated one, respectively. Different kinds of chiral compounds, such as amino acid enantiomer, drug enantiomer, and peptide enantiomer were efficiently separated utilizing a separation length of 37 mm coupled with in-column amperometric detection on the PNE-coated PDMS microchips. This facile mussel-inspired PNE-based microchip system exhibited strong recognition ability, high-performance, admirable reproducibility, and stability, which may have potential use in the complex biological analysis.

A validated gas chromatography mass spectrometry method for simultaneous determination of cathinone related drug enantiomers in urine and plasma

A sensitive and selective method for detection and quantitation of 31 synthetic cathinones using GC-MS has been developed and validated. They were separated into their optical enantiomers after derivatization with L-TPC and nikethamide was used as IS.

Isolation and structural determination of non-racemic tertiary cathinone derivatives

In this paper the dynamic resolution of racemic tertiary cathinones is demonstrated through co-crystallization with enantiopure aromatic tartaric acids.

Electromigrative separation techniques in forensic science: combining selectivity, sensitivity, and robustness

In this review we introduce the advantages and limitations of electromigrative separation techniques in forensic toxicology. We thus present a summary of illustrative studies and our own experience in the field together with established methods from the German Federal Criminal Police Office rather than a complete survey. We focus on the analytical aspects of analytes' physicochemical characteristics (e.g. polarity, stereoisomers) and analytical challenges including matrix tolerance, separation from compounds present in large excess, sample volumes, and orthogonality. For these aspects we want to reveal the specific advantages over more traditional methods. Both detailed studies and profiling and screening studies are taken into account. Care was taken to nearly exclusively document well-validated methods outstanding for the analytical challenge discussed. Special attention was paid to aspects exclusive to electromigrative separation techniques, including the use of the mobility axis, the potential for on-site instrumentation, and the capillary format for immunoassays. The review concludes with an introductory guide to method development for different separation modes, presenting typical buffer systems as starting points for different analyte classes. The objective of this review is to provide an orientation for users in separation science considering using capillary electrophoresis in their laboratory in the future.

Analysis and characterization of the novel psychoactive drug 4-chloromethcathinone (clephedrone)

Novel psychoactive drugs, such as amphetamine-, cathinone-, benzofury- and tryptamine derivatives, gained high popularity on the global drug market in the last years. These drugs are sold via the Internet as for example "research chemicals", "room odorizers" or "lawn fertilizers" by different online suppliers. They are also known as "Legal Highs", among them, cathinone derivatives play an important role. Well known substituted cathinone derivatives are mephedrone, brephedrone and flephedrone. Since a couple of weeks, a chlorine substituted methcathinone derivative, namely clephedrone (4-chloromethcathinone), is commercially available via the Internet from www.deboralabs.com. The goal of this study was to confirm identity of this substance, which was done successfully by GC-MS and NMR. Since all cathinone derivatives are chiral, it was found out, whether the purchased sample was present as a racemic mixture. For this purpose, methods for enantioseparation by GC and CE were developed and applied successfully. In case of CE a chiral selector was added, whereas chiral separation with GC-MS was done indirectly, after derivatization of clephedrone with trifluoroacetyl-l-prolyl chloride.

Enantiomeric separation by microchip electrophoresis using bovine serum albumin conjugated magnetic core-shell Fe3 O4 @Au nanocomposites as stationary phase

In this work, a novel enantioselective MCE was developed employing BSA-conjugated Fe3 O4 @Au nanoparticles (Fe3 O4 @Au NPs) as stationary phase. Fe3 O4 @Au NPs with high magnetic responsively, excellent solubility, and high dispersibility in water were prepared through a sonochemical synthesis strategy. BSA was then immobilized onto the Fe3 O4 @Au NPs surfaces through the well-developed interaction between Au NPs and amine groups of BSA to form Fe3 O4 @Au NPs-BSA conjugates, which were then locally packed into PDMS microchannels with the help of magnets. The resultant Fe3 O4 @Au NPs-BSA conjugates not only have the magnetism of Fe3 O4 NPs that make them easily manipulated by an external magnetic field, but also have the larger surface and excellent biocompatibility of Au shell, which can incorporate much more biomolecules and well maintain their biological activity. In addition, the successful BSA decorations endowed Fe3 O4 @Au NPs-BSA conjugates with pH-tunable water solubility related to the pI of BSA (pI 4.7) and led to enhanced stability against high ionic strength. Compared with the native PDMS microchannel, the modified surfaces exhibited more stable and suppressed electroosmotic mobility, and less nonspecific adsorption toward analytes. Successful separation of chiral amino acids (tryptophan and threonine) and ofloxacin enantiomers demonstrate that the constructed MCE columns own ideal enantioselectivity. The results are expected to open up a new possibility for high-throughput screening of enantiomers with protein targets as well as a new application of magnetic NPs.