Capillary electrophoretic enantioseparation of selegiline, methamphetamine and ephedrine using a neutral beta-cyclodextrin epichlorhydrin polymer

Enzyme-free colorimetric sensor based on molecularly imprinted polymer and ninhydrin for methamphetamine detection

Digital image colorimetry was applied to introduce a rapid, portable, and non-enzymatic test for methamphetamine measurements in urine. Imprinted polymer was synthesized in a simple, low-cost process and utilized for selective extraction of analyte from the sample in combination with the well-known ninhydrin color test. Applying the digital camera on a mobile phone, RGB basic color data were obtained, and calibration curves were developed for different concentrations of methamphetamine. Optimization of the test condition was carried out by changing some effective parameters such as extraction time and pH. The results were compared with some similar structural compounds indicating great potential for use as a selective and semi-quantitative field test for this drug. An acceptable linear range (5-100 μM) and detection limit (1.44 μM) as well as good agreement with the reference method, makes this fast portable method, an easy and reliable test for the analysis of methamphetamine in biological samples.

Simultaneous Determination of Selegiline, Desmethylselegiline, R/S-methamphetamine, and R/S-amphetamine on Dried Urine Spots by LC/MS/MS: Application to a Pharmacokinetic Study in Urine

Objective: Chiral analysis is a crucial method to differentiate selegiline intake from drug abuse. A dried urine spot (DUS) analytical method based on spotting urine samples (10 μL) onto dried spot collection cards, and followed by air-drying and extraction, was developed and validated for the determination of selegiline, desmethylselegiline, R/S-methamphetamine, and R/S-amphetamine. Methods: Methanol (0.5 mL) was found to be the ideal extraction solvent for target extraction from DUSs under orbital-horizontal stirring on a lateral shaker at 1,450 rpm for 30 min. Determinations were performed by direct electrospray ionization tandem mass spectrometry (ESI-MS/MS) under positive electrospray ionization conditions using multiple reaction monitoring mode. The chromatographic system consisted of a ChirobioticTM V2 column (2.1 × 250 mm, 5 μm) and a mobile phase of methanol containing 0.1% (v/v) glacial acetic acid and 0.02% (v/v) ammonium hydroxide. Results and conclusions: The calibration curves were linear from 50 to 5,000 ng/mL, with r > 0.995 for all analytes, imprecisions ≤ 15% and accuracies between -11.4 and 11.7%. Extraction recoveries ranged from 48.6 to 105.4% with coefficients of variation (CV) ≤ 13.7%, and matrix effects ranged from 45.4 to 104.1% with CV ≤ 10.3%. The lower limit of quantification was 50 ng/mL for each analyte. The present method is simple, rapid (accomplished in 12 min), sensitive, and validated by a pharmacokinetic study in human urine collected after a single oral administration of SG.

Determination of six anti-Parkinson drugs using cyclodextrin-capillary electrophoresis method: application to pharmaceutical dosage forms

Addition of β-cyclodextrin to the background electrolyte improves the separation efficiency of multi-component mixtures through inclusion complex formation.

Chiral separation and determination of R/S-methamphetamine and its metabolite R/S-amphetamine in urine using LC-MS/MS

Methamphetamine (MA) and amphetamine (AM) are widely abused drugs. Differentiation of MA and/or AM abuse from therapeutic ingestion of MA and/or AM or one of their precursor drugs is therefore of relevance in clinical and forensic toxicology. The aim of the study was to develop a simple, rapid, and accurate method for the chiral separation and determination of R/S-MA and R/S-AM in urine using liquid chromatography electrospray ionization tandem mass spectrometry operating in the positive ion multiple-reaction monitoring (MRM) mode. 20 μL of urine was diluted 500 times and 20 μL was injected. The chromatographic system consisted of a Chirobiotic™ V2 column (2.1 mm × 250 mm, 5 μm), and the mobile phase was methanol containing 0.1% (v/v) glacial acetic acid and 0.02% (v/v) ammonium hydroxide. The method was fully validated through assessments of its linearity (0.05-50.00 mg/L, r(2)>0.994 for all analytes), and LOQ (0.05 mg/L for all analytes). No matrix effect was observed. The method was successfully applied to 86 urine samples from suspected MA abusers. Only the S-isomers of MA and AM were detected in 72 samples. The concentrations of R-MA ranged from below the LOQ to 13.76 mg/L in 14 urine samples with both enantiomers of MA and/or AM. Pure S-MA is the most common found analyte in urine and principally used by abusers.

Extractive determination of ephedrine hydrochloride and bromhexine hydrochloride in pure solutions, pharmaceutical dosage form and urine samples

Simple, rapid, sensitive, precise and accurate spectrophotometeric methods for the determination of ephedrine hydrochloride (E-HCl) and bromhexine hydrochloride (Br-HCl) in bulk samples, dosage form and in spiked urine samples were investigated. The methods are based on the formation of a yellow colored ion-associates due to the interaction between the examined drugs with picric acid (PA), chlorophyllin coppered trisodium salt (CLPH), alizarin red (AR) and ammonium reineckate (Rk) reagents. A buffer solution had been used and the extraction was carried out using organic solvent, the ion associates exhibit absorption maxima at 410, 410, 430 and 530 nm of (Br-HCl)with PA, CLPH, AR and Rk respectively; 410, 410, 435 and 530 of (E-HCl) with PA, CLPH, AR and Rk respectively. (E-HCl) and (Br-HCl) could be determined up to 13, 121, 120 and 160; 25, 200, 92 and 206 μg mL(-1), using PA, CLPH, AR and Rk respectively. The optimum reaction conditions for quantitative analysis were investigated. In addition, the molar absorptivity, Sandell sensitivity were determined for the investigated drug. The correlation coefficient was ≥0.995 (n=6) with a relative standard deviation (RSD) ≤1.15 for five selected concentrations of the reagents. Therefore the concentration of Br-HCl and E-HCl drugs in their pharmaceutical formulations and spiked urine samples had been determined successfully.

Chiral selectors in CE: recent developments and applications

This review article provides an overview of the recent advances in enantioanalysis by use of electrophoretic techniques. Due to the big number of publications in the subject mentioned above, this article is focused on chiral method developments and applications published from 2008 until 2011, and it demonstrates chiral selectors used in CE. Numerous chiral selectors have been used over the years, and these include the cyclic and the linear oligo- and polysaccharides, the branched polysaccharides, the polymeric and monomeric surfactants, the macrocyclic and other antibiotics, and the crown ethers. Different dual-selector systems are also presented in this article, and the results are compared with those obtained by use of a single chiral selector. Finally, several pharmaceutical and biomedical applications based on chiral recognition are summarized.

Enantiomeric separation of some common controlled stimulants by capillary electrophoresis with contactless conductivity detection

CE methods with capacitively coupled contactless conductivity detection (C(4)D) were developed for the enantiomeric separation of the following stimulants: amphetamine (AP), methamphetamine (MA), ephedrine (EP), pseudoephedrine (PE), norephedrine (NE) and norpseudoephedrine (NPE). Acetic acid (pH 2.5 and 2.8) was found to be the optimal background electrolyte for the CE-C(4)D system. The chiral selectors, carboxymethyl-β-cyclodextrin (CMBCD), heptakis(2,6-di-O-methyl)-β-cyclodextrin (DMBCD) and chiral crown ether (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid (18C6H(4)), were investigated for their enantioseparation properties in the BGE. The use of either a single or a combination of two chiral selectors was chosen to obtain optimal condition of enantiomeric selectivity. Enantiomeric separation of AP and MA was achieved using the single chiral selector CMBCD and (hydroxypropyl)methyl cellulose (HPMC) as the modifier. A combination of the two chiral selectors, CMBCD and DMBCD and HPMC as the modifier, was required for enantiomeric separation of EP and PE. In addition, a combination of DMBCD and 18C6H(4) was successfully applied for the enantiomeric separation of NE and NPE. The detection limits of the enantiomers were found to be in the range of 2.3-5.7 μmol/L. Good precisions of migration time and peak area were obtained. The developed CE-C(4)D method was successfully applied to urine samples of athletes for the identification of enantiomers of the detected stimulants.

Advanced CE for chiral analysis of drugs, metabolites, and biomarkers in biological samples

An analysis of recent trends indicates that CE can show real advantages over chromatographic methods in ultratrace enantioselective determination of biologically active compounds in complex biological matrices. It is due to high separation efficiency and many applicable in-capillary electromigration effects in CE (countercurrent migration, stacking effects) enhancing significantly (enantio)separability and enabling effective sample preparation (preconcentration, purification, analyte derivatization). Other possible on-line combinations of CE, such as column coupled CE-CE techniques and implementation of nonelectrophoretic techniques (extraction, membrane filtration, flow injection) into CE, offer additional approaches for highly effective sample preparation and separation. CE matured to a highly flexible and compatible technique enabling its hyphenation with powerful detection systems allowing extremely sensitive detection (e.g. LIF) and/or structural characterization of analytes (e.g. MS). Within the last decade, more as well as less conventional analytical on-line approaches have been effectively utilized in this field and their practical potentialities are demonstrated on many new application examples in this article. Here, three basic areas of (enantioselective) drug bioanalysis are highlighted and supported by a brief theoretical description of each individual approach in a compact review structure (to create integrated view on the topic), including (i) progressive enantioseparation approaches and new enantioselective agents, (ii) in-capillary sample preparation (preconcentration, purification, derivatization), and (iii) detection possibilities related to enhanced sensitivity and structural characterization.

Spectrophotometric study of the charge-transfer and ion-pair complexation of methamphetamine with some acceptors

The charge-transfer (CT) complexes of methamphetamine (MPA) as a n-donor with several acceptors including bromocresolgreen (BCG), bromocresolpurple (BCP), chlorophenolred (CPR), picric acid (PIC), and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) have been studied spectrophotometrically in chloroform solutions in order to obtain some information about their stoichiometry and stability of complexation. The oscillator strengths, transition dipole moments and resonance energy of the complex in the ground state for all complexes have been calculated. Vertical ionization potential of MPA and electron affinity of acceptors were determined by ab initio calculation. The acceptors were also used to utilize a simple and sensitive extraction-spectrophotometric method for the determination of MPA. The method is based on the formation of 1:1 ion-pair association complexes of MPA with BCG, BCP and PIC in chloroform medium. Beer's plots were obeyed in a general concentration range of 0.24-22 microg ml(-1) for the investigated drug with different acceptors. The proposed methods were applied successfully for the determination of MAP in pure and abuse drug with good accuracy and precision.

Separation of enantiomers of deprenyl with various CDs in CE and the effect of enantiomer migration order on enantiomeric impurity determination of selegiline in active ingredients and tablets

Opposite affinity pattern of enantiomers of the antiparkinsonian chiral drug deprenyl (DEP) was observed towards various neutral and charged derivatives of -CD. The effect of the enantiomer migration order on the LOD of enantiomeric impurity of R-DEP (selegiline) was studied for the standard substances and in the tablets from three different suppliers. The influence of injection mode on the LOD of a minor enantiomeric impurity was also studied and the CE method was compared with the pharmacopoeial HPLC method using a commercially available chiral column Chiralcel OD-H. The optimized CE method was more suitable for low-level enantiomeric impurity determination in selegiline compared to the pharmacopoeial HPLC method.

Chiral separations by capillary electrophoresis: Recent developments and applications

This paper provides an overview of the different classes of chiral selectors that are used in CE. The main properties of every class are described, together with the mechanism of enantioseparation. Newly introduced selectors are also discussed. Pharmaceutical and biomedical applications published from January 2004 till March 2005 are summarized.

Characterization of sulfatedβ-cyclodextrins and determination of enantiomeric purity of (1R,2S)-ephedrine by capillary zone electrophoresis

Matrix-assisted laser-desorption ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy were employed to characterize two different sulfated beta-cyclodextrins (HS-beta-CD). It was found that the HS-beta-CDs have broad heterogeneity in terms of sulfation degree. The average sulfate contents were in the range of 6 to 8 per CD molecule. Furthermore the sugar moieties of both HS-beta-CDs were sulfated either at position 6 or at positions 2 and 6, but not at position 3. Enantiomeric separation by capillary zone electrophoresis (CZE) using the HS-beta-CDs as chiral selectors showed that these CDs exhibited similar chiral selectivity and resolution of the ephedrine enantiomers. One of the CDs was employed for the enantiomeric purity evaluation of (1R,2S)-ephedrine (or (-)-ephedrine) by capillary zone electrophoresis. Quantification was done by comparison between the corrected peak areas of the minor enantiomer and (-)-ephedrine.

Simultaneous chiral analysis of methamphetamine and related compounds by capillary electrophoresis

A capillary electrophoretic method for the simultaneous chiral analysis of nine cationic drugs (18 enantiomers) has been developed. These drugs are methamphetamine (MA), amphetamine, dimethylamphetamine, ephedrine (EP), norephedrine, methylephedrine, 3,4-methylenedioxymethamphetamine, 3,4-methylenedioxyamphetamine and 3,4-methylenedioxy-N-ethylamphetamine. The chiral selector, which was added to the electrolyte, was a mixture of beta-cyclodextrin and heptakis(2,6-di-O-methyl)-beta-cyclodextrin. The detection limits of all enantiomers were 0.1 microg/ml, and the intermediate precisions of migration time and peak area of within-run assays (n=6) were under 0.3% and 1.4%, respectively. The calibration curves of the peak area of (1R,2S)-(-)-EP and S-(+)-MA were linear in the range 0.2-500 microg/ml. This method was applicable to urine analysis.

Determination of enantiomeric amphetamines as metabolites of illicit amphetamines and selegiline in urine by capillary electrophoresis using modified beta-cyclodextrin

The determination of enantiomeric amphetamine and methamphetamine in urine samples is important in order to distinguish use of the prescription drug selegiline (metabolized to R(-)-A and R(-)-MA) from the illicit use of S(+)-A and S(+)-MA. For the analysis of enantiomeric amphetamine (A) and methamphetamine (MA) in biological samples, the optimization of analytical condition was performed by capillary electrophoresis using chiral selectors including beta-cyclodextrin, carboxymethyl-beta-cyclodextrin and 2-hydroxypropyl-beta-cyclodextrin. We have examined the factors to obtain the best chiral resolutions, separation efficiency and sensitivity, and wide concentration linearity. Optimum resolutions were achieved using 100 mM phosphate buffer, pH 2.5, containing 10 mM of carboxymethyl-beta-cyclodextrin. This method was applied for the quantitative determination of enantiomeric amphetamine and methamphetamine in urine samples obtained from patients taking illicit amphetamines or from rats and patients taking selegiline. Acceptable quantitative results in terms of resolution, precision, sensitivity and linearity were obtained from the real urine samples containing wide-ranging concentrations of A and MA by using two concentrations of internal standards, alpha(+)- (1 microg/ml) and beta-phenylethylamine (50 microg/ml).

Enantiomer separation of drugs by capillary electromigration techniques

The review summarizes the most recent developments in the field of enantioseparation of chiral drugs using capillary electromigration techniques. The basic principles of enantioseparations in CE are discussed. Recent developments in sample introduction, separation and detection in capillary electrophoresis and capillary electrochromatography are summarized. The applications are arbitrarily divided into the following three groups: (a) racemates and artificial mixtures of enantiomers, (b) drug forms and (c) chiral drugs and their metabolites in biological fluids. Among the various techniques involved the relatively new developments such as CEC in aqueous and nonaqueous buffers, on-line CE-MS coupling, etc. are emphasized.

Chiral separations in capillary electrophoresis

The marked increase in the number of communications on the utilization of electrophoresis for practical chiral separations within the last three years is the most evident, and the most important fact. It reveals that the basic period of intensive research in the field is finished. The search for chiral selectors discriminating racemates in a reasonably analytical manner and the study of both the mechanism and physicochemical aspects of the chiral discrimination process were the main features of that period. Here, we review the state of the art in the field and state the references of the related literature up to the end of 1998.

Capillary electrophoresis enantioseparation of drugs using beta-cyclodextrin polymer: intramolecular synergistic effect

Enantiomers of eight basic compounds of pharmaceutical interest were studied by capillary electrophoresis (CE) using a soluble cyclodextrin (CD) polymer and native CD as chiral selectors. The effects of the polymer concentration and the pH of the buffer solution on resolution were examined. It was found that the beta-CD polymer shows higher stereoselectivity than its parent cyclodextrin. Such improvement is due to the structural difference between beta-CD and beta-CD polymer. These results suggested the existence of an intramolecular synergistic effect in CE.

Methamphetamine--properties and analytical methods of enantiomer determination

Methamphetamine is one of the most frequently abused drugs of today. Due to its stereogenic center, it can exist as single enantiomer. Like many other chiral compounds, methamamphetamine enantiomers exhibit different pharmacological effects on living organisms. For this reason, it is necessary to develop enantioselective and sufficiently sensitive methods of determination. This review focuses on methamphetamine with an accent on analytical chemistry and especially on chiral separations of this toxicologically important compound.

Enantioselectivity in chiral capillary electrophoresis with polysaccharides

This review surveys enantiomer separation by capillary electrophoresis (CE) using polysaccharides as chiral selectors. Many ionic or electrically neutral polysaccharides, such as heparin, chondroitin sulfate, dextrin, etc., have been employed successfully for the CE separation of enantiomers. The operational conditions that affect the enantioselectivity of the chiral separation system will be described. The mechanism of enantioseparation will also be discussed briefly.

Controlling enantioselectivity in chiral capillary electrophoresis with inclusion-complexation

The separation of chiral compounds is of key importance in different fields of application, e.g., pharmaceutical, industrial, forensic, biological, clinical etc. Capillary electrophoresis (CE) is a powerful analytical method applied in chiral analysis and inclusion-complexation is one of the most frequently used mechanism to improve the selectivity of the enantiomeric separation. Cyclodextrins and their derivatives or modified crown-ethers have been successfully applied in CE for the enantiomeric separation of a wide number of analytes. This review surveys the separation of enantiomers by CE when chiral selectors, forming inclusion-complexation, are used. The control of enantioselectivity can be done carefully by considering several experimental parameters such as chiral selector type and concentration, pH, ionic strength and concentration of the background electrolyte, electroosmotic flow, organic modifier etc. The review presents a list of the latest separation of enantiomers by CE where inclusion-complexation plays a key role in the stereoselective separation mechanism.

Capillary electrophoretic separations of enantiomers using cyclodextrin-containing background electrolytes

The 1996 primary literature papers which deal with the separation of enantiomers using cyclodextrins are reviewed here. Though the majority of the papers still use the neutral native cyclodextrins or the neutral derivatized cyclodextrins as resolving agents, there was a significant increase in number of separations which relied on charged cyclodextrins, both weak electrolytes and strong electrolytes, as resolving agents. Also, there was an increase in the number of papers which reported binding constants and correlated them with other physical or chemical characteristics of the analytes. Several successful minor enantiomer determinations were presented, pushing the reliable quantitation levels below 0.1%. Work continued on the simultaneous use of neutral and charged cyclodextrins to improve separation selectivity or peak resolution.