Separation of fluoroquinolones in acidic buffer by capillary electrophoresis with contactless conductivity detection

A method to determine five fluoroquinolones (FQs), namely, rufloxacin (RUF), ciprofloxacin (CIP), enrofloxacin (ENO), gatifloxacin (GAT) and moxifloxacin (MOX), in acidic buffer by capillary electrophoresis (CE)-capacitively coupled contactless conductivity detection (C⁴D) technique is presented. Separation was carried out in a fused-silica capillary (42 cm × 50 μm) using a buffer composed of 10 mM tartaric acid, 14 mM sodium acetate and 15% (v/v) methanol at pH 3.8. The RSDs of the migration times and peak areas were 0.65% and 12.3% (intraday), 1.28% and 8.8% (interday), respectively. CE-C⁴D in combination with liquid–liquid extraction (LLE) as clean-up and preconcentration procedure, allows detection of the FQs in fortified chicken muscle samples with detection limits of 6.8–11.7 ng/g. This method shows potential in rapid determination of FQs in samples with complex matrix.     

Simultaneous determination of atropine,anisodamine, and scopolamine in plant extract by nonaqueous capillary electrophoresis coupled with electrochemiluminescence and electrochemistry dual detection

A rapid and simple method was demonstrated for the analysis of atropine, anisodamine, and scopolamine by nonaqueous capillary electrophoresis (NACE) coupled with electrochemiluminescence (ECL) and electrochemistry (EC) dual detection. The mixture of acetonitrile (ACN) and 2-propanol containing 1 M acetic acid (HAc), 20 mM sodium acetate (NaAc), and 2.5 mM tetrabutylammonium perchlorate (TBAP) was used as the electrophoretic buffer. Although a short capillary of 18 cm was used, the decoupler was not needed and the separation efficiency was good. The linear ranges of atropine, anisodamine, and scopolamine were 0.5–50, 5–2000, and 50–2000 μM, respectively. For six replicate measurements of 100 μM scopolamine, 15 μM atropine, and 200 μM anisodamine, the RSDs of ECL intensity, EC current, and migration time were less than 3.6%, 4.5%, and 0.3%, respectively. In addition, because the organic buffer was used, the working electrode (Pt) was not easily fouled and did not need reactivation. The method was also applied for the determination of these three alkaloids in Flos daturae extract.     

On-line stacking and sweeping capillary electrophoresis for detecting heroin metabolites in human urine

Heroin metabolites including morphine, codeine, and 6-acetylmorphine were determined by cation-selective exhaustive injection and sweeping micellar electrokinetic chromatography (CSEI–sweep-MEKC). Liquid–liquid extraction was used for urine pretreatment. An uncoated fused silica capillary (Ld = 30 cm, 50 μm ID) was filled with phosphate buffer (50 mM, pH 2.5) containing 30% methanol, then high conductivity buffer (100 mM phosphate, 41.3 kPa for 18 s) was followed. Samples were injected electrokinetically (20 kV, 300 s). The sweeping and separation were performed at −25 kV using phosphate buffer (20 mM, pH 2.5) and 80 mM sodium dodecyl sulfate. The baseline separation was done within 10 min. During method validation, the calibration curves were linear over a range of 50–500 ng/mL (r ≧ 0.994). The RSD and RE values in intra-day and inter-day assays were all below 20%, which showed good precision and accuracy. Their detection limits were 10 ng/mL (S/N = 3). The optimized method was applied to determine real urine samples from addicts. These samples were confirmed by liquid chromatography/mass spectrometry.     

Development and validation method for determination of fluoxetine and its main metabolite norfluoxetine by nonaqueous capillary electrophoresis in human urine

A simple, rapid and sensitive procedure using nonaqueous capillary electrophoresis (NACE) to measure fluoxetine and its main metabolite norfluoxetine has been developed and validated. Optimum separation of fluoxetine and norfluoxetine, by measuring at 230 nm, was obtained on a 60 cm × 75 μm capillary using a nonaqueous solution system of 7:3 methanol-acetonitrile containing 15 mM ammonium acetate, capillary temperature and voltage 25 °C and 25 kV, respectively and hydrodynamic injection. Paroxetine was used as internal standard. Good results were obtained for different aspects including stability of the solutions, linearity, and precision. Detection limits of 10 μg L⁻¹ were obtained for fluoxetine and its metabolite. This method has been used to determine fluoxetine and it main metabolite at clinically relevant levels in human urine. Before NACE determination, the samples were purified and enriched by means of extraction-preconcentration step with a preconditioned C₁₈ cartridge and eluting the compounds with methanol.     

Determination of ethylenediaminetetraacetic acid, ethylenediaminedisuccinic acid and iminodisuccinic acid in cosmetic products by capillary electrophoresis and high performance liquid chromatography

A capillary electrophoresis (CE) and a high performance liquid chromatography (HPLC) method are described for the simultaneous determination of ethylenediaminetetraacetic acid (EDTA), S,S′-ethylenediaminedisuccinic acid (EDDS) and R,S-iminodisuccinic acid (IDS) complexing agents as their Fe(III) complexes in cosmetics like shower cream and foam bath. The non-biodegradable EDTA is used in combination with biodegradable analogues like EDDS and IDS in many commercial products. The HPLC method involves separation by reversed-phase ion pair chromatography on a C₁₈ column using methanol-formate buffer (20 mM tetrabutylammonium hydrogen sulfate, 15 mM sodium formate adjusted to pH 4.0 with formic acid) (10:90, v/v) as mobile solvent at a flow rate of 0.8 mL min⁻¹ at 24 °C using UV detection at 240 nm. The CE separation was performed in a fused silica capillary of 50 μm i.d. with the total length of 50 cm with a 10 mM MES and MOPSO (pH 5.5) at an applied voltage of −25 kV. The samples were introduced by applying a 50 mbar pressure for 2 s. Absorbances at 215 and 225 nm were monitored for the detection of the complexes. The methodology performance of the two methods was evaluated in terms of linearity, limit of detection (LOD), limit of quantitation (LOQ) and reproducibility. The LOD values obtained from HPLC are low when compared with CE. The applicability of both the methods was demonstrated for the analysis of cosmetic products such as shower cream and foam bath. The results obtained by both CE and HPLC were found to be comparable and in good agreement.     

Far infrared-assisted extraction followed by capillary electrophoresis for the determination of bioactive constituents in the leaves of Lycium barbarum Linn.

In this work, a method based on capillary electrophoresis with amperometric detection and far infrared-assisted extraction has been developed for the determination of rutin, gentisic acid, and quercetin in the leaves of Lycium barbarum Linn. The effects of detection potential, irradiation time, and the voltage applied on the infrared generator were investigated to acquire the optimum analysis conditions. The detection electrode was a 300-μm-diameter carbon disc electrode at a detection potential of +0.90 V. The three analytes could be well separated within 12 min in a 40 cm length fused-silica capillary at a separation voltage of 12 kV in a 50 mM borate buffer (pH 9.2). The relation between peak current and analyte concentration was linear over about 3 orders of magnitude with the detection limits (S/N = 3) of 0.31, 0.48, and 0.78 μM for rutin, gentisic acid, and quercetin, respectively. The proposed method has been applied to determine the three bioactive constituents in real plant samples.     

Determination of bisphenol A and naphthols in river water samples by capillary zone electrophoresis after cloud point extraction

As a first attempt, cloud point extraction (CPE) was developed to preconcentrate bisphenol A (BPA), α-naphthol and β-naphthol prior to performing capillary zone electrophoresis (CZE) analysis. The parameters influencing the CPE efficiency, such as Triton X-114 concentrations, pH value, extraction time and temperature were systematically evaluated.After diluting with acetonitrile, the surfactant-rich phase of CPE can be injected directly into the CE instrument. The CZE baseline separation was achieved with running buffer (pH 9.5) composed of 50 mM sodium tetraborate in 30% (v/v) methanol, and an applied voltage of 25 kV. Under the optimized CPE and CZE conditions, an preconcentration factor of 50 times could be obtained and the limit of quantification for the three analytes were found to be 1.67 μg L⁻¹, 0.80 μg L⁻¹ and 0.67 μg L⁻¹ for BPA, α-naphthol and β-naphthol, respectively. The proposed methods have shown to be a green, rapid and effective approach for determination of three analytes present in river water samples.     

Laser induced fluorescence coupled to capillary electrophoresis for the determination of fluoroquinolones in foods of animal origin using molecularly imprinted polymers

A method for the simultaneous determination of four fluoroquinolones of veterinary use (ciprofloxacin, danofloxacin, enrofloxacin and sarafloxacin) in two complex matrixes, such as bovine raw milk and pig kidney, has been established and validated. The method is based on the use of capillary electrophoresis (CE) coupled with a very sensitive detection mode, such as laser induced fluorescence (LIF) detection, due to the fact the all the compounds selected show native fluorescence. In order to achieve high selectivity in the sample treatment procedure, a commercially available molecularly imprinted polymer has been used for the solid phase extraction of the analytes. Once the retention and elution processes were optimized, the final extract was analyzed by CE-LIF using a 325 nm He–Cd laser. Optimum separation was obtained in a 70 cm × 75 μm capillary using a 125 mM phosphoric acid solution at pH 2.8 with 36% methanol as background electrolyte. The method provided very low detection limits, ranging from 0.17 to 0.98 μg/kg for milk and 1.10 to 10.5 μg/kg for kidney, with acceptable precision and satisfactory recoveries.     

Development of a microbioreactor with ecto-nucleoside triphosphate diphosphohydrolase 2 (NTPDase2) immobilized on a polyacrylamide-coated capillary at the outlet

A simple and fast method of immobilization of cell membrane suspension containing human ecto-nucleoside triphosphate diphosphohydrolase 2 (NTPDase2) on a polyacrylamide-coated capillary was developed. The enzyme microbioreactor was prepared by hydrodynamic injection of a small plug of the polycationic electrolyte hexadimethrine bromide (HDB) followed by a suspension of an enzyme-containing membrane preparation. In order to shorten the enzyme assay time and to increase the throughput of the assay, the capillary was coated from the outlet end and all injections were performed from the outlet end of the capillary. For the monitoring of the enzymatic reaction, the substrate ATP dissolved in reaction buffer (140 mM NaCl, 5 mM KCl, 1 mM MgCl₂, 2 mM CaCl₂, and 10 mM Hepes, pH 7.4, internal standard: 10 μM UMP) in the absence or presence of inhibitor was injected electrokinetically and incubated in the microbioreactor for 1 min with 1 kV of applied voltage. Then, the electrophoretic separation of the reaction products was initiated by applying a constant current of 60 μA. A 50 mM phosphate buffer (pH 6.5) was used for the separations and the products were detected by UV absorbance at 260 nm. The new method was compared with an at-capillary-inlet method without immobilization of the enzyme. The results (K_m values, K_i values for inhibitor) obtained with both methods were similar and comparable with literature data. The developed outlet immobilized enzyme microreactor using a coated capillary is very fast, simple and most economic allowing multiple use of the enzyme.     

Determination of inorganic oxyanions of As and Se by HPLC-ICPMS

A liquid chromatographic separation of inorganic oxyanions of As (As(V) and As(III)) and Se (Se(VI) and Se(IV)) using mixed ion-pairing reagents followed by ICPMS detection is described. The separation was accomplished in less than 4 min on Capcell C18 RP column using mixed ion-pairing modifier containing 5 mM of butane sulfonic acid (BSA), 2 mM malonic acid, 0.30 mM hexane sulfonic acid (HSA) and 0.5% methanol of pH 2.5. All four species were resolved with retention times of 2.4, 2.6, 3.0, and 3.1 min for Se(VI), As(V), As(III), and Se(IV), respectively. The detection limits were less than 0.08 and 0.77 μg l⁻¹ for arsenic and selenium species, respectively. The relative standard deviation of the proposed method for arsenic (at 2.5 μg l⁻¹) and selenium (at 10 μg l⁻¹) was less than 3.7 and 4.8%, respectively. The technique was used to determine inorganic oxyanions of As and Se in water samples (tap, well, and river) and extracts of coal fly ash and sediment. Low power microwave digestion was employed for extraction from fly ash and sediment samples.     

Sensitive quantitative determination of oxymatrine and matrine in rat plasma by capillary electrophoresis with stacking induced by moving reaction boundary

A quantitative method of capillary electrophoresis with sample stacking induced by moving reaction boundary (MRB) was developed for sensitive determination of oxymatrine (OMT) and matrine (MT) in rat plasma. The experimental conditions were optimized firstly. Below are the optimized experimental conditions: 20 mM sodium formate solution (HCOONa, adjusted to pH 10.70 by ammonia) as sample solution, 3 min 14 mbar sample injection, 40 mM formic buffer (HCOOH-HCOONa, pH 2.60) as stacking buffer, 7 min 14 mbar injection of stacking buffer, 100 mM HCOOH-HCOONa (pH 4.80) as separation buffer, 73 cm capillary (effective length 64 cm), 21 kV voltage, 210 nm wavelength. Under the optimized conditions, higher than 60-fold sensitivity improvement of the stacking was simply achieved as compared with capillary zone electrophoresis, and the detectable limits obtained for OMT and MT were 0.26 and 0.19 μg mL⁻¹, respectively. Then, numerous demonstrations were carefully performed for the methodological validations of OMT and MT in rate plasma, including high specificity of method, good linearity (r = 0.9993 for OMT, r = 0.9991 for MT), fair wide linear concentration range (1.30-65.00 μg mL⁻¹ for OMT, 0.84-42.00 μg mL⁻¹ for MT), low limit of detection (1.03 μg mL⁻¹ for OMT, 0.38 μg mL⁻¹ for MT), less than 5% intra- and inter-day variance value, and higher than 96% recovery of OMT and MT in plasma. The developed method could be used for the trace analyses of OMT and MT in plasma and was finally used for the investigation on pharmacokinetic study of OMT in rat plasma.     

Determination of aflatoxins in food samples by automated on-line in-tube solid-phase microextraction coupled with liquid chromatography–mass spectrometry

A simple and sensitive automated method for determination of aflatoxins (B1, B2, G1, and G2) in nuts, cereals, dried fruits, and spices was developed consisting of in-tube solid-phase microextraction (SPME) coupled with liquid chromatography–mass spectrometry (LC–MS). Aflatoxins were separated within 8 min by high-performance liquid chromatography using a Zorbax Eclipse XDB-C8 column with methanol/acetonitrile (60/40, v/v): 5 mM ammonium formate (45:55) as the mobile phase. Electrospray ionization conditions in the positive ion mode were optimized for MS detection of aflatoxins. The pseudo-molecular ions [M+H]⁺ were used to detect aflatoxins in selected ion monitoring (SIM) mode. The optimum in-tube SPME conditions were 25 draw/eject cycles of 40 μL of sample using a Supel-Q PLOT capillary column as an extraction device. The extracted aflatoxins were readily desorbed from the capillary by passage of the mobile phase, and no carryover was observed. Using the in-tube SPME LC–MS with SIM method, good linearity of the calibration curve (r > 0.9994) was obtained in the concentration range of 0.05–2.0 ng/mL using aflatoxin M1 as an internal standard, and the detection limits (S/N = 3) of aflatoxins were 2.1–2.8 pg/mL. The in-tube SPME method showed >23-fold higher sensitivity than the direct injection method (10 μL injection volume). The within-day and between-day precision (relative standard deviations) at the concentration of 1 ng/mL aflatoxin mixture were below 3.3% and 7.7% (n = 5), respectively. This method was applied successfully to analysis of food samples without interference peaks. The recoveries of aflatoxins spiked into nuts and cereals were >80%, and the relative standard deviations were <11.2%. Aflatoxins were detected at <10 ng/g in several commercial food samples.     

Strategies for the on-line preconcentration and separation of hypolipidaemic drugs using micellar electrokinetic chromatography

Three strategies were investigated for the simultaneous separation and on-line preconcentration of charged and neutral hypolipidaemic drugs in micellar electrokinetic chromatography (MEKC). A background electrolyte (BGE) consisting of 20 mM ammonium bicarbonate buffer (pH 8.50) and 50 mM sodium dodecyl sulfate (SDS) was used for the separation and on-line preconcentration of the drugs. The efficiencies of sweeping, analyte focusing by micelle collapse (AFMC), and simultaneous field-amplified sample stacking (FASS) and sweeping, were compared for the preconcentration of eight hypolipidaemic drugs in different conductivity sample matrices. When compared with a hydrodynamic injection (5 s at 50 mbar, 0.51% of capillary volume to detection window) of drug mixture prepared in the separation BGE, improvements of detection sensitivity of 60-, 83-, and 80-fold were obtained with sweeping, AFMC and simultaneous FASS and sweeping, respectively, giving limits of detection (LODs) of 50, 36, and 38 μg/L, respectively. The studied techniques showed suitability for focusing different types of analytes having different values of retention factor (k). This is the first report for the separation of different types of hypolipidaemic drugs by capillary electrophoresis (CE). The three methods were validated then applied for the analysis of target analytes in wastewater samples from Hobart city.     

Development and validation of a capillary zone electrophoresis method for the determination of propranolol and N-desisopropylpropranolol in human urine

A simple, rapid and sensitive procedure using solid phase extraction and capillary zone electrophoresis for the determination of propranolol (a beta-blocker) and one of its metabolites, N-desisopropylpropranolol, has been developed and validated. The optimum separation of both analytes was obtained in a 37 cm × 75 μm fused silica capillary using 20 mmol/L phosphate buffer (pH 2.2) as electrolyte, at 25 kV and 30 °C, and hydrodynamic injection for 5 s. Prior to the electrophoretic separation, the samples were cleaned up and concentrated using a C₁₈ cartridge and then, eluted with methanol, allowing a concentration factor of 30.Good results were obtained in terms of precision, accuracy and linearity. The limits of detection were 28 and 30 μg/L for N-desisopropylpropranolol and propranolol, respectively. Additionally, a robustness test of the method was carried out using the Plackett-Burman fractional factorial model with a matrix of 15 experiments.The presented method has been applied to the determination of both compounds in human urine.     

Determination of terbinafine in pharmaceuticals and dialyzates by capillary electrophoresis

A capillary electrophoresis method has been developed for the separation and determination of terbinafine (TER) in various pharmaceutically relevant matrices. Capillary zone electrophoresis (CZE) separation and UV absorbance photometric detection were carried out in a 160 mm capillary tube with a 300 μm i.d., hydrodynamically (membrane) closed. The influences of pH, carrier cation and counterion on migration parameters of TER were studied and the following conditions were selected: a 20 mmol l⁻¹ glycine running buffer adjusted to pH 2.7 with acetic acid, 0.2% (w/v) methylhydroxyethylcellulose (m-HEC) as an electro-osmotic flow (EOF) suppressor, a 250 μA driving current, and 20 °C. The optimized separation conditions were convenient for the determination of TER in commercial tablets and spray and in dialyzates. Here, the dialysis was used to investigate in vitro permeation of TER through the skin from the gel. The samples of dialyzates were examined with and without simple extraction procedure and the results were compared. A permeation profile of the drug present in the gel of given composition was obtained analyzing pretreated samples. The proposed electrophoretic method was successfully validated. It was suitable for the simple, sensitive, rapid and highly reproducible assay of TER. CZE analysis was completed within 5.5 min. The detection limit of TER was 1.73 μmol l⁻¹ at a 224 nm detection wavelength. The intra- and inter-laboratory precisions over the concentration range 6.0-60.0 μmol l⁻¹ were between 0.32-0.69% and 1.04-1.44% including R.S.D. of migration times and peak areas, respectively. The mean absolute recoveries of drugs from samples were found to be 98.34 (tablets) and 99.47% (spray). It is suggested that there are potentialities to determine TER present in unpretreated complex samples, as CZE in a hydrodynamically closed separation system may be easily on-line combinable with purification and preconcentration CE modes (e.g., isotachophoresis, ITP).     

Determination of sinomenine in Sinomenium acutum by capillary electrophoresis with electrochemiluminescence detection

A Ru(bpy)₃²⁺-based electrochemiluminescence (ECL) detection coupled with capillary electrophoresis (CE) has been established for the determination of sinomenine for the first time. Optimum separation was achieved with a fused-silica capillary column (50 cm × 25 μm i.d.) and a background electrolyte of 50 mM sodium phosphate (pH 5.0) at a separation voltage of 15 kV. The content of sinomenine was detected by ECL at the detection voltage of 1.15 V (versus Ag/AgCl) with 5 mM Ru(bpy)₃²⁺ in 75 mM phosphate solution (pH 8.0) when a chemically modified platinum electrode by europium(III)-doped prussian blue analogue (Eu-PB) was used as a working electrode. Under the optimized conditions, the ECL intensity was in proportion to sinomenine concentration in the range from 0.01 to 1.0 μg mL⁻¹ with a detection limit of 2.0 ng mL⁻¹ (3σ). The relative standard derivations of migration time and ECL intensity were 0.93 and 1.11%, respectively. The level of sinomenine in Sinomenium acutum Rehd. et Wils was easily determined with recoveries between 98.6 and 102.7%.     

High-performance liquid chromatographic determination of glyphosate in water and plant material after pre-column derivatisation with 9-fluorenylmethyl chloroformate

This paper describes a robust and sensitive HPLC method for determination of glyphosate in water and plant material after pre-column derivatisation with 9-fluorenylmethyl chloroformate (FMOC-Cl) using single and coupled polymeric amino columns, respectively. New findings about optimisation of the derivatisation reaction and chromatographic behaviour of glyphosate and AMPA on polymeric amino column are also presented.The best HPLC conditions for the separation of glyphosate and AMPA in water samples were achieved using a single polymeric amino column and mobile phase at pH 10 which contained 55% (v/v) acetonitrile and 50 mM phosphate buffer. The method was validated by analysing 10 fortified rainwater samples at a level of 1 μg/l. The average recovery was 94% with relative standard deviation (R.S.D.) of 5.4% and the method detection limit of 0.16 μg/l.The HPLC separation of glyphosate (only) in plant material entailed the coupling of two polymeric amino columns via a switching valve to separate interfering products from the desired analyte. The method was validated using grass samples spiked at the level of 1 mg/kg and gave a method detection limit of 0.3 mg/kg for glyphosate and a recovery of 82.4% with R.S.D. of 10.3%.     

Capillary electrophoresis-electrospray ionization mass spectrometry using uncoated fused-silica capillaries and alkaline buffer solution for the analysis of small carboxylic acids

A simple and cost-effective capillary electrophoresis/mass spectrometric (CE/MS) method for the analysis of small carboxylic acids including succinate, malate, tartarate, maleinate and citrate, is described. All CE/MS experiments were performed with uncoated fused-silica capillaries and with alkaline volatile buffer solution (ammonium formate buffer, pH 10). Since sheath liquids have significant effects on the sensitivity in typical CE/MS applications, the effects of type and flow rate of the sheath liquids on the sensitivity of carboxylic acids were investigated. As the result, the best sensitivity was obtained with the alkaline sheath liquid (5 mM ammonium hydroxide in water/methanol (50/50, v/v) solution) at 6 μl min⁻¹. With the alkaline volatile buffer solution, sufficient electroosmotic flow (EOF) to carry all small carboxylic acids toward the cathode (MS side) was obtained, although all analytes had different electrophoretic mobilities toward the anode (the CE inlet). Taking advantage of the relatively higher EOF velocity, several carboxylic acids could be detected by MS in ESI-negative mode with a short analysis time. The R.S.D. values (n=5) for the migration time and the peak area of the carboxylic acids tested were less than 0.6 and 4.2%, respectively. The method was applied to the CE/MS analysis of carboxylic acids in apple juice to demonstrate the applicability to real samples.     

In-vial liquid–liquid microextraction-capillary electrophoresis method for the determination of phenolic acids in vegetable oils

An in-vial liquid–liquid microextraction method was developed for the selective extraction of the phenolic acids (caffeic, gallic, cinnamic, ferulic, chlorogenic, syringic, vanillic, benzoic, p-hydroxybenzoic, 2,4-dihydroxybenzoic, o-coumaric, m-coumaric and p-coumaric) in vegetable oil samples. The optimised extraction conditions for 20 g sample were: volume of diluent (n-hexane), 2 mL; extractant, methanol: 5 mM sodium hydroxide (60:40; v/v); volume of extractant, 300 μL (twice); vortex, 1 min; centrifugation, 5 min. Recoveries for the studied phenolic acids were 80.1–119.5%. The simultaneous determination of the phenolic acid extracts was investigated by capillary electrophoresis (CE). Separations were carried out on a bare fused-silica capillary (50 μm i.d. × 40 cm length) involving 25 mM sodium tetraborate (pH 9.15) and 5% methanol as CE background electrolyte in the normal polarity mode, voltage of 30 kV, temperature of 25 °C, injection time of 4 s (50 mbar) and electropherograms were recorded at 200 nm. The phenolic acids were successfully separated in less than 10 min. The validated in-vial LLME-CE method was applied to the determination of phenolic acids in vegetable oil samples (extra virgin olive oil, virgin olive oil, pure olive oil, walnut oil and grapeseed oil). The developed method shows significant advantages over the current methods as lengthy evaporation step is not required.     

Enantiomeric analysis of rivastigmine in pharmaceuticals by cyclodextrin-modified capillary zone electrophoresis

Chiral separation method development is usually very time-consuming due to the diversity in chemical structures of pharmaceutical drug substances as well as the suitable separation conditions and the problem to choose the appropriate chiral selector. This paper shows capillary zone electrophoresis (CZE) which was developed for chiral separation of a basic compound - rivastigmine (RIV) using 30 cm × 50 μm i.d. polyacrylamide (PAA)-coated fused-silica capillary (effective length 20 cm), amine-modified phosphate buffer of pH 2.5 and sulfated-β-CD (S-β-CD) as chiral selector. Other selected native or derivatized cyclodextrins (CDs) were also tested: β-CD (5, 30 mM), carboxymethyl-β-CD (5, 30 mM), dimethyl-β-CD (15 mM), hydroxypropyl-β-CD (5, 30 mM), hydroxypropyl-α-CD (5, 30 mM) and hydroxypropyl-γ-CD (5, 30 mM). Complete enantiomeric separation of RIV was achieved at 20 kV, 18 °C and detection at 200 nm within 8 min with R.S.D. for the absolute migration time reproducibility of less than 2.1%. Rectilinear calibration range was 5.0-500.0 μM of each enantiomer (r = 0.9994-0.9995). The CZE method proposed was used for the control of chiral purity of pharmaceutically active S-RIV and for the analysis of Exelon caps preparation.