Separation and determination of five major opium alkaloids with mixed mode of hydrophilic/cation-exchange monolith by pressurized capillary electrochromatography

A method for the separation and determination of five major opium alkaloids (narcotine, papaverine, thebaine, codeine, and morphine) in pericarpium papaveris by pressurized CEC (pCEC) with monolithic column has been developed. Under the optimum condition, linear calibration ranges of narcotine, papaverine, thebaine, codeine, and morphine were obtained as 2-85, 2-85, 5-75, 10-65, and 10-65 microg/mL, respectively. LODs of these analytes were 1.5-6.0 microg/mL. The RSD (n=7) of the migration time and peak area were 1.94-5.24 and 4.05-8.21%, respectively. The proposed method was successfully applied to the analysis of pericarpium papaveris samples. Average recoveries of 79.0-95.9% at different fortified levels of alkaloids were achieved with RSD less than 4.6%. Meanwhile, the mechanism of the separation of the alkaloids on the monolithic column was also discussed. The result showed that the separation of alkaloids was mainly based on the mixed mode of hydrophilic interaction (HI) and cation exchange.     

Enantiomeric separation and quantification of ephedrine-type alkaloids in herbal materials by comprehensive two-dimensional gas chromatography

The separation of ephedrine-type alkaloids and their enantiomers in raw herbs and commercial herbal products was investigated by carrying out enantioselective separation in the first-dimension column (containing beta-cyclodextrin as the chiral selector) of a comprehensive two-dimensional gas chromatography (GC x GC) system, whereas a polar polyethylene glycol capillary column was used for separation in the second dimension. Naturally occurring ephedrine-type alkaloids and their synthetic analogues (enantiomeric counterparts) were adequately resolved from each other, as well as from potential interference species in the sample matrix using GC x GC, whereas single column GC analysis was unable to separate all the alkaloids of interest. Detection limits in the order of 0.1-1.3 microg/mL and linearity of calibration with R(2)>or=0.999 over approximately the range of 0.5-100 microg/mL for the quantitative determination of various ephedrine-type alkaloids were obtained. The commercial herbal products tested contained mostly (-)-ephedrine, (+)-pseudoephedrine, (-)-N-methylephedrine and (-)-norephedrine, with concentrations in the range of 40-2100, 0-1,300, 15-300 and 0-30 microg/g of the product, respectively, and repeatability of analysis was generally in the range of 1-5%. The present GCxGC method is effective and useful for the determination of the dosage levels of the principle ephedrine-type alkaloids in commercial health supplements and complex raw herb formulations, as well the differentiation of ephedrine-containing products that were derived from natural plant or synthetic sources, e.g., simply by visualizing the presence or absence of the enantiomeric pairs of (+/-) ephedrine and (+/-)-N-methylephedrine in the GC x GC chromatograms.     

Determination of quinolizidine alkaloids in traditional Chinese herbal drugs by nonaqueous capillary electrophoresis.

A rapid method for the determination of quinolizidine alkaloids by nonaqueous capillary electrophoresis was developed. A total of 10 alkaloids (matrine, sophocarpine, oxymatrine, oxysophocarpine, sophoridine, cytisine, sophoramine, aloperine, lehmannine and dauricine) could be easily separated within 18 min. A running buffer composed of 50 mM ammonium acetate, 10% tetrahydrofuran and 0.5% acetic acid in methanol was found to be the most suitable for this separation. Five of these alkaloids were selected for further studies. The linear calibration ranges were 2.51-50.1 microg/ml for sophoridine and sophocarpine, 2.71-54.2 microg/ml for matrine, 3.30-65.9 microg/ml for oxymatrine, and 3.10-62.0 microg/ml for oxysophocarpine. The recovery of the five alkaloids was 98.0-101.3% with relative standard deviations from 1.03 to 2.68% (n=5). The limits of detection for all 10 alkaloids were over the range 0.93-2.31 microg/ml. The method was successfully applied to the phytochemical analysis of alkaloid extracts from three commonly used traditional Chinese herbal drugs: Sophora flavescens Ait. (Kushen), S. alopecuroides L. (Kudouzi or Kugancao) and S. tonkinensis Gapnep (Shandougen).     

Determination of scopolamine, atropine and anisodamine in Flos daturae by capillary electrophoresis.

A capillary electrophoresis method was developed for the separation and determination of tropane alkaloids in Flos daturae plants. Separation was performed on a fused silica capillary(42.1 cm x 50 microm i.d.) at an applied voltage of 20 kV. Scopolamine, atropine and anisodamine were well separated in the buffer of 50 mmol/L phosphate buffer (pH 5.0) containing 20% (v/v) tetrahydrofuran (THF). Beer's law was obeyed in the range of concentration of 2.4-21.8 microg/mL for scopolamine, 4.0-36.0 microg/mL for atropine and 2.6-23.7 microg/mL for anisodamine, respectively, and the correlation coefficients were over 0.999 (n = 6). The developed method was applied for the analysis of herb samples.     

Microemulsion electrokinetic chromatography with laser-induced fluorescence detection for sensitive determination of ephedrine and pseudoephedrine

A selective and sensitive microemulsion electrokinetic chromatography with laser-induced fluorescence detection method was developed for the quantification of ephedrine (E) and pseudoephedrine (PE) derivatized with 4-chloro-7-nitrobenzo-2-oxa-1, 3-diazol. By a series of optimization, a running buffer composed of 20 mM borate + microemulsion (23.3 mM Sodium dodecyl sulfate/180.85 mM 1-butanol/16.4 mM n-heptane) +8% acetonitrile was applied for the separation of the derivatives. A linear relationship for E and PE was obtained in the range of 0.058-11.58 microg.mL(-1) (correlation coefficient: 0.9993 for E, 0.9995 for PE), and the detection limits for E and PE were 5.3 and 3.9 ng.mL(-1). The method was applied to the analysis of the two alkaloids in Chinese traditional herbal preparations with recoveries in the range of 96.9-105.4%.     

Analysis of yohimbine alkaloid from Pausinystalia yohimbe by non-aqueous capillary electrophoresis and gas chromatography-mass spectrometry

In the present work, the qualitative and quantitative analysis of Pausinystalia yohimbe-type alkaloids in the barks of Rubiaceae species is presented using different analytical approaches. Extracts of P. yohimbe were first examined by GC-MS and the major alkaloids were identified. The quantitation of yohimbine was then accomplished by non-aqueous CE (NACE) with diode array detection. This approach was selected in order to use a running buffer fully compatible with samples in organic solvent. In particular, a mixture of methanol containing ammonium acetate (20 mM) and glacial acetic acid was used as a BGE. The same analytical sample was subjected to GC-MS and NACE analysis; the different selectivity displayed by these techniques allowed different separation profiles that can be useful in phytochemical characterization of the extracts. The linear calibration ranges were all 10-1000 microg/mL for yohimbine by GC-MS and NACE analysis. The recovery of yohimbine was 91.2-94.0% with RSD 1.4-4.3%. The LOD for yohimbine were 0.6 microg/mL by GC-MS and 1.0 microg/mL by NACE, respectively. The GC-MS and NACE methods were successfully validated and applied to the quantitation of yohimbine.     

Simultaneous determination of anthraquinones in radix Polygoni multiflori by capillary gas chromatography coupled with flame ionization and mass spectrometric detection

A rapid, accurate and reliable analytical method was developed for the simultaneous determination of five major anthraquinones, aloe-emodin, chrysophanol, emodin, physcion, and rhein, in radix Polygoni multiflori, a traditional Chinese herbal medicine. The method comprises a fast ultrasonic extraction with methanol and derivatization with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA)+1% trimethylchlorosilane (TMCS) followed by capillary gas chromatographic (GC) separation. The effect of reaction time on the derivatization of anthraquinones was examined. A baseline separation of the anthraquinone and internal standard derivatives was achieved in 15min. The detection limits range from 0.22 to 0.60microg/mL for the five anthraquinones. The calibration curves are linear over the concentration range studied (from the detection limits to 40.0microg/mL) with the squares of correlation coefficients, R2, greater than 0.998. The developed method was successfully applied to the simultaneous determination of anthraquinones in radix P. multiflori samples. The peak identification was confirmed using GC-MS. The contents of anthraquinones in radix P. multiflori samples studied were 27.41, 289.6, 64.22, 202.1, 288.6microg/g for chrysophanol, emodin, aloe-emodin, physcion, rhein, respectively. All relative standard deviations are less than 3.2%. The recoveries range from 80.2% to 119.3% for the five analytes. To the authors' best knowledge, this is the first GC method reported for the simultaneous determination of the five anthraquinones in radix P. multiflori.     

Analysis of ephedra-alkaloids using sweeping and cation-selective exhaustive injection and sweeping micellar electrokinetic chromatography methods

Two stacking methods of capillary electrophoresis (CE) were developed for the separation of very dilute solutions of ephedra-alkaloids, namely ephedrine, pseudoephedrine, methylephedrine, methylpseudoephedrine, norephedrine, and norpseudoephedrine. A sweeping method which uses a carrier comprised of phosphoric acid, sodium dodecyl sulfate (SDS), diethylamine and acetonitrile permits the detection of the alkaloids down to the 10(-1) microg/mL level, and the cation-selective exhaustive injection and sweeping micellar electrokinetic chromatography (CSEI-Sweep-MEKC) method using phosphoric acid, SDS, and acetronitrile as electrolytes can detect down to the 10(-3) microg/mL level. The former requires the conductance of the sample solution to be adjusted beforehand, and only five peaks were observed, two of which were overlapped. The latter is capable of separating the six alkaloids but has a somewhat poorer reproducibility. Using an optimized injection time, it was found that the more diluted a solution is, the greater the sweeping effect will be. The CSEI-Sweep-MEKC method with a 600 s injection time and a 10(-1) microg/mL solution concentration provides an amplification effect of approximately 10(4). The method is suitable for analyses of dilute herb drug extracts and mouse sera. The effect of buffers on the separation and validation of the methods in this study are also discussed.     

Determination of anthocyanins in cranberry fruit and cranberry fruit products by high-performance liquid chromatography with ultraviolet detection: single-laboratory validation

A single-laboratory validation study was conducted on an HPLC method for the detection and quantification of cyanidin-3-O-galactoside (C3Ga), cyanidin-3-O-glucoside (C3GI), cyanidin-3-O-arabinoside (C3Ar), peonidin-3-O-galactoside (P3Ga), and peonidin-3-O-arabinoside (P3Ar) in cranberry fruit (Vaccinium macrocarpon Aiton) raw material and finished products. An extraction procedure using a combination of sonication and shaking with acidified methanol was optimized for all five anthocyanins in freeze-dried cranberry fruit and finished products (commercial extract powder, juice, and juice cocktail). Final extract solutions were analyzed by HPLC using a C18 RP column. Calibration curves for all anthocyanin concentrations had correlation coefficients (r2) of > or = 99.8%. The method detection limits for C3Ga, C3Gl, C3Ar, P3Ga, and P3Ar were estimated to be 0.018, 0.016, 0.006, 0.013, and 0.011 microg/mL, respectively. Separation was achieved with a chromatographic run time of 35 min using a binary mobile phase with gradient elution. Quantitative determination performed in triplicate on four test materials on each of 3 days (n = 12) resulted in RSD(r) from 1.77 to 3.31%. Analytical range, as defined by the calibration curves, was 0.57-36.53 microg/mL for C3Ga, 0.15-9.83 microg/mL for C3GI, 0.28-17.67 microg/mL for C3Ar, 1.01-64.71 microg/mL for P3Ga, and 0.42-27.14 microg/mL for P3Ar. For solid materials prepared by the described method, this translates to 0.06-3.65 mglg for C3Ga, 0.02-0.98 mg/g for C3Gl, 0.03-1.77 mg/g for C3Ar, 0.10-6.47 mg/g for P3Ga, and 0.04-2.71 mg/g for P3Ar.     

Determination of quinolizidine alkaloids in Sophora flavescens and its preparation using capillary electrophoresis

A simple and accurate capillary electrophoresis method was developed for the determination of four quinolizidine alkaloids in Sophora flavescens and Kuhuang injection. Optimum separation of the analytes was obtained on a 65 cm x 75 microm i.d. uncoated fused-silica capillary using a aqueous buffer system of 60 mmol L(-1) sodium borate at pH 8.5, with applied voltage and capillary temperature of 12 kV and 25 degrees C, respectively. Detection wavelength was set at 204 nm and jatrorrhizine was used as the internal standard. Good linear relationships between peak-area ratios and concentrations of the analytes were observed over the concentration range 0.044-0.792 mg mL(-1) for matrine, 0.142-1.926 mg mL(-1) for oxymatrine, 0.0377-0.3393 mg mL(-1) for sophocarpine and 0.0664-1.062 mg mL(-1) for sophoridine. The recoveries of four alkaloids ranged between 93.08 and 101.4% with relative standard deviations from 0.7 to 9.2% (n = 6) as determined by standard addition. The limits of detection for four alkaloids were determined to be over the range 8.8-48.0 microg mL(-1). Contents of four alkaloids in Sophora flavescens and three alkaloids in Kuhuang injection were successfully determined under the optimum conditions.     

Simultaneous determination of phenytoin and dextromethorphan in urine by solid-phase extraction and HPLC-DAD

A rapid and simple high-performance liquid chromatographic method with photodiode array detection was developed for the separation and the simultaneous determination of phenytoin and dextromethorphan in human urine. Analysis was performed in less than 4.5 min in isocratic mode on a reversed-phase C18 column (5 microm; 150 x 4.6 mm) using a mobile phase composed of acetonitrile-buffer phosphate 0.01 M (60:40, v/v) adjusted to pH 6.0, at 1 mL/min flow rate and UV absorbance at 210 nm. The elution order of analytes was dextromethorphan (DXM), Internal Standard (IS), and phenytoin (PHT). Calibration curves were linear in the 7.5-25 microg/mL range for PHT and in the 10-30 microg/mL range for DXM. Spike recoveries for urine samples prepared at three spiking levels ranged from 97.8 to 102.3% for PHT and from 94.8 to 100.4% for DXM. The detection limit (LOD) values ranged from 0.08 microg/mL for PHT to 0.5 microg/mL for DXM. The quantitation limit (LOQ) values ranged from 0.3 microg/mL for PHT to 1.6 microg/mL for DXM. The sample preparation method involves a rapid and simple procedure based on solid-phase extraction using a C18 reversed-phase column. Validation of the optimised method was carried out according to the ICH guidelines. The method developed in this study allows the reliable simultaneous analysis of PHT and DXM, drugs that were never quantified together in previously reported analytical methods. The described method has the advantage of being rapid and easy and it could be applied in therapeutic monitoring of these drugs in human urine of epileptic patients.     

Separation and determination of toxic pyrrolizidine alkaloids in traditional Chinese herbal medicines by micellar electrokinetic chromatography with organic modifier

A simple and rapid micellar electrokinetic chromatography (MEKC) method was developed for the separation and determination of four toxic pyrrolizidine alkaloids (PAs) (senkirkine, senecionine, retrorsine, and seneciphylline) in two traditional Chinese herbal medicines (Qian liguang and Kuan donghua). Separation was performed in the running buffer consisting of 20 mM borate, 30 mM SDS, and 20% methanol at pH 9.1. With the optimized separation conditions, four PAs were separated in 17 min by a single run. The calibration curves showed good linearity with correlation efficiencies (R(2)) between 0.9940 and 0.9988. RSDs in migration time and peak area were 0.31, 0.40, 0.39, 0.48% and 3.28, 3.48, 4.16, 3.42% for senkirkine, senecionine, retrorsine, and seneciphylline, respectively. Limits of detection (S/N = 3) varied from 1.19 to 2.70 microg/mL. The proposed method was applied to determine the PAs extracted from Chinese herbal medicines (Qian liguang and Kuan donghua). PA of senkirkine in Kuan donghua was detected and the amount was found to be 79.1 microg/g. The results obtained indicate that the proposed MEKC method could potentially become an effective alternative tool for qualification control and quantitative analysis of herbal medicines in pharmaceutical industry.     

Nonaqueous capillary electrophoresis-electrospray ionization-ion trap-mass spectrometry analysis of pyrrolo- and pyrido[1,2-a]azepine alkaloids in Stemona

Stemona alkaloids represent an outstanding class of natural compounds due to their pharmacological profile and their complex and unusual molecular structures. The aim of this study was the development of the first CE method for the separation, identification and quantification of these pyrrolo- and pyrido[1,2-a]azepine derivatives in three Stemona species. The best results were obtained with a NACE-ESI-IT-MS method, utilizing an electrolyte of 50 mM ammonium acetate, 1 M acetic acid and 10% methanol in ACN and a separation voltage of 30 kV. Samples were injected voltage-assisted with 20 kV for 1 s. Isopropanol:water (1:1) was used as ESI sheath liquid at a flow rate of 3 microL/min. The assay was applied for the qualitative profiling of Stemona alkaloids in S. curtisii, S. collinsae and S. tuberosa. For unambiguous peak assignment of more than forty unidentified alkaloids MS/MS experiments were performed and fragmentation patterns studied. Subsequently the method was validated for the quantitative determination of four selected derivatives (RSD inter- and intraday <6%, LODs <7.5 microg/mL, LOQs <25.0 microg/mL, for all analytes, recovery rates >98.9%) in several Stemona sp. extracts.     

Assay of aromatic amino acid enantiomers in rice-brewed suspensions by chiral ligand-exchange CE

The aim of this work was to assay seasoning D- or L-aromatic amino acids (AAs) in rice-brewed suspensions, Laozao in Chinese, by chiral ligand-exchange CE with UV detection and Zn(II) complex as a chiral selecting system. Resolution and peak retention were found to be parallel to the basicity of the AA chiral ligands, and basic L-Arg was known to work the best at pH 8.20 compared with L-Lys and other AA ligands. Baseline separation of DL-aromatic AAs and partially separation of some FMOC-labeled nonaromatic AAs have been achieved using a running buffer of 5 mM ammonium acetate, 100 mM boric acid, 3 mM ZnSO(4), and 6 mM L-Arg at pH 8.20. The aromatic amino acids in four brands of Laozao were measured in a range of 0.25-20 microg/mL for Typ, 1.00-120 microg/mL for Phe, and 2.50-200 microg/mL for Tyr, with linear regression coefficient all over 0.999. The LOD (S/N=3) was 0.15 microg/mL for Typ, 0.50 microg/mL for Phe, and 1.25 microg/mL for Tyr. The recovery of the method determined by spiking with the supernates of Laozao as background was 94.0-112.9%. The RSDs of migration time and peak area measured from six injections of tyrosine were 0.2 and 2.7%, respectively, for run-to-run, and 1.6 and 3.2%, respectively for day-to-day. Interestingly, there were only L-Trp, D-Tyr, and L-Tyr found in the assayed four brands of Laozao. They may serve as an index to recognize the brand of Laozao.     

Determination of active components in Cynanchum chinense R. Br. by capillary electrophoresis

A method for the determination of 7-O-alpha-l-rhamnopyranosyl-kaempferol-3-O-beta-d-glucopyranoside (GL) and 7-O-alpha-l-rhamnopyranosyl-kaempferol-3-O-alpha-l-rhamnopyranoside (RH) in the traditional Chinese herb Cynanchum chinense R. Br. by capillary electrophoresis has been developed. With botate buffer (30 mmol/L, pH 9.50) as running buffer and an applied voltage of 20 kV, the compounds were completely separated within 6 min and detected at UV 254 nm. The correlation coefficients of the calibration curves for GL and RH were 0.9990 and 0.9992, respectively, over the concentration ranges (15.0-1000.0 and 12.0-1000.0 microg/mL), and the recoveries were from 91.4 to 107.1%.     

Resonance Rayleigh scattering for detection of proteins in HPLC

An HPLC-resonance Rayleigh scattering (RRS) (HPLC-RRS) detection system is described for separation and detection of proteins. This system is based on the modification of a commercial HPLC instrument involving the addition of a pump and a T-shaped interface, and a common fluorescence detector was used for detection. The detection principle is based on the change of RRS intensity of the ion-association complex formed from biebrich scarlet (BS) and protein. The RRS signal was detected at lambdaex=lambdaem=376 nm. The utility of the presented method was demonstrated by the separation and determination of four proteins involving cytochrome (Cyt-c), lysozyme (Lys), HSA, and gamma-globulin (gamma-Glo). An LOD of 0.2-1.0 microg/mL was reached and a linear range was found between peak area and concentration in the range of 0.20-3.0 microg/mL for Cyt-c, 0.25-2.5 microg/mL for Lys, 1.5-10 microg/mL for HSA, and 2.0-15 microg/mL for gamma-Glo, with linear regression coefficients all above 0.99. The method presented has been applied to determine HSA and gamma-Glo in human serum samples synchronously.     

Enantioselective HPLC-UV method for determination of eslicarbazepine acetate (BIA 2-093) and its metabolites in human plasma

Eslicarbazepine acetate (BIA 2-093) is a novel central nervous system drug undergoing clinical phase III trials for epilepsy and phase II trials for bipolar disorder. A simple and reliable chiral reversed-phase HPLC-UV method was developed and validated for the simultaneous determination of eslicarbazepine acetate, oxcarbazepine, S-licarbazepine and R-licarbazepine in human plasma. The analytes and internal standard were extracted from plasma by a solid-phase extraction using Waters Oasis HLB cartridges. Chromatographic separation was achieved by isocratic elution with water-methanol (88:12, v/v), at a flow rate of 0.7 mL/min, on a LichroCART 250-4 ChiraDex (beta-cyclodextrin, 5 microm) column at 30 degrees C. All compounds were detected at 225 nm. Calibration curves were linear over the range 0.4-8 microg/mL for eslicarbazepine acetate and oxcarbazepine, and 0.4-80 microg/mL for each licarbazepine enantiomer. The overall intra- and interday precision and accuracy did not exceed 15%. Mean relative recoveries varied from 94.00 to 102.23% and the limit of quantification of the assay was 0.4 microg/mL for all compounds. This method seems to be a useful tool for clinical research and therapeutic drug monitoring of eslicarbazepine acetate and its metabolites S-licarbazepine, R-licarbazepine and oxcarbazepine.     

Continuous capillary electrophoresis with flow injection and its application for determination of Ephedrine and Pseudo-ephedrine in Chinese medicinal preparations

This article presents a new, simple and rapid continuous separation method by combination of flow injection with capillary electrophoresis designed for the analysis of basic traditional Chinese medicines. The device was produced using commercial capillary and components readily available in analytical laboratory. In double-T configuration, the designed horizontal separation channel was 25 microm i.d. x 146 mm length (an effective separation length of 93 mm) quartz capillary, with two vertical elicitation arms produced from 0.5 mm i.d. pump tubing. The capillary was embedded in a 40 x 20 x 3 mm organic glass base. Using the double-T configuration, continuous introduction of a series of samples was achieved. More than 3.00 resolution for ephedrine and pseudo-ephedrine were obtained using 100 mm borate buffer (pH 9.80) within 8 min in 25 microm separation channel with an electrical field strength of 137 V/cm (UV detection at 215 nm). The linear calibration range was 50-1500 microg/mL (ephedrine, r = 0.9982; pseudo-ephedrine, r = 0.9990) for both analytes. The limits of detection were 2.65 micro g/mL for ephedrine and 2.92 microg/mL for pseudo-ephedrine. In this device, the contents of ephedrine and pseudo-ephedrine in five Chinese medicinal preparations were determined with RSDs (n = 5) in range 1.16-4.51% and recoveries in range 90.4-114.6%.     

Enhanced separation of purine and pyrimidine bases using carboxylic multiwalled carbon nanotubes as additive in capillary zone electrophoresis

This paper describes the enhanced separation of adenine (A), hypoxanthine (HX), 8-azaadenine (8-AA), thymine (T), cytosine (C), uracil (U) and guanine (G) by CZE dispersing carboxylic multiwalled carbon nanotubes (c-MWNTs) into the running buffer. The effect of important factors such as c-MWNT nanoparticle concentration, the acidity and concentration of running buffer, and separation voltage were investigated to acquire the optimum conditions. The seven purine and pyrimidine bases could be well separated within 16 min in a 35 cm effective length fused-silica capillary at a separation voltage of +8.0 kV in a 23 mM tetraborate buffer (pH 9.2) containing 8.0 x 10(-5) g/mL c-MWNTs. Under the optimal conditions, the linear ranges were of 2-250 microg/mL for A (R2 = 0.995), 3-200 microg/mL for U (R2 = 0.990) and G (R2 = 0.992), 3-250 microg/mL for T (R2 = 0.998), 2-200 microg/mL for C (R2 = 0.985) and 4-200 microg/mL for HX (R2 = 0.988) and 8-AA (R2 = 0.990). The detection limits were 0.9 microg/mL for A (S/N = 3), 2.4 microg/mL for U, 2.0 microg/mL for T, 1.5 microg/mL for C, 2.5 microg/mL for G and 3.0 microg/mL for HX and 8-AA. The proposed method was successfully applied for determining five purine and pyrimidine bases in yeast RNA.     

Application of dimethyl-beta-cyclodextrin as a chiral selector in capillary electrophoresis for enantiomer separation of ephedrine and related compounds in some drugs

Dimethyl-beta-cyclodextrin (DM-beta-CD) modified capillary electrophoresis has been developed for chiral separation of ephedrine and related compounds, such as (+/-)-norephedrine, (+/-)-N-methylephedrine, (+/-)-ephedrine and (+)-pseudoephedrine. The influence of some crucial parameters such as buffer concentration, pH value, DM-beta-CD concentration, applied voltage and separation temperature on the separation was investigated. Under the optimum conditions, i.e. 40 mM DM-beta-CD in 75 mM Tris (pH 2.5) as the running electrolyte, separation voltage +25 kV and temperature 25 degrees C, a satisfactory separation of the enantiomers was accomplished. The detection limits (S/N = 3) ranged from 65 to 161 ng/mL and the linear range was 0.15 to 101.0 microg/mL for pressure injection. The present method was successfully applied for the analysis of a series of drugs such as anti-tussive, the drug for rheum, the drug for rhinitis and a Chinese traditional herbal medicine, Ephedrae herba (Ma-Huang in Chinese). The recoveries of ephedrine and related compounds in real samples ranged from 97.6 to 103.5%. This method is useful in the simple and rapid analysis of ephedrine derivatives in marketed products.