Quantitative determination of clenbuterol, salbutamol and tulobuterol enantiomers by capillary electrophoresis

Enantiomers of clenbuterol, salbutamol and tulobuterol were directly separated and quantitated from a spiked sample by capillary electrophoresis (CE) using sulfated β-cyclodextrin (SCD) as chiral selector and phosphate as running buffer. The SCD and buffer concentration, pH and field strength were the parameters studied to optimize the separation. Optimal separation was obtained using 50 mM of phosphate monobasic at pH = 2.24, 0.25% (w/w) of sulfated cyclodextrin and a field strength of 10 kV, with 20 min total time analysis. Comparison between two different injection modes (hydrodynamic and electrokinetic) was made. In the hydrodynamic mode, repeatability (expressed as relative standard deviation, RSD) was less than 1.2% for migration times for all the analyte peaks and less than 2% for peak area percentages. With respect to reproducibility, RSD was less than 3.8% for migration time and less than 3% for peak area percentages. Calibration curves were set up for two different sample concentration ranges (1 to 10 μg mL^–1 and 160– 800 ng mL^–1, of each of the racemates studied). Although the electrokinetic injection mode for an aqueous sample appeared to suffer from some enantiodiscrimination, calibration curves were linear in the range between 1 and 10 ng mL^–1 with regression coefficients ranging from 0.9996 to 0.9952. As in the case of hydrodynamic injection, the method was tested with a spiked sample.     

毛细管电泳电化学法分离检测盐酸克伦特罗、特布他林和沙丁胺醇

建立了毛细管电泳电化学法对盐酸克伦特罗、特布他林和沙丁胺醇进行分离检测。方法采用胶束电泳体系,以铂圆盘为工作电极,考察了检测电位、缓冲液浓度和pH、十二烷基硫酸钠(SDS)浓度、分离电压等因素的影响。3个分离物在10 kV的分离电压、缓冲体系为15 mmol/L(pH 9.0)硼砂+20 mmol/L SDS条件下得到分离。盐酸克伦特罗、特布他林和沙丁胺醇的线性范围分别为2.0～400,3.5～700,5.0～1000μg/L。方法已用于猪肉样品的检测。     

Quantitative determination of salbutamol in tablets by multiple-injection capillary zone electrophoresis

A multiple-injection capillary zone electrophoresis (MICZE) method has been developed for the assay of salbutamol in Ventoline Depot tablets (GlaxoSmithKline). In the developed method, seven sample sets, each consisting of three samples, were sequentially injected into the capillary and analyzed within a single run. This enabled a total of twenty-one sequential injections, i.e., six standards and fifteen samples, containing salbutamol and the injection marker oxprenolol. The injected sample plugs were separated by plugs of background electrolyte, through application of a short-term voltage (30kV) over the capillary for different time periods, i.e., t(PE1) and t(PE2). The samples in each set were isolated from each other by partial electrophoresis for 2.35min (t(PE1)), while the sample sets were separated for 10.50min (t(PE2)). After the final injection, all the applied samples were subjected to electrophoresis for a time period corresponding to that in conventional single-injection CZE. The method was validated regarding linearity, accuracy, precision and robustness before it was applied to the determination of salbutamol in 15 tablets of Ventoline Depot with a labeled content of 8mg salbutamol. The average salbutamol content was determined to 7.8mg (+/-0.3mg) from simultaneous analyses of the 15 different tablets.     

Field-amplified on-line sample stacking for separation and determination of cimaterol, clenbuterol and salbutamol using capillary electrophoresis

A capillary electrophoresis method, using field-amplified sample injection (FASI), was developed for separation and determination of some beta 2-agonists, such as cimaterol, clenbuterol and salbutamol. The optimum conditions for this system had been investigated in detail. The precision of the migration time, peak height and accuracy were determined in both intra-day (n = 5) and inter-day (n = 15) assays. Under the optimum conditions, the detection limits (defined as S/N = 3) of this method were found to be lower than 2.0 ng/mL for all of these three beta 2-agonists, which were much lower than that of the conventional electro-migration injection method, the enhancement factors were greatly improved to be 30-40-fold. Such lower detection limit lets this method to be suitable for determination of above-mentioned beta 2-agonists in the urine sample. The mean recoveries in urine were higher than 96.2%, 95.6% and 95.3% for cimaterol, clenbuterol and salbutamol, respectively, with relative standard deviations lower than 3.5%.     

Rapid analysis of clenbuterol, salbutamol, procaterol, and fenoterol in pharmaceuticals and human urine by capillary electrophoresis

Capillary electrophoresis (CE) with UV detection for the simultaneous and short-time analysis of clenbuterol, salbutamol, procaterol, fenoterol is described and validated. Optimized conditions were found to be a 10 mmoll(-1) borate buffer (pH 10.0), an separation voltage of 19 kV, and a separation temperature of 32 degrees C. Detection was set at 205 nm. Under the optimized conditions, analyses of the four analytes in pharmaceutical and human urine samples were carried out in approximately 1 min. The interference of the sample matrix was not observed. The LOD (limits of detection) defined at S/N of 3:1 was found between 0.5 and 2.0 mgl(-1) for the analytes. The linearity of the detector response was within the range from 2.0 to 30 mgl(-1) with correlation coefficient >0.996.     

Simultaneous determination of dopa and carbidopa enantiomers by capillary zone electrophoresis

Dopa and carbidopa, components of the dual therapy for Parkinson's disease treatment, are both provided as single enantiomers, since their D-forms are inactive. To ensure the efficiency and safety of the therapy, these D-enantiomers, therefore, should be considered as impurities. In this paper, the enantioseparation power of different types of cyclodextrins, both neutral and charged ones, on dopa and carbidopa enantiomers was tested. Three methods of simultaneous separation of dopa and carbidopa enantiomers were developed, using highly sulfated beta-cyclodextrin and sulfated beta-cyclodextrin as chiral selector, in normal and reversed polarity mode. Two methods among these three were found sensitive enough for the quantitation of 0.1% D-enantiomers in L-forms (impurity level). After the optimization study, the best method was selected, using 16 mM sulfated beta-cyclodextrin in 15 mM sodium phosphate buffer pH 2.45, an uncoated fused-silica capillary (50 num inner diameter, 30 cm total length), and an applied voltage of -12 kV. This method is robust and efficient, with very high resolution for all peaks within a short analysis time of 10 min. Quantitatively, the method offers a limit of detection (LOD) of 0.2 nug/mL and a limit of quantitation (LOQ) of 0.5 nug/mL for both D-dopa and D-carbidopa, which is equivalent to 0.02% and 0.05% against the respective L-enantiomers. A linear relationship was found between the concentration of the analyte and the corresponding peak area in a range of 0.5-2.0 nug/mL.     

Rapid determination of salbutamol in pharmaceutical preparations by chiral capillary electrophoresis

A fast and simple method of chiral capillary electrophoresis (CE) has been applied to the analysis of salbutamol in different pharmaceutical preparations. Using of a 25 mM acetate buffer (pH 5.0), containing 13.1 mg/mL carboxymethyl-beta-cyclodextrin (CM-beta-CD), an applied voltage of 20 kV and a temperature of 25 degrees C, the enantiomers of salbutamol could be separated in about 2 min. Three different pharmaceutical preparations (two syrups, one oral solution, and two kind of tablets) containing a racemate of salbutamol were injected directly in the CE system, following dilution in dimethyl sulfoxide (DMSO). Appreciable differences in the retention times were observed for salbutamol enantiomers in the different formulations studied, which were attributed to the effect of the matrix components on the electrophoretic mobility. The standard addition method was used for the calibration due to the existence of matrix interferences. Finally, the stability of the enantiomers of salbutamol in the oral solution was studied calculating the enantiomeric ratio values when the solution was injected immediately after being opened in the first case and after being opened and stored in the fridge for two months in the second case.     

Separation and determination of abused drugs clenbuterol and salbutamol from complex extractants in swine feed by capillary zone electrophoresis with simple pretreatment

A simple but efficient capillary zone electrophoresis (CZE) method was developed for the fast separation and determination of two misused beta2-agonists clenbuterol (CLB) and salbutamol (SAL) from complex background extractants existing in swine feed samples. The proper experimental conditions were achieved as 20.0 mmol/l pH 10.5 Na(2)HPO(4)-NaOH buffer, 20 kV applied voltage, fused-silica capillary of 60.5 cm x 75 microm i.d. (50 cm to detector). Under the proper conditions, the two abused drugs can be online isolated from the complex extractants and the separation between CLB and SAL is good, all of the target analytes can be detected within 4.5 min. The linear response of CLB and SAL concentration ranges from 2.0 to 100.0 microg/ml with high correlation coefficient (R(2)=0.9990) and (R(2)=0.9986), respectively. Limit of detection (LOD) and limit of quantification (LOQ) was calculated to be 0.95 and 3.17 microg/ml for CLB, 1.07 and 3.57 microg/ml for SAL. The precision values (expressed as R.S.D.) of intra- and inter-day were 1.24-2.36% and 0.90-3.85% for CLB, 0.47-1.64% and 0.91-3.46% for SAL. Recoveries spiked at levels 5.0, 25.0, 80.0 microg/ml ranged between 93.30% and 104.33% with R.S.D. less than 5%. Finally, the developed method has been applied to the analysis of real swine feed samples and has achieved satisfactory results.     

Simultaneous determination of disopyramide and mono-N-dealkyldisopyramide enantiomers in human plasma by capillary electrophoresis

In this paper, a rapid method for the enantioselective analysis of the antiarrhythmic drug disopyramide and its main metabolite mono-N-dealkyldisopyramide in human plasma by capillary electrophoresis employing the cyclodextrin-modified electrokinetic chromatography mode is described. Sample clean-up was carried out by alkalinization with sodium hydroxide followed by liquid-liquid extraction with toluene. The complete enantioselective analysis was performed within less than 5 min using 20 mmol/L sodium acetate buffer, pH 5.0, containing 0.2% w/v sulfated beta-cyclodextrin as chiral selector. A 40 cm uncoated fused-silica capillary was used for the analysis, performed at a voltage of 15 kV and at 20 degrees C. The calibration curves were linear over the concentration range of 62.5-1850 ng/mL and 125-1850 ng/mL for each enantiomer of disopyramide and mono-N-dealkyldisopyramide. The mean recoveries for disopyramide and mono-N-dealkyldisopyramide enantiomers were up to 87 and 69%, respectively. All four enantiomers studied could be quantified at three different concentrations (200, 400 and 600 ng/mL) with coefficient of variation and % relative error not higher than 15%. The quantitation limit was 62.5 ng/mL for (+)-(S)-and (-)-(R)-disopyramide and (-)-(R)-mono-N-dealkyldisopyramide and 125 ng/mL for (+)-(S)-mono-N-dealkyldisopyramide, using 1 mL of human plasma.     

Enantiomeric separation of racemic clenbuterol by capillary zone electrophoresis

A method for capillary electrophoretic enantiomeric separation of a racemic clenbuterol has been established with hydroxypropyl-β-cyclodextrin as the chiral selector. General equations and data analysis are presented to relate mobility to the equilibrium constants in simple binding equilibria and used to determine binding constants and thermodynamic parameters for host-guest complexation of clenbuterol enantiomers with hydroxypropyl-β-cyclodextrin as a selector. The effects of β-cyclodextrin type and concentration, buffer type, concentration and pH, as well as separation voltage and capillary temperature were investigated in detail. A maximal resolution of 6.78 was obtained. The binding constants of the host-guest complex of clenbuterol enantiomers with hydroxypropyl-β-cyclodextrin, K _R-CD and K _S-CD are 22.50 and 43.09 l mol^-1, respectively.     

超高效合相色谱法拆分和测定克伦特罗对映体

建立了基于超高效合相色谱技术(UPC²)的克伦特罗对映体拆分方法,并对所建立的方法进行了方法学考察及应用。实验考察了两种克伦特罗对映体标准溶液的稳定性,并对手性色谱柱、助溶剂、系统背压、色谱柱温度等色谱分离条件进行了优化。采用Acquity Trefoil AMY1 (150 mm×3.0 mm, 2.5 μm)手性色谱柱进行分离,以超临界CO₂-含0.5%(v/v) 10 mol/L醋酸铵的甲醇溶液为流动相,以流速2.0 mL/min梯度洗脱,检测波长为241 nm,进样体积为10 μL,系统背压为13.8 MPa,柱温为40 ℃时,两种克伦特罗对映体分离效果最好。两种克伦特罗对映体的线性范围为1.0~20.0 mg/L,相关系数均大于0.9997,仪器检出限(S/N=3)均为0.5 mg/L。10.0 mg/L混合标准工作溶液重复进样6次,(+)、(-)克伦特罗对映体峰面积的相对标准偏差(RSD, n=6)分别为0.65%和0.76%。应用该方法对市售克伦特罗外消旋体标准品进行拆分,采用外标定量法计算克伦特罗外消旋体标准中间溶液10.0 mg/L中两种克伦特罗对映体含量,其中(+)-克伦特罗的含量为5.6 mg/L, (-)-克伦特罗的含量为5.5 mg/L。该计算结果与文献报道的工业品克伦特罗外消旋体中(+)-克伦特罗与(-)-克伦特罗的比例为1.02∶1.00基本相符。该方法具有分析速度快、分离效果好、有机溶剂消耗少等特点,适用于克伦特罗对映体的拆分,为其他手性化合物的拆分、药效精细分析和产品质量评定提供了可靠的技术支持。     

Determination of clenbuterol by capillary electrophoresis immunoassay with chemiluminescence detection

A competitive immunoassay for clenbuterol (CLB) based on capillary electrophoresis with chemiluminescence (CL) detection was established. The method was based on the competitive reaction of horseradish peroxidase (HRP)-labeled CLB (CLB-HRP) and free CLB with anti-CLB antiserum. The factors affecting the electrophoresis and CL detection were systematically investigated with HRP as a model sample. Under the optimal conditions, the tracer CLB-HRP and the immunoassay complex were separated, and the linear range and the detection limit (S/N = 3) for CLB were 5.0-40 nmol l⁻¹ and 1.2 nmol l⁻¹, respectively. The proposed method has been applied satisfactorily in the analysis of urine sample.     

Separation of reboxetine enantiomers by means of capillary electrophoresis

The novel antidepressant reboxetine, a selective norepinephrine reuptake inhibitor, is increasingly used in the treatment of different forms of major depression. Reboxetine is a chiral compound, and is marketed as a racemic mixture of (R,R)- and (S,S)-reboxetine; however, the pharmacokinetic and toxicological profiles of the two enantiomers are rather different. For this reason, a simple capillary electrophoretic method for the separation of reboxetine enantiomers has been developed. Sulfobutyl ether-beta-cyclodextrin was chosen as the chiral selector, and several parameters, such as cyclodextrin and buffer concentration, buffer pH and capillary temperature were investigated in order to obtain good separation and acceptable run times. Using an uncoated, fused-silica capillary (internal diameter 50 microm, total length 48.5 cm, effective length 40.0 cm) and a background electrolyte consisting of a pH 3.0, 100 mM phosphate buffer containing 1.25 mM cyclodextrin, reboxetine enantiomers were baseline separated (resolution > 4) with a voltage of 20 kV in less than 16 min. Since pure enantiomers of reboxetine were not available, they were obtained from the racemic powder by means of direct-phase, high-performance liquid chromatography and their identity confirmed by circular dichroism spectra.     

Separation of enantiomers by capillary electrophoresis using pentosan polysulfate

Pentosan polysulfate, a semisynthetic polysaccharide, was employed as a chiral run buffer additive in capillary electrophoresis. Twenty-eight racemic analytes were resolved. The separations were successful only at low pH when the analytes were significantly protonated. This suggests that ionic interactions were the dominant associative interactions between the anionic pentosan polysulfate and the positively charged analytes. Compared to other linear, carbohydrate-based chiral selectors (i.e., chondroitin sulfates, heparin and dextran sulfate) pentosan polysulfate has some characteristics common of anionic polysaccharides; yet it has several differences in its structure and properties which account for its unusual enantioselectivity. The effects of pH, concentration of phosphate buffer, concentration of pentosan polysulfate and the type and concentration of organic modifier on the enantiomeric separations were investigated. The optimization of these separations were dependent on the nature of the analytes and could be achieved by the proper choice of experimental conditions.     

Separation and determination of norepinephrine, epinephrine and isoprinaline enantiomers by capillary electrophoresis in pharmaceutical formulation and human serum

A capillary electrophoresis method with ultraviolet (UV) detection was developed and optimized for the enantiomer separation of norepinephrine (NE), epinephrine (EP) and isoprenaline (IP) using dual cyclodextrins (CDs) of 2-hydroxypropyl-beta-CD (HP-beta-CD) and heptakis (2,6-di-o-methyl)-beta-CD (DM-beta-CD) as chiral selectors. Optimal separation was obtained using a running buffer of 50mM phosphate containing 30mM HP-beta-CD and 5mM DM-beta-CD at pH 2.90 and a field strength of 20kV in 45cmx75mum (40cm effective length) uncoated capillary. The UV absorbance detection was set at 205nm. A 0.1% (w/w) polyethylene glycol or 0.1% (v/v) acetonitrile was used to enhance the detection sensitivity. There was a wide and excellent linear calibration graph for each enantiomer in the range 1.0x10(-3) to 1.0x10(-6)M and the detection limit (S/N=3) was found from 8.5x10(-7) to 9.5x10(-7)M. The method has been applied for the determination of isoprenaline in isoprenaline hydrochloride aerosol and to the analysis of serum samples. The recoveries of NE and EP in serum and IP in drug were ranged from 90 to 110%. The relative standard deviations of all the analyte peaks were less than 2.8% for migration time and less than 4.8% for peak area.     

Separation of enantiomers of butorphanol and cycloamine by capillary zone electrophoresis

Butorphanol tartrate is a synthetic opioid agonist-antagonist used as analgesic, possessing three chiral centres in the basic part of the molecule. Its chiral purity is routinely controlled only by optical rotation. A new capillary zone electrophoresis method, capable to separate the enantiomers of butorphanol and intermediate of its synthesis, cycloamine, was developed. Different electrolyte composition (type and concentration of carrier ion, pH, and organic solvent addition), and type and concentration of several chiral selectors (natural and modified cyclodextrins) were tested. Using the optimized conditions (acidic electrolyte with the addition of highly sulphated gamma-cyclodextrin) as low as 0.05% of undesirable enantiomers can be detected. Selected method characteristics, i.e., linearity (0-50 mg/l), precision (2.5% at 20 mg/l), and accuracy (101 +/- 2% at 20 mg/l) were evaluated. The optimized method was applied for the analysis of real batches of butorphanol and cycloamine. It was found that butorphanol tartrate manufactured by IVAX Pharmaceuticals contains less than 0.05% of undesirable enantiomer.     

毛细管区带电泳法拆分匹伐他汀钙对映体

建立了匹伐他汀钙对映体的毛细管区带电泳(CZE)拆分方法。分别考察了电泳电压,缓冲溶液种类、浓度及pH值,环糊精种类及浓度,添加剂种类及浓度等参数对实验结果的影响,从而确定了匹伐他汀钙对映体的最佳拆分条件: 电泳电压为18 kV;运行缓冲溶液为80 mmol/L的Tris-HCl缓冲体系,pH值为3.20,其中含有50 mmol/L HP-β-CD(羟丙基-β-环糊精)和5 mmol/L SDS(十二烷基磺酸钠);采用重力进样,进样高度17 cm,进样时间为2 s。在优化的实验条件下,匹伐他汀钙对映体得到了较好的分离,分离度可达2.17。实验结果表明该方法可用于匹伐他汀钙对映体的分离,具有快速、便捷、准确性好等优点。     

Chiral separation of highly negatively charged enantiomers by capillary electrophoresis

The separation of two highly negatively charged enantiomeric organic disulfates containing two chiral centers was investigated by capillary electrophoresis using cyclodextrin based chiral selectors added to the run buffer. The optimum separation for the enantiomers was achieved in less than 3 min at 25 degrees C with a run buffer of 10 mM glycine pH 2.4 and 5 mM QA-beta-CD, which is a positively charged quaternary ammonium beta-cyclodextrin derivative. The method resulted in baseline resolution, excellent linearity, and highly reproducible migration times allowing facile evaluation of the enantiomeric purity of the individual isomers. Detection limits for the enantiomeric pair were determined to be 0.3 ng/microl (S/N = 3). The nature of the selector-enantiomer interaction and a quantitative measurement of the apparent stability constants that governed chiral discrimination of the enantiomers with QA-beta-CD were also investigated by UV-Vis spectroscopy and electrospray ionization mass spectrometry.