Separation and simultaneous determination of quinolone antibiotics by capillary zone electrophoresis

Summary The potential of capillary zone electrophoresis has been investigated for the separation and quantitative determination of some quinolone antibiotics. The influence of different conditions, such as the nature and concentration of the electrophoretic electrolyte, on migration time, peak symmetry, efficiency and resolution was studied. A buffer consisting of 100mm HEPES adjusted to pH 8.5 containing 10% (v/v) acetonitrile was found to furnish a very efficient and stable electrophoretic system for the separation of exoxacin, ciprofloxacin, ofloxacin, oxolinic acid, nalidixic acid and pipemedic acid. A linear relationship between concentration and peak area for each compound was obtained in the concentration range 0.25–40 μg mL⁻¹; detection limits were approximately 0.25 ng mL⁻¹. It was demonstrated that the method can be used for the simultaneous determination of these six antibiotics in serum and urine samples.     

Determination of preservatives by integrative coupling method of headspace liquid-phase microextraction and capillary zone electrophoresis

An integrative coupling method of headspace liquid-phase microextraction (HS-LPME) and capillary zone electrophoresis (CZE) was proposed in this paper. In the method, a separation capillary was used to create a microextraction droplet of the running buffer solution of CZE, hold the droplet at the capillary inlet, extract analytes of sample solutions in the headspace of a sample vial, inject concentrated analytes into the capillary and separate the analytes by CZE. The proposed method was applied to determine the preservatives of benzoic acid and sorbic acid in soy sauce and soft drink samples, in which the running buffer solution of 50 mmol/L tetraborate (pH 9.2) was directly used to form the acceptor droplet at the capillary inlet by pressure, and the preservatives in a 6-mL sample solution containing 0.25 g/mL NaCl were extracted at 90°C for 30 min in the headspace of a 14-mL sample vial. Then the concentrated preservatives were injected into the capillary at 10 cm height difference for 20 s and separated by CZE. The enrichment factors of benzoic acid and sorbic acid achieved 266 and 404, and the limits of detection (LODs) were 0.03 and 0.01 μg/mL (S/N=3), respectively. The recoveries were in the range of 88.7-105%. The integrative coupling method of HS-LPME and CZE was simple, convenient, reliable and suitable for concentrating volatile and semi-volatile organic acids and eliminating matrix interferences of real samples.     

Rapid capillary zone electrophoresis method for the determination of metal cations in beverages

A rapid and reliable capillary zone electrophoresis method for the determination of inorganic cations was developed. The complete separation of K⁺, Ba²⁺, Ca²⁺, Na⁺, Mg²⁺, Mn²⁺, Ni²⁺, Cd²⁺, Li⁺ and Cu²⁺ can be achieved in 4 min with a simple electrolyte composed by 10 mM imidazole as the carrier buffer and background absorbance provider and acetic acid as the complexing agent (pH 3.60). Injection was performed hydrostatically by elevating the sample at 10 cm for 30 s. The running voltage was +25 kV at room temperature. Indirect UV-absorption detection was achieved at 185 nm. The detection limit was in the range between 0.06 mg/l (Mg²⁺) and 0.57 mg/l (K⁺) and the quantification limits ranged from 0.10 mg/l (Ni²⁺) to 0.80 mg/l (Cu²⁺). The calibration graphs were linear in the concentration range from the quantification limit till at least 1 g/l in K⁺, 10 mg/l in Ba²⁺, Ca²⁺, Mg²⁺, Mn²⁺, Ni²⁺ and Cd²⁺, 40 mg/l in Na⁺ and 12 mg/l in Li⁺ and Cu²⁺. The repeatability, intraday and interday analysis were ≤1.55% and ≤3.64% for migration time and ≤3.38% and ≤3.63% for peak area. The method developed has been applied to several beverage samples with only a simple dilution and filtration treatment of the sample. The proposed method is simple, fast, cheap and it is achieved with common products in either laboratory. For these reasons, it is a very useful method for routine analysis.     

毛细管区带电泳对羟基苯甲酸三种异构体的分离研究

考察了邻羟基苯甲酸、间羟基苯甲酸和对羟基苯甲酸在毛细管区带电泳分离时的行为。研究了缓冲液pH、浓度和分离电压对三种羟基苯甲酸异构体分离的影响,结果表明在10 mmol/L Na2HPO4缓冲体系(pH 10.15),运行电压25kV,实验温度25℃的分离条件下,采取压力进样(3.4 kPa×3 s),检测波长210nm;3种异构体在7 min内获得基线分离。邻羟基苯甲酸、间羟基苯甲酸、对羟基苯甲酸在2~100μg/mL范围内,峰面积与质量浓度具有较好的线性关系,检出限分别是0.96,1.27和1.07μg/mL。     

Para-hydroxybenzoic acid as an indirect detection buffer in capillary zone electrophoresis

Summary Para-hydroxybenzoic acid (p-HBA) has been used as indirect UV detection buffer in capillary zone electrophoresis (CZE). Being an UV-absorbing dibasic acid, p-HBA provides both the necessary buffering for pH control over a wide range and UV absorbance for indirect detection. With sodium dodecyl sulfate (SDS) as a probe, a CZE method using p-HBA solution as running buffer was developed to analyze anions, especially ones with low electrophoretic mobilities. The method was used to separate homologous series of sulfonates, SDS in a formulation sample, and SDS in a standard.     

高效毛细管区带电泳法快速测定尿液中的肌酐

建立了一种快速测定尿中肌酐浓度的高效毛细管电泳方法。利用非涂层石英毛细管(64.5 cm×50μm i.d),以pH 2.5,0.1 mmol/L H3PO4作为电泳缓冲液,检测波长191 nm,用0.05 Pa压力进样4 s,在电压16 kV快速分离尿液中的肌酐,采用外标法定量。肌酐的迁移时间约为5.5 min,肌酐浓度在34.5~8840μmol/L范围内呈良好的线性(r2=0.999)。平均日内精密度为2.5%,日间精密度为3.0%。回收率94.1%~99.0%。与全自动生化分析仪碱性苦味酸速率法相比有良好的相关性(r=0.990,n=56)。高效毛细管电泳法测定尿肌酐可应用于临床样品的检测。     

Determination of azelaic and sorbic acid in pharmaceduticals by capillary electrophoresis

Summary Capillary electrophoresis with indirect UV detection at 254 nm was applied to simultaneous determination of ∼20% of azelaic acid and ∼0.1% of sorbic acid in AKNOREN cream. The acids were separated in fused silica capillary (45 cm × 50 μm) at 30 kV. Optimised back-ground electrolyte was 30 mM benzoate buffer (pH∼6, adjusted with TRIS) containing 7 mM β-cyclodextrin and 5% of methanol; internal standard was 2-hydroxysobutyric acid (HIBA). Rectilinear calibration ranges were 0.4–4 mg mL⁻¹ for azelaic acid and 2–20 μg mL⁻¹ for sorbic acid and the recoveries were 97.2–100.5%. A single analysis took <15 min.     

Fast determination of chlorogenic acid in tobacco residues using microwave-assisted extraction and capillary zone electrophoresis technique

In this work, for the first time, capillary zone electrophoresis (CZE) technique combined with microwave-assisted extraction (MAE) was developed for the fast quantification of chlorogenic acid (CA) in tobacco residues. CA in tobacco residue samples were extracted by MAE technique, and then analyzed by CZE. As a new sample preparation method for tobacco residues, the MAE procedure is optimized, validated and compared with conventional methods including ultrasonic extraction (USE) and reflux extraction (RE). It is found that MAE gives the best result due to the highest extraction efficiency within shortest extraction time (only 4.0 min). Here, CA is determined by CZE based on the calibration curve of its authentic standard. The method linearity, detection limit, precision and recovery are studied. The results show that the combined MAE and CZE method has a linearity (R² 0.991, 0.003-0.5 mg ml⁻¹), a limit of detection (0.003 mg ml⁻¹), a limit of quantification (0.01 mg ml⁻¹), good precision (R.S.D. = 4.28%) and a finer recovery (89.0%). The proposed method was successfully applied to the analysis of CA in tobacco residue samples. The experiment results have demonstrated that the CZE combined with MAE is a convenient, fast, economical and reliable method for the determination of CA in tobacco residues.     

Method development and validation for the simultaneous determination of five selective serotonin reuptake inhibitors by capillary zone electrophoresis

Summary A capillary zone electrophoresis method is proposed for the separation of five antidepressants. Optimum conditions for the separation were investigated. A background electrolyte solution consisting of 40 mM phosphate buffer adjusted to pH 2.5, hydrodynamic injection, and a 28 kV separation voltage were used. Relative standard deviations (RSD) were <0.9% and <1.7% for migration time and corrected peak area (n=21), respectively. The detection limits for the five antidepressants ranged from 0.3 to 0.7 mg L⁻¹. The stability of the solutions, linearity, accuracy, and precision were examined during validation of the method. The method is rapid and sensitive, when it was tested for the analysis of pharmaceutical formulations the recoveries obtained were between 98 and 103% of the nominal content.     

A capillary zone electrophoresis for determination of thiolic peptides in biological samples

A new method to improve the analyses of thiolic peptides (cysteine, γGlu-Cys, glutathione, phytochelatins and desglycyl-phytochelatins) derivatized with monobromobimane (mBrB) in complex biological samples by CZE is described. The method involves a SPE using Sep-Pak Light C18 Cartridges after derivatization and a later CZE analysis. Elution of mBrB-thiols was achieved with 10 mM HCl + 70% methanol v/v in deionised water. Electrophoretic parameters, such as BGE pH and concentration, different organic additives (methanol and trifluoroethanol), applied voltage and capillary length were studied in order to establish suitable analytical conditions. Optimum separation of the mBrB-thiolic peptides was obtained with 100 mM sodium borate buffer at pH 7.60. The electrophoretic conditions were +15 kV, capillary length of 90 cm from inlet to detector (98 cm total length, 50 μm ID), samples were loaded into the capillary by hydrodynamic injection (50 mbar, 20 s) and detection was performed at 390 nm. The improved method showed good reproducibility, linearity and sensitivity. The LODs and LOQs estimated using a standard of GSH were 1.41 and 4.69 μM respectively.     

Capillary zone electrophoresis for simultaneous determination of seven nonsteroidal anti-inflammatory drugs in pharmaceuticals

A simple capillary zone electrophoresis (CZE) method has been developed for analyzing seven nonsteroidal anti-inflammatory drugs (NSAIDs)—sulindac (SU), ketoprofen (KE), indomethacin (IN), piroxicam (PI), nimesulide (NI), ibuprofen (IB), and naproxen (NA). The separation was run using borate buffer (60 mmol L^–1, pH 8.5) containing 13% (v/v) methanol at 20 kV, and detected at 200 nm. Several conditions were studied, including concentration and pH of borate buffer, methanol percentage, and separation voltage. In method validation, the calibration plots were linear over the range 40.0–500.0 mol L^–1. In intra-day and inter-day analysis, relative standard deviations (RSD) and relative errors (RE) were all less than 5%. The limits of detection were 10 mol L^–1 for SU, IN, PI, and 20 mol L^–1 for KE, NI, IB, NA (S/N = 3, sampling 6 s by pressure). All recoveries were greater than 95%. This method was applied to the quality control of six NSAIDs in pharmaceuticals using NI as internal standard (IS). The assay results were within the labeled amount required by USP 25.     

毛细管区带电泳法测定粉针剂中头孢拉定的含量

用毛细管区带电泳法测定头孢拉定的含量 ,未涂层毛细管柱 (75 μm×48.5cm ,有效长度 40cm) ,电压 2 8kV ,检测波长 2 3 0nm ,温度 2 0℃ ,进样 5×1 0 3Pa× 3s。运行缓冲液为 2 5mmol/L硼砂缓冲液。方法的线性范围 3 1 .2 2μg/mL～ 749.2 8μg/mL ,检测限为 1 .1 7μg/mL。     

Online preconcentration in capillary electrophoresis with contactless conductivity detection for sensitive determination of sorbic and benzoic acids in soy sauce

A sensitive method of online preconcentration followed by capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C⁴D) is evaluated as a novel approach for the determination of benzoic acid and sorbic acid in soy sauce. The online preconcentration technique, namely field-enhanced sample injection, coupled with CE-C⁴D were successfully developed and optimized. In order to reduce the complex matrix interference resulting from the constituents of soy sauce, a suitable sample clean-up procedure was also investigated for real sample pretreatment. Under optimized conditions, sorbic acid and benzoic acid were well separated within 10 min, and the detection limits were 0.05 μM (5.6 μg L⁻¹) and 0.08 μM (9.8 μg L⁻¹), respectively. The accuracy was tested by spiking 10.0 mg L⁻¹ and 100.0 mg L⁻¹ of standards in the soy sauce samples, and the recoveries were 95-99%, respectively. Results of this study show a great potential for the proposed method as a tool for the fast screening of benzoic acid and sorbic acid in a complex matrix.     

Assay for the simultaneous determination of guanidinoacetic acid, creatinine and creatine in plasma and urine by capillary electrophoresis UV-detection

Guanidinoacetic acid (GAA) measurement has recently become of great interest for the diagnosis of creatine (Cn) metabolism disorders, and research calls for rapid and inexpensive methods for its detection in plasma and urine in order to assess a large number of patients. We propose a new assay for the measurement of GAA by a simple CZE UV-detection without previous sample derivatization. Plasma samples were filtered by Microcon-10 microconcentrators and directly injected into the capillary, while for urine specimens a simple water dilution before injection was needed. A baseline separation was obtained in less than 8 min using a 60.2 cm x 75 microm uncoated silica capillary, 75 mmol/L Tris-phosphate buffer pH 2.25 at 15 degrees C. The performance of the developed method was assessed by measuring plasma creatinine and Cn in 32 normal subjects and comparing the data obtained by the new method with those found with the previous CE assay. Our new method seems to be an inexpensive, fast and specific tool to assess a large number of patients both in clinical and in research laboratories.     

Identification and determination of aesculin and aesculetin in ash barks by capillary zone electrophoresis

Summary A capillary zone electrophoresis method for identification and determination of aesculin and aesculetin has been established using borate-phosphate buffer containing 30% ethanol with on-column UV detection. A detailed investigation of the influence of changes in borate concentration, pH, applied voltage, temperature and organic modifier was then carried out. For both aesculin and aesculetin, a linear plot of migration time (MT) against borate concentration was obtained, and ln[measured peak area (MA)] and lnMT both gave linear plots against ln(applied voltage) with correlation coefficient r>0.999, which also resulted in a linear correlation between MA and MT (r≥0.9998) under varied voltage. Ethanol as organic modifier to the background electrolytes helped in separating aesculin and aesculetin from other components in ash barks. The reproducibility with relative standard deviation in MT and in normalized peak area(NA) and linearity based on NA against concentration were evaluated. Finally, the method was successfully applied to monitor the quality of different ash barks and to compare the effect of sample preparation on content of bioactive components in ash bark. Results indicate that CZE promises to be applicable to quality control of traditional Chinese medicines containing aesculin and aesculetin.     

食品中苯甲酸和山梨酸的气相色谱法分离分析

用毛细管气相色谱法对食品中的防腐剂苯甲酸和山梨酸进行了分离分析。样品用乙醚萃取，萃取物蒸发至干，残渣用氯仿溶解后直接进行色谱分析，FFAP石英毛细管柱，柱温220℃，邻苯二甲酸二甲酯为内标物。两种化合物在0.25mg/mL-4.00mg/mL范围内具有良好的线性关系。     

Validation of a capillary zone electrophoresis method for the comparative determination of etoricoxib in pharmaceutical formulations

A CZE method was developed and validated for the analysis of etoricoxib in pharmaceutical dosage forms, using prilocaine as an internal standard. The CZE method was carried out on a fused-silica capillary (50 microm id, effective length 40 cm). The BGE consisted of 25 mM tris-phosphate solution at pH 2.5. The capillary temperature was maintained at 35 degrees C, the applied voltage was 25 kV, the injection was performed using the pressure mode at 50 mbar for 5 s, with detection at 234 nm using a photodiode array detector. The method was linear in the range of 2-150 microg/mL (r(2) = 0.9999). The specificity and stability-indicating capability were proven through the degradation studies and showing also that there was no interference of the excipients of the formulation. The accuracy was 99.49% with RSD of 0.66%. The limits of quantitation and detection were 2 and 0.58 microg/mL, respectively. Moreover, method validation demonstrated acceptable results for the precision, sensitivity, and robustness. The proposed method was successfully applied for the quantitative analysis of etoricoxib pharmaceutical formulations, and the results compared to the HPLC and LC-MS/MS methods, showing nonsignificant difference (p >0.05).     

Determination of baicalin, chlorogenic acid and caffeic acid in traditional chinese medicinal preparations by capillary zone electrophoresis

Summary A capillary zone electrophoresis (CZE) method was developed for the simultaneous assay of three bioactive components—baicalin, chlorogenic acid and caffeic acid—in seven traditional Chinese medicinal preparations. The analytes were separated successfully within 3.5 min using 10 mM borate buffer (pH8.6). Regression equations revealed linear relationships (correlation coefficients 0.9942–0.9996) between the peak area and concentration of the three analytes. The relative standard deviations of the migration times and the peak areas of the three constituents were 1.12–2.68% and 1.62–5.73%, respectively. Recovery of the three constituents ranged from 89 to 107%. The extraction efficiencies of different extraction solutions are also discussed. The contents of the three components in seven different Chinese medicinal preparations containing Honeysuckle flower and/orScutellariae radix were determined by the CZE method with satisfactory results.