Simple Capillary Zone Electrophoresis Method Research Articles

Capillary zone electrophorsis for the analysis of naturally occurring 2-hydroxycitric acids and their lactones.

A simple capillary zone electrophoresis method with direct ultraviolet detection has been developed for the analysis of naturally occurring diastereomeric 2-hydroxycitric acid lactones. Using 50mM sodium phosphate buffer of pH 7, a baseline resolution Rs > 3.0 was observed for all organic acids selected for the present study. This method was employed for the quantitative determination of title acids present in the plant sources namely Garcinia cambogia fruit rinds and Hibiscus sabdariffa calyx. Conversion of 2-hydroxycitric acids to their lactones on heating the above plant sources is deliberated. The Hydrolysis of hydroxycitric acid lactones in aqueous solution is reported for the first time.

Application of capillary electrophoresis to the simultaneous determination and stability study of four extensively used penicillin derivatives

The applicability of capillary electrophoresis for the analysis of four extensively used penicillin derivatives (benzylpenicillin, ampicillin, amoxicillin, oxacilllin) has been studied. Because of structural similarities, the electrophoretic behavior of these derivatives is very similar; consequently an efficient separation using the conventional capillary zone electrophoresis is hard to be achieved. Their simultaneous separation was solved by using micellar electrokinetic capillary chromatography, the separation being based on the differential partition of the analytes between the micellar and aqueous phase. Using a buffer solution containing 25 mM sodium tetraborate and 100 mM sodium dodecyl sulfate as surfactant, at a pH of 9.3, applying a voltage of + 25 kV at a temperature of 25 °C, we achieved the simultaneous separation of the studied penicillin derivatives in less then 5 minutes. The separation conditions were optimized and the analytical performance of the method was evaluated in terms of precision, linearity, limit of detection, and quantification. Also, a simple capillary zone electrophoresis method was applied to study the stability of the studied penicillin derivatives in water at different temperatures, using ciprofloxacin hydrochloride as internal standard. It was observed that the extent of the hydrolysis of penicillins in water is highly dependent on the time and also temperature.

A capillary electrophoresis method for the determination of selected biogenic amines and amino acids in mammalian decomposition fluid

A simple capillary zone electrophoresis method for the determination of selected biogenic amines (tyramine and tryptamine) and amino acids (tryptophan, phenylalanine and tyrosine) in mammalian decomposition fluids is presented. Separations were carried out in a fused silica capillary (75microm i.d., total length 65cm, effective length 56cm) with detection by ultraviolet absorbance spectrophotometry at 200nm. In order to improve resolution and total analysis time, the method was subjected to optimisation utilising a chemometric approach. A screening design was carried out followed by a central composite design (CCD), using peak resolution and total analysis time as response factors. The influences of four experimental variables (pH, background electrolyte concentration, percentage of organic modifier (methanol) and applied voltage) were investigated. Optimum separation conditions were determined to be; a background electrolyte of boric acid (70mM) adjusted to pH 9.5 with 0.1M sodium hydroxide with 32% methanol (v/v). Applied voltage was 30kV, with the resulting current being less than 26microA. Under these conditions the analytes were separated within 12min. Tryptamine, tyramine, tryptophan, tyrosine and phenylalanine were identified by migration time and spiking in porcine decomposition fluids.

Analysis of the molecular size distribution of polyethylene glycols by CE‐UV versus HPLC with evaporative light scattering detection

A simple capillary zone electrophoresis method has been developed for the separation of polyethylene glycols (PEGs) consisting of differing amounts of polymers with different monomer numbers up to an average molecular mass of 1500. To provide both charge and detectability, the analytes were derivatized with phthalic anhydride according to a conventional method and a newly developed microwave-assisted method. While obtaining nearly equal amounts of single and double esterificated PEGs with the conventional method, the fraction of single derivatized PEGs is considerably reduced by microwave-assisted reaction. In order to compare the capillary zone electrophoresis results, an HPLC method with evaporative light scattering detection has been established. This method was successfully applied to the analysis of underivatized PEG 400, 1000 and 1500.

Validation and application of capillary electrophoresis for the analysis of lidocaine in a skin tape stripping study

A fast and simple capillary zone electrophoresis method was developed and validated for the determination of lidocaine in skin using tape samples. Separation was performed in a 350 mm (265 mm to window) x 50 microm i.d. fused silica capillary using a background electrolyte of phosphoric acid-Tris pH 2.5. The extraction of lidocaine from tape samples was achieved using methanol, which was diluted to 50% with water before injection. Procaine was the internal standard. The migration times for procaine and lidocaine were 2.9 and 3.2 min, respectively. The limit of quantification for lidocaine was 50 microg, with signal to noise ratio greater than 10. The calibration curve was linear from 50 to 1000 microg with r(2) greater than 0.99. The CV for both within- and between-assay imprecision and the percentage of inaccuracy for the quality control samples including lower and upper limits of quantitation were <or=2% and <or=14%, respectively. The absolute recovery of lidocaine was >97%. The accuracy and selectivity of this method allowed the measurement of lidocaine in tape samples obtained from a skin tape stripping study of local anesthetics in healthy subjects.

Simultaneous multiresponse optimization applied to epinastine determination in human serum by using capillary electrophoresis

Experimental design and optimization techniques were implemented for the development of a rapid and simple capillary zone electrophoresis method (CZE) for the determination of epinastine hydrochloride in human serum. The effects of five factors were studied on the resolution between the peaks for the target analyte (epinastine hydrochloride) and lidocaine hydrochloride, used as internal standard, as well as on the analysis time. The factors were the concentration and pH of the buffer, the injection time, the injection voltage and the separation voltage. The separation was carried out by using an uncoated silica capillary with 50 μm i.d. and total length 64.5 cm (150 μm of path length) and UV detection (200 nm). Multiple response simultaneous optimization by using the desirability function was used to find experimental conditions where the system generates desirable results. The optimum conditions were: sodium phosphate buffer solution, 16.0 mmol L −1; pH 8.50; injection voltage, 20.0 kV; injection time, 30 s; separation voltage, 26.7 kV. The method was confirmed to be linear in the range of 2.0–12 ng mL −1. The injection repeatability of the method was evaluated by six injections at three concentration levels, while intra-assay precision was assessed by analysing a single concentration level, yielding a CV's of ca. 1% for standard and 2% for serum samples. Accuracy was evaluated by recovery assays and by comparing with an HPLC method, the results being acceptable according to regulatory agencies. The rudgeness was evaluated by means of an experimental Plackett–Burman design, in which the accuracy was assessed when small changes were set in the studied parameters. Clean-up of human serum samples was carried out by means of a liquid–liquid extraction procedure, which gave a high extraction yield for epinastine hydrochloride (93.00%).

Separation and determination of in vitro oxidized phospholipids by capillary zone electrophoresis

A simple capillary zone electrophoresis (CZE) method was used to determine in vitro oxidized phosphatidyl choline (ox-PC). To optimize the capillary electrophoresis (CE) conditions, organic buffer additives, buffer ionic strength, buffer pH, and applied voltage were examined. The optimal CE separation buffer chosen was an aqueous–organic solvent system containing 10% sodium phosphate buffer (5 mM, pH 7.40), 80% methanol, and 10% acetonitrile. One major peak with a small shoulder was found for phosphatidyl choline (PC), whereas one major peak and a complex region containing several lower-mobility peaks were found for ox-PC. The lower-mobility species of ox-PC has high levels of conjugated dienes characterized by strong absorbance at 234 nm. The electropherograms of PC and ox-PC were significantly different and highly reproducible. The intensities of lower-mobility species decreased significantly when the antioxidant vitamin C concentration was increased from 6 to 600 μM. This study provides a simple CZE method to differentiate in vitro oxidized from nonoxidized PC molecular species.

Simultaneous determination of organic acids in beverages by capillary zone electrophoresis

A rapid, reliable and simple capillary zone electrophoresis method for the determination of organic acids in beverages was developed. The complete separation of oxalic, formic, tartaric, malic, succinic, maleic, glutaric, pyruvic, acetic, lactic, citric, butyric, benzoic, sorbic, ascorbic and gluconic acids can be achieved in less than 3.5 min with a simple electrolyte composed by phosphate as the carrier buffer (7.5 mM NaH 2PO 4 and 2.5 mM Na 2HPO 4), 2.5 mM TTAOH as electroosmotic flow modifier and 0.24 mM CaCl 2 as selectivity modifier, adjusting the pH at 6.40 constant value. Injection was performed in hydrodynamic mode (30 s) and the detection mode was UV direct at 185 nm. The running voltage was −25 kV at thermostated temperature of 25 °C. 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 fast because the separation time decrease two, four or, even, six times the separation times of the previous reported CZE methods. It is also simple and cheap due to a low consumption of chemicals and samples. These reasons permit it to be considered adequate for routine analysis of organic acids in beverage samples.

Method development and validation for the simultaneous determination of rosiglitazone and metformin in pharmaceutical preparations by capillary zone electrophoresis

A novel and simple capillary zone electrophoresis method was developed and validated for the simultaneous determination of rosiglitazone and metformin in pharmaceutical preparations. The optimum separation for these analytes was achieved in <9 min at 25 °C with a fused-silica capillary column (80.5 cm × 75 μm i.d., effective length 72.0 cm) and a running buffer containing 25 mM acetate buffer at pH 4.0. The samples were injected hydrodynamically for 3 s at 50 mbar and the applied voltage was +25.0 kV. Detection wavelength was set at 203 nm. Verapamil was used as internal standard. The method was suitably validated with respect to specificity, linearity, limit of detection and quantitation, accuracy, precision, and robustness. The limits of detection and quantitation were 0.5 and 1.0 μg mL −1 for rosiglitazone and metformin, respectively. The method developed was successfully applied to the simultaneous determination of rosiglitazone and metformin in pharmaceutical preparations. The results were compared to a liquid chromatographic method reported in the literature and no significant difference was found statistically.

Determination of levodopa by capillary zone electrophoresis using an acidic phosphate buffer and its application in the analysis of beans

A simple capillary zone electrophoresis method has been developed for the quantification of levodopa in broad bean and lentil. The dependence of effective mobility of levodopa on pH was investigated in the range of 1.64–11.20; and the simulated apparent dissociation constant values of levodopa were 2.30, 8.11 and 9.92, respectively, which were consistent with literature values. Meanwhile, we obtained the isoelectric point for levodopa was 5.20. Levodopa could be well separated from sample matrix and determined with conditions of 35 mM NaH 2PO 4, pH 4.55, 17.5 kV and 30 °C. A plot of the peak area on levodopa concentration was linear over the range of 5.0–300 μg/mL with a correlation coefficient of 0.9994. The method was validated for the quantification of levodopa in beans. The recoveries of added levodopa in different samples were 99.8% and 105.0%, respectively.

Quantitative enantiomeric analysis of chlorcyclizine, hydroxyzine, and meclizine by capillary electrophoresis.

A simple capillary zone electrophoresis method was developed for the quantitative enantiomeric analysis of piperazine antihistamines with teratogenic suspicion in animals. Enantioseparation of chlorcyclizine, hydroxyzine, and meclizine was performed in glycine buffer (0.6 mol L(-1); pH 3.00) with sulfated beta-cyclodextrin (5 mg mL(-1)) as a chiral selector; and the separated drugs were monitored by ultra-violet detector. The lower quantitation of the individual enantiomer is attainable at 10 micro mol L(-1), using an achiral piperazine drug (cyclizine) as internal standard. The method is simple and rapid with a short run time (<5 min) for the analysis of chlorcyclizine, hydroxyzine or meclizine enantiomers.

Development and validation of a simple capillary zone electrophoresis method for the analysis of kanamycin sulfate with UV detection after pre-capillary derivatization

Capillary zone electrophoresis was successfully applied to separate eight related substances of kanamycin and several minor unknowns from the main component. Strategies to enhance derivatization and selectivity and to optimize separation parameters involved the application of experimental designs. This chemometrical approach considers main effects as well as interactions of the influential parameters, thus conducting a more thorough investigation of the method than the common step-by-step approach. Central composite face centered designs established optimal separation conditions: 30 m M borax buffer, pH 10.0 containing 16.0% (v/v) methanol and optimal composition of derivatization reagent: 27 mg/ml 1,2-phthalic dicarboxaldehyde and 25 μl/ml mercaptoacetic acid in borate buffer, pH 10.4. The standard curves were linear over the concentration range of 0.007–1.01 mg/ml for the main component and 0.003–0.1 mg/ml for the related substances. The limit of quantitation was 0.14% (m/m) for the related substances and impurities ( S/ N=10). The assay method was used to determine the composition of several commercial samples. Quantitative analysis indicates potential usefulness of capillary electrophoresis as an alternative to the assay method prescribed in the European Pharmacopoeia and the United States Pharmacopeia.

Quantitative chiral analysis of carbinoxamine, doxylamine, and orphenadrine by capillary zone electrophoresis

A simple capillary zone electrophoresis method is described for the simultaneous separation and quantitation of chiral carbinoxamine maleate, doxylamine succinate, and orphenadrine citrate using achiral diphenhydramine⋅HCl as an internal standard. The chiral analysis of these drugs was performed in a Tris buffer (100 mM; pH 4.60) with sulfated β-cyclodextrin (15 mg/mL) as a chiral selector. Several parameters affecting the separation were studied, including the pH of the buffer and the concentrations of buffer and chiral selector. Quantitation of the individual enantiomer (prepared from the related racemate) is attainable at 25–125 μM for carbinoxamine maleate, doxylamine succinate, or orphenadrine citrate. The migration order of the separated enantiomers is compared to that of a structurally related dexchlorpheniramine, an S-enantiomer of chlorpheniramine. © 2000 John Wiley & Sons, Inc. J Micro Sep 12: 366–370, 2000

Determination of Maprotiline Hydrochloride by Capillary Zone Electrophoresis

A simple capillary zone electrophoresis method using a fused silica capillary was developed for the quantitation of maprotiline hydrochloride in Maprotilin tablets and Ludiomil ampoules. The sample was pressure-injected into the capillary (3psi s−1) in a run buffer of methanol-phosphate buffer. The optimum running voltage was 20kV and UV detection was at 200 nm. Linearity, precision and reproducibility of the method were good. The developed method is simple and rapid (approx. 10min) and can be used for the routine analysis of maprotiline.

Determination of icariin in Chinese traditional medicine by capillary zone electrophoresis.

Icariin in Chinese traditional medicine was determined by an accurate and simple capillary zone electrophoresis method which used 30 mmol/L of borate solution containing 10% of acetonitrile as running buffer and needed no pretreatment.

Simultaneous determination of the beta-blocker atenolol and several complementary antihypertensive agents in pharmaceutical formulations and urine by capillary zone electrophoresis.

A simple capillary zone electrophoresis method is developed for the quantitation of the beta-blocker atenolol and the complementary antihypertensive agents bendroflumethiazide, amiloride, and hydrochlorothiazide in human urine samples. The electrophoretic separation is performed using a 78-cm x 75-micron-i.d. (70-cm effective length) fused-silica capillary. A borate buffer (pH 9) is used as running electrolyte. The sample is hydrostatically introduced for 20 s, and the running voltage is 25 kV at the injector end of the capillary. The analysis of urine samples requires the optimization of solid-phase extraction methods, achieving recoveries > or = 61% for all the drugs and good separation from the urine matrix. The method is successfully applied to the determination of these compounds in pharmaceutical formulations and in urine samples collected after the intake of Neatenol Diu (100 mg atenolol-5 mg bendroflumethiazide) and Kalten (50 mg atenolol-25 mg hydrochlorothiazide-2.5 mg amiloride). The method is validated in terms of reproducibility, linearity, and accuracy.

Capillary Zone Electrophoretic Method for the Quantitative Determination of the β-Blocker Atenolol in Human Urine

A simple capillary zone electrophoresis method was developed for the quantitation of the β-blocker 4-[2-hydroxy-3-[(l-methylethyl)amino]propoxy] benzeneacetamide, atenolol. The electrophoretic separation was performed using a 78 cm × 75 μm I. D. fused silica capillary. The electrolyte consisted of a buffer Na2HPO4 (25mM)-Na2B4O7 (25 mM) (50−50; V/V), pH 9.7. The introduction of the sample was made hydrostatically for 25 s and the running voltage was 20 KV at the injector end of the capillary. Photometric detection was used and a wavelength of 214 nm. The method was applied to the determination of atenolol in urine samples obtained from a hypertensive patient under medical treatment with the pharmaceutical formulation “Tenormin 100 mg” (atenolol 100 mg), another patient under treatment with the pharmaceutical combination “Tenoretic” (atenolol 100 mg + chlorthalidone 25 mg), and also in urine samples obtained from a healthy volunteer after the ingestion of a 100 mg atenolol tablet, “Tenormin 100 mg”. Using a simple solid phase extraction, a recovery of 70.69±3.27% and a very good separation from the urine matrix are achieved. A good reproducibility, linearity, and accuracy are obtained, and a quantitation limit of 0.1 μg/mL in urine, allows the method to be applied to pharmacokinetic studies of the compound.