Coupling sweeping-micellar electrokinetic chromatography with tandem mass spectrometry for the therapeutic monitoring of benzimidazoles in animal urine by dilute and shoot.

A new method based on micellar electrokinetic chromatography-tandem mass spectrometry (MEKC-MS/MS) has been developed for the identification and simultaneous quantification of thirteen benzimidazoles in animal urine. In order to obtain an appropriate separation with the highest sensitivity, different electrophoretic parameters were evaluated. Under optimum conditions, the separation was performed using ammonium perfluorooctanoate as volatile surfactant and electrophoretic buffer (50mM, pH 9). To increase the sensitivity, a stacking mode named sweeping was applied, using water as injection solvent at 50mbar for 75s, obtaining sensitivity enhancement factors from 50 to 181. The method was applied to different animal urine samples, including sheep, cow and goat. The sample treatment consisted of a 1:10 (v/v) dilution with water. Calibration using sheep urine samples can be used for both goat and cow urine samples with a relative bias below 25% and relative standard deviations lower than 8%. The limits of detection were below 70µgL-1. As a result, the applicability of this rapid, simple, sensitive, and environmentally friendly method for therapeutic drug monitoring of benzimidazoles based on the analysis of animal urine has been demonstrated.

Novel MEKC method for determination of sodium 2-mercaptoethanesulfonate in human plasma with in-capillary derivatization and UV detection.

Sensitive electrophoretic method for determination of total sodium 2-mercaptoethanesulfonate (mesna) in human plasma, based on the stacking with high salt concentration in MEKC and in-capillary derivatization with 2-chloro-1-methyllepidinium tetrafluoroborate followed by UV detection was developed. In the method 0.03molL(-1)pH 7 phosphate buffer with the addition of 0.01molL(-1) SDS, and 10% ACN was used as a BGE. The limit of quantification (LOQ) of the method was 0.5µmolL(-1). Linearity in detector response was observed over the range of 0.5-10µmolL(-1) with the correlation coefficient 0.9971. The intra- and inter-day accuracy (three concentration levels, 5 days, n=3) of the method ranged from 97.2 to 110.0% and from 94.0 to 101.2%, respectively. The novel MEKC method with UV detection proved to be suitable for determination of total mesna in human plasma.

Simultaneous and rapid determination of caffeine and taurine in energy drinks by MEKC in a short capillary with dual contactless conductivity/photometry detection.

A method has been developed for the simultaneous determination of taurine and caffeine using a laboratory-made instrument enabling separation analysis in a short 10.5 cm capillary. The substances are detected using a contactless conductometry/ultraviolet (UV) photometry detector that enables recording both signals at one place in the capillary. The separation of caffeine and taurine was performed using the MEKC technique in a BGE with the composition 40 mM CHES, 15 mM NaOH, and 50 mM SDS, pH 9.36. Under these conditions, the migration time of caffeine is 43 s and of taurine 60 s; LOD for caffeine is 4 mg/L using photometric detection and LOD for taurine is 24 mg/L using contactless conductometric detection. The standard addition method was used for determination in Red Bull energy drink of caffeine 317 mg/L and taurine 3860 mg/L; the contents in Kamikaze drink were 468 mg/L caffeine and 4110 mg/L taurine. The determined values are in good agreement with the declared contents of these substances. RSD does not exceed 3%.

In-capillary formation of polymer/surfactant complexes-assisted reversed-migration micellar electrokinetic chromatography for facile analysis of neutral steroids.

In this study we developed a novel approach, using in-capillary formation of polymer/surfactant complexes (IPSC)-assisted reversed-migration MEKC (RM-MEKC), for the analysis of neutral steroids. This process involved two sequential events: in-capillary polymer/surfactant complexes formation during sample preconcentration, followed by IPSC separation. The procedure began with a polymer-filled capillary. Initially, on-line preconcentration of the sample was performed at the sample plug. Meanwhile, free surfactants migrated to interact with polymers, forming polymer-surfactant complexes. Analytes were then kinetically partitioned between the mixed phases (micelles and polymer-SDS complexes). Sodium dodecyl sulfate (SDS) and poly(N-isopropylacrylamide) (PNIPAAm) were employed as pseudo-stationary phases (PSPs). This system allowed the successful separation of five steroids (testosterone, hydrocortisone 21-acetate, dexamethasone, prednisolone, hydrocortisone) in acetate buffer and the determination of urinary free hydrocortisone; it also exhibited excellent performance for sample on-line concentration. The limit of detection for hydrocortisone was 20.98 ng/mL (R(2)=0.9995). The polymer size, concentrations, end-group charges, and SDS concentrations were evaluated. This IPSC/RM-MEKC system, which can be adopted in commercial CE instruments, is easy to operate, suitable for combination with several sample preconcentration options, sensitive, robust, and environmentally sustainable. We suspect that such systems might have potential applications in clinical analyses and in microanalytical devices.

Direct and fast determination of paclitaxel, morphine and codeine in urine by micellar electrokinetic chromatography.

A micellar electrokinetic chromatography (MEKC) method was developed for the determination of paclitaxel, morphine and codeine in human urine from patients under cancer treatment. The background electrolyte consisted of a borate buffer (pH 9.2; 20 mM) with sodium dodecyl sulfate (60 mM) and 5% MeOH. The applied voltage was 25 kV, temperature was 20 °C and the sample injection was performed in the hydrodynamic mode. All analyses were carried out in a fused silica capillary with an internal diameter of 75 µm and a total length of 57 cm. The detection of target compounds was performed at 212 nm. Under these conditions, a complete separation of paclitaxel, morphine and codeine was achieved in less than 15 min. According to the validation study, the developed method was proved to be accurate, precise, sensitive, specific, rugged and robust. This method was applied to the analysis of six urines samples from different cancer patients undergoing treatment with paclitaxel or/and codeine. In all the urine paclitaxel determination were done.

Determination of amino acids and catecholamines derivatized with 3-(4-chlorobenzoyl)-2-quinolinecarboxaldehyde in PC12 and HEK293 cells by capillary electrophoresis with laser-induced fluorescence detection.

An effective micellar electrokinetic capillary chromatography with laser-induced fluorescence detection (MEKC-LIF) method has been proposed for the separation and the determination of 16 amino acids and two catecholamines using a new fluorogenic reagent, 3-(4-chlorobenzoyl)-2-quinolinecarboxaldehyde (Cl-BQCA), as the derivatizing reagent. The highest derivatization efficiency was achieved in pH 8.0 borate buffer at 50 °C for 50 min. The optimal separation of Cl-BQCA-labeled amines was obtained with a running buffer (pH 9.15) containing 120 mM boric acid, 38.5 mM sodium dodecyl sulfate, and 17% acetonitrile. The detection limit (S/N = 3) was found to be as low as 1.4 nM. The present method has been successfully used to detect amino acids and catecholamines in HEK293 and PC12 cell samples. This study explores the potential of MEKC-LIF with Cl-BQCA labeling as a tool for monitoring amino acids and catecholamines during the complex physiological and behavioral processes in various matrices.

Analysis of ammonia and aliphatic amines in environmental water by micellar electrokinetic chromatography and QSPR modeling of electrophoretic migration time.

In this paper, a rapid and sensitive method for the determination of ammonia and 22 aliphatic amines derivatized was established by cyclodextrin (CD) modified micellar electrokinetic chromatography with laser-induced fluorescence detection using 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole as a derived reagent. By a series of unvaried studies, the best conditions were selected using 20mM tetraborate (pH 9.70) containing 25 mM SDS, 7 mM beta-CD, 10% acetonitrile, 0.5M urea, and applied voltage 25 kV. Under the optimum conditions, ammonia and 22 aliphatic amines were separated successfully in 19 min. The signal response was linear over three-order of concentrations. The intra-day and inter-day relative standard deviations (RSD) were less than 0.81% and 1.00% for migration times, 1.76% and 2.01% for peak areas. Limits of detection (LOD) for the analytes was (S/N=3) approximate 10(-9)-10(-12)M. The method was applied to the determination of ammonia and aliphatic amines in environmental water with recoveries in the range of 90.2-110.8%. In addition, a quantitative structure-property relationship (QSPR) model for the estimation of the electrophoretic migration time was established with the comprehensive descriptors for structural and statistical analysis (CODESSA) program for the first time. The multilinear regression (MLR) equation contained two theoretical descriptors and had the following statistical indices: R(2)=0.9668, F=290.7839, R(cv)(2)=0.9576 and S(2)=0.8149.

Quantitative determination of S-alk(en)ylcysteine-S-oxides by micellar electrokinetic capillary chromatography.

A novel method for determination of S-alk(en)ylcysteine-S-oxides by capillary electrophoresis has been developed and validated. The method is based on extraction of these sulfur amino acids by methanol, their derivatization by fluorenylmethyl chloroformate and subsequent separation by micellar electrokinetic capillary chromatography. Main advantages of the new method are simplicity, sensitivity, high specificity and very low running costs, making it suitable for routine analysis of a large number of samples. Employing this method, the content of S-alk(en)ylcysteine-S-oxides was determined in 12 commonly consumed alliaceous and cruciferous vegetables (e.g. garlic, onion, leek, chive, cabbage, radish, cauliflower and broccoli). The total content of these amino acids in the Allium species evaluated varied between 0.59 and 12.3mg g(-1) fresh weight. Whereas alliin was found only in garlic, isoalliin was the major S-alk(en)ylcysteine-S-oxide in onion, leek, chive and shallot. On the other hand, the cruciferous species analyzed contained only methiin in the range of 0.06-2.45mg g(-1) fresh weight.

Micellar electrokinetic capillary chromatography as a powerful tool for pharmacological investigations without sample pretreatment: a precise technique providing cost advantages and limits of detection to the low nanomolar range.

A number of pharmaceuticals (e.g., acetaminophen, salicylic acid, sulfamethoxazole, theophylline, tolbutamide and trimethoprim) have been determined in human plasma by micellar electrokinetic chromatography (MEKC), without sample pretreatment, using underivatized fused-silica capillaries. The total analysis time was only 10 min. A sodium dodecyl sulfate (SDS)-containing borate buffer (60 mM with 200 mM SDS) at pH 10 was used. Between runs, proteins adsorbed to the capillary wall are removed by rinsing with SDS buffer and either acetonitrile (e.g., 50% v/v) or isopropanol (e.g., 10% v/v). Other rinsing procedures are discussed (salts, enzyme-containing solutions, organic solvents, sodium hydroxide, hydrofluoric acid). The separation system is tested in a concentration range between 10 ng/mL and 100 microg/mL; a detection limit of about 20 ng/mL can readily be obtained. The sensitivity was substantially improved using isopropanol as buffer additive. A day-to-day precision for relative peak areas of 1-2% relative standard deviation (RSD, n > 40) was reached in the upper concentration range. Under repeatability conditions, these values could also be obtained for low microg/mL concentrations. Thus, not only drug monitoring but also pharmacokinetic investigations from blood plasma become possible without further sample pretreatment.