Serum lamotrigine analysis by capillary electrophoresis

Lamotrigine, a new antiepileptic drug, is analyzed by capillary zone electrophoresis. Samples were deproteinized with acetonitrile containing an internal standard, acidified with dilute acetic acid and injected into the capillary. The drug migrated rapidly with the cationic compounds in about 3.5 min far from any interfering substances. The test was linear between 0.5–10 mg/l. The analysis time was about 5 min. The CE values correlated well with an HPLC method (r=0.97; n=35). The mean serum concentration of 121 patients on this drug was 3.7 mg/l. Incubating the serum with ß-glucuronidase for 1 h increased the peak height of lamotrigine by about 24%.     

Quantification of daunorubicin and daunorubicinol in plasma by capillary electrophoresis

Capillary electrophoresis (CE) with laser-induced fluorescence detection was applied to quantify daunorubicin and daunorubicinol in plasma. Separation was carried out in a 47 cm×50 μm I.D. fused-silica capillary, with a running buffer, pH 5 containing 60 μM spermine and 70% acetonitrile. Sample preparation was done either by protein precipitation with acetonitrile or by liquid–liquid extraction. The assay can be applied in a concentration range from 40 mg/l down to 2 μg/l for daunorubicin and from 1 mg/l to 2 μg/l for daunorubicinol. Precision and accuracy were between 2.9 and 14.5% (n=6) on 1 day and between 1.0 and 14.7% from day to day (n=6) for both analytes. Thus, the CE method enables precise and accurate quantification of daunorubicin and daunorubicinol in small sample volumes over a wide concentration range.     

Analysis of ibuprofen in serum by capillary electrophoresis

A rapid method for analysis of the analgesic drug ibuprofen in serum by capillary zone electrophoresis in a borate buffer 160 mmol/l pH 8.5 is described. The method involves deproteinization with acetonitrile to remove serum proteins followed by direct injection on the capillary. The recoveries of standards added to the serum were 84–92%. The method is suited for analysis of samples with concentrations >10 mg/l. Many other analgesics such as ketoprofen, daypro and salicylates can also be determined by this method.     

Comparison of a capillary electrophoresis method with high-performance liquid chromatography for the determination of biogenic amines in various food samples

A capillary electrophoresis (CE) and a high-performance liquid chromatography (HPLC) method to analyze biogenic amines in food were compared. An automated precolumn derivatization with o-phthaldialdehyde (OPA) allows for the determination of aliphatic amines and amino acids by HPLC. In contrast, for the measurement of histamine and tyramine by CE, no laborious sample pretreatment was necessary. The biogenic amines were separated by CE or HPLC in less than 9 or 20 min, respectively. The calibration curves were linear to at least 100 mg/kg (r=0.999) and 1,000 mg/kg for HPLC and CE, respectively, with detection limits for histamine of 0.5 mg/kg (fluorescence detector) or 1 mg/kg (diode array detector) with HPLC and 2 mg/kg with CE. The detection limits for tyramine were 1.5 mg/kg with HPLC and 6 mg/kg with CE and for further amines (e.g., putrescine, spermidine, cadaverine, agmatine) ranging from 1.0 to 8.5 mg/kg with HPLC. There was a good correlation between CE and HPLC (correlation coefficient for histamine: 0.994).     

Capillary electrophoresis enantioselective separation of vigabatrin enantiomers by precolumn derivatization with dehydroabietylisothiocyante and UV-vis detection

A simple and reliable capillary electrophoresis (CE) method with UV-vis detection is presented for the enantioselective separation and determination of vigabatrin enantiomers. Dehydroabietylisothiocyante (DHAIC), a novel chiral derivatizing reagent, was used for precolumn derivatization of vigabatrin enantiomers. Optimal separation was obtained with a running buffer consisting of 50 mM Na2HPO4 (pH 9.0), 17 mM sodium dodecyl sulfate (SDS) and 25% acetonitrile. The enantiomeric separation of vigabatrin derivatives was achieved within 25 min, and the resolution was found to be 2.1. Detection was followed by direct UV absorptiometric measurements at 202 nm. A calibration curve ranging from 0.3 to 6.0 microg/ml was shown to be linear, and the limit of detection was 0.15 microg/ml. The developed method has been applied to the determination of vigabatrin enantiomers spiked in human plasma, no interferences were found from endogenous amino acids.     

Development of a urinary free cortisol assay using solid-phase extraction–capillary electrophoresis

In clinical practice, the measurement of urinary free cortisol (UFC) provides the most sensitive and specific diagnostic information for excess adrenal production of cortisol. The existing methodologies (RIA and HPLC) are time consuming, costly, involve tedious extractions, derivatizations and problems with non-specific interactions with cortisol metabolites in urine. In the present study, we describe the development of an SPE–CE method for the rapid analysis of UFC. UFC was concentrated using SPE C₁₈ cartridges (3M Empore) under a vacuum and eluted with acetonitrile–SDS. The use of 10% acetone to wash cartridges before final elution with acetonitrile–SDS showed significant improvements in the free cortisol recovery. The complete extraction was accomplished in 10–15 min with a recovery of 89–94%. CE analysis was done on a Beckman P/ACE 5010 with detection at 254 nm using a neutral capillary. Detection limits of free cortisol in urine was improved to 10 μg/l with SPE compared to 500 μg/l without SPE. No interferences either from BSA or other urinary cortisol metabolites affected the free cortisol determinations. The results showed the feasibility of a rapid UFC detection with improved sample handling capacity.     

Size-exclusion liquid chromatography and capillary electrophoresis of pollen allergens

Allergens from the pollen of Phleum pratense, Dactylis glomerata. Arrhenatherum elatius, Secale cereale, Lolium perrene and Festuca sp. were analysed by size-exclusion chromatography (SEC) and capillary electrophoresis (CE). SEC was used for the determination of the molecular masses of main allergens. A CE method, using either 150 mmol/1 phosphoric acid (pH 1.8) or a micellar system consisting of 50 mmol/l sodium dodecyl sulphate-20 mmol/l borate (pH 9.35), was developed as a rapid and efficient alternative to SEC, especially for process control of allergenic preparations. The results obtained by the two methods confirmed similarities in the structures of the studied pollen allergens.     

Characterization of proteins in the human serum proteome.

This paper presents a multidimensional profile of the human serum proteome, produced by a two-dimensional protein fractionation system based on liquid chromatography followed by characterization with capillary electrophoresis (CE). The first-dimension separation was done by chromatofocusing over a pH range from 8.5 to 4.0, where proteins were separated by their isoelectric points (pI). In this dimension, fractions were collected based on pH. The first-dimension pI fractions were then resolved in the second dimension by high-resolution, reversed-phase chromatography with a gradient of trifluoroacetic acid (TFA) in acetonitrile and TFA in water. A selected protein fraction collected from the second dimension by time was characterized by CE for molecular-weight estimation and for presence of isoforms. Molecular-weight estimation was done by sodium dodecyl sulfate capillary gel electrophoresis, where proteins were separated in the range of 10,000-225,000 Da. Detection of isoforms was done by capillary isoelectric focusing over a pH range of 3-10. A selected second-dimension fraction that contained the putative serum iron-binding protein transferrin was analyzed by these two CE techniques for molecular-weight determination and the presence of isoforms. The combination of two-dimensional protein fractionation and CE characterization represents an advanced tool for proteomics.     

Determination of ascorbic acid in individual rat hepatocyte by capillary electrophoresis with electrochemical detection

A method for the direct determination of ascorbic acid (AA) in individual rat hepatocyte based on capillary electrophoresis (CE) coupled with electrochemical detection (ECD) using a new kind of homemade carbon fiber micro-disk bundle electrode has been described. Individual rat hepatocytes were injected into a fused-silica capillary with an inner diameter of 25 microm, and lysed by 0.1% sodium dodecylsulfate (SDS) as cell lysis solution. The following conditions were suitable for the determination of AA: running buffer, 1.83 x 10(-2) mol/l Na2HPO4-1.70 x 10(-3) mol/l NaH2PO4 (pH 7.8); separation voltage, 20.0 kV; detection potential, 0.80 V (vs. saturated calomel electrode (SCE)). The concentration limit of detection (LOD) of the method was 1.7 x 10(-6) mol/l at a signal-to-noise (S/N) ratio of 3, and the mass LOD was 3.0 fmol. The linear dynamic range was from 5.0 x 10(-6) to 5.0 x 10(-4) mol/l with a correlation coefficient of 0.9962 for the injection voltage of 5.0 kV and injection time of 10s. The relative standard deviation (R.S.D.) was 0.85% for the migration time and 1.8% for the peak current. This method was successfully applied to AA determination in rat hepatocyte. The recovery was between 91% and 97%, and the amount of AA in single rat hepatocyte ranged from 28 to 63 fmol.     

Determination of free amino acids and related compounds in amniotic fluid by capillary electrophoresis with contactless conductivity detection

A capillary electrophoretic (CE) method with contactless conductivity detection (CCD) has been developed for the determination of free amino acids (AAs) in the amniotic fluid. Apart from 20 proteinogenic AAs, 12 other biogenic compounds have been identified including ethanolamine, choline, beta-alanine, 2-aminobutyric acid, 4-aminobutyric acid, creatinine, ornithine, carnitine, citrulline, 4-hydroxyproline, 1-methylhistidine and 3-methylhistidine. The running electrolyte consisted of 1.7 M acetic acid and 0.1% hydroxyethyl-cellulose (pH 2.15). An addition of acetonitrile to the sample improved the separation of AAs significantly and permitted an increase in the amount of the sample injected. As a result, the sensitivity of the determination increased and the limit of detection (LOD) decreased by a factor of ca. 4, as compared with our previous study. The LOD values were between 1.5 microM (arginine) and 6.7 microM (aspartic acid). The CE/CCD method has then been applied to clinical analyses of the amniotic fluid collected from 20 pregnant women aged over 35 years and 24 pregnant women with whom abnormal foetus development was suspected. The latter group of women was found to exhibit systematically enhanced amniotic levels of most of the AAs studied.     

Solid phase extraction--non-aqueous capillary electrophoresis for determination of metformin, phenformin and glyburide in human plasma

Solid phase extraction (SPE) was coupled at line to capillary electrophoresis (CE) for the determination of three basic and neutral diabetic drugs (metformin, phenformin and glyburide) in human plasma. The SPE procedure employed a C(18) cartridge to remove most of the water and proteins from the plasma sample. Analyte detectability was increased due to trace enrichment during the SPE process. Elution of metformin, phenformin and glyburide was achieved with methanol+3% acetic acid. CE analysis was performed using a non-aqueous buffer, acetonitrile+5mM ammonium acetate+5% acetic acid, which afforded rapid separation of metformin from phenformin within 3 min. Glyburide, with a migration time longer than 6 min, did not cause any interference. The present SPE-CE method, with an electrokinetic injection time of 6s and UV detection at 240 nm, was useful for monitoring down to 1 microg/mL of metformin and phenformin in human plasma. When the electrokinetic injection time was increased to 36s, the detection limits were improved to 12 ng/mL for metformin and 6 ng/mL for phenformin.     

毛豆中腈菌唑残留量的气相色谱法测定

采用气相色谱法定量分析毛豆上腈菌唑的微量残留量。样品经乙腈提取,液液分配,中性氧化铝柱层析净化后,以气相色谱电子俘获检测器法(GC-ECD)测定,DB-1701毛细管柱、氮气为载气,柱温150℃20℃/min 260℃(10 min),气化室温度240℃,检测器温度300℃,外标法定量。该方法快速、准确,在0.05~2.00 mg/L范围内线性相关系数r²=0.9998,平均回收率91.1%~99.0%,变异系数1.22%~2.94%,最小检测量1.0×10^-12 g,最低检出浓度5.0×10^-4 mg/kg。     

Simultaneous determination of mycophenolic acid and its phenolic glucuronide in human plasma using an isocratic high-performance liquid chromatography procedure

Simultaneous determination of mycophenolic acid (MPA) and mycophenolic acid glucuronide (MPAG) in plasma was accomplished by isocratic HPLC with UV detection. After protein precipitation and phase separation with saturated sodium dihydrogenphosphate, chromatographic separation was achieved on a monolithic column "Chromolith Performance RP-18e", with acetonitrile/0.01 M phosphate buffer, pH 3, (25:75, v/v), as the mobile phase; flow rate 3.3 ml/min and measurement at 214 nm. Linearity was verified up to 40 mg/l for MPA and up to 400 mg/l for MPAG. Detection limits based on the analysis of 50 microl plasma were 0.05 and 0.5 mg/l for MPA and MPAG, respectively. Accuracy was 99.6-104% for MPA and 95.6-105% for MPAG and total imprecision (CV) was <7% for both compounds. Analytical recovery was >95% for MPA and MPAG. The method is simple, rapid, accurate and suitable for routine determination of MPA and MPAG in plasma.     

Determination of rifabutin by high-performance liquid chromatography using on-line concentration and column switching

A simple HPLC method has been developed that allows the sensitive determination of rifabutin (RBT) in human serum using on-line concentration and column switching. After pretreatment of the serum with acetonitrile and centrifugation, the samples were applied to a concentration column (CC) (Zorbax CN). Washing with phosphate buffer-methanol removed most of the contaminating substances. Via a six-port valve the CC was switched to the analytical mode. RBT was separated on a Chromspher RP 8 column (acetonitrile-phosphate buffer pH 7.4/sodium chloride) and determined photometrically at 278 nm. The lower limit of quantification for 200 μl serum precipitated with 200 μl acetonitrile and after injection of 2×150 μl was 33 μg/l and linearity was observed up to 27 mg/l. Different modes of sample application (single, repeated, and different injection volume portions), as well as washing time, cycle time and different CC materials were investigated.     

Determination of idarubicin and idarubicinol in plasma by capillary electrophoresis

A rapid and sensitive capillary electrophoretic method for the determination of idarubicin and its metabolite idarubicinol in plasma has been developed and validated. Plasma is extracted by liquid-liquid extraction using chloroform. Idarubicin, idarubicinol and the internal standard daunorubicin can be separated in less than 5 min using a phosphate buffer of pH 5 with 70% acetonitrile. Laser-induced fluorescence detection with an Ar ion laser operated at 488 nm provides a sensitive and selective detection method without interferences from biological fluids. The small sample volume of 100 μl is of particular advantage for studies in pediatric oncology. The reproducibility of the method has been shown to be sufficient for drug monitoring or pharmacokinetic studies. The limit of quantification for idarubicin in plasma is 0.5 ng/ml.     

Determination of metabolites of pirimicarb in human urine by gas chromatography–mass spectrometry

The analytical method described permits the determination of 2-dimethylamino-5,6-dimethyl-4-hydroxypyrimidine (DDHP), 2-methylamino-5,6-dimethyl-4-hydroxypyrimidine (MDHP) and 2-amino-5,6-dimethyl-4-hydroxypyrimidine (ADHP) in human urine. These hydroxypyrimidines are metabolites of pirimicarb (2-dimethylamino-5,6-dimethylpyrimidin-4-yldimethylcarbamate) which is applied as insecticide. The analytes are extracted into a mixture of diethyl ether and acetonitrile. Pentafluorobenzyl bromide serves as derivatising reagent. The derivatives are analysed using capillary gas chromatography with mass selective detection. 2-Amino-4-hydroxy-6-methylpyrimidine and 4-hydroxy-6-trifluoromethylpyrimidine are used as internal standards. The detection limits are 0.5 μg/l (DDHP), 1 μg/l (MDHP) and 4 μg/l (ADHP), respectively. The method was used for analysing seven urine samples collected from workers who had applied pirimicarb. The three metabolites were found in every sample in concentrations up to 60 μg/l.     

Determination of perhexiline and hydroxyperhexiline in plasma by liquid chromatography-mass spectrometry

A method for the quantitative determination of perhexiline and its main hydroxylated metabolites in human plasma, based on liquid chromatography-mass spectrometry (LC-MS), was developed. The method used protein precipitation with acetonitrile followed by dilution with water and subsequent direct injection of the extract into the LC-MS system. Hexadiline was used as internal standard and the intra-assay coefficients of variation were 相似文献   

Direct and fast capillary zone electrophoretic method for the determination of Gleevec and its main metabolite in human urine

A capillary zone electrophoretic (CZE) method was investigated for the determination of Gleevec and its main metabolite (N-demethylated piperazine derivative) in human urine using a fused-silica capillary (75 microm I.D.x60 cm total length, 10 cm effective length). The separation was performed with an hydrodynamic injection time of 10 s (0.5 p.s.i.) a voltage of -25 kV, a capillary temperature of 25 degrees C and a 100 mM phosphoric acid adjusted to pH 2 with the addition of triethanolamine. Under these conditions, the analysis takes about 5 min. A linear response over the 0.4-30.0 mg l(-1) concentration range was investigated for two compounds. A dilution of the sample was the only step necessary before the electrophoresis analysis. Detection limits of 0.1 mg l(-1) for Gleevec and its metabolite (S/N=3) were obtained. The developed method is easy, rapid and sensitive and has been applied to determine Gleevec and its main metabolite in clinical urine samples.     

Enantioselective determination of zopiclone and its metabolites in urine by capillary electrophoresis

A method has been developed for the stereoselective determination of zopiclone and its main metabolites in urine. After the addition of the internal standard zolpidem the urine samples were extracted at pH 8 with chloroform-isopropanol (9:1). Analyses were carried out using capillary electrophoresis (CE) with β-cyclodextrin as the chiral selector. The analytes were detected using UV laser-induced fluorescence detection with a He-Cd laser operated at 325 nm. Urine samples of two volunteers after oral administration of 7.5 mg zopiclone were investigated. The S-(+)-enantiomers of zopiclone and its metabolites were always excreted in higher amounts than the R-(−)-enantiomers. With the same method the zopiclone enantiomers were quantified in saliva. Compared to high-performance liquid chromatography, the CE method is very fast and simple.     

Gas chromatographic determination of meprobamate in human plasma

A simplified and rapid gas chromatographic method has been developed for the determination of meprobamate in human plasma. The procedure includes a single-step extraction of alkalinized sample with chloroform, and chromatography on a non-polar fused-silica capillary column with flame ionization detection. The method is accurate (97.7 ± 5.7% at 20 mg/l) and precise (maximum coefficient of variation of 9.5%). It provides an alternative to existing methods and is particularly suitable for toxicological studies.