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Derivatization Step (derivatization + step)
Selected AbstractsDetermination of vigabatrin in human plasma by means of CE with LIF detectionELECTROPHORESIS, Issue 19 2007Alessandro Musenga Abstract A method has been developed for the quantitation of the antiepileptic drug vigabatrin (VGB) in human plasma. It is based on CE with LIF detection. The effect of the pH of the buffer and of N -methylglucamine (GLC) as BGE constituent was investigated. The final BGE consisted of 50,mM borate buffer, pH,9.0, with 100,mM GLC and enabled separation within 12,min at 20,kV voltage. An SPE procedure was used for the pretreatment of biological samples, based on mixed-mode lipophilic-cation exchange cartridges, followed by a derivatization step with 6-carboxyfluorescein- N -succinimidyl ester (CFSE). Fluorescence was excited by an Ar-ion laser (,exc,=,488,nm). Linearity was observed in the 10,120,,g/mL plasma concentration range. Extraction yield was >96%, precision (expressed as RSD) <6.7% and accuracy (recovery) was between 97.0 and 101.6%. The method has been successfully applied to the analysis of VGB in plasma of epileptic patients undergoing therapy with the drug. [source] Determination of sertraline and N -desmethylsertraline in human plasma by CE with LIF detectionELECTROPHORESIS, Issue 11 2007Alessandro Musenga Abstract A method has been developed for the analysis of the antidepressant drug sertraline together with its main metabolite N -desmethylsertraline (DMS) in human plasma. It is based on CE with LIF detection (,,=,488,nm). A SPE procedure is employed for biological sample pretreatment, followed by a derivatization step with FITC; reboxetine was the internal standard. The effect of CD, acetone and N -methyl- D -glucamine (GLC) as constituents of the BGE for analyte separation was investigated. The final BGE consisted of 20,mM carbonate buffer, pH,9.0, with 2.5,mM heptakis(2,6-di- O -methyl)-,-CD, 50,mM GLC and 20% v/v acetone. With 30,kV applied voltage, the electrophoretic run is completed in 7.5,min. Linearity was observed in the plasma concentration range from 3.0 to 500,ng/mL for sertraline and 4.0 to 500,ng/mL for DMS. Extraction yield was >97.1%, precision , expressed as RSD% , was <3.7, accuracy (recovery) was >95.6%. Due to its sensitivity and selectivity, the method was suited for the analysis of plasma samples from patients undergoing therapy with sertraline. [source] Rapid and sensitive determination of phosphorus-containing amino acid herbicides in soil samples by capillary zone electrophoresis with diode laser-induced fluorescence detectionELECTROPHORESIS, Issue 23 2005Eva Orejuela Abstract A straightforward and sensitive method has been developed for the analysis of phosphorus-containing amino acid herbicides (glufosinate and aminomethylphosphonic acid, the major metabolite of glyphosate) in soil samples. For this purpose, the analytical features of two indocyanine fluorescent dyes, sulfoindocyanine succinimidyl ester (Cy5) and 1-ethyl-1-[5-(N -succinimidyl-oxycarbonyl)pentyl]-3,3,3,3-tetramethyl-indodicarbocyanine chloride, as labeling reagents for the determination of these herbicides by CZE with diode LIF detection were investigated. Practical aspects related to the labeling chemistry and CZE separation showed that the two probes behave similarly, Cy5 being the best choice for the determination of these herbicides on account of its higher sensitivity. The optimum procedure includes a derivatization step of the pesticides at 25°C for 30,min and direct injection to CZE analysis, which is conducted within about 14,min using ACN in the running buffer. The lowest detectable analyte concentration ranged from 0.025 to 0.18,µg/L with a precision of 3.6,5.4%. These results indicate that indocyanine fluorescence dyes are useful as rapid and sensitive labels for the determination of these herbicides when compared with typical fluorescein dyes such as FITC and 5-(4,6-dichloro- s -triazin-2-ylamino) fluorescein, because they provide faster labeling reactions even at room temperature and the excess of reagent practically does not interfere the determination. Finally, the Cy5 method was successfully applied to soil samples without a preliminary clean-up procedure, and the herbicides were measured without any interference from coexisting substances. The recoveries of these compounds in these samples at fortification levels of 100,500,ng/g were 90,93%. [source] Quantification of fudosteine in human plasma by high-performance liquid chromatography-electrospray ionization mass spectrometry employing precolumn derivatization with 9-fluorenylmethyl chloroformateJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 5 2006Fengguo Xu Abstract This paper describes a novel method for the sensitive and selective determination of fudosteine in human plasma. The method involves a derivatization step with 9-fluorenylmethyl chloroformate (FMOC-Cl) in borate buffer and detection based on high-performance liquid chromatography-electrospray ionization mass spectrometry (LC/ESI/MS). After acetonitrile-induced protein precipitation of plasma samples, fudosteine was derivatized with FMOC-Cl, then extracted by ethyl acetate, evaporated, reconstituted and injected using an LC/ESI/MS instrument. Separation was achieved using an ODS column and isocratic elution. Excellent linearity was obtained for the entire calibration range from 0.05 to 20 µg/ml. Validation assays of the lower limit of quantification (LLOQ) as well as for the intra- and inter-batch precision and accuracy met the international acceptance criteria for bioanalytical method validation. Using the developed analytical method, fudosteine could be detected for the first time in human plasma with a low limit of detection (LLOD) of 0.03 µg/ml. The proposed method has been successfully applied to study the pharmacokinetics of fudosteine in healthy Chinese volunteers after single and multiple oral administration. Copyright © 2006 John Wiley & Sons, Ltd. [source] Rapid screening assay of congenital adrenal hyperplasia by measuring 17,-hydroxyprogesterone with high-performance liquid chromatography/electrospray ionization tandem mass spectrometry from dried blood spotsJOURNAL OF CLINICAL LABORATORY ANALYSIS, Issue 1 2002Chien-Chen Lai Abstract A rapid, simple, and specific method was developed for the diagnosis of congenital adrenal hyperplasia (CAH) from dried blood spots on newborn screening cards based on high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC/ESI-MS/MS). The usefulness of 17,-hydroxyprogesterone (17OH-P) determination on dried filter-paper blood samples from patients with CAH caused by 21-hydroxylase deficiency was evaluated. The LC/MS/MS detection of 17OH-P was rapid, <4 min. The intra- and interday accuracy and precision of the method were <7%. Our procedure maintained good linearities (R2 > 0.992) and recovery rate (>83%). We used this new method to directly determine the 17OH-P levels in dried blood specimens from abnormal children of various ages, with a detection limit of 20 ng/ml (,240 pg), to avoid the time-consuming derivatization steps required by the gas-chromatography/mass spectrometry (GC/MS) method. Four dried filter-paper blood samples of CAH patients (three girls and one boy, 1,14 years old) were all quantified in an LC/MS/MS study and revealed high 17OH-P levels (>90 ng/ml). After treatment, all of the elevated 17OH-P levels either decreased or disappeared. Compared with CAH patients, 17OH-P was nearly undetectable (<20 ng/ml) in the normal infants by LC/MS/MS. This LC/MS/MS assay is not only useful for both diagnosis and monitoring of treatment of CAH in all other age groups, it also can be used as a screening test for CAH infants. In this study, we provided the first data on 17OH-P in dried blood specimens affected with CAH using HPLC/ESI-MS/MS. J. Clin. Lab. Anal. 16:20,25, 2002. © 2002 Wiley-Liss, Inc. [source] Rapid screening of polysaccharide-based plasma volume expanders dextran and hydroxyethyl starch in human urine by liquid chromatography,tandem mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 7 2008Sven Guddat Abstract The increasing number of samples and target substances in doping control requires continuously improved screening methods, combining high-throughput analysis, simplified sample preparation, robustness and reliability. Hence, a rapid screening procedure based on liquid chromatography,electrospray ionization,tandem mass spectrometry with in-source collision-induced dissociation was developed. The detection of the polysaccharide-based plasma volume expanders dextran and hydroxyethyl starch (HES) in human urine was established without further sample preparation. The in-source fragmentation strategy of the approach represented a valuable tool in the analysis of the polysaccharide-based compounds, allowing the use of tandem mass spectrometry. After direct injection of urine specimens, analytes were chromatographically separated on a monolithic reverse-phase column and detected via multiple reaction monitoring of diagnostic ions at detection limits of 10 µg/mL for HES and 30 µg/mL for dextran. Validation was performed regarding the parameters specificity, linearity, precision (8,18%) and accuracy (77,105%) and the method was applied to the investigation of approximately 400 doping control samples and seven dextran and two hydroxyethyl starch post-administration samples. The approach demonstrated its capability as a rapid screening tool for the detection of dextran and hydroxyethyl starch and represents an alternative to existing screening procedures since time consuming hydrolysis or derivatization steps were omitted. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||