Determination of methyl ethyl ketone and its metabolites in urine using capillary gas chromatography

A method is described for the determination of the concentration of methyl ethyl ketone and its metabolites: 2-butanol, 3-hydroxy-2-butanone and the meso- and d,l-isomers of 2,3-butanediol in urine. The analytes were isolated from urine by solid-phase extraction and analysed by capillary gas chromatography. The recovery rates were 50-70% for the 2,3-butanediol isomers and 88-96% for the other analytes. The precision of the method ranged from 5 to 12% (S.D.%). The detection limit was 1.0 and 1.4 mg/l for meso- and d,l-2,3-butanediol, respectively, and ranged from 0.1 to 0.15 mg/l for the other analytes.     

Determination of nifedipine and its three principal metabolites in plasma and urine by automated electron-capture capillary gas chromatography

A sensitive, efficient, linear and reproducible capillary gas chromatographic method with electron-capture detection was developed for the quantitation of nifedipine and its primary metabolite M-I in plasma together with the urinary and principal metabolites M-II and M-III. On-column, rather than split-splitless, injection was employed to obviate oxidative degradation of nifedipine to M-I. The photosensitivity of nifedipine was re-examined under laboratory conditions and nifedipine was found to have a half-life in excess of two days when amber glassware and darkroom manipulations under red light were used. The method can determine nifedipine and its metabolites in plasma and urine after a single oral dose of 5 mg and can be applied to measure M-I production by human liver microsomes.     

Determination of pethidine and its major metabolites in human urine by gas chromatography

Procedures based on gas chromatography were established to determine pethidine and its major metabolites in human urine. The chromatographic system consisted of a glass column packed with 3% (w/w) SP2250 on Chromosorb W (80-100 mesh) linked to a nitrogen-phosphorus detector. Diethyl ether was used as the extraction solvent. Pethidinic and norpethidinic acids, and their conjugated metabolites (after beta-glucuronidase treatment) were determined after conversion into pethidine and norpethidine by acid-catalysed esterification. The retention times of pethidine, norpethidine and chlorpheniramine (internal standard) were 3.3, 4.5 and 7.5 min, respectively. The amount of unchanged drugs and metabolites excreted varied considerably among the subjects. The mean 24-h urinary recoveries in eight patients of pethidine, norpethidine, pethidinic acid, norpethidinic acid, and the glucuronides of pethidinic and norpethidinic acids were 6.62 +/- 5.05, 4.33 +/- 1.19, 18.9 +/- 6.29, 9.10 +/- 4.26, 15.1 +/- 3.02 and 7.57 +/- 2.28%, respectively. This indicates that the major metyabolic pathways of pethidine in the eight patients were hydrolysis followed by conjugation. Over 60% of the dose was accounted for in 24 h after intramuscular administration of 1 mg/kg pethidine.     

Determination of butoxyacetic acid in urine by capillary gas chromatography

Summary A simple, rapid and reliable method is presented for the determination of butoxyacetic acid (BAA), the main metabolite of ethylene glycol monobutyl ether (Butyl Cellosolve). The urine is acidified with hydrochloric acid and passed through a cation-exchange column. BAA which is quantitatively found in the filtrate is subsequently adsorbed on XAD-4 resin. After desorption with diethyl ether an aliquot of the eluate is evaporated in a nitrogen stream and methylated with diazomethane in diethyl ether. A forty-fold enrichment is achieved by this procedure. The gas-chromatographic separation is performed on a 60 m fused silica capillary column DB-1 (100% dimethyl-polysiloxane). Flame ionization is used for detection. Pentoxyacetic acid (PAA) serves as internal standard. The detection limit of BAA in urine is 0.02 mg/l. Linearity has been tested up to 50 mg/l. The losses by the clean-up steps are between 10.0% and 22.7%. The average recovery is 100.9%. Within-series imprecision (n=10) has been determined for three concentrations and ranges between 4.8% and 12.6%.

---

Capillar-gas-chromatographische Bestimmung von Butoxyessigsäure in Harn

     

Determination of polyol profiles in human urine by capillary gas chromatography

A new rapid capillary gas chromatographic method is described for the profile analysis of urinary polyols as their trifluoroacetyl derivatives. Ten urinary polyols: erythritol, threitol, fucitol, ribitol, arabinitol, xylitol, mannitol, glucitol, galactitol and myo-inositol were completely determined for the first time. Iditol was newly found in normal urine. Urinary polyols were verified by gas chromatography/mass spectrometry.     

Determination of pyrethroid metabolites in human urine by capillary gas chromatography-mass spectrometry

Summary An analytical method for the simultaneous determination of the pyrethroid metabolites cis and trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid, cis 3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane carboxylic acid, 3-phenoxybenzoic acid and 4-fluoro-3-phenoxybenzoic acid in human urine samples is described. The urine is subjected to acid-induced hydrolysis followed by exhaustive solvent extraction, covering both conjugated and free acids, followed by a common derivatisation step yielding the corresponding methyl esters. Quantitation was by diastereomeric, capillary gas chromatography-mass spectrometry. It appears that 4-fluoro-3-phenoxybenzoic acid is a characteristic urinary marker for cyfluthrin exposure. The limits of determination are 0.5–1.0 g L^–1 urine depending on the metabolites concerned. The applicability of the method was tested on urine samples from pest control operators exposed occupationally to cypermethrin and cyfluthrin.     

Determination of caffeine and its metabolites in urine by capillary electrophoresis-mass spectrometry

The caffeine content of foods and beverages varies considerably, interfering with our ability to obtain valid interpretations in many human studies with regard to the mechanism of action(s) of caffeine and/or its metabolites. The rate of metabolism of caffeine and other xanthine drugs also varies greatly from one individual to another. Therefore, it is extremely important to develop accurate, reliable analytical methods to quantify caffeine and its metabolites in simple and complex matrixes. A simple method is described for the separation and characterization of caffeine and its major metabolites employing capillary electrophoresis (CE) coupled to ultraviolet-absorption and mass spectrometry (MS) detection. After optimization of the electrophoresis separation conditions, a reliable separation of caffeine and 11 of its major metabolites was achieved in 50 mM ammonium carbonate buffer, pH 11.0. The volatile aqueous electrolyte system used with a normal electroosmotic flow polarity also provided an optimal separation condition for the characterization of the analytes by MS. The CE method achieved baseline resolution for all 12 compounds in less than 30 min. The CE-MS method is suitable for use as a routine procedure for the rapid separation and characterization of caffeine and its metabolites. The usefulness of this method was demonstrated by the extraction, separation, and identification of caffeine and its 11 metabolites from normal urine samples. The urine specimens were first acidified to obtain optimum binding efficiency to the sorbents of the off-line, solid-phase extraction procedure employed here, and an acidified eluent solvent was employed for the desorption step to maximize the recovery of the bound analytes.     

Determination of sulfinpyrazone and two of its metabolites in human plasma and urine by gas chromatography and selective detection

A selective and sensitive gas chromatographic method for simultaneous determination of sulfinpyrazone and two of its metabolites (the para-hydroxylated metabolite and the sulfone metabolite) in biological fluids using alkali flame ionization detection (AFID), electron capture detection (ECD) and mass fragmentographic detection is described. The compounds are extracted from the samples, methylated and separated on 2% OV-17 or 3% OV-225 columns. Phenylbutazone is used as internal standard. Standard curves are linear. The coefficient of variation at 10 microgram/ml of sulfinpyrazone in plasma was shown to be 1.8% (AFID), and the detection limits were 0.1 microgram/ml (AFID) and 10 ng/ml (ECD). Mass spectra of the methylated compounds are shown and serum concentration curves after oral administration of 100 mg sulfinpyrazone to two persons are determined together with the excreted amounts of drug and metabolites.     

Analysis of lamotrigine and its metabolites in human plasma and urine by micellar electrokinetic capillary chromatography

A reliable micellar electrokinetic capillary chromatographic method was developed and validated for the determination of lamotrigine and its metabolites in human plasma and urine. The variation of different parameters, such as pH of the background electrolyte (BGE) and Sodium dodecyl sulfate (SDS) concentration, were evaluated in order to find optimal conditions. Best separation of the analytes was achieved using a BGE composed of 10 mM borate and 50 mM SDS, pH 9.5; melatonin was selected as the internal standard. Isolation of lamotrigine and its metabolites from plasma and urine was accomplished with an original solid-phase extraction procedure using hydrophilic-lypophilic balance cartridges. Good absolute recovery data and satisfactory precision values were obtained. The calibration plots for lamotrigine and its metabolites were linear over the 1-20 microg/mL concentration range. Sensitivity was satisfactory; the limits of detection and quantitation of lamotrigine were 500 ng/mL and 1 microg/mL, respectively. The application of the method to real plasma samples from epileptic patients under therapy with lamotrigine gave good results in terms of accuracy and selectivity, and in agreement with those obtained with an high-performance liquid chromatography (HPLC) method.     

Determination of polyamines in urine of normal human and cancer patients by capillary gas chromatography

A capillary gas chromatographic method is described for the determination of polyamines (putrescine, spermidine and spermine) in the urine of normal human and cancer patients. Morning urine after acid hydrolysis is cleaned up on a silica gel column and derivatized with trifluoroacetic-anhydride. Creatinine in human urine is used as internal standard. Recoveries of polyamines are 96.7% putrescine, 102.6% spermidine (Spd), and 98.7% spermine. SD of the method for Spd is 1.949 +/- 0.041 (micrograms/mg creatinine, mean +/- SD, n = 5). The results show that the mean level of polyamines in cancer patients urine is much higher than that in normal human urine. The mean of total polyamines in the normal human and the cancer patients is 2.01 and 44.74, respectively (g/mg creatinine).     

Determination of ibuprofen and its major metabolites in human urine by high-performance liquid chromatography

A sensitive and selective high-performance liquid chromatographic assay for free and total ibuprofen and its major metabolites in human urine is described. Urine is acidified, drug and metabolites are extracted into hexane-propanol, back-extracted into sodium bicarbonate, neutralized and chromatographed. Ibufenac (4-isobutylphenylacetic acid) and 2-phenylpropionic acid were employed as internal standards. The extraction efficiencies were 94-100% for all compounds. The two metabolites and their internal standard were separated using an isocratic chromatographic system, followed by an abrupt step gradient to a second eluent for separation of ibuprofen and its internal standard with a total run time of 18 min. Detection was by a fixed-wavelength detector (214 nm). Sample-to-sample and day-to-day reproducibility studies yielded coefficients of variability of less than 9% for all compounds. The sensitivity was sufficient to determine 2.5 micrograms/ml free ibuprofen in 100 microliters urine.