Rapid trace analysis of barbiturates in blood by high pressure liquid chromatography

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Rapid trace analysis of barbiturates in blood by high pressure liquid chromatography

     

Determination of sodium phenobarbital in animal chow by high-pressure liquid chromatography

An analytical procedure is described for determining residues of sodium phenobarbital in animal chow at levels as low as 0.14 ppm. The methanol extract is subjected to a liquid-liquid cleanup at pH 13 and 1, further cleaned up on a silica gel column and assayed by high-pressure liquid chromatography by using an ultraviolet absorption detector at 210 nm. Data concerning extraction efficiency, partition values and stability of the chemical in animal chow are also presented.     

Determination of pyrethroid metabolites in human urine using liquid phase microextraction coupled in-syringe derivatization followed by gas chromatography/electron capture detection

Metabolites of synthetic pyrethroids such as cis-3-(2,2-dibromovinyl)-2,2-di-methylcyclo-propane-1-carboxylic acid, cis- and trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid), 3-phenoxybenzoic acid (3-PBA), and 4-fluoro-3-PBA are biomarkers for exposure to phenothrin, tetramethrin, cyfluthrin, cypermethrin, deltamethrin, and permethrin. In this study, the pyrethroid metabolites in workers’ urine samples were monitored for the first time with a novel sample pretreatment process combining hollow fiber liquid phase microextraction (HF-LPME) and in-syringe derivatization (ISD) followed by gas chromatography–electron capture detector (GC-ECD) analysis. A micro-syringe pre-filled with derivatizing agents and syringe needle connected to an extracting solvent impregnated hollow fiber segment was used as the LPME probe. Pyrethroid metabolites were extracted and enriched simultaneously from urine samples by HF-LPME sampling and acid hydrolysis at 70 °C for 10 min. After sampling, the ISD was performed by mixing the extracting solution and derivatizing agents through plunger movements, followed by GC-ECD analysis. Parameters influencing the HF-LPME efficiency and ISD were investigated and optimized. Under optimum conditions, the method provided enrichment factors of 69.8–154.6, repeatability from 5.0 to 12% (n = 5), and good linearity (R ² = 0.9980–0.9998) for interested analytes spiked in urine samples. The method detection limits ranged from 1.6 to 17 ng/mL. A comparison was performed between the proposed method and conventional methods. The proposed method was applied to analyze pyrethroid metabolites in the urine samples collected from workers of pesticide formulation plants. The results suggested that the proposed HF-LPME coupled ISD method was a rapid, simple, efficient, and eco-friendly technique in the biomonitoring of metabolites of pyrethroids in workers’ urine.     

气相色谱-微池电子捕获器检测尿液中的三唑仑

建立了气相色谱-微池电子捕获检测器(GC-μECD)检测尿液中三唑仑的方法。筛选了pH值、提取溶剂、涡旋时间,优化了液-液萃 取条件。在0.2～50 ng/mL范围内,线性关系良好,相关系数为0.9995;方法的检出限为0.1 ng/mL,日内和日间测定的相对标准偏差分 别为4.17%和5.31%,平均回收率为93.9%。该方法操作简便、灵敏度高、线性范围广、回收率高,完全能够满足日常检测工作的需要。     

Determination of trichloroethanol at therapeutic and overdose levels in blood and urine by electron capture gas chromatography.

A specific and sensitive gas chromatographic method for the determination of trichloroethanol, the active metabolite of chloral hydrate, in blood and urine is reported. A simple dilution of the sample with an ethanolic solution of internal standard followed by gas chromatography with electron capture detection is described. The method has been used to determine plasma levels after therapeutic dosing with chloral preparations.     

The use of the electron capture detector in human and equine doping analysis by gas chromatography

Summary The possibilities, applications and limitations of the electron capture detector (ECD) in human and equine doping analysis are considered. As many stimulants and/or their metabolites possess and amino group the introduction of halogen containing groupings by acylation results in improved chromatographic performance almost combined with enhanced sensitivity and selectivity when using the ECD. Several examples of the confirmation of doping agents like amphetamines, ephedrine, phenylbutazone, pemoline and procaine by GC/ECD are given.Presented at the 7^th International Symposium on Biomedical Applications of Chromatography, Hradec Králové, Czechoslovakia; 6–9 Sept. 1982.     

Determination of the metabolites of gestrinone in human urine by high performance liquid chromatography, liquid chromatography/mass spectrometry and gas chromatography/mass spectrometry

Gestrinone was studied by high performance liquid chromatography (HPLC) for screening and by gas chromatography/mass spectrometry (GC/MS) for confirmation. When the chromatograms of blank, spiked urine and dosed urine were compared by HPLC, two unknown metabolites were found and these were excreted as the conjugated forms. Metabolites 1 and 2 were tested by LC/MS and LC/MS/MS and both had parent ions at m/z 325. The fragment ion of metabolite 1 was at m/z 263 and ions for metabolite 2 were m/z 307 [MH - H(2)O](+), 289, 279 and 241. LC/MS/MS of m/z 263 as the parent ion of metabolite 1 gave fragment ions at m/z 245 and 217, which were assumed to be [263 - H(2)O](+) and [235 - H(2)O](+), respectively. The trimethylsilyl (TMS)-enol-TMS ether derivative of gestrinone displayed three peaks in its GC/MS chromatogram, formed by tautomerism.     

Microdetermination of hyaluronic acid in human urine by high performance liquid chromatography.

A high performance liquid chromatographic (HPLC) system is described for determination of the unsaturated disaccharide (delta Di-HA) derived from hyaluronic acid (HA) in human urine by digestion with hyaluronidase SD. The effects of eluents on the separation of delta Di-HA and delta Di-0S, which is derived from the reaction of chondroitin with the enzyme, have been studied. The established chromatographic conditions were as follows--column: a stainless steel tube (4 mm i.d. x 250 mm) packed with TSKgel NH2-60; eluent: a mixture of acetonitrile and 0.1 M Tris-HCl buffer containing 0.1 M boric acid and 10 mM sodium sulphate, pH 7.0 (64:36, v/v). The strong fluorescence of unsaturated disaccharide after the reaction with 2-cyanoacetamide in alkaline medium was used for post-column detection. The calibration curve for delta Di-HA was linear in the range 5 pmol-5nmol with a practical detection limit of 2 pmol. The assay coefficients of variation (n = 5) at 200 pmol for delta Di-HA and delta Di-0S were 1.7 and 1.5%, respectively. This HPLC system has been applied to the determination of HA in human urine.     

Determination and excretion study of gestrinone in human urine by high performance liquid chromatography and gas chromatography/mass spectrometry

Gestrinone was studied by HPLC for screening and by GC/MS for confirmation. Three unknown peaks were found by HPLC which are probably the metabolites of gestrinone, and conjugated gestrinone in dosed human urine. The metabolites and gestrinone were excreted as the conjugated forms. The total amounts of metabolite 1 and conjugated gestrinone, recovered after 48 h, were 0.20 and 0.32 mg, respectively. When metabolite 1 was tested by LC/MS and LC/MS/MS, the parent ion was m/z 327, [MH](+), and fragment ions were seen at m/z 309 [MH - H(2)O](+), 291 [MH - 2H(2)O](+), 283, 263 and 239. The TMS-enol-TMS ether derivative of gestrinone has three peaks in the GC/MS chromatogram formed by tautomerism. The reproducibility of the derivatization method was stable and recoveries were over 87% when spiked into blank urine.     

Determination of thiosulfate in human urine by high performance liquid chromatography

Thiosulfate is a sulfate analogue with a thiosulfur substituent and is found in human samples. Its concentration in urine is increased in some diseases and after exposure to hydrogen sulfide gas. We have developed a sensitive, simple and cheap method for thiosulfate determination in urine. The method is based on precolumn derivatization with 2-chloro-1-methylquinolinium tetrafluoroborate followed by reversed-phase liquid chromatography separation and ultraviolet detection of 1-methyl-2-thioquinolone at 375 nm. The calibration curve for thiosulfate was linear in the tested range 0.5-50 μmol L⁻¹ with correlation coefficient better than 0.999. The analytical recovery and relative standard deviation values for precision within the calibration range were from 90.1% to 104.2% and from 2.39% to 5.59%, respectively. The lower limit of detection and quantitation were 0.3 and 0.5 μmol L⁻¹, respectively. The mean (range) concentration of thiosulfate normalized against creatinine for apparently healthy seven women and six men was 2.21 (1.45-2.77) and 2.51 (1.36-4.89) mmol mol⁻¹ creatinine, respectively. We monitored thiosulfate in urine samples from one volunteer for 24 h. The urinary excretion of thiosulfate was 21.4 μmol per 24 h. This method can be used for routine clinical monitoring thiosulfate in urine. Cysteine and cysteinylglycine can be measured concurrently, if needed.     

Analysis of trace levels of trichothecene mycotoxins in Austrian cereals by gas chromatography with electron capture detection

Summary Various analytical methods developed for trichothecene determination, including TLC, HPLC, GC, supercritical fluid chromatography (SFC) and enzyme immuno assay (EIA) are reviewed. In addition a new method is described for the simultaneous determination of the trichothecene mycotoxins deoxynivalenol (DON), nivalenol (NIV), 3-acetyldeoxynivalenol (3-ADON), diacetoxyscirpenol (DAS), T-2 toxin (T-2), HT-2 toxin (HT-2) and T-2 triol (TRIOL), in Austrian wheat and corn samples by GC-ECD. A clean-up procedure has been developed using a combination of liquid-liquid and liquid-solid extraction. Trichothecenes were detected as their heptafluorobuturyl esters or alternatively as trimethylsilyl ethers (only sensitive for deoxynivalenol and nivalenol) using nandrolone or chloramphenicol as internal standard. Four derivatization techniques using HFBI, HFBA+DMAP on polystyrene, TMSI and TMSI+BSA+TMCS have been studied and the advantages and disadvantages of each are discussed. Quantification of trichothecenes from 10 to 1000 ppb in cereals could be accomplished routinely.Presented at the 19th ISC, Aix-en-Provence, France, September 13–18, 1992.     

Determination and identification of amiloride in human urine by high-performance liquid chromatography and gas chromatography-mass spectrometry.

A simple and sensitive high-performance liquid chromatographic method was developed to screen and determine amiloride (I) in human urine. The detection limit of the method is 0.12 micrograms/ml and the recovery of amiloride from urine was 80.4-85.5% at different concentrations. The coefficients of variation were less than 2.8 and 4.4% for intra- and inter-assays, respectively. Total urinary excretion of I in 24 h after oral administration of 5 mg or 15 mg of I ranged from 22.0 to 33.3% of the total dose for three different subjects. I could be detected in urine up to at least 44 h after a 5-mg dose and 72 h after a 15-mg dose. A gas chromatographic-mass spectrometric (GC-MS) confirmatory method was established based on the methanolysis of I to methyl 3,5-diamino-6-chloropyrazine-carboxylate (II). The di-N-trimethylsilyl derivative of II showed very good GC-MS properties and provided reliable structure information for confirmation analysis of I. This is the first time that a reliable GC-MS method has been reported for the detection of urinary I.     

Automated determination of nifedipine in human plasma by capillary gas chromatography with electron capture detection

A rapid, sensitive, and reliable method for the determination of nifedipine in human plasma is described. Using a single-step solvent extraction and capillary gas chromatography combined with electron capture detection, an assay sensitivity of 2 ng/ml is achieved routinely using 0.5 ml of plasma. Intact nifedipine is quantitated and separated from its nitroso- and nitropyridine-derivatives. The suitability of the assay for pharmacokinetic studies is illustrated.     

Determination of cetirizine in human urine by high-performance liquid chromatography.

A high-performance liquid chromatographic method for the determination of the histamine H1-receptor antagonist cetirizine in human urine was developed. Cetirizine and the internal standard are extracted from acidified (pH 5) urine (0.5 ml) into chloroform and the organic layer is evaporated to dryness. The residue is chromatographed on a Spherisorb 5ODS-2 column using Pic A (5 mM aqueous tetrabutylammonium phosphate)-methanol-tetrahydrofuran (33:65:2, v/v) as the mobile phase with ultraviolet detection (230 nm). The calibration graph is linear from 0.1 to 10 micrograms/ml and using 0.5 ml of urine the detection limit is 20 ng/ml. The within-run relative standard deviation is less than 6% and the accuracy is within 10% of the theoretical value at concentrations between 0.1 and 10 micrograms/ml in urine. There is a good correlation (r = 0.99606) with a previously described capillary gas chromatographic assay.