Determination of cereal herbicide residues in environmental samples by gas chromatography

Gas chromatographic analysis of cereal herbicide residues in water, soil, plant and air is reviewed. Herbicides widely used in spring and winter cereals, i.e., phenoxyacids, benzonitriles, ureas, triazines, dinitroanilines, chloroacetamides and thiocarbamates, are considered. The main procedures used in the residue analysis, extraction, clean-up, derivatization and gas chromatographic determination are summarized and discussed.     

Determination of bitertanol residues in strawberries by liquid chromatography with fluorescence detection and confirmation by gas chromatography/mass spectrometry

Heart rate (HR) and blood oxygen saturation (SaO2) were monitored before and during clinically indicated MR examinations of newborns to (a) identify any temporal relationship between MR scanning and vital sign fluctuations and (b) assess the reliability of SaO2 monitoring of dynamic changes. Fluctuations in HR (but not in SaO2) that are temporally linked to the MR image acquisition occur in most neonates during routine clinical MR examinations.     

Solid-phase microextraction applied to the analysis of pesticide residues in honey using gas chromatography with electron-capture detection

The possibilities of using solid-phase microextraction to determine residues of pesticides in honey have been examined. For this purpose, three types of fiber have been assayed: polyacrylate of 85 microns thickness, and polydimethylsiloxane of 7 and 100 microns thickness. They have been applied to the extraction of 21 pesticides of different chemical families. The effects of the temperature, extraction time and ionic strength on the microextraction have been studied, proposing the most adequate for each fiber. Under optimized conditions, precision, intervals of linearity and detection limits were evaluated.     

A method for determination of the absolute configuration of chiral glycerol residues in natural products using TEMPO oxidation and characterization of the glyceric acids formed

A method has been developed for determination of the absolute configuration of glycerol residues in natural products. It is required that the glycerol moiety contain a primary nonsubstituted hydroxymethyl group or that such a group can be obtained by modification without racemization. The method employs TEMPO oxidation of the primary hydroxyl group, hydrolysis, butanolysis with chiral 2-butanol, and acetylation. The acetylated (+)-2-butyl esters of the glyceric acid formed by oxidation are analyzed by gas-liquid chromatography. The esterification can also be performed with other chiral alcohols, e.g., (-)-2-octanol. The method is general and applicable to both primary and secondary substituted glycerols. It has recently been used for determination of the chiral glycerol-1-phosphate residue of the Escherichia coli O28 O-antigen, and now we report the absolute configurations of the glycerol moieties in Streptococcus pneumoniae type 18A and Streptococcus agalactaie type III. All studied glycerol residues were found to have the D-configuration.     

固相微萃取-气相色谱法测定煤气中萘

采用特制采样瓶收集煤气后,应用固相微萃取(SPME)对样品进行前处理,采用气相色谱(GC)对煤气中的萘进行测定。通过试验确定了SPME的最佳萃取条件为:采用100 μm聚二甲基硅氧烷(PDMS)萃取涂层,于转速为800 r/min时室温下萃取5 min,气相色谱解吸时间为3 min。在丙酮溶剂峰存在的情况下,基线平稳,丙酮峰对萘的测定并无影响。实验结果表明,萘在5～200 mg/m³范围内有良好的线性关系,相关系数为0.999 9。方法检出限为0.08 mg/m³。实验方法用于煤气中萘的测定,相对标准偏差(RSD,n=7)为2.6%～4.9%,加标回收率为85%～108%。     

Determination of embutramide in biological matrices by gas chromatography with nitrogen-phosphorus detection

Embutramide is a general anesthetic having a strong narcotic effect on the central nervous system where it paralyzes the brain center that controls respiration. It is a constituent of T61, a veterinary euthanasia drug. This paper describes a gas chromatographic procedure using nitrogen-phosphorus detection for the determination of embutramide in biological matrices. The drug and the internal standard (ambucetamide) are extracted with dichloromethane under alkaline conditions. The method is linear from 100 to 3000 ng/ml. The within-day and day-to-day coefficients of variation range from 5.1 to 5.7% and from 9.1 to 10.0%, respectively. The recovery is above 80% while the minimum detectable level under the conditions described is 40 ng/ml analyzing a 1-ml or a 1-g aliquot of a sample (blood or tissue). The method is also applied to different samples from dogs euthanized with T61.     

Determination of cysteamine and cystamine by gas chromatography with flame photometric detection

A gas chromatographic method for the determination of cysteamine and its disulphide cystamine is described. Cysteamine and cystamine are converted into N,S-diisobutoxycarbonyl and N,N-diisobutoxycarbonyl derivatives, respectively. The derivatives are analysed by gas chromatography with flame photometric detection, using a DB-210 capillary column. The calibration curves for cysteamine and cystamine in the range of 0.2-5.0 nmol are linear and sufficiently reproducible for quantitative analysis, and the detection limit is about 0.5 pmol injected. Cysteamine in mouse tissues is found in the free reduced, free oxidized and protein-bound forms. Free oxidized and protein-bound forms are reduced to free cysteamine by the use of sodium borohydride, and then derivatized. Cysteamine and cystamine in mouse tissues can be measured without any interference from coexisting substances by this method. The recoveries of cysteamine and cystamine added to the tissue samples are 91-106%, and their reproducibilities are found to be satisfactory. Analytical results for the determination of various forms of cysteamine in mouse tissues are presented.     

Determination of N,N',N"-triethylenthiophosphoramide in biological samples using capillary gas chromatography

A sensitive assay for the determination of N,N',N"-triethylenthiophosphoramide (thioTEPA) in microvolumes of human plasma and urine has been developed. ThioTEPA was analysed using gas chromatography with selective nitrogen-phosphorus detection, after extraction with ethyl acetate from the biological matrix. Diphenylamine is the internal standard. The limit of quantitation was 0.1 ng/ml, using only 100 microl of sample; recoveries ranged between 85 and 100% and both accuracy and precision were less than 10%. Using a flame ionisation nitrogen-phosphorus detector, the assay was not linear over the concentration range of 2-1000 ng/ml for plasma and 10-1000 ng/ml for urine. Linearity was accomplished in the range of 1-1000 ng/ml for plasma and urine when a thermionic nitrogen/phosphorous detector was used. The stability of thioTEPA in plasma proved to be satisfactory over a period of 3 months, when kept at -20 degrees C, whereas it was stable in urine for at least 1 month at -80 degrees C. ThioTEPA plasma concentrations of two patients treated with thioTEPA are presented demonstrating the applicability of the assay.     

Determination of triazolam in serum by deactivated metal capillary gas chromatography with electron-capture detection

A method for the determination of trace amounts of triazolam in serum by deactivated metal capillary gas chromatography with electron-capture detection was established. The column used exhibits excellent thermostability in high-temperature analysis and easy handling and a long lifetime of the column and well shaped peaks on the chromatograms are obtained. With the metal capillary column, it was found to be easier to maintain suitable analytical conditions for the routine assay of triazolam than with a fused-silica column. With this method, 0.5 ng/ml of triazolam in serum can be determined. The method is useful for pharmacokinetic and therapeutic purposes.     

Determination of cyanide in whole blood by capillary gas chromatography with cryogenic oven trapping

Cyanide, one of the most important toxic substances, has been found measurable with high sensitivity by capillary gas chromatography (GC) with cryogenic oven trapping upon injection of headspace (HS) vapor samples. The entire amount of cyanide in the HS sample could be cryogenically trapped prior to on-line GC analysis. A 0.5-mL volume of blood in the presence or absence of cyanide and propionitrile (internal standard, IS) was added to a vial containing 0.25 mL of distilled water, 0.3 g of Na2-SO4, 0.2 mL of 50% H3PO4, and 0.1 g of ascorbic acid (when needed), and the mixture was heated at 70 degrees C for 15 min. A 5-mL volume of the HS vapor was introduced into a GC capillary column in the splitless mode at -30 degrees C oven temperature that was programmed up to 160 degrees C for GC analysis with nitrogen-phosphorus detection. A sharp peak was obtained for cyanide under the present conditions, and backgrounds were very clean. The extraction efficiencies of cyanide and IS were 2.89-3.22 (100 or 500 ng/mL) and 2.42%, respectively. The calibration curve showed good linearity in the range of 25-1000 ng/mL and the detection limit was approximately 2 ng/mL. The coefficients of intraday and interday variations were 2.9 and 11.8%, respectively. The mean blood cyanide level measured for actual fire victims was 687 +/- 597 ng/mL (mean +/- SD, n = 9). Endogenous blood cyanide concentration for healthy subjects was 8.41 +/- 3.09 ng/mL (mean +/- SD, n = 6).     

Determination of paeonol in the root of Cynanchum paniculatum (Bge.) Kitag. by gas chromatography

A method for the determination of paeonol in the root of Cynanchum paniculatum by macro-reticular resin-GC has been established. The experimental result shows that the standard curve is linear in the detection range and the recovery is 99.42% (RSD = 2.28%, n = 5).     

Determination of amino acids in biological fluids by capillary gas chromatography with nitrogen-phosphorus selective detection

A selective and sensitive method for the determination of protein and non-protein amino acids in biological fluids by capillary gas chromatography (GC) has been developed. The amino acids in the samples were directly converted into their N(O,S)-isobutoxycarbonyl methyl ester derivatives and measured by GC with nitrogen-phosphorus selective detection (NPD) using a DB-17ht capillary column. Using this method, the derivatives of the 21 protein amino acids and the 25 non-protein amino acids provided excellent NPD responses and were quantitatively and reproducibly resolved within 28 min. The lower detection limits of these amino acids, at a signal-to-noise ratio of 3, were ca. 6-150 pg injected. The calibration curves for each amino acid in the range of 0.02-2 micrograms were linear and sufficiently reproducible for quantitative analysis. This method was successfully applied to small urine and serum samples without prior clean-up; there was no evidence of interference from coexisting substances. Overall recoveries of amino acids added to urine and serum samples were 83-112%. The intra-assay and inter-assay R.S.D. of amino acids in these samples were 0.3-8.9% (n = 3) and 1.9-15.8% (n = 3), respectively.     

Determination of dapoxetine, an investigational agent with the potential for treating depression, and its mono- and di-desmethyl metabolites in human plasma using column-switching high-performance liquid chromatography

A column-switching high-performance liquid chromatographic (HPLC) method is described for the determination of dapoxetine and its mono- and di-desmethyl metabolites in human plasma. The analytes, including an internal standard, were extracted from plasma at basic pH with hexane-ethyl acetate. The organic extract was evaporated to dryness and the residue reconstituted with acetonitrile. The analytes were separated from late-eluting endogenous substances on a Zorbax RX-C8 pre-column. The front-cut fraction containing the analytes was further separated on a second RX-C8 column. The analytes were detected by their native fluorescence, using excitation and emission wavelengths of 230 and 330 nm, respectively. The limit of quantitation was determined to be 20 ng/ml, and the response was linear from 20 to 200 ng/ml. The method has been successfully applied to human plasma samples in a Phase I study.     

Determination of the absolute configuration at C-20 and C-24 of ergosterol in Ascomycetes and Basidiomycetes by proton magnetic resonance spectroscopy

Samples of ergosterol isolated from Saccharomyces cerevisiae, Neurospora crassa, and Agaricus sp., and commercial ergosterol all displayed identical proton magnetic resonance (PMR) spectra at 220 MHz. From the effects produced on the doublet for C-21 by epimerization at C-20 and C-24 in sterols of known configuration, the absolute configurations at these positions in ergosterol were determined. The data demonstrate that ergosterol from both Ascomycetes and Basidiomycetes is the same and that at C-20 and C-24, the two H-atoms are on the alpha-side of the asymmetric carbon atoms and that C-22 is trans-oriented with respect to C-13 about the 17(20)-bond.