Ethanol analysis by headspace gas chromatography with simultaneous flame-ionization and mass spectrometry detection.

Ethanol is the most frequently identified compound in forensic toxicology. Although confirmation involving mass spectrometry is desirable, relatively few methods have been published to date. A novel technique utilizing a Dean's Switch to simultaneously quantitate and confirm ethyl alcohol by flame-ionization (FID) and mass spectrometric (MS) detection after headspace sampling and gas chromatographic separation is presented. Using 100 µL of sample, the limits of detection and quantitation were 0.005 and 0.010 g/dL, respectively. The zero-order linear range (r(2) > 0.990) was determined to span the concentrations of 0.010 to 1.000 g/dL. The coefficient of variation of replicate analyses was less than 3.1%. Quantitative accuracy was within ±8%, ±6%, ±3%, and ±1.5% at concentrations of 0.010, 0.025, 0.080, and 0.300 g/dL, respectively. In addition, 1,1-difluoroethane was validated for qualitative identification by this method. The validated FID-MS method provides a procedure for the quantitation of ethyl alcohol in blood by FID with simultaneous confirmation by MS and can also be utilized as an identification method for inhalants such as 1,1-difluoroethane.

Determination of organotins in aquatic food by gas chromatography with pulsed flame photometric detection.

A method based on gas chromatography (GC)-pulsed flame photometric detection (PFPD) was developed to determine the levels of organotins in aquatic food. After being purified by gel-permeation chromatography in ethyl actate-tetrahydrofuran, the organotin compounds were derivatized by pentylmagnesium bromide. The derivative products were injected into the GC system and detected by PFPD (sulfur mode). The method was validated by analysis of the certified reference material and spiked samples. Recoveries of organotins ranged from 84.1 to 116.6% with relative standard deviation between 1.3 and 16.0% when spiked at levels of 2, 10, and 40 microg/kg. The limits of detection varied from 0.1 to 1.2 microg/kg for shellfish and 0.1 to 0.5 microg/kg for fish. The proposed method was suitable for determining organotins in aquatic foods.

Simple GC-FID method development and validation for determination of alpha-tocopherol (vitamin E) in human plasma.

This paper describes the development and validation of a novel GC-FID method for the determination of alpha-tocopherol concentration in human plasma which does not requires derivatization. The standard solutions and the plasma working solutions were prepared in absolute ethanol. To determine the concentration of alpha-tocopherol in human plasma, an aliquot of the plasma sample was deproteinized with ethanol. alpha-tocopherol was extracted with a mixture of hexane and dichloromethane (9:1). GC separation was performed using a HP-5 capillary column. Nitrogen was used as carrier gas at a flow-rate of 2 ml min(-1). Calibration curves were linear over the concentration range 1-30 microg ml(-1) (for standard solutions and solutions without endogenous alpha-tocopherol in plasma) and 5-34 microg ml(-1) (for solutions with endogenous alpha-tocopherol in plasma). Absolute recovery, precision, sensitivity and accuracy assays were carried out. The analytical recovery of alpha-tocopherol from plasma averaged 97.44%. The limit of quantification (LOQ) and the limit of detection (LOD) of method for standard samples were 0.35 microg.ml(-1) and 0.30 microg.ml(-1), respectively. Within-day and between-day precision, expressed as the relative standard deviation (RSD) were less than 4%, and accuracy (relative error) was better than 8%. This novel method, developed and validated in our laboratory, could be successfully applied to the in-vivo determination of alpha-tocopherol. The endogenous alpha-tocopherol amounts in blood of twelve healthy volunteers with no vitamin drug usage were measured with this method.

Method development and validation for the GC-FID assay of tributyl phosphate in a phospholipid emulsion.

This paper describes the development and validation of an isothermal GC-FID method for the assay of tributyl phosphate in a phospholipid emulsion. The emulsion is used as a topical ointment to deliver Triton X-100, a spermicide. The tributyl phosphate is added to the emulsion as a plasticizer or softening agent. The chromatographic conditions of the method employ a J&W DB-Wax capillary column (30 m x 0.53 mm, film thickness 1 microm), isothermal elution with He at a column flow of 2.0 ml/min, injector, detector, and oven temperatures at 210 degrees C, a split ratio of 18.0/2.0, and a 3-microl injection volume. Sample calibration was performed with tributyl phosphate purchased from Aldrich (USP Reference Standard is not available). The linearity of the tributyl phosphate peak area responses was demonstrated from approximately 50 to 150% of the analytical concentration of 100 microg/ml. System precision was determined from five replicate injections of a standard and sample solution. Reproducibility of the tributyl phosphate peak area responses showed R.S.D. of 1.2 and 0.4%, respectively. Method precision was performed by assaying five samples by two different analysts on different days. The mean %LC was 95.5% (R.S.D.=1.0%) for the first analyst, and 95.6% (R.S.D.=1.0%) for the second analyst. The mean %LC value for all ten sample preparations was 95.5% (R.S.D.=0.9%). The limits of detection and quantitation were determined to be 0.2 and 0.7 microg/ml, respectively.

Determination of gliclazide in pharmaceutical preparations by capillary gas chromatography with cool on-column injection and elimination of the matrix effect.

Conditions were established for the identification and quantitation of gliclazide in pharmaceutical preparations by capillary gas chromatography with flame ionization detection and cool on-column injection. Gliclazide was extracted with methanol and, after filtration, assayed on a (25 m x 0.25 mm id, 0.2 microm film thickness) CP-WAX 58 (FFAP)-CB WCOT fused silica column. Because the available preparations were of various origins and, therefore, could differ in auxiliary substances and their qualitative parameters, the influence of the matrix constituents on the analytical results was taken into account. Good separation conditions were established for the developed method. The retention time of gliclazide is about 36 min and differs from the retention times of the internal standard (approximately 29 min) and additional peaks present in chromatograms (20-26 min), which were assigned to matrix constituents. The recoveries of gliclozide were high and reached 96.5%. The developed method is characterized by selectivity and precision (relative standard deviation 0.38-1.26%), a wide range of linearity (0.1-10.0 mg/mL), and a limit of detection of 30 ng. In addition, the results of chromatographic analyses calculated in 3 ways were compared with those obtained by UV spectrophotometry. The suggested technique of cool on-column injection, in contrast with split-splitless injection (used in preliminary investigations), reduces to a minimum the possibility of thermal decomposition of gliclazide.

[The gas chromatographic analysis of volatile compounds on the compact MKhP chromatograph]. / Gazokhromatograficheskii analiz letuchikh soedinenii na malogabaritnom khromatografe MKhP.

Methods of analysis of biological specimens, alcohol beverages, and technological liquids in columns with standard adsorbents carbopaque B and C with carbowax 20M, widely used abroad, are described and examples of analyses presented. A special portable chromatographer (MCP) with flame ionization detector has been designed. It is intended for analysis of volatile organic compounds (alcohols, carbohydrates, organochlorine compounds, glycols, esters, etc.) in columns of different polarity. The system of processing of chromatographic findings permits a quantitative analysis of complex chromatograms and automated identification of substances in biological samples by using the available database.

[The concentration of methane and trace organic admixtures in the air expired by submariners during a dive simulation in a hyperbaric chamber]. / Kontsentratsiia metana i nekotorykh organicheskikh mikroprimesei v vydykhaemom vozdukhe vodolazov pri imitatsii pogruzheniia v giperbaricheskoi kamere.

The article describes the procedure of determining methane and some organic trace elements in expired air during simulated "dive" in a hyperbaric chamber. Partial pressures of methane breathed out by divers in 29 experiments are reported. Concentrations of 8 trace organic components have been measured in the expired air of two divers. The results obtained show that expired methane increases by 3-10 times during simulated descent down to 80-115 m.