毛细管气相色谱法测定二乙基二硫的含量

采用毛细管气相色谱法(GC)测定了二乙基二硫的含量.结果表明,二乙基二硫含量在0.01⁰.4g/L范围内具有良好的线性关系,平均回收率为99.91%;该方法简便、准确、重复性好,可方便地用于二乙基二硫含量的测定.     

Preconcentration and determination of naphthalene in air and water using activated carbon adsorption,carbon disulfide extraction and gas chromatography

A new method for the determination of naphthalene in air and water has been developed. The naphthalene was preconcentrated using activated carbon adsorption with carbon disulfide extraction and determined by gas chromatography with flame ionization detection. The chromatographic peak of naphthalene was separated well from the potential interferents turpentine, terpenene, isoborneol, camphor and isobornyl acetate. The detection limit was 0.52 g/ml of CS₂, equivalent to 2.6 g/m³ of air or 0.05 g/ml in 50 ml of water. The precision for 10 g/ml naphthalene was 1.7%. The adsorption capacity, sampling efficiency and desorption efficiency of 100 mg of activated carbon for naphthalene in air were 8.8 mg, 98.8% and 95.2%, respectively. The extraction efficiency of 5 ml of carbon disulfide for naphthalene in water was 97.6%. The method was successfully applied to the determination of naphthalene in air and water from an industrial plant.     

Simple and accurate method for determining dissolved inorganic carbon in environmental water by reaction headspace gas chromatography

We investigate a simple and accurate method for quantitatively analyzing dissolved inorganic carbon in environmental water by reaction headspace gas chromatography. The neutralization reaction between the inorganic carbon species (i.e. bicarbonate ions and carbonate ions) in environmental water and hydrochloric acid is carried out in a sealed headspace vial, and the carbon dioxide formed from the neutralization reaction, the self‐decomposition of carbonic acid, and dissolved carbon dioxide in environmental water is then analyzed by headspace gas chromatography. The data show that the headspace gas chromatography method has good precision (relative standard deviation ≤ 1.63%) and accuracy (relative differences ≤ 5.81% compared with the coulometric titration technique). The headspace gas chromatography method is simple, reliable, and can be well applied in the dissolved inorganic carbon detection in environmental water.     

Simultaneous determination of ethylbenzene, indan, indene and acenaphthene in air by capillary gas chromatography

An attempt was made to establish a method for the simultaneous determination of ethylbenzene, indan, indene and acenaphthene by capillary gas chromatography with flame ionization detection. The air was sampled on charcoal tubes and extracted with carbon disulfide-methanol (60:1, v/v). The four analytes were separated by gas chromatography using a capillary column of cross-linked 5% phenylmethylsilicone. Under the applied conditions the method showed detection limits of 1.8 microg/m3 for ethylbenzene, 2.1 microg/m3 for indan, 2.8 microg/m3 for indene and 3.4 microg/m3 for acenaphthene. Relative standard deviations were as follows: ethylbenzene, 6.2%; indan, 9.9%; indene, 13.6%; and acenaphthene, 14.4%. The recoveries for these compounds were 98.6, 97.9, 55.7 and 52.1%, and the accuracies were 2.5, 3.0, 44.3 and 47.8%, a working range of 1.5-30 ng/microl for ethylbenzene and 0.75-15 ng/microl for indan, indene and acenaphthene. The method was found to be suitable for the determination of environmental and occupational analysed ethylbenzene, indan, indene and acenaphthene exposure.     

Screening method for pesticides in air by gas chromatography/tandem mass spectrometry

A multiresidue method for determining more than 70 pesticides in air has been validated using a single injection with gas chromatography/tandem mass spectrometry (GC/MS/MS). The method validation considered both stages of sampling and analysis. The sampling method, based on active sampling using sorption in sorbent cartidges, was validated by generating standard atmospheres. Performance parameters of the method were evaluated, with a reduction in the limits of quantification by injecting a higher volume of sample extract, and increase of selectivity by the use of MS/MS detection mode. The method was based on solid-phase extraction, which permits a degree of automation. The best adsorbents were found to be Chromosorb 106 and Tenax TA. The retention capacity of these sampling sorbents allows up to 1440 L of air to be sampled without any breakthrough for most of the compounds. Data were generated for assessing the potential exposure of bystanders. The application of the method to the analysis of the air in urban locations near agricultural areas showed that pesticides were present in most of the samples.     

Experimental design optimization of the analysis of gasoline by capillary gas chromatography

An optimization procedure for multi-step temperature programmed capillary GC was investigated for the detailed hydrocarbon analysis of gasoline. A set of twelve responses, represented by the value of the resolution of the most difficult separations, was selected from several isothermal analyses. The variation of these responses versus the temperature programming conditions was then modeled using a Doehlert matrix for experimental design. Optimal experimental conditions for the twelve responses were then obtained from a response surface optimization. The predicted and experimental resolutions were in good agreement.     

Determination of carbon monoxide,methane and carbon dioxide in refinery hydrogen gases and air by gas chromatography

This paper illustrates a method for determining trace amounts of CO, CH4 and CO2 with the detection limit of 0.15, 0.15 and 0.20 microg/l, respectively, in refinery hydrogen gases or in air. A simple modification of a gas chromatograph equipped with a flame-ionization detector is presented. A Porapak Q column, additionally connected with a short molecular sieve 5A packed column and a catalytic hydrogenation reactor on the Ni catalyst have been applied. The principle of the analytical method proposed is the separation of CO from O2 before the introduction of CO to the methanizer. The analytical procedure and examples of the results obtained have been presented. The modification applied makes it possible to use the GC instrument for other determinations, requiring utilization of the Porapak Q column and the flame-ionization detector. In such cases, the short molecular sieve 5A column and the methanizer can be by-passed.     

A continuous preconcentration/extraction method for organic trace analysis by capillary gas chromatography

Summary A slightly modified steam distillation-extraction device is described for the continuous extraction and preconcentration of organic traces in aqueous samples, prior to capillary G.C.-analysis. The quantitative performance, both theoretically and practically, is studied using phenols as the test substances. The final recovery is determined by the flow-ratio of the water and the extracting solvent and by the extraction coefficient. The process is found to be highly reproducible even at low concentration levels (ppb’s). Using 30 ml. samples with a concentration of 30 ppb (1:10^9), 100 % recoveries are obtained for the phenolic substances studied, with a relative standard deviation of about 3 %, both for methylene chloride and ethylacetate as the extracting solvents. Using methylene chloride as the extracting solvent, for phenol a maximum recovery of 80 % was obtained. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

A new method for the determination of residual piperazine in pharmaceuticals by capillary gas chromatography

A new selective open tubular capillary gas chromatographic method is developed for the determination of trace amounts of piperazine. Piperazine is extracted from pharmaceuticals into cyclohexane and is partitioned with water. The aqueous solution is then injected into a 5% crosslinked Ph-Me silicone column programmed at 50-180 degrees C for 10 min. Piperazine is eluted after 3.18 min under isothermal conditions. The lower limit of determination is 0.4 ppm. This method has been successfully applied for the assay of piperazine in pharmaceutical formulations and its trace determination in fluoroquinolone drugs such as norfloxacin and ciprofloxacin. The method is reproducible and the standard and relative standard deviation for 10 repeated injections of 2 mug piperazine are 0.7 and +/-2.1% respectively.     

An improved method for steroid profile analysis using capillary gas chromatography

Summary Steroid conjugates are hydrolysed enzymatically using β-glucuronidase after extraction from urine using a solid phase extraction cartridge. After hydrolysis the free steroids are removed from the matrix, again utilising solid phase extraction. Derivatisation of the free hydroxyl groups using Hydrox-Sil AQ produces the respective TMS ethers which are extracted into hexane, in which solvent they are stable for many days. Capillary GC analysis with flame ionisation detection produces a profile of the steroids present in the sample. This technique is suitable for following changes in the urinary excretion profiles of patients undergoing investigation for a variety of steroid production-related diseases.     

A simple method for the determination of glyphosate residues in soil by capillary gas chromatography with nitrogen phosphorus

A simple method was developed to determine the residues of glyphosate, N-(phosphonomethyl)glycine, in soil. The residues were extracted from soil matrices with 2 M NH₄OH, derivatized by trifluoroacetic anhydride and trifluoroethanol, and, then, determined by gas chromatography with a nitrogen-phosphorus detector (GC-NPD). The results were further confirmed by gas chromatography-mass spectrometry (GC-MS). The limit of detection was estimated to be 9 × 10⁻¹² g, and the minimum determination concentration of glyphosate in the samples was 0.01 mg/kg. The ranges for the average recoveries and relative standard deviation (RSD) of the method were 84.4–94.0% and 8.1–13.7%, respectively, in agreement with the directives for method validation in residue analysis. The proposed method was successfully employed for the determination of glyphosate residue levels and dissipation retes in the soil from an apple orchard. The text was submitted by the authors in English.     

Profiling propolis flavonoids by means of micellar electrokinetic capillary chromatography, capillary gas chromatography and bactericidal action

Summary There is no proportional correlation between increasing organic solvent polarity from hexane to methanol and the extractability of propolis solids by the solvents or the bactericidal action of the propolis extracts obtained. Hexane (17.7%) and chloroform (62.1%) were the poorest and the best extractants, respectively, for propolis solids. The antibiotic activity of the extracts againstStaphylococcus strains decreased in the order hexane≥ethanol>methanol. Different capillary GC profiles were obtained for persilyl derivatives of propolis extracted with hexane and methanol and for propolis collected in different Brazilian provinces, suggesting the influence of flora variability on propolis composition. Wavelength-selected DAD detection revealed MEKC to be an innovative and sensitive method for monitoring the occurrence in propolis of the flavonoids and phenolcarboxylic acids thought to be responsible for the antimicrobial activity of propolis.     

A simple gas chromatography method for the analysis of monoethanolamine in air

A simple method determining airborne monoethanolamine has been developed. Monoethanolamine determination has traditionally been difficult due to analytical separation problems. Even in recent sophisticated methods, this difficulty remains as the major issue often resulting in time-consuming sample preparations. Impregnated glass fiber filters were used for sampling. Desorption of monoethanolamine was followed by capillary GC analysis and nitrogen phosphorous selective detection. Separation was achieved using a specific column for monoethanolamines (35% diphenyl and 65% dimethyl polysiloxane). The internal standard was quinoline. Derivatization steps were not needed. The calibration range was 0.5-80 μg/mL with a good correlation (R(2) = 0.996). Averaged overall precisions and accuracies were 4.8% and -7.8% for intraday (n = 30), and 10.5% and -5.9% for interday (n = 72). Mean recovery from spiked filters was 92.8% for the intraday variation, and 94.1% for the interday variation. Monoethanolamine on stored spiked filters was stable for at least 4 weeks at 5°C. This newly developed method was used among professional cleaners and air concentrations (n = 4) were 0.42 and 0.17 mg/m(3) for personal and 0.23 and 0.43 mg/m(3) for stationary measurements. The monoethanolamine air concentration method described here was simple, sensitive, and convenient both in terms of sampling and analytical analysis.     

Analysis of triglycerides by capillary gas chromatography with programmed-temperature injection

The capillary gas chromatographic analysis of complex naturally occurring and food-product triglyceride mixtures is accomplished qualitatively and quantitatively on columns coated with methyl and methyl-phenyl (65%) silicones using programmed-temperature split/splitless and on-column injection. Faster analysis times are achieved using elevated initial column oven temperatures with cold initial injector temperatures.     

Practical method for the measurement of Alkyl mercaptans in natural gas by multi-dimensional gas chromatography, capillary flow technology, and flame ionization detection

Volatile sulfur compounds such as alkylmercaptans are undesired impurities in natural gas streams. As a result, natural gas treatment and purification services are essential in many industries that utilize natural gas either as a fuel or in a chemical process. While there are many analytical methods that can be employed for the measurement of mercaptans, a simple, practical, and easy-to-implement method is required for remote field deployment. An analytical method, based on multi-dimensional gas chromatography (MDGC), capillary flow technology and flame ionization has been successfully developed for the application described. Results based on the technique showed alkylmercaptans can be accurately measured with a minimum detection limit of 200 ppb (v/v) or better, a linear range of up to 100 ppm (v/v), and a relative standard deviation (n=10) of 1.2% or less were obtained by manual injection with a total sample-to-sample analysis time of less than 15 min.     

On-line analysis of products from hydrogenation of carbon monoxide by capillary gas chromatography with thermal conductivity detection

A combination of thermal conductivity detectors with capillary columns is used for on-line analysis of the products from a micropolit plant for the study of carbon monoxide hydrogenation. The system includes an automatically operated heated tenport sampling valve, a HP-5890-A gas chromatograph fitted with two capillary columns and thermal conductivity detectors, and a logging/controlling system. The single column design means that two analyses can be done simultaneously in one chromatograph and offers high versatility with the possibility of combining different capillary columns to cope with the needs of variable process conditions and catalyst selectivities.