Direct injection, gas chromatography

Analytical methods used are described by Bianchi et al. (1997). Methods 3M 3500 and 3M 3520 involve absorption onto a butadiene-specific activated charcoal, followed by desorption with carbon disulfide or with dichloromethane, respectively, and analysis by direct-injection gas chromatography with flame ionization detection. 

Voznakova and Popl [43,44] departed from the usual approach to phenol analysis by gas chromatography made by earlier workers, ie direct injection gas chromatography or solvent extraction followed by gas chromatography. These workers described a method for determining phenol, o-cresol and 2,6-xylenol in water in which the phenols are sorbed... 

Fujii, T. The Determination of Traces of Organohalogen Compounds in Aqueous Solution by Direct Injection Gas Chromatography-Mass Spectrometry and Single Ion Detection, Analytica Chimica Acta 92, 117 (1977)... 

Buttery, R.G., R. Teranishi, Measurement of fat oxidation and hrowning aldehydes in food vapors by direct injection gas chromatography, J. Agric. Food Chem., 11, p. 58, 1963. 

The solubility of HCB in aqueous solutions of Tween 60, Tween 80 and Triton X-100 was measured in completely mixed batch reactors over a surfactant concentration range of 0 to 2,000 mg/L. Each 35-mL glass reactor contained excess HCB which was deposited as a thin film on the bottom of the reactor. Analysis of HCB in aqueous surfactant solutions was achieved using a direct injection gas chromatography technique (S). This analytical method yielded more accurate and reproducible results than conventional solvent extraction methods, which resulted in the formation of persistent macroemulsions between the organic solvent and aqueous phases. 

Direct hydration, of ethylene, 10 538 Direct hydrogenation, 6 827 Direct immunosensors, 14 154 Direct ingot (dingot) method, 25 409 Direct initiation, 14 270 Direct injection (DI) diesel engines, 12 421 Direct inlet injection, gas chromatography, 6 383, 415-416 Directional couplers, 17 446 Directional drilling techniques, in sulfur extraction, 23 572 Directive 89/107/EEC (EU), 12 36 Direct liquefaction, 6 827 Direct marketing, technical service personnel and, 24 343 Direct metal nitridation, 17 211-213 aerosol flow reactor, 17 211-212 Direct methanol fuel cells (DMFC),... 

Fujii T. 1977. Direct aqueous injection gas chromatography-mass spectrometry for analysis of organohalides in water at concentrations below the parts per billion level. J Chromatogr 139 297-302. 

Hauser, B., P. Popp, and E. Kleine-Benne (2002). Membrane-assisted solvent extraction of triazines and other semi-volatile contaminants directly coupled to large-volume injection-gas chromatography-mass spectrometric detection. J. Chromatogr. A, 963 27-36. 

Zwank L., Schmidt T., Haderlein S., and Berg M. (2002) Simultaneous determination of fuel oxygenates and BTEX using direct aqueous injection gas chromatography mass spectrometry (DAI/GC/MS). Environ. Sci. Technol. 36(9), 2054-2059. 

R.A. Baker, "Phenolic Analyses by Direct Aqueous Injection Gas Chromatography , Journal of the American Waterworks Association, v. 58, 1966, p. 751-60. 

Sampling of both the gaseous and liquid phases was made as a function of time (300 pL for the gaseous phase and 50 pL for the liquid phase). The gaseous sample was analyzed directly by gas chromatography. The liquid one was first diluted into 3 mL of chlorobenzene at 0 °C and 100 pL of the resulting solution were injected into the gas chromatograph. 

Preparing a Volatile Sample Gas chromatography can be used to separate analytes in complex matrices. Not every sample that can potentially be analyzed by GG, however, can be injected directly into the instrument. To move through the column, the sample s constituents must be volatile. Solutes of low volatility may be retained by the column and continue to elute during the analysis of subsequent samples. Nonvolatile solutes condense on the column, degrading the column s performance. 

An on-line supercritical fluid chromatography-capillary gas chromatography (SFC-GC) technique has been demonstrated for the direct transfer of SFC fractions from a packed column SFC system to a GC system. This technique has been applied in the analysis of industrial samples such as aviation fuel (24). This type of coupled technique is sometimes more advantageous than the traditional LC-GC coupled technique since SFC is compatible with GC, because most supercritical fluids decompress into gases at GC conditions and are not detected by flame-ionization detection. The use of solvent evaporation techniques are not necessary. SFC, in the same way as LC, can be used to preseparate a sample into classes of compounds where the individual components can then be analyzed and quantified by GC. The supercritical fluid sample effluent is decompressed through a restrictor directly into a capillary GC injection port. In addition, this technique allows selective or multi-step heart-cutting of various sample peaks as they elute from the supercritical fluid... 

The alkyl chain distribution of the base alcohol in alcohol sulfates is easily determined by gas chromatography. However, alcohol sulfates and alcohol ether sulfates are not volatile and require a previous hydrolysis to yield the free alcohol. The extracted free alcohol can be injected directly [306] or converted to its trimethylsilyl derivative before injection [307]. Alternatively, the alcohol sulfate can be decomposed by hydroiodic acid to yield the alkyl iodides of the starting alcohols [308]. A preferred method forms the alkyl iodides after hydrolysis of the alcohol sulfate which are analyzed after further extraction of the free alcohol, thus avoiding the formation of hydrogen sulfide. This latter method is commonly used to determine the alkyl chain distribution of alcohol ether sulfates. 

One of the most frequent techniques for analyzing 1,4-dioxane is gas chromatography. Birkel et al. [319] proposed in 1979 a gas chromatographic method based on partial vacuum distillation of the sample, analyzing polysorbate 60 and 80 with sensitivity to the 0.5 ppm. Stafford et al. [320] proposed a direct injection GC method which meant an improvement to the Birkel s technique. Robinson and Ciurczak [321] described a direct GC method for the analysis of... 

Sulfonylureas are not directly amenable to gas chromatography (GC) because of their extremely low volatility and thermal instability. GC has been used in conjunction with diazomethane derivatization, pentafluorobenzyl bromide derivatization, and hydrolysis followed by analysis of the aryl sulfonamides. These approaches have not become widely accepted, owing to poor performance for the entire family of sulfonylureas. Capillary electrophoresis (CE) has been evaluated for water analysis and soil analysis. The low injection volumes required in CE may not yield the required sensitivity for certain applications. Enzyme immunoassay has been reported for chlorsulfuron and triasulfuron, with a limit of detection (LOD) ranging from 20 to 100 ng kg (ppt) in soil and water. 

Oxime carbamates are not directly amenable to gas chromatography (GC) because of their high thermal instability, which often leads to their breakdown at the injection port or in the column during analysis. Analysis of oxime carbamates by GC with sulfur detection or flame photometric detection involves oxidation of the intact insecticides or alkaline hydrolysis to form the more volatile but stable oxime compound. Enzymatic techniques have been reported for the analysis of these compounds. Enzyme-linked immunosorbent assay (ELISA) has been used to determine aldicarb and its sulfone and sulfoxide metabolites and methomyl in water, soil, and sediment samples. 

The advent of high-resolution capillary gas chromatography (HR-CGC) with on-column injection has resulted in improved GC analysis of polymer additives [92-94]. The solution of the additive mixture is injected directly into the cold end of the capillary column by means of a cold injector. Thus, sample discrimination, the instantaneous evaporation of the sample solvent, is avoided. The nonvaporising, on-column injection combined with very high resolution of the capillary columns allows accurate separation, identification and quantification of additives of complex mixtures. With the solvent venting technique, the sample is introduced into the column without splitting and sample concentrations... 

Gas chromatography is commonly used to analyse mixtures for quantification. A wide variety of special detectors with adequate linear response ranges are available for quantification of various classes of compounds (cf. Table 4.14). Quantification by direct injection may be used to determine additives, residual monomers and solvents in product formulations, coated films, and solid materials [109]. On the other hand, reliable quantification by means of solid-injection PTV-GC, HS-GC and PyGC techniques is not always trivial. 

SFE-GC-MS is particularly useful for (semi)volatile analysis of thermo-labile compounds, which degrade at the higher temperatures used for HS-GC-MS. Vreuls et al. [303] have reported in-vial liquid-liquid extraction with subsequent large-volume on-column injection into GC-MS for the determination of organics in water samples. Automated in-vial LLE-GC-MS requires no sample preparation steps such as filtration or solvent evaporation. On-line SPE-GC-MS has been reported [304], Smart et al. [305] used thermal extraction-gas chromatography-ion trap mass spectrometry (TE-GC-MS) for direct analysis of TLC spots. Scraped-off material was gradually heated, and the analytes were thermally extracted. This thermal desorption method is milder than laser desorption, and allows analysis without extensive decomposition. 

The first experiments directed to trace analysis were carried out in correlation gas chromatography ( 2 ). However, in the recent years much attention was paid to correlation HPLC, because the detection is generally more a problem than in GC and because injection is inherently easier. Results with a first experimental set-up and an off-line computer calculation of the CCF were very promising. 

The course of the reaction can conveniently be followed by gas chromatography. A sample of the reaction mixture is withdrawn at intervals, neutralized with solid sodium bicarbonate, dried over magnesium sulfate, and injected directly into a gas chromatography column consisting of 15% phenyldiethanola-mine succinate (PDEAS) substrate coated on 60/80 mesh, acid-washed fire brick contained in a i in. by 5 ft. spiral-shaped copper... 

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