Gas-liquid chromatographic GLC methods

A gas liquid chromatographic (GLC) method was described for determining residues of Bayer 73 (2-aminoethanol salt of niclosamide) in fish muscle, aquatic invertebrates, mud, and water by analyzing for 2-chloro-4-nitroaniline, a hydrolysis product of Bayer 73 [83]. Residues were extracted with acetone-formic acid (98 + 2), and partitioned from water samples with chloroform. After sample cleanup by solvent and acid base partitioning, the concentrated extract was hydrolyzed with 2N NaOH and H202 for 10 min at 95°C. The 2-chloro-4-nitroaniline was then partitioned hexane ethyl ether (7 + 3) and determined by electron capture GLC. Average recoveries were 88% for fish, 82% for invertebrates, 82% for mud, and 98% for water at 3 or more fortification levels. 

Later, an enzymatic method based on oxidation of ethanol by alcohol dehydrogenase (ADH) and nicotinamide adenine dinucleotide (NAD) followed by spectrophotometric analysis was reported. Current methods for detecting ethanol in body fluids are predominantly based on physicochemical techniques. A gas-liquid chromatographic (GLC) method is the most widespread because it is easy, rapid, and has high specificity and accuracy. Analytical methods used to determine alcohol in body fluids are siunma-rized in Table 1. 

Chromatographic methods have also been developed for quantitative determination of the AUC of pectin. Uronic acids have been analyzed using gas-liquid chromatography (GLC) after conversion to L-galactono-1,4-lactone via potassium borohydride reduction and lactonization using methanolic hydrogen chloride. The derived lactone was then analyzed by GLC as the trimethylsilyl derivative (Perry... 

A simple and sensitive gas-liquid chromatographic method (28) has been developed for the quantitative determination of clonidine and some structurally related imidazolidines in rat brain tissues. The aqueous brain homogenates are first purified and then extracted into benzene. Samples are injected directly to GLC column (2 m x 2 mm I.D.) packed with 3% OV-17 on chromosorb 750 (80-100 mesh) was used at an oven temperature of 200-270 and an injector temperature of 280 the carrier gas was helium flow rate 30 ml/min. 

Gas-liquid chromatography (GLC) is the most commonly used method for the forensic and clinical analysis of ethanol. Cadman and Johns in 1958 first reported a GLC method for determining blood ethanol concentrations. They extracted ethanol from samples prior to analysis by adding equal volume of n-propyl acetate (1ml) to a blood sample (1ml) to extract ethanol. No internal standard was used. A fixed volume of extract (35 pi) was injected into a GL chromatograph equipped with a thermal... 

A difficulty in finding inborn errors of pyrimidine metabolism by metabolite screening procedures is the absence of a typical end-product, like uric acid is in the purine metabolism. Moreover, pyrimidine metabolism is not easily accessible for simple chromatographic screening techniques. Nevertheless, with more complicated methods we are able to evaluate patterns of urinary pyrimidine bases and nucleosides. With routine gas-liquid chromatography (GLC) as is used for urinary organic acid analysis strongly increased uracil and thymine concentrations can be discovered. 

The analysis of essential oils by means of GC began in the 1950s, when professor Liberti [31] started analyzing citrus essential oils only a few years after James and Martin first described gas-liquid chromatography (GLC), commonly referred to as GC [32], a milestone in the evolution of instrumental chromatographic methods. 

Pantothenic acid, its salts, and panthenol as such are not volatile enough for direct gas-liquid chromatography (GLC). However, it is possible to use this chromatographic technique after derivatization of the polar hydroxyl and carboxyl groups of the vitamin (23,38,72,73,75-79). The majority of the developed methods are, however, applicable only to relatively pure and simple samples such as multivitamin preparations, and certain biological samples, such as urine (75-77). Only a few methods are suitable for the determination of the vitamin in complex matrices such as foods. An overview of methods was given by Velisek et al. (5). 

The basic analytical requirement is to determine the level of a particular fatty acid in a complex mixture of fatty acids combined as triglycerides in an oil or fat. Hence the method must be based on a chromatographic separation of the fatty acids derived from the triglycerides, followed by a suitable detection system. In practical terms, therefore, the only analytical approaches are those based on the separation of the methyl esters of the fatty acids by variants of gas-liquid chromatography (GLC) and thin-layer chromatography (TLC). The degree of selectivity and sophistication of the chosen method will depend on the complexity of the sample. 

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