Preparative flame ionisation detector

The most common detectors for GC are the non-selective flame ionisation detector and thermal conductivity detector. For element speciation, selectivity is definitely advantageous, allowing less sample preparation and less demanding separation. Of the conventional GC detectors, the electron capture detector is very sensitive for electrophilic compounds and therefore has some selectivity for polar compounds containing halogens and metal ions. It has been used widely... 

Narkis and Henfield-Furie [578] have described a direct method for the identification and determination of volatile water-soluble Ci C5 acids in municipal waste water and raw sewage. The method involves direct injection of the sewage into a gas chromatograph equipped with a Carbowax 20m on acid-washed Chromosorb W column and a flame ionisation detector. Preliminary preparation of the sample is limited to the addition of solid metaphosphoric acid to the sewage and removal of precipitated proteins and suspended solids by centrifuging. 

The experimental scheme for anaerobic decomposition is shown in Fig. 5-4. Exactly 1.5 g of each substrate was added to a modified 1 litre Sohngen flask and autoclaved at 120°C and 15 psi to ensure sterility, after which each flask was filled to capacity with a sterile inorganic nutrient medium and pH adjusted. Next 50 ml of a heterogeneous innoculum prepared from muds from a local lake was injected into each flask as "inoculates", while 50 ml. of sterile nutrient medium was used for control samples. Headspace C1-C4 hydrocarbons were measured prior to incubation to provide baseline concentrations. Minimum detection limits were 3 ppb on a volume basis using a high-sensitivity gas chromatograph equipped with a flame ionisation detector. Samples were incubated at 25°C and 36°C over a five week period. 

Excellent separations have been demonstrated with self prepared capillary columns (26). The comparison between packed columns and glass capillary columns revealed a 100 fold improvement in sensitivity of the glass capillary column measured with flame ionisation detector (26). 

Fatty acid esterification and gas chromatography (GC) Phospholipids spots obtained on TLC were scraped to analyse the endogenous (unlabelled) fatty acids of the phospholipids fraction from the different calli. Fatty acid (FA) methyl esters were prepared by transesterification with 0.2 M of sodium methoxyde for 15 min in darkness. Then, 4 mL of chloroform and 1.5 mL of deionized water were added. After homogenisation, the mixture were centrifuged (2000 g, 4 °C, 10 min) to remove remaining silica gel particles. FA were estimated on 3 mL of the chloroformic phase and separated by gas liquid chromatography (Packard 427, fitted with a flame ionisation detector and a Ross injector). FA were analysed with a fused silica capillary column of 25 m x 0.32 mm internal diameter coated with a CP wax 52 CB phase immobilised in situ in a film thickness of... 

The flame ionisation detector (FID) has been used in analytical SFC and could be used in preparative SFC by by-passing a very small fraction of the mobile phase flow through to the detector. Obviously the FID could not operate in a largely carbon dioxide atmosphere and would respond to many modifiers. The photoionisation detector (PID) has been used in analytical SFC but is better suited to highly sensitive detection of specific types of compound. 

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