Ross injector

The Ross injector is more scarcely used than those mentioned previously and it allows the injection of large volumes. It is composed of a glass needle approximately 10 cm long placed in a tube equipped with a leak valve and drilled with two lateral orifices (one for the arrival of the carrier gas and the other for the injection of the sample). The sample is placed on the needle. The carrier gas flow allows the evaporation of the solvent that is eliminated by the leak before putting down the needle into the injection port where the sample is vaporized. 

This injection mode is particularly useful for trace analysis in environmental matrices. It allows the injection of large sample volumes and successive introductions in order to concentrate analytes on the needle it also allows avoidance of solvent injection, thus increasing the lifetime of the analytical column. However, it does not allow analysis of very volatile products as they evaporate with the solvent. 

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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... 

Figure 14. Variation of characteristic velocity with spacing of injector orifices for a showerhead injector (Ross)...

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