Comparison of TLC-FID system with gas chromatography

TLC-FID produced comparable results to those obtained by GC in the analysis of commercial mixtures of acylglycerides (Ranny et al, 1983). Furthermore, owing to cost considerations, the TLC-FID method was found to be preferable for serial analysis in process control or technical quality control. 

In a comparative study of the reproducibility of results obtained by the two techniques for the analysis of blood lipids Mares et al. (1983) concluded that the variations obtained with the TLC-FID system were much higher than those obtained by GC. However, recent improvements in the latroscan detection system are likely to increase significantly the reproducibility for this type of analyses. Sebedio and Ackman (1981) analysed a synthetic mixture of fatty acid methyl esters on silver-nitrate-impregnated Chroma-rods and compared the results with those obtained from conventional GC. Comparable results were obtained by the two methods for all methyl esters, except for methyl linolenate, the quantity of which was substantially overestimated by the TLC-FID method. 

Bascoul et al. (1986) compared the levels of polar oxysterols as measured by TLC-FID and GC. The values obtained by TLC-FID analysis were considerably higher (341 65 ppm) than those obtained by GC (124 50 ppm). Bascoul et al. considered that the results obtained by TLC-FID were more accurate, because they agreed more closely with values of cholesterol content, corrected for the expected losses during heating, (376 37 ppm). 

Nevertheless, GC is a better method for the analysis of cholesterol autoxida-tion products, because of its superior resolution capabilities. 

Since the introduction of the Mark V latroscan model, there have been no further technical improvements to the TLC-FID system. However, the development of vapour phase detectors (such as the flame thermionic ionization detector for compounds containing nitrogen and halogens, and the flame emission photometric detector which detects compounds containing sulphur and phosphorus) should extend the range of applications of the TLC-FID system. 

---