Flame photometric detector for thin-layer chromatography

A new flame photometric detector for thin-layer chromatography (TLC) was studied to determine sulfur and phosphorus containing compounds in materials with a high boiling point. The detector was integrated with a flame ionization detector into the Iatroscan TLC–flame ionization detection analyzer. The principle of the detector is based on the photometric detection of flame emission of heteroatom in a hydrogen–air flame. The emission spectra of sulfur and phosphorus were measured using dibenzothiophene (DT) and phosphoric acid as source materials. Interference filters of 394 and 526 nm were chosen for spectral isolation of the sulfur and phosphorus emissions. The effects of variation in air flow-rate and scan speed as related to both sulfur and phosphorus compounds were studied in order to define optimum detection conditions. The best result for the detection of DT as a sulfur compound was obtained under combined hydrogen and air flow-rates of 160 and 500 ml/min, respectively, with a scan speed of 30 s/rod. The response to DT was linear in the range of 0.25–4 μg. On the other hand, the most suitable conditions for detecting phosphatidylcholine (PC) as a phosphorus compound were combined hydrogen and air flow-rates of 160 and 1500 ml/min, respectively, with a scan speed of 40 s/rod. The response to PC was linear in the range of 0.25–16 μg. Application of the instrument with selective detection of sulfur and phosphorus compounds was demonstrated using heavy oils and human serum lipids.