Thin-layer chromatography offers various detection methods of sulfur (II) compounds, most of which are based on general rather than specific techniques. The presence of a sulfur (II) compound is necessary for the iodine-azide reaction to take place (selective induction) and only these compounds can be perceived on the thin-layer plate after treating with iodine-azide reagent. The developed plates were sprayed with a mixture of sodium azide and iodine solution. The modified procedure included spraying the developed plate with sodium azide and starch solution and afterwards exposing it to iodine vapor. In RP-HPTLC mode, sodium azide became constituent of the mobile phase. The catalytic effect of C-S, C=S, P-S, P=S bonds resulted in white spots emerging on the violet-gray background. It was found out, however, that the detection limits were as low as pmol per dot and their origins were discussed. The method was used to distinguish different thiols in biological samples, such as urine or blood serum, pesticides and drugs. The outcome of the derivatization process with phenyl isothiocyanate or buthyl isothiocyanate is the transformation of the amino acids, biogenic amines and amphetamines into inductors (PTC, BTC or PTH derivative) of the iodine-azide reaction.