Determination of microgram amounts of 2-thiohydantoins by means of the induced iodine-azide reaction

A simple method for the determination of 2-thiohydantoins based on the induction of the iodine-azide reaction was developed. The consumption of iodine is proportional to the amount of the inductor. The inducing properties of different compounds (S 2− ) were estimated from the induction coefficient ([I]/[S]) which indicates how many times the consumption of iodine in the induced reaction is higher than that in the iodimetric reaction. Under analytically optimum conditions the induction coefficients were in the range 270–307 for six 2-thiohydantoins and 138–192 for four 3-phenyl-2-thiohydantoins. The applicability of the iodine-azide reaction for the determination of microgram amounts of 2-thiohydantoins after their separation by thin-layer chromatography is demonstrated. The iodine-azide method is sensitive, selective, accurate, cheap and rapid.