The paper presents the application of post-chromatographic iodine-azide reaction for the determination of three thiouracils (6-benzyl-, 6-methyl-, and 6-propyl-2-thiouracil) in high-performance thin-layer chromatography (HPTLC). The HPTLC plates developed by methanol were sprayed with a freshly prepared mixture of sodium azide, potassium iodide, and starch solution adjusted to pH 5.5, and exposed to iodine vapour for 5 s. Because of the induction properties of the C-S and C=S bonds of thiouracil molecule in the iodine-azide reaction, the spots became visible as white spots on a violet-brown background.Scanning of the HPTLC plates was performed on a PC scanner and analysed by TLSee software. Determination range was 7–16 pmol per spot, 80–160 nmol per mL of urine, or 133–266 nmol per 1 mL of serum.
R. Wilson, M. Choppra, H. Bradley, J.H. McKillop, Clin. Endocrinol. 77 (1990) 149–153.