Thin layer chromatographic detection and spectrophotometric determination of the trisodium salt of 1,3,6-pyrenetrisulfonic acid in D&C Green No. 8.

A thin layer chromatographic method is presented for separating the reaction by-product 1,3,6-pyrenetrisulfonic acid (trisodium salt) (PTS) from D&C Green No. 8 (8-hydroxy-1,3,6-pyrenetrisulfonic acid). PTS is detected visually, extracted from the adsorbent, and determined spectrophotometrically. Recoveries of PTS added at 0.75-6.73% levels to 8-hydroxy-1,3,6-pyrenetrisulfonic acid ranged from 80.0 to 94.8%.