2,4,6-Triphenylpyrylium Cations as Derivatization Reagents for Sulfide Ions Detection in TLC

Abstract

We report a study of the use of 2,4,6-triphenylpyrylium salts as derivatization reagents for the simple detection of sulfide ions in thin-layer chromatography (TLC). The principle of the presented method is based on the transformation of 2,4,6-triphenylpyrylium compounds into the parent thiopyrylium derivatives upon reaction with sulfide ions. The derivatization reaction took place in a tube or directly on the TLC plate before the developing step. As a consequence of the reaction of sulfide with the 2,4,6-triphenylpyrylium derivatives, the spots became visible as yellow or blue spots on a colorless background. Spots were stable for several hours. The detection limit is at pmol per spot level and depends on the triphenylpyrylium salt used and on the detection method.

A derivatization approach using pyrylium salts for the sensitive and simple determination of sulfide in spring water by high performance liquid chromatography

“…The most important advantages of the LN1 and L1 derivatization reagents are their sensitivity and specificity for sulfide ions. Previous studies have shown that pyrylium salts do not react with fluoride, bromide, chloride, iodide, phosphate, sulfate, nitrate, cyanide, acetate, benzoate, MESNA, cysteine, or octanethiol [25][26][27]. Under certain conditions some amines have been reported to react with 4-[p-(N,N-dimethylamino)phenyl]-2,6-diphenylpyrylium to give yellow derivatives ( = 460 nm) [31], however no amines were expected to be present in the tested water samples.…”

“…The addition of acetonitrile into the derivatization mixture is necessary due to the poor solubility of L1 and LN1 in pure water [25][26][27] and the volume of this organic solvent has a clear effect in the yield of the derivatization reaction. In order to optimize the volume of acetonitrile in the derivatization mixture, different volumes of this organic solvent in the range of 0-6 mL were tested.…”

“…The reactions between sulfide and LN1 or L1 pyrilium cations described in previous reports were carried out in an alkaline solution [25][26][27]. In order to find the optimum pH of the reaction mixture, TRIS buffer and phosphoric buffer solutions (0.1 mol L −1 ) in the 7.0-12.0 pH range were prepared.…”

“…The impact of hydrochloric acid on the cyclization of the reaction intermediate and the derivatization procedure was described previously [26,27]. In order to estimate its optimum volume, different amounts of hydrochloric acid (36%) in the range of 0-600 L were transferred into the 10 mL flasks where the reaction took place.…”

“…The procedure proposed in this paper is based on a prechromatographic reaction of sulfides with pyrylium salts (4-[p-(N,Ndimethylamino)phenyl]-2,6-diphenylpyrylium perchlorate (LN1) or 2,4,6-triphenylpyrylium tetrafluoroborate (L1), and the conversion of the derivatization reagent into the corresponding LN3 and L3 thiopyrylium cations [25][26][27] (Fig. 1).…”