Ionic liquids as separation enhancers of haloperidol and its two metabolites in high-performance thin-layer chromatography supported with mass spectrometry

High-performance thin-layer chromatography (HPTLC)–densitometric method of haloperidol (HP) and its two metabolites (reduced haloperidol [RHP], 4-(4-chlorophenyl)-4-hydroxypiperidine [CPHP]) from human plasma has been developed by use of mobile-phase additives. The influence of the type of inorganic/ organic additive on the retention of the studied compounds was evaluated. The chromatographic process was carried out with traditional mobile phase modifiers and 1-alkyl-imidazolium ionic liquid as separation enhancers, in the presence of chlorpromazine as internal standard. 1-Ethyl-3-methylimidazolium tetrafluoroborate ([emim][BF4]) ionic liquid offered good selectivity in comparison with traditional mobile phase additives. The studied drugs were well distributed as the RF values were 0.31 for chlorpromazine hydrochloride (CPZ), 0.38 for HP, 0.44 for CPHP, and 0.58 for RHP, respectively, with no apparent broadening and overlapping of spots. The test compounds were extracted using acetonitrile as precipitatio...