Use of 4-(6-methylnaphthalen-2-yl)-4-oxobut-2-enoic acid as a reagent for the spectrophotometric and fluorimetric determination of aliphatic thiol drugs

Abstract

The aroylacrylic acid 4-(6-methylnaphthalen-2-yl)-4-oxobut-2-enoic acid is proposed as a useful reagent for the spectrophotometric and fluorimetric determination of aliphatic thiol compounds. Under mild reaction conditions (pH 7.4, room temperature) the compound reacts rapidly (reaction complete in 15 min) and selectively with thiol compounds to give stable fluorescent thiol adducts. The adducts can be determined in the presence of the reagent excess by spectrophotometric (conventional and second- or third-derivative procedures) and fluorimetric (λ_em.= 445 nm, λ_ex.= 300 nm) methods. All the described procedures have been successfully applied to the determination of thiol drugs such as N-acetylcysteine, mercaptopropionylglycine and captopril in commerical dosage forms.