CONVENTIONAL AND THERMAL LENS SPECTROPHOTOMETRIC DETERMINATION OF P-AMINOBENZOIC ACID AND ARYLAMINE DIURETICS PREVIOUS AZODYE FORMATION IN A MICELLAR MEDIUM

The determination of the diuretics hydrochlorothiazide, bendroflumethi azide and furosemide by both conventional and thermal lens spectrophot ometry (TLS, 100 mW of pump power at 514.5 nm) following previous hydr olysis, diazotization and coupling with N-(naphthyl)ethylenediamine (N ED) in a sodium dodecyl sulphate (SDS) micellar medium of pH almost-eq ual-to 1 was studied. p-Aminobenzoic acid (PABA) was used as a model c ompound to optimize the derivatization procedures. 3-Substituted indol es, such as 5-hydroxyindole-3-acetic acid and tryptophan, gave N-nitro so derivatives which interfered with the determination of the diuretic s in urine. The derivatized diuretics in urine were separated using HP LC with a Spherisorb ODS-2 C18 column, and a 0.1M SDS mobile phase con taining 5% n-propanol and 0.01M sodium dihydrogen phosphate (pH 3). Th e diuretics gave limits of detection (LODs) of ca. 5 x 10(-9)M for the TLS procedure. The LODs were 20-50-fold higher for the corresponding spectrophotometric procedure.