The present study reports a new automated, generic anal. method for the determination of the pharmaceutically active thiols captopril (CAP), N-acetylcysteine (NAC), and D-Penicillamine (PEN).The proposed sequential injection (SI) method is based on the online reaction of the selected thiols with o-phthalaldehyde/glycine in alk. medium (pH = 9.5) to form highly fluorescent -indole derivativesThe effect of all major flow and reaction variables was investigated, while validation was carried out in terms of linearity/range (2.5-7.5 mg L-1), limits of detection (1.6-2.3 μ g L-1), quantification (5.3-7.7 μ g L-1), precision (0.9-1.2% for repeatability and 3.5-4.9% for intermediate precision), selectivity, and accuracy (98.3-102.8%).The developed method was applied to the assay and dosage uniformity tests of various pharmaceutical formulations at a sampling rate of 73 h-1.