Spectrophotometric determination of thiocyanate by sequential injection analysis

A sequential injection analysis (SIA) system was developed for the spectrop hotometric determination of thiocyanate as Fe(SCN)(2+). The physical parame ters (flow rate, sample and reagent volumes, holding coil and reaction coil internal diameter and length) which influence dispersion in a SIA system w ere optimized. The effect of the reagent concentration and nitric acid conc entration tin the reagent solution and carrier stream, respectively), were also studied. Reagent consumption was effectively reduced by introducing th e reagent as a zone into the nitric acid carrier stream, compared to flow i njection analysis where the reagent itself is the carrier stream. The syste m is fully computerized and able to monitor thiocyanate in samples at 24 sa mples per hour with a relative standard deviation of <1.20% for samples and standards with thiocyanate concentrations above 10.0 mg l(-1). The calibra tion graph is linear from 2.0 to 150.0 mg l(-1) with a 3 sigma detection li mit of 1.1 mg l(-1). The system has been applied to the determination of th iocyanate in process solutions and waste waters. (C) 2000 Elsevier Science B.V. All rights reserved.