MULTICOMMUTATION IN FLOW-ANALYSIS .2. BINARY SAMPLING FOR SPECTROPHOTOMETRIC DETERMINATION OF NICKEL, IRON AND CHROMIUM IN STEEL ALLOYS

Multicommutation now systems for the spectrophotometric determination of nickel, iron and chromium in acid solutions of steel alloys employi ng a binary sampling approach are described. Dimethylglyoxime, salicyl ic acid and diphenylcarbazide were used as chromogenic reagents for ni ckel, iron and chromium, respectively. The now networks were designed with active devices in order to provide facilities to handle reagent s olutions employing a single pumping channel to propel all reagent solu tions. Interference caused by iron on the nickel determination was sup pressed on-line by using triethanolamine as masking agent. For sample concentrations ranging from 5 to 50 mg/l, the proposed method is chara cterized by a throughput of 60 determinations per hour and a relative standard deviation of about 1%. Consumptions of potassium peroxodisulp hate and dimethylglyoxime solutions were 56 and 78 mu l per determinat ion, respectively. Iron and chromium were determined sequentially, wit h a reagent consumption of 80 mu l and 26 mu l, respectively. For samp le concentrations ranging from 25 to 200 mg/l Fe and 20 to 60 mg/l Cr a throughput of 130 determinations per hour was achieved. Results comp ared well with those obtained by inductively coupled argon plasma atom ic emission spectrometry.