Simultaneous kinetic spectrophotometric determination of cyanide and thiocyanate using the partial least squares (PLS) regression.

The partial least squares (PLS-1) calibration model based on spectrophotometric measurement, for the simultaneous determination of CN(-) and SCN(-) ions is described. The method is based on the difference in the rate of the reaction between CN(-) and SCN(-) ions with chloramine-T in a pH 4.0 buffer solution and at 30 degrees C. The produced cyanogen chloride (CNCl) reacts with pyridine and the product condenses with barbituric acid and forms a final colored product. The absorption kinetic profiles of the solutions were monitored by measuring absorbance at 578nm in the time range 20-180s after initiation of the reaction with 2s intervals. The experimental calibration matrix for partial least squares (PLS-1) calibration was designed with 31 samples. The cross-validation method was used for selecting the number of factors. The results showed that simultaneous determination could be performed in the range 10.0-900.0 and 50.0-1200.0ng mL(-1) for CN(-) and SCN(-) ions, respectively. The proposed method was successfully applied to the simultaneous determination of cyanide and thiocyanate in water samples.