Colorimetric determination of thiocyanate ion using modified polymer resins

Abstract

A new method for thiocyanate determination in milk samples based on the formation of dithiocyanato dipyridine copper(II) [Cu(SCN)2(Py)2] complex on polymer resin surface is proposed. Amberlite XAD-7 resin on was modified with copper-pyridine complex and used as the material for detection. The color of resin changed from blue to green with the increase of thiocyanate concentration. It could be observed by naked-eye and the color intensity used as quantitative data was measured via Image-J software. The effect of various parameters was investigated including Cu2+ concentration, time for resin modification with reagents, sample volume, detection time and pyridine volume. Under the optimal condition, the linear range from 11.6 – 116.0 mg/L was obtained with the limit of detection and quantification of 3.6 mg/L and 8.0 mg/L, respectively. To detect thiocyanate in milk samples, the standard addition method was performed to overcome the matrix effect. The recovery of thiocyanate in milk samples observed by proposed method was 93.4 – 104.6% with the relative standard deviations in the range of 1.2 – 4.2%. The proposed method was successfully applied to detect thiocyanate in milk samples with acceptable accuracy and precision.