Acid digestion and microplate reading method for milk iodine determination

ABSTRACT

Main shortcomings in existing methods for iodine determination in milk samples are non safe alkaline solution, harsh thermal conditions, and their being time consuming. In this study, for determination of total iodine content in milk, a simple and rapid kinetic catalytic colorimetric, acid digestion and rapid microplate reading format method, was investigated. Sample digestion was done on 50 micro L milk in metavanadate/perchloric acid, at 230°C for 10 min. After digestion, iodine determination was based on famous Sandell - Kolthoff reaction. The reaction results were read in 96 wells microplate by ELISA reader. Work range of the assay was between 2-40 micro g/dl. The within-run coefficient of variation percent ranged from 6. 7 to 9. 3 and between-run coefficients of variation ranged from 8.6 to 12.3%. The results obtained [n = 70] by the optimized method had good correlation with the results of alkaline incineration as the reference method [p < 0.000, n = 70 r2 = 0.907 y = 0. 952x-0.084]. Recovery tests for accuracy assessment were between 91.3 to 113%. This method enabled us to achieve 0.1 micro g/dl sensitivity. This study showed that, fast acid digestion, mild thermal, fast results reading and low sample volume, were the main advantages of the acid digestion and microplate reading format investigated