Studies on Secondary Amines in Foods

I. Modified Cu-dithiocarbamate Colorimetric Method for the Determination of Secondary Amines

Abstract

A modified Cu-dithiocarbamate method was devised for determining secondary amines in foods. Procedure is as follows: A 5ml of trichloroacetic acid (TCA) extract of food sample and 1ml of 2% TCA solution are taken into a 50ml separatory funnel to which are added 10ml of 5% CS₂-chloroform and 0.2ml of the alkali reagent, and the funnel is shaken vigorously by a mechanical shaker for 2 minutes. Then 1ml of the Cu-reagent is added to the funnel and it is shaken vigorously for 1 minute. Immediately after shaking, 1ml of 30% acetic acid solution is added to the reaction mixture, then the funnel is shaken for a few seconds. The lower layer (CHCl₃) in the funnel is separated in a test tube to which 0.4g of anhydrous Na₂SO₄ is added to remove moisture. The color intensity of the CHCl₃ solution is determined at 435mμ by a spectrophotometer. Similar test is conducted with the test solution containing 5μg of standard dimethylamine-nitrogen (DMA-N) (1ml of 5μg/ml of DMA-N is added to 5ml of the test solution). The concentration of secondary amines may be calculated by the following equation:
where, C; concentration of secondary amine-N (DMA-N equivalent, p. p. m.)
A₁; absorbance obtained with a test solution
A₂; absorbance obtained with the test solution containing 5μg of standard DMA-N
*; amount of standard DMA-N added (5μg)
The recovery of DMA-N added to food samples is approximately 97%.