Abstract: The colour reaction between BCA (2,2'-biquinoline-4,4＇-dicarboxylic acid disodium salt) and copper was developed for determining trace copper in foods. In the presence of pH 11.0 buffer solution and hydroxylamine hydrochloride, BCA could react with copper (II) to form a purple complex with a ratio of 2:1. The molar absorbance constant was 7.72 × 103 L/(mol ·cm) at 562 nm. The absorbance obeyed Beer s law in the range of 0－4.8μg/mL Cu (Ⅱ). The established method was used for the determination of trace copper in tea and kelp. The determination results are consistent with the results from atomic absorption spectrometry (AAS) method. In conclusion, this method has the advantages of good accuracy, stability and can therefore be applied to the determination of trace copper in foods.

Key words: copper, determination, BCA method, spectrophotometry