Progress on cupric acetate-pyridine colorimetric method for specific quantitative determination of acid value.

Acid value (AV) indicates the content of free fatty acids (FFA) in oils and fats, which is one of the most important quality and safety indicators of oils and fats and oily foodstuffs. In view of the commonness and non-specificity limitations of the current acid-base neutralization titration techniques for AV determination standards, a new idea for the specific quantification of FFA or AV in complex matrix samples is aimed to offer. The research progress of cupric acetate-pyridine complexation colorimetry, the most representative technology for the specific determination of FFA in the nearly 70 years, was reviewed. The conflict resolution process between the toxicity of organic phase solution and color intensity, the evolution history of cupric acetate-pyridine colorimetric aqueous phase dyeing solution, the structure analysis process of cupric acetate-pyridine complex of FFA, and the new development of complexation color theory from the classical theory with pH regulation to the new theory...