Highly selective colorimetric detection of putrescine in fish products using o-phthalaldehyde derivatization reaction

A highly selective colorimetric detection method for putrescine on the basis of an optimized derivatization reaction was established. With the aids of o-phthalaldehyde (OPA) and thioglycolic acid (TGA), putrescine was derived to become red derivatives (PUT-RD), the form that can be detected qualitatively and quantitatively by visual inspection and UV-vis spectrophotometer at lambda(max) of 490 nm, respectively. Key parameters affecting the experiment were investigated by one-factor-at-a-time and response surface analysis. At the optimal condition, this colorimetric method achieved good linearity at putrescine concentrations ranging from 0.8 to 200 mu M with detection limit of 0.44 mu M. The method also has good selectivity when common amino acids and inorganic ions, as well as ethylenediamine, 1,3-propanediamine, 1,5-pentanediamine, and 1,6-hexanediamine were used as interferences. The established colorimetric method was successfully employed for the detection of putrescine in 10 commercial fish products.