Introduction of a new nitrite-selective optical sensor for food analysis using a copper(II) Schiff base complex

Abstract

A copper(II) Schiff base complex, methyl-2-{[1-methyl-2-(4-methoxy-phenolate)mehylidynenitrilo]ethyl}amino-1-cyclopentene dithiocarboxylate copper(II), [Cu(cd4OMeSalMeen)], was incorporated into triacetylcellulose membrane and applied as ionophore in order to develop an anion-selective optical sensor for the analysis of nitrite by absorption spectrophotometry. At optimum pH 3.0, a linear calibration curve was observed for nitrite in the range of 0.50 to 7.00 mg L-1) with a detection limit of 0.04 mg L-1. The response time of the optode (t95%) was found to be 8–10 min, depending on the nitrite ion concentration. The proposed sensor was fully recovered in nitric acid solution (0.1 M) and had acceptable reproducibility (RSD=1.9%). The optode was exhibited good selectivity toward nitrite ion according to hard-soft acid base (HSAB) principle and the formation constant was calculated. The application of the sensor for determination of nitrite content in meat products was quiet successful.