Determination of Nitrite Ion in Water Samples using a Copper (II) Schiff-base Optical Sensor Immobilized on Triacetylcellulose Membrane

Recently, greener analytical methods which minimize the use of toxic chemicals and/or eliminate the generation of toxic wastes are strongly demanded, in order to prevent the environmental pollution. Nitrate is an important pollutant found in environmental samples. Nitrate and nitrite pose various environmental as well as health hazards [1]. Different methods of determining nitrite in various environmental samples developed during previous years include spectrophotometric, chemiluminescence, electrochemical detection, chromatographic, capillary electrophoretic, spectrofluorimetric methods [2]. The synthesis and structure of polydentate Schiff bases and their metal complexes is fascinating, because it reveals a great richness of structural, physico-chemical and catalytic properties. Given the simplicity and ease of access to multidentate Schiff bases and their metal complexes, investigation of such compounds is essential to precise and understand structure–property relationships in order to optimize and improve their use in a wide range of fields, including catalysis, supramolecular chemistry, magnetism, electrochemistry, nanoscience, energy materials, and biological applications [3].In this research, method based on spectroscopic detection of nitrite has been discussed, due to its easy availability, high sensitivity, low detection limit, economical and facile nature. A copper(II) Schiff base, 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. Several samples of water were collected at different locations around Shiraz. The application of the sensor for determination of nitrite content in water samples was quiet successful.