New spectro photometric method based on electrophilic coupling reaction for the determination of trace amounts of nitrite in environmental samples had been developed. Replacement of toxic reagents was explored to attain the standards of clean chemistry. This method utilizes phenoxazine and sulfadiazine (SZX), the well-established drug in the presence of limited amount of hydrochloric acid. The method is based on the oxidation of sulfadiazine (SZX), by nitrite in hydrochloric acid medium and coupling with phenoxazine (PNZ), which yielded red colored derivative having absorbance maximum at 525 nm and is stable for about 1h. Beer’s law was obeyed for nitrite in the concentration range 0.08 – 0.68μg ml-1 . The reaction conditions and other important analytical parameters were optimized to get maximum sensitivity of the method. Interference if any, by non-target ions was also investigated. The method can be applied successfully for determining nitrite in environmental samples. The performance of this method was evaluated by applying student’s t-test and variance ratio F-test to find out the significance of proposed method over the reference spectro photometric method.
