Novel reactions for simple and sensitive spectrophotometric determination of nitrite

Nine spectrophotometric methods based on new reactions for the determination of tracer amounts of nitrite in environmental samples were developed. Replacement of toxic reagents was explored to attain the standards of clean chemistry. These methods utilize two classes of compounds namely; phenoxazines and sulphonamides, the well established drugs in the presence of limited amounts of hydrochloric acid. The methods were based on the oxidation of sulfanilamide (SAA), sulfadoxine (SDX) or sulfamethoxazole (SMX) by nitrite in hydrochloric acid medium and coupling with phenoxazine (PNZ), 2-chlorophenoxazine (CPN) or 2-trifluoromethylphenoxazine (TPN) which yielded red colored derivatives having an absorbance maximum in the range 530-540 nm and were stable for about 4 h. Beer's law was obeyed for nitrite in the concentration range 0.13-1.60 μg mL⁻¹. The reaction conditions and other important analytical parameters were optimized to enhance the sensitivity of the methods. Interference if any, by non-target ions was also investigated. The methods were applied determining nitrite in environmental samples. The performance of these methods were evaluated in terms of Student's t-test and variance ratio F-test to find out the significance of proposed methods over the reference spectrophotometric method.