Simultaneous determination of nitroaniline isomers in binary mixtures by novel spectrophotometric methods

Nitroanilines are an important kind of chemical raw materials, mainly used as intermediates of azo dyes, engineering plastics, pharmaceuticals, gum inhibitors, agrochemicals, and corrosion inhibitors. Since these compounds have a significant water solubility, they are often present in wastewater discharges from such manufacturing facilities [1-2]. Therefore, recognition of the nitroaniline isomers could be one of the important studies of environmental analysis. The simultaneous determination of a nitroaniline isomer mixture by spectrophotometric methods is a difficult problem in analytical chemistry due to spectral interferences. By the novel spectrophotometric methods such as the extended ratio subtraction method (EXRSM) [3], constant center coupled with spectrum subtraction method (CC–SS)[4], and ratio H-point standard addition method (R-HPSAM) [5], the concentration of nitroaniline isomers in binery mixtures can be obtained.In this work, first, a mixture of ortho and meta isomers were determined by the three methods EXRSM, R-HPSAM, and CC-SS. The effects of different parameters including the pH, concentration of the divisor, and interferences were investigated for both isomers by the three methods. For three methods, the linear dynamic ranges for ortho and meta isomers were found to be 5-25 and 5-30 μg mL-1, respectively. Then a mixture of the ortho and para isomers were determined by these methods. The effects of the above-mentioned parameters were investigated for both isomers by the three methods. The linear concentration ranges for the ortho and para isomers were found to be 2-20 and 0.5-10 μg mL-1, respectively. The developed methods were successfully used for the determination of various spiked water samples with different nitroaniline isomer ratios.