determination of phosphate anion in food samples by near ir spectrophotometry

Abstract: phosphorus (p) is a required nutrient for life, it plays a main role in the metabolism of both plants and animals. it is a growth-limiting nutrient, which makes it an important parameter to control in the environment. phosphate exists in three forms: orthophosphates (mainly), condensed phosphates, and organic phosphates [1]. several analytical methods have been reported for the determination of orthophosphates such as chromatography, electrochemical, fluorescence, and molybdenum blue (mb) spectrophotometric method [2]. in this work, the amount of phosphate anion in food samples was measured by nir-spectrometry method. the measurement was based on the formation of molybdophosphoric acid by adding the defined amount (48 mm) of ammonium molybdate to beverage samples (soda). then, the reduction of molybdophosphoric acid complex (mo(v)) was done by the addition of ascorbic acid to form molybdenum blue complex (mo(vi)) in strong acidic conditions (ph: 1-2). the reaction conditions as well as the various experimental parameters affecting the development and stability of the prepared coloured complex were investigated and optimized for the quantitative determination of phosphate existing in various samples. this complex has a maximum absorption at 815 nm, which can be used to determine the amount of phosphate in beverage samples. so, different concentrations of phosphate (0.5-80 ppm) were prepared to form the molybdenum blue complexes; then, the absorbance of each sample at 815 nm was measured with three repetitions (rsd = 5%). the calibration curve showed a good correlation coefficient (r2) of 0.98. to examine whether light scattering is interfering or not, the absorption of the molybdenum blue complex was measured by the dual-wavelength method. the results show that the nir spectrometry method based on the formation of the molybdenum blue complex is a good candidate to measure the phosphate anion in food samples as it provides fast, easy, and reliable measurement.