FT-IR Spectrometric Analysis of Aluminum Triphosphate

Fourier transform infrared spectrometry (FT-IRS) was applied to assaying of aluminum triphosphate (AlH2P3O10·2H2O) in the presence of the main impurities,aluminum metaphosphate and aluminum dihydrogen phosphate,produced during its preparation. As shown in the IR absorption spectra,absorption maxima of aluminum triphosphate (Al-TP) and aluminum metaphosphate (Al-MP) were found at the wavenumbers of 986 cm-1 and 740 cm-1 respectively,while no absorption peak of aluminum dihydrogen phosphate was observed in this wavelength region. It was proposed that aluminum metaphosphate was used as the internal standard,and a plotting of ratio of values of peak height of Al-TP to Al-MP against ratio of values of concentration of Al-TP to Al-MP was made to obtain a linear calibration curve by method of curve-fitting or minimum baseline calculation. Ratio of contents of Al-TP to Al-MP of the sample was found in this way with elimination of the interference of aluminum metaphosphate. Contents of aluminum dihydrogen phosphate and moisture of the sample were determined individually by methods given in the standards 浙B/HG 204-88 and GB/T 1714-1979. Finally,the content of aluminum triphosphate in the sample was calculated by substraction as given by the formula given.