[A Quantitative Analysis Method of Water-Soluble Inorganic Ions with ATR-FTIR Spectroscopy]

A method of fast nondestructive determination of three kinds of water-soluble inorganic ions including SO₄²⁻, NO₃⁻ NH₄⁺ in aerosol was disscussed. The method of IC measurement values was used on the control of the three kinds of inorganic ion content. The quantitative calibration models of the inorganic ions were developed by using ATR-FTIR spectroscopy combined with PLS algorithm and the model was evaluated. Markov distance discriminant method was used to identify and eliminate outliers, different mathematical treatments for spectra processing and different wavelength ranges were compared to determine the best model and the optimal model parameters was determined. The results showed that second derivative analysis after eliminating outliers can improve the prediction, PLS analysis can get better results for SO₄²⁻ in the range of 1220-900 cm⁻¹, for NO₃⁻ in the range of 1521-900 cm⁻¹ and for NH in the range of 1521-1220 cm⁻¹, the RMSEP were 1.736 7, 1.023 9 and 1.482 3, respectively. The foundation of real-time fast quantitative analysis of the three kinds of inorganic ion in a large number of aerosol samples was established.