Quantitative analysis of component contents in AS/PDM composite coagulant by infrared spectroscopy

Abstract

In order to establish a quantitative analysis method for the components in the composite coagulant aluminum sulfate/poly dimethyl diallyl ammonium chloride (AS/PDM), this study first compared different sample preparation methods for infrared spectroscopy analysis. The electric hot plate drying method was selected due to its rapid sample preparation time and low moisture content. Based on the linear relationship between the mass ratio values of organic and inorganic components and the relative peak area ratio values of their characteristic infrared spectra, the mass ratio values were divided into four segments by order of magnitude. Samples were prepared for each segment, and their infrared spectra and corresponding relative peak area ratios were obtained. Different peak area calculation methods were compared, and four standard curves were constructed, with precision and recovery rates validated. Based on the measured mass ratio relationships between the components, the inorganic component Al₂O₃ content was determined using the EDTA back-titration method, completing the development of the quantitative analysis method for both components. Finally, verification using samples from four different mass ratio value segments demonstrated that when a linear lower bound for integration was used to calculate peak areas, the maximum relative error within the selected mass ratio value range was less than 5 %, which was significantly better than the results obtained using a curve as the lower bound for integration. Therefore, this method provides experimental evidence for the quantitative analysis of AS/PDM components and supports the establishment of quality standards for the product.