Optimization of extraction method for quantitative analysis of Si/Al in soil phytoliths

Elemental information carried by phytoliths plays a crucial indicative role in geochemical research. For instance, it serves as an indicator of the carbon pool effect in phytoliths and aids in the elucidation of silicon sources. However, early extraction methods for soil phytoliths primarily focused on obtaining their morphological and quantitative information, lacking efficient techniques for quantitative elemental analysis. In this study, we aimed to extract Si/Al information from soil phytoliths. Considering the need for complete extraction of phytolith, six extraction methods were developed and further by alkaline dissolution to determine Si/Al. Six methods were compared in terms of enrichment capacity, the weight of extracted phytoliths, and Si/Al differences. The results indicated that the addition of Ammonia-Catechol in the commonly used heavy liquid flotation method effectively improved phytolith extraction capability and the accuracy of Si/Al results. Additionally, the inclusion of an acetic acid step before alkaline dissolution further removed surface-adsorbed impurities and enhanced the analytical quality of Si/Al in phytolith. The comparison of the data in this study with other published data shows that our method is relatively robust. The improved method proposed in this study can provide a new idea for the quantitative analysis of other elements in soil phytoliths.