A refined method for phosphite detection in freshwater ecosystems

Abstract The prevalent existence of phosphite in the contemporary, oxidizing aquatic environments is noteworthy, and its overlooked role in the phosphorus cycle needs further elucidation. While existing methods for quantifying phosphite have limited applicability due to inherent constraints. We propose a novel approach that integrates various techniques, termed diffusive gradients in thin films (DGT)–ion chromatography (IC)–inductively coupled plasma mass spectrometry (ICP‐MS/MS), which differs from traditional high‐performance liquid chromatography (HPLC)–ICP‐MS. This method converts the detection target of P + ( m / z = 31) to PO + ( m / z = 47), effectively mitigating MS interference and enhancing detection performance, enabling the method detection limit to 0.033 μ g P L −1 , significantly lower than that of the HPLC–ICP‐MS. Under the premise of separation of IC, the precision (coefficient of variation= 0.6–1.4%) and accuracy (recovery = 98.2–99.6%) were tested as excellent for the phosphite measurement range from low to high concentration. When combined with the enrichment of DGT, even the amount of phosphite below the method detection limit can be determined, applications of this method to the natural samples with complex matrix ensure that the > 95.2% recovery accurately quantifies phosphite. This method reduced the method detection limit for phosphite and realized the accurate quantitative analysis, providing an important basis for further studys of phosphite in freshwater ecosystems.