On-site Determination of Total Phosphorus in Natural Waters Using a Novel Peroxymonosulfate-Based Mild Digestion Method Without High Temperature or Pressure

Abstract

Total phosphorus is a key indicator of eutrophication, but conventional total phosphorus methods face challenges such as complex operational procedures, bulky instrumentation, and safety risks, limiting on-site rapid analysis. In this study, an on-site total phosphorus determination method was developed by integrating peroxymonosulfate-based advanced oxidation processes with the phosphomolybdenum blue spectrophotometric method. The system was composed of a portable thermal cup for mild sample digestion and a compact spectrophotometer for quantitative analysis, enabling rapid on-site determination of total phosphorus in natural waters without the need for high temperature or pressure. Compared with traditional laboratory methods, operational complexity and equipment footprint were significantly reduced providing a practical solution for real-time water quality monitoring. The effects of initial solution pH, digestion temperature, digestion duration, and peroxymonosulfate concentration on digestion efficiency were systematically investigated, and optimal on-site digestion conditions were determined using response surface methodology. The method exhibited excellent linearity in the range of 0.0-0.6 mg·L⁻¹ and a detection limit of 0.008 mg·L⁻¹. Spiked recoveries in various matrices were 107.5%-116.5%, indicating broad applicability in diverse aquatic environments. Results from actual water samples, were consistent with those obtained by the standard method, confirming the reliability and accuracy of the proposed approach for on-site total phosphorus determination.