T/CAIA SH025-2025 Determination of Total Phosphorus in Surface Water by Automatic Digestion-spectrophotometry
T/CAIA SH025-2025 Determination of Total Phosphorus in Surface Water by Automatic Digestion-spectrophotometry
Basic Information
Scope
Scope: This document describes the method for determining the total phosphorus content using an automatic dissolution photometry method. This document is applicable to the determination of total phosphorus content in surface water. The method has a detection limit of 0.01 mg/L (calculated as P) and a measurement range of 0.04 mg/L to 1.20 mg/L. Other types of water samples can refer to this document for implementation. Main technical content: Under high-temperature and high-pressure conditions, potassium persulfate converts phosphorus-containing compounds into orthophosphate. In an acidic medium, orthophosphate reacts with ammonium molybdate to form phosphomolybdenic acid in the presence of antimony salts, which is reduced by ascorbic acid to form a blue complex. The total phosphorus content is determined by photometry. A calibration curve is established based on the absorbance value after subtracting the blank and its corresponding total phosphorus content.