Total Phosphorus
This method is used for the determination of total phosphorus in water and wastewater. The EPA range of this method is 0.01 to 20.0 mg/L as P. However, this method is also applicable to other ranges.
Summary
Samples are digested to hydrolyze phosphorus to ortho-phosphate. The acidic digestate is neutralized and analyzed for ortho-phosphate. Ortho-phosphate reacts with molybdenum (VI) and antimony (III) in an acid medium to form a phosphoantimonylmolybdenum complex. This complex is subsequently reduced by ascorbic acid to a heteropolyblue with an absorbance maximum at 660 nm.
Limitations
Ferric iron up to 70 mg/L, copper up to 10 mg/L and silica up to 10 mg/L do not interfere. Turbid samples must be filtered before determination. Samples with background absorbance at the analytical wavelength may interfere.
Availability
| System | Method # | Range(s) |
| Flow System | A050 | 1 – 500 µg/l as P 4 - 200 µg/l as P 5 – 1000 µg/l as P 0.01 - 2 mg/l as P0.02 - 20 mg/l as P |
| Astoria 2 | A050 | 1 – 500 µg/l as P 4 - 200 µg/l as P 5 – 1000 µg/l as P 0.01 - 2 mg/l as P0.02 - 20 mg/l as P |
| rAPID-T | D050 | 0.02–2.0 mg/l PO4 as P |