This method is used for the determination of ortho-phosphate in water and wastewater. The EPA range of this method is 0.01 to 1.0 mg/L as Phosphorus. However, this method is also applicable to other ranges.
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 or 880 nm.
Ferric iron up to 70 mg/L, copper up to 10 mg/L and silica up to 10 mg/L do not interfere. Filter turbid samples prior to analysis.
|Flow System||A203||0.002-0.5, 0.02-2, 2-50, 10-1000 µg/l as P|
|Astoria 2||A203||0.002-0.5, 0.02-2, 2-50, 10-1000 µg/l as P|
|rAPID-T||D203||0.02-2.0 mg/l as P|
Ortho-Phosphate in Sea Water
This method is used for the determination of ortho-phosphate in seawater and is applicable to many ranges.
Ortho-phosphate reacts with molybdic acid to form phosphomolybdic acid. This complex is subsequently reduced with hydrazine to phosphomolybdous acid. Absorbance is measured at 820 nm.
Turbid samples must be filtered before determination. Samples with background absorbance at the analytical wavelength may interfere.
|Flow System||A204||0.06-3.0 µM o-PO|
|Astoria 2||A204||0.06-3.0 µM o-PO|