Method SM 4500-P E

Phosphorus by Ascorbic Acid

This method is for the determination of phosphorus in drinking water, surface water and wastewater. The sample is digested with ammonium molybdate and potassium antimonyl tartrate and analyzed using a spectrophotometer.

Filtration through a 0.45mm membrane filter separates dissolved from suspended forms of phosphorus. Filter the sample in the field immediately after collection if dissolved forms of phosphorus are needed.

Do not store samples containing low concentrations of phosphorus in plastic bottles unless kept in a frozen state because phosphates may be adsorbed onto the walls of plastic bottles. Rinse all glass containers with hot dilute HCl, then rinse several times in distilled water. Never use commercial detergents containing phosphate for cleaning glassware used in the phosphate analysis.

(Standard Methods)


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Method Data

Hold Times, Preservatives, Preps, Collection, Analytical & Documentation
Holding Time:   28 days from sample collection to analysis.
Preservatives:   Preserve by freezing the sample at or below -10°C. Add 40 mg HgCl2/L to the samples when they are to be stored for long periods. If total phosphorus alone is to be determined, add H2SO4 or HCl to pH<2 and cool to 4°C, or freeze without any additions.
Required Preps:   250mL glass bottle with a Teflon-lined lid
Collection Method:   Grab sampling
Analytical Methodology:   Spectrophotometer
Documentation:   SM 4500 P E

Analyte List*

Analyte Formula CAS Number Detection Limit

* The analytes and detection limits listed for each method represent the typical detection limits and analytes reported for that particular method. Keep in mind that analyte lists may vary from laboratory to laboratory. Detection limits may also vary from lab to lab and are dependent upon the sample size, matrix, and any interferences that may be present in the sample.