Phosphorus

 Phosphorus by Ascorbic Acid (By SM 4500-P-E)

Scope:

This method is most suited for measuring phosphorus in water.

Ammonium molybdate and potassium antimonyl tartrate react in acid medium with orthophosphate to form a heteropoly acid-phosphomolybdic acid-that is reduced to intensely colored molybdenum blue by ascorbic acid.

Method Data

Method SM 4500_P_E
Hold Time28 days
PreservationTo preserve samples for later analysis, adjust the sample pH to less than 2 with concentrated sulfuric acid (approximately 2 mL per liter). No acid addition is necessary if the sample is tested immediately. Keep the preserved samples at or below 6 °C.
Sample Volume
Collection MethodCollect samples in glass bottles that have been rinsed several times with sample. Do not use plastic containers, which can adsorb quaternary ammonium compounds.
InstrumentationWenner Four Pin
Method RefernceSM 4500_P_E

Analyte List

AnalyteFormulaCAS Number
Phophorus, Total
Phophorus, Ortho

* The typical detection limits and analytes are displayed for this particular method. Please contact Specialty Analytical if other analytes or detection limits are required in addition to the 200.8 Analyte List.

Phosphorus

-Phosphorus, All Forms (Colorimetric, Ascorbic Acid, Two Reagent (By EPA 365.3)

Scope:

This method can determine dissolved and total orthophosphate, hydrolyzable phosphate, and phosphorus (all forms) in drinking, surface and saline waters; domestic and industrial wastes.

The sample is pretreated to select the phosphorus forms of interest; the forms are then converted to orthophosphate (which is amenable to the color chemistry of the method). A sample is filtered to select dissolved forms. Polyphosphates are converted to orthophosphate by sulfuric acid hydrolysis. Organic phosphorus is converted to orthophosphate using persulfate digestion.
Ammonium molybdate and antimony potassium tartrate react in an acid medium with dilute solutions of phosphorus to form an antimony-phospho-molybdate complex, which is reduced with ascorbic acid to form an intense blue-colored complex. The absorbance of the complex is measured, and is proportional to the orthophosphate concentration.

 

Method Data

Method E365.3
Hold Time28 days
PreservationSamples should be collected in plastic or Pyrex glass containers. Samples should be preserved with 2 mL of concentrated sulfuric acid and refrigerated at 4oC.
Sample Volume48 hours (orthophosphate, dissolved), 28 days (Hydrolyzable and Total), 24 hours (Total Dissolved).
Collection MethodCollect samples in glass bottles that have been rinsed several times with sample. Do not use plastic containers, which can adsorb quaternary ammonium compounds.
InstrumentationSpectroscopy
Method RefernceE365.3

Analyte List

AnalyteFormulaCAS Number
CaCO3

* The typical detection limits and analytes are displayed for this particular method. Please contact Specialty Analytical if other analytes or detection limits are required in addition to the 200.8 Analyte List.

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