USGS Test Method I-2606


Method information displayed is provided for informational purposes only.
ALS - Columbia may or may not offer methods shown. Please contact us to learn about ALS - Columbia's latest available methods. No warranty (express or implied) is made as to the website accuracy, completeness, or applicability (such as the age of a method and whether or not it applies to your project).

Analytical testing dots

PDF IconView Actual USGS Method I-2606 (PDF File)


Source:
USGS

Method Name:
Phosphorus, orthophosphate plus hydrolyzable, dissolved, colorimetric, ASF. Official Name: Phosphorus, orthophosphate, low ionic-strength water, colorimetry,phosphomolybdate, automated-segmented flow

Description:
Orthophosphate ion reacts with ammonium molybdate in acidic solution to form phosphomolybdic acid, which upon reduction with ascorbic acid produces an intensely blue complex. Antimony potassium tartrate is added to increase the rate of reduction (Murphy and Riley, 1962; Gales and others, 1966; Pai and others, 1990).

Scope:
This method is used to analyze samples of precipitation or natural water with a specific conductance of less than 100 uS/cm containing from 0.001 to 0.20 mg/L of orthophosphate-phosphorus. Concentrations greater than 0.20 mg/L must be diluted. The method was implemented in the National Water Quality Laboratory in March 1986 and modified in May 1989.

Citation:
M.J. Fishman, 1993, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory--Determination of inorganic and organic constituents in water and fluvial sediments: U.S. Geological Survey Open-File Report 93-125

Interferences:
Barium, lead, and silver interfere by forming a phosphate precipitate but the effect is negligible in natural water. The interference from silica, which forms a pale-blue complex, is slight and also negligible. Nitrite interferes but can be oxidized to nitrate with hydrogen peroxide before analysis. Residual chlorine needs to be removed by boiling the sample.Arsenic as arsenate produces a color similar to phosphate (Murphy and Riley, 1962) and might cause a positive interference. Arsenic concentrations as much as 100 ug/L do not interfere.

QC Requirements:
Calibrate instrument using calibration standards (CAL); quality control samples (QCS); and laboratory blanks (LB) analyzed at a minimum of 1 for every 10 samples.

Maximum Holding Time:
30 days

Media:
WATER

Subcategory:
Inorganic

Concentration:
0.001 to 0.20 mg/L

Precision:
Precision calculation based on 22 determinations.

Detection:
Reporting Level defined as smallest measured concentration of a constituent that may be reliably reported using a given analytical method.

Revision Number:
Mar-86

Analytical testing dots

Related Methods:
Test Method 500001    Test Method 500007    Test Method 500021    Test Method 500061    Test Method 500071    Test Method 500076    Test Method 500081    Test Method 500086    Test Method 500090    Test Method 500201   


<-- Search again



*Method information displayed is provided as a convenience only. No warranty (express or implied) is made as to its accuracy, completeness, or applicability (such as the age of a method and whether or not it applies to your project).

Suggestions? The test methods page continues to expand and improve. If you have suggestions for improvement, we would enjoy hearing from you. Please contact the webmaster here.


Analytical testing dots