USGS-NWQL: I-3630-85: Potassium in Water by Atomic Absorption Spectrometry, Total Recoverable

Summary
Analytes
Revision
Data and Sites

Official Method Name

Potassium, Atomic Absorption Spectrometric, Direct

Current Revision

1989

Media

WATER

Instrumentation

Flame Atomic Absorption

Method Subcategory

Inorganic

Method Source

USGS-NWQL

Citation

Methods for the Determination of Inorganic Substances in Water and Fluvial Sediments, Techniques of Water-Resources Investigations of the United States Geological Survey, Book 5, Chapter A1 Edited by Marvin J. Fishman and Linda C. Friedman

Brief Method Summary

Potassium is determined by atomic absorption spectrometry by direct aspiration of the sample solution into an air-acetylene flame (Fishman and Downs, 1966).

Scope and Application

This method may be used to analyze atmospheric precipitation, water, brines, and water-suspended sediment. Two analytical ranges for potassium are included: from 0.01 to 1.0 mg/L and from 0.10 to 10.0 mg/L. Sample solutions containing potassium concentrations greater than 10 mg/L need to be diluted and needs to undergo preliminary digestion-solubilization before being determined.

Applicable Concentration Range

0.01 - 10.0 (undiluted)

Interferences

Of the substances commonly occurring in water, only sodium has been found to interfere, and its interference is greatly minimized if a reducing flame is used and the burner is raised to approximately 0.05 cm below the optical light path. Alternatively, an excess of sodium or cesium may be added to all samples and standards. Such additions essentially eliminate the effects of the then comparatively minor contributions of sodium present in the samples.

Quality Control Requirements

Quality-control samples area analyzed at a minimum of one in every ten samples. These QC samples include at least one of each of the following: blanks, quality control samples, third party check solutions, replicates, and spikes. Correlation coefficients for calibration curves must be at least 0.99. QC samples must fall within 1.5 standard deviations of the mean value. If all of the data-acceptance criteria in the SOPs are met, then the analytical data are acceptable.

Sample Handling

Description: 250 mL Polyethylene bottle, acid-rinsed. Treatment and Preservation: Filter through 0.45-um filter, use filtered sample to rinse containers and acidify sample with nitric acid (HNO₃) to pH < 2.

Maximum Holding Time

180 days from sampling

Relative Cost

Less than $50

Sample Preparation Methods

Method I-3485, TWRI Book 5, Ch. A1, p.50

This method has 1 analyte associated with it.

Analyte	Detection Level	Bias	Precision	Pct False Positive	Pct False Negative	Spiking Level
Potassium(7440-09-7) K Potassium	0.010 mg/L	N/A	N/A

Precision Descriptor Notes:	Precision for dissolved potassium within the range of 0.01 to 1.0 mg/L in terms of the percent relative standard deviation by a single operator is as follows: Eighteen, 12, 11, 10 and 11 replicates were analyzed with 0.023, 0.078, 0.358, 0.585, and 1.02 mg/L recoveries and 38.9, 9.7, 2.7, 1.8 and 4.6 %-RSD, respectively. Precision for dissolved potassium for 36 samples within the range of 0.09 to 26.1 mg/L may be expressed as S = 0.113X - 0.050, where S = the overall precision in mg/L and X = the concentration of potassium in mg/L. The correlation coefficient is 0.9350.
Detection Level Note:	Method detection limits (MDLs) were determined for this method using the procedures of the U.S. Environmental Protection Agency (1997).

Precision Descriptor Notes:

Precision for dissolved potassium within the range of 0.01 to 1.0 mg/L in terms of the percent relative standard deviation by a single operator is as follows: Eighteen, 12, 11, 10 and 11 replicates were analyzed with 0.023, 0.078, 0.358, 0.585, and 1.02 mg/L recoveries and 38.9, 9.7, 2.7, 1.8 and 4.6 %-RSD, respectively. Precision for dissolved potassium for 36 samples within the range of 0.09 to 26.1 mg/L may be expressed as S = 0.113X - 0.050, where S = the overall precision in mg/L and X = the concentration of potassium in mg/L. The correlation coefficient is 0.9350.

Detection Level Note:

Method detection limits (MDLs) were determined for this method using the procedures of the U.S. Environmental Protection Agency (1997).

Revision	PDF/Link
1989

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USGS-NWQL: I-3630-85: Potassium in Water by Atomic Absorption Spectrometry, Total Recoverable

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