Standard Methods: 3500-K B: Potassium by Flame Photometry

Summary
Analytes
Revisions
Data and Sites

Official Method Name

3500-K B. Flame Photometric Method

Current Revision

Standard Methods Online

Media

WATER

Instrumentation

Flame Emission

Method Subcategory

Inorganic

Method Source

Standard Methods

Citation

Standard Methods Online - Standard Methods for the Examination of Water and Wastewater

Brief Method Summary

Trace amounts of potassium can be determined in either a direct-reading or internal-standard type of flame photometer at a wavelength of 766.5 nm. Because much of the information pertaining to sodium applies equally to the potassium determination, carefully study the entire discussion dealing with the flame photometric determination of sodium (3500-Na B) before making a potassium determination.

Scope and Application

The method is applicable to drinking water, wastewater, and surface waters.

Applicable Concentration Range

Interferences

Interference in the internal-standard method may occur at sodium-to-potassium ratios of 5:1 or greater. Calcium may interfere if the calcium-to-potassium ratio is 10:1 or more. Magnesium begins to interfere when the magnesium-to-potassium ratio exceeds 100:1.

Quality Control Requirements

See Section 3020 Quality Assurance/Quality Control.

Sample Handling

Do not store samples in soft-glass bottles because of the possibility of contamination from leaching of the glass. Use acid-washed polyethylene or borosilicate glass bottles. Adjust sample to pH < 2 with nitric acid. This will dissolve potassium salts and reduce adsorption on vessel walls.

Maximum Holding Time

6 months (See Section 1060)

Relative Cost

Less than $50

Sample Preparation Methods

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	0.100 mg/L	2Rel. Error (ML)	15.50 % RSD (ML)			3.10 mg/L

Precision Descriptor Notes:	A synthetic sample containing 3.1 mg K+/L, 108 mg Ca2+/L, 82 mg Mg2+/L, 19.9 mg Na+/L, 241 mg Cl-/L, 0.25 mg NO2--N/L, 1.1 mg NO3--N/L, 259 mg SO42-/L, and 42.5 mg total alkalinity/L (contributed by NaHCO3+) was analyzed in 33 laboratories by the flame photometric method, with a relative standard deviation of 15.5% and a relative error of 2.3%.
Detection Level Note:	Potassium levels of approximately 0.1 mg/L can be determined.

Revision	PDF/Link
Standard Methods Online
As Method 3500-K D in Standard Methods 18th Edition (1992)
As Method 3500-K D in Standard Methods 19th Edition (1995)
Standard Methods 18th, 19th, 20th ed.

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Standard Methods: 3500-K B: Potassium by Flame Photometry

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