USGS-NWQL: I-2030-85: Alkalinity of water samples

Summary
Analytes
Revision
Data and Sites

Official Method Name

Alkalinity, Electrometric Titration, automated

Current Revision

1985

Media

WATER

Instrumentation

Titration

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

Alkalinity is determined by titrating the water sample with a standard solution of a strong acid. The end point of the titration is selected as pH 4.5.

Scope and Application

This method is suitable for analyzing water with any amount of alkalinity. Sample aliquots for analysis and maximum titration volume of standard acid will depend on specifications in the manufacturer's instruction manual.

Applicable Concentration Range

0.0-1000 mg/L as CaCO₃ (undiluted)

Interferences

Any ionized substance that reacts with a strong acid can contribute to alkalinity if the reaction occurs at a pH above that of the specified end point; examples are salts of weak inorganic and organic acids. Oils and greases, if present, may tend to foul the electrode and prevent its proper operation.

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 or 500 mL Polyethylene bottle. Treatment and Preservation: Filter through 0.45-um filter. Use filtered sample to rinse containers.

Maximum Holding Time

30 days from sampling

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
Alkalinity(471-34-1) Alkalinity Calcium Carbonate Carbonic acid, calcium salt Marble	N/A	N/A	N/A

Precision Descriptor Notes:	The standard deviation for the alkalinity within the range of 18.4 to 303 mg/L for 17 samples was found to be independent of concentration. The 95-percent confidence interval for the average standard deviation of 6.7 mg/L ranged from 5.8 to 7.9 mg/L (as mg/L CaCO₃).
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
1985

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USGS-NWQL: I-2030-85: Alkalinity of water samples

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