NEMI Method Summary

Method Summary Information

Method Number: I-3447 Media: WATER
Revision: 1985
Method Source: U.S. Geological Survey (USGS)
Subcategory: INORGANIC Analytes in this method
Official Name: Magnesium, atomic absorption spectrometric, direct
Descriptive Name Magnesium, total recoverable, FLAA
Source Info: USGS Branch of Information Services
Box 25286, MS 417
Federal Center
Denver, CO 80225-0286
Phone: 303-202-4700
Citation: USGS Methods, Volume A1
301745 Byte file
Brief Method
Summary:
 Magnesium is determined by flame atomic absorption spectrometry (Fishman and Downs, 1966). Lanthanum chloride is added to mask interferences. This procedure may be automated by the addition of a sampler, a proportioning pump, and either a strip-chart recorder or a printer or both.
Scope And
Application:
 This method maybe used to analyze water-suspended sediment. Two analytical ranges for magnesium are included: from 0.01 to 5.0 mg/L and from 2.5 to 50 mg/L. Sample solutions containing magnesium concentrations greater than 50 mg/L need to be diluted. Total recoverable magnesium in water-suspended sediment needs to undergo preliminary digestion-solubilization by method I-3485.
Applicable
Conc Range:
 0.01 mg/L to 50 mg/L
Interferences: The interference caused by aluminum concentrations greater than 2,000 ug/L is masked by addition of lanthanum. Because low magnesium values result if the pH of the sample is above 7, standards are prepared in hydrochloric acid solution and samples are preserved in the field with use of nitric acid solution.
Nitrate, sulfate, and silica interfere, but in the presence of lanthanum chloride-hydrochloric acid solution at least 2,000 mg/L, 1,000 mg/L, and 200 mg/L, respectively, can be tolerated. The addition of nitric acid at the time of collection to preserve the samples causes no problem in the following procedure. Sodium, potassium, and calcium cause no interference at concentrations less than 400 mg/L.
QC Requirements: Calibrate instrument using calibration standards (CAL). Quality control samples (QCS) and laboratory blanks (LB) analyzed at a minimum of I each after every 10 samples
Sample Handling: Container Description: 250 mL Polyethylene bottle, acid-rinsed.
Treatment and Preservation: Use unfiltered sample to rinse bottles, then acidify collected sample with HNO3 to pH < 2.
Max Holding Time:
 180 days
Sample Prep Met I-3485
Relative Cost: Less than $50
5667
Page 1