Method 1631

Mercury in Water by Oxidation, Purge and Trap, and Cold Vapor Atomic Fluorescence Spectrometry

This method is for determination of mercury (Hg) in filtered and unfiltered water by oxidation, purge and trap, desorption, and cold-vapor fluorescence atomic spectrometry (CVAFS). This method is for use in EPA’s data gathering and monitoring programs associated with the Clean Water Act, the Resource Conservation and Recovery Act, the Comprehensive Environmental Response, Compensation and Liability Act, and the Safe Drinking Water Act. The method is based on a contractor-developed method and on peer-reviewed, published procedures for the determination of mercury in aqueous samples, ranging from seawater to sewage effluent. This method is accompanied by Method 1669: Sampling Ambient Water for Determination of Trace Metals at EPA Water Quality Criteria Levels (Sampling Method). The sampling method is necessary to preclude contamination during the sampling process. This method is designed for determination of Hg in the range of 0.5-100 ng/L (parts-per-trillion) and may be extended to higher concentrations by selection of a smaller sample size. This method is not intended for determination of metals at concentrations normally found in treated and untreated discharges from industrial facilities. Existing regulations typically limit concentrations in industrial discharges to the part-per-billion (ppb) range, whereas ambient mercury concentrations are normally in the low part-per-trillion (ppt) range.

(EPA 40 CFR Part 136)


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Method Data

Hold Times, Preservatives, Preps, Collection, Analytical & Documentation
Holding Time:   Samples must be acid preserved within 48 hours after sampling.
Preservatives:   5 mL/L of pre-tested 12 N HCl (to allow both total and methyl Hg determination) or 5 mL/L BrCl solution, if total Hg only is to be determined. For dissolved Hg, samples are filtered through a 0.45 mm capsule filter. Samples may be shipped to the laboratory unpreserved if they are (1) collected in fluoropolymer bottles, (2) filled to the top with no head space, (3) capped tightly, and (4) maintained at 0-4 °C from the time of collection to preservation.
Required Preps:   Cleaned, pre-tested fluoropolymer (FEP, PTFE) bottles or glass bottles; polyethylene bottles must not be used
Collection Method:   Method 1669
Analytical Methodology:   Cold-vapor atomic fluorescence spectrometry
Documentation:   1631

Analyte List*

Analyte Formula CAS Number Detection Limit

* The analytes and detection limits listed for each method represent the typical detection limits and analytes reported for that particular method. Keep in mind that analyte lists may vary from laboratory to laboratory. Detection limits may also vary from lab to lab and are dependent upon the sample size, matrix, and any interferences that may be present in the sample.