NEMI Method Summary

Method Summary Information

Method Number: 1631 Media: WATER
Revision: Revision C, March 2001
Method Source: U.S. EPA Engineering and Analysis Division
Subcategory: INORGANIC Analytes in this method
Official Name: Mercury in Water by Oxidation, Purge and Trap, and Cold Vapor Atomic Absorption Fluorescence Spectrometry
Descriptive Name Mercury in Water Using CVAFS
Source Info: 4303 USEPA Headquarters
Ariel Rios Building
1200 Pennsylvania Avenue, N. W.
Washington, DC 20460
Citation: EPA Method Guidance CD-ROM (includes MCAWW Methods, and most current EPA Methods)
842639 Byte file
Brief Method
Summary:
 Mercury in a sample is oxidized using BrCl. Oxidized mercury in the sample is then reduced to volatile elemental mercury using SnCl2. Elemental mercury is purged with nitrogen and collected on a gold sand trap. After sufficient mercury has been collected, the trap is heated and desorbed mercury is purged into a cold-vapor atomic fluorescence spectrometer (CVAFS). The concentration of desorbed mercury is measured using the CVAFS system.
Scope And
Application:
 This method determines mercury in filtered and unfiltered water.
Applicable
Conc Range:
 0.5 - 100 ng/L
Interferences: (A) Contamination by carryover: Samples known or suspected to contain the lowest concentration of mercury should be analyzed first followed by samples containing higher levels.
(B) Contamination by samples: Samples known or suspected to contain Hg concentrations greater than 100 ng/L should be diluted prior to bringing them into the clean room or laboratory processing trace metals samples.
(C) Contamination by indirect contact: Every piece of apparatus directly or indirectly used in the collection, processing, and analysis of water samples must be thoroughly cleaned.
(D) Contamination by airborne particulate matter: Samples may be contaminated by airborne dust, dirt, particles, or vapors from unfiltered air supplies; nearby corroded or rusted pipes, wires, or other fixtures; or metal-containing paint.
(E) Contamination from reagents: Use high purity reagents.
(F) Iodide concentrations from 30 to 100 mg/L; at iodide concentrations greater than 3 mg/L, pre-reduce with SnCl2.
QC Requirements: The minimum requirements include an initial demonstration of laboratory capability, ongoing analysis of standards and blanks as a test of continued performance, and the analysis of matrix spikes (MS) and matrix spike duplicates (MSD) to assess accuracy and precision.
Sample Handling: (A) Collect samples in rigorously cleaned fluoropolymer bottles with fluoropolymer caps or borosilicate glass bottles (if Hg is the only target analyte). Polyethylene bottles must not be used.
(B) For dissolved Hg, filter samples and field blanks through a 0.45um capsule filter.
(C) Preserve samples by adding either 5 mL/L of pretested 12N HCl or 5 mL/L BrCl solution. If a sample will be used for the determination of methyl mercury, it should be preserved with 5 mL/L HCl solution only. Maintain samples at 0-4oC for the time of collection to preservation. Acid preserve samples within 48 hours of collection. The best approach is to add BrCl directly to the sample bottle at least 24 hours before analysis, however, if other Hg species are to be analyzed, these aliquots must be removed first.
Max Holding Time:
 Acid- and BrCl- preserved samples are stable for 28 days.
 
Relative Cost: $51 to $200
4818
Page 1