USGS-NWQL: I-2464-01:  Organic plus Inorganic Mercury in Filtered Natural Water by Cold-Vapor AFS

  • Summary
  • Analytes
  • Revision
  • Data and Sites
Official Method Name
Methods of Analysis by the U.S. Geological Survey National Water Quality Laboratory - Determination of Organic Plus Inorganic Mercury in Filtered and Unfiltered Natural-Water with CV-AFS
Current Revision
2001
Media
WATER
Instrumentation
Cold Vapor Atomic Fluoresence Spectrophotometer
Method Subcategory
Inorganic
Method Source
  USGS-NWQL
Citation
Garbarino, J.R., and Damrau, D.L., 2001, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory--Determination of organic plus Inorganic mercury in filtered and unfiltered natural water with cold vapor--atomic fluorescence spectrometry: U.S. Geological Survey Water-Resources Investigations Report 01-4132.
Brief Method Summary
Concentrations of organic plus inorganic mercury in filtered natural-water samples are determined by CV-AFS. The method is based on U.S. Environmental Protection Agency (1999) Method 1631, but does not use gold amalgamation for mercury preconcentration. By eliminating the preconcentration procedure, the MDL is at least a factor of 10 greater, yet the method provides the determination of mercury at ambient concentrations. Mercury species in a natural-water sample are oxidized to mercury (II) inside the borosilicate-glass sample bottle by using bromine monochloride; excess oxidant is neutralized with hydroxylamine hydrochloride. Mercury (II) is reduced to elemental mercury by using stannous chloride, and is purged from the solution with ultrapure argon gas into a cell in which the mercury concentration is measured by atomic fluorescence emission at 253.7 nm.
Scope and Application
This method is used to determine concentrations of organic plus inorganic mercury in filtered natural-water samples. Bromine monochloride is used to oxidize elemental mercury, mercury complexes, various alkyl- and phenyl-mercury compounds, and other forms of mercury. The upper limit of the linear concentration is 125 ng/L mercury. The short-term method detection limit is 5 ng/L mercury.
Applicable Concentration Range
5 - 125
Interferences
Contamination must be avoided because of the inherently low mercury concentration found in natural water. Gold, silver, and iodide interfere with the determination of mercury by this method. Buildup of condensation in the vapor generator or fluorescence cell will degrade the analytical signal. Ultrapure argon (99.998) percent must be used for the purge gas to minimize the possibility of fluorescent quenching by impurities.
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 mL Glass bottle, acid-rinsed. Treatment and Preservation: Filter through 0.45-um filter, use filtered sample to rinse containers and acidify collected sample with 2 mL of 6N (6 normal) hydrochloric acid (HCl).
Maximum Holding Time
180 days from sampling
Relative Cost
$51 to $200
Sample Preparation Methods