EPA Method 321.8

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EPA Method 321.8:
Bromate by IC/ICP-MS. Official Name: Determination of Bromate in Drinking Waters by Ion Chromatography Inductively Coupled Plasma - Mass Spectrometry

Summary:
A sample is passed through a preparatory cartridge which removes the trisubstituted haloacetic acids that interfere with determination of bromate. The bromate in the sample is then separated from other compounds using an ion chromatography (IC) system. The concentration of bromate that is eluted from the IC system is measured using an inductively couple plasma/mass spectrometer (ICP/MS).

Scope:
This method determines bromate in drinking water.

Citation:
Methods for the Determination of Organic and Inorganic Compounds in Drinking Water, Volume 1 (EPA/815-R-00-014)

Interferences:
(A) Abundance sensitivity: The wing overlap of large and small peaks can interfere with small peaks. This interference can be minimized by optimizing instrument resolution.(B) Isobaric molecular ion interferences: Molecular ions formed in the plasma can interfere. Minimize interference by monitoring an appropriate isotope or using correction equations. Note: effects are minimal because most sample matrix is removed by processing.(C) Physical Interferences: Differences in sample and standard matrix (e.g., viscosity) creates differences in the response of standards and samples (due to effects on transport, nebulization, and ionization). Effects can be minimized by using the internal standard technique to quantify elements. Note: effects are minimal because most sample matrix is removed by processing.(D) Memory effects: Sample carryover can bias results, but can be minimized by rinsing the chelation column and instruments with blanks between sample analyses.(E) Loss of analyte: Low recoveries may be encountered if the sample contains chelating agents or colloids that compete with the chelation column. Acid solubilization of the sample minimizes this interference.(F) Chromatographic interferences: Known chromatographic interferences and their retention times are provided in the method, as well as extensive remedies.(G) Retention time shifts: Retention time shifts, due to weak eluent strengths and high ionic strength matrices are minimized using the conditions in the method. If shifts continue to occur, effects can be further minimized by diluting the sample.

QC Requirements:
Initial Demonstration of Capability (IDC) and the periodic analysis of laboratory calibration blanks, fortified blanks, and calibration solutions as a continuing check on performance.

Maximum Holding Time:
Not Provided.

Media:
WATER

Subcategory:
Inorganic

Concentration:
10 - 50 ug/L is suggested.

Precision:
Precision and accuracy values were calculated using data from the analyses of five replicate fortified ozonated water samples in a single laboratory. The samples has a natural background concentration of 0.8 ug/L of bromate. Additional data are available in the method.

Detection:
MDL procedure is equivalent to the procedure at 40 CFR part 136, Appendix B. MDLs were determined using the standard deviation of 7 replicate analyses of an analyte-fortified reagent water sample multiplied by the t-value for 6 degrees of freedom at the 99% confidence level (3.14). Detailed instructions for how MDLs are determined are found in Section 9.2.4 of the Method.

Revision Number:
Revision 1.0, December 1997