EPA Method 1668A

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EPA Method 1668A:
Chlorinated Biphenyl Congeners in Water, Soil, Sediment, and Tissue by HRGC/HRMS

Summary:
Samples are spiked with isotopically labeled analogs of target analytes, and extracted according to a procedure specified for the matrix being analyzed. After extraction, a labeled cleanup standard is spiked into the extract which is then cleaned up using appropriate chromatographic procedures (e.g., gel permeation). After cleanup, the extract is concentrated. Immediately prior to injection, labeled injection internal standards are added to each extract and an aliquot of the extract is injected into the gas chromatograph. The analytes are separated by the GC and detected by a high-resolution (>=10,000) mass spectrometer (HRGC-HRMS). Two exact mass/charge ratios (m/z's) are monitored at each level of chlorination (LOC) throughout a pre-determined retention time window. An individual CB congener is identified by comparing the GC retention time and ion-abundance ratio of two exact m/z's with the corresponding retention time of an authentic standard and the theoretical or acquired ion-abundance ratio of the two exact m/z's. Quantitative analysis is performed in one of two ways specified in the method using selected ion current profile (SICP) areas.

Scope:
This method determines chlorinated biphenyl congeners (CBs) in water, soil, sediment, biosolids, tissue, and other sample matrices by high resolution gas chromatography/high resolution mass spectrometry.

Citation:
Method 1668, Revision A: Chlorinated Biphenyl Congeners in Water, Soil, Sediment, and Tissue by HRGC/HRMS (EPA 821-R-00-002)

Interferences:
(A) Contamination: Glassware must be thoroughly cleaned and all materials used must be demonstrated to be free of contamination by running reference matrix blanks. Specific selection of reagents and purification of solvents by distillation in all-glass systems may be required to remove contaminants. Also, samples should be prepared in an area free from air contaminated with target analytes (e.g., glove box)(B) Co-extracted interferences: The most frequently encountered interferences are chlorinated dioxins and dibenzofurans, methoxy biphenyls, hydroxydiphenyl ethers, benzylphenyl ethers, brominated diphenyl ethers, polynuclear aromatics, polychlorinated naphthalenes, and pesticides. Because very low levels of chlorinated biphenyls (CBs) are measured by the method, the elimination of interferences is essential. The cleanup steps given in Section 13 of the method can be used to reduce or eliminate these interferences, permitting reliable determination of the CBs.(C) Lipids in tissue: The natural lipid content of tissue can interfere in the analysis of tissue samples for the CBs. Lipids must be removed by an anthropogenic isolation column procedure, followed by the gel permeation chromatography procedure as described in the method. Florisil is recommended as an additional cleanup step.

QC Requirements:
The minimum quality control (QC) requirements consist of an initial demonstration of laboratory capability, analysis of samples spiked with labeled compounds to evaluate and document data quality, and analysis of standards and blanks as tests of continued performance. Laboratory performance is compared to established performance criteria to determine if the results of analyses meet the performance characteristics of the Method. If the Method is to be applied to sample matrix other than water (e.g., soils, filter cake, compost, tissue) the most appropriate alternate reference matrix is substituted for the reagent water matrix in all performance tests.

Maximum Holding Time:
1 year

Media:
SOILS/SEDIMENT

Subcategory:
Organic

Concentration:
1-2000 ng/kg

Precision:
Not Applicable.

Detection:
Method 1668A was validated and preliminary data were collected in a single laboratory. Estimated Method Detection Limits (EMDLs) and Estimated Minimum Levels (EMLs) were determined with common laboratory interferences present. Those provided are the EMDLs for solid/semi-solid samples; additional data are provided in the method. Without interferences, EMDLs and EMLs will be, respectively, 5 and 10 pg/L for aqueous samples, 0.5 and 1.0 ng/kg for soil, tissue, and mixed-phase samples, and EMLs for extracts will be 0.5 pg/uL.

Revision Number:
Revision A, December 1999

Instrument used for this test:
HRGC/HRMS