ASTM D6160 for Determination of Polychlorinated Biphenyls (PCBs) in Waste Materials by Gas Chromatography
4. Summary of Test Method
4.1 The sample is extracted with solvent and the extract is treated to remove interfering substances, if needed. The sample extract is injected into a gas chromatograph. The components are separated as they pass through the capillary column and polychlorinated biphenyl compounds, if present, are detected by an ECD.
NOTE 2 - Portions of this test method are similar to EPA Methods 608, 680, and 8082.
4.2 For screening (Tier I), instrument performance is monitored by a 2-uL injection of a standard containing Aroclors 1016 and 1260. For low level work (1 ppm) the instrument is checked with a standard concentration of 0.01 ug/mL (each) and for higher level work (10 ppm), the instrument is checked with a 0.1 ug/mL standard.
4.3 Identification involves a pattern comparison of the chromatograms of an unknown sample with that of a standard obtained under identical instrumental conditions.
4.4 When quantification is required (Tier II), an external standards method (ESTD) is used. The quantitation technique typically requires a comparison of five peaks (minimum of three) between the chromatograms of an unknown sample and that of standard Aroclor obtained under identical conditions. Quantitation of either Aroclors 1016 or 1260 is performed using a five-point calibration of a mixed Aroclor standard containing Aroclors 1016 and 1260. All remaining Aroclors are quantitated from single point calibrations. Calibration is verified daily by comparison of results obtained for analysis of the midpoint calibration standard of Aroclar 1016 and 1260 to the five-point calibration curve. (See Appendix X1 for an example chromatogram and calibration table.)
5. Significance and Use
5.1 This test method provides sufficient PCB data for many regulatory requirements. While the most common regulatory level is 50 ppm (dry weight corrected), lower limits are used in some locations. Since sensitivities will vary for different types of samples, one shall demonstrate a sufficient method detection limit for the matrix of interest.
5.2 This test method differs from Test Method D4059 in that it provides for more sample clean-up options, utilizes a capillary column for better pattern recognition and interference discrimination, and includes both a qualitative screening and a quantitative results option.
6. Interferences
6.1 The ECD has selective sensitivity to alkyl halides, conjugated carbonyls, nitrogen compounds, organometallics, and sulfur. Therefore, the chromatogram obtained for each sample shall be carefully compared to chromatograms of standards to allow proper interpretation.
6.2 Solvents, reagents, glassware, and other sample processing hardware may yield artifacts or interferences, or both, to standard analysis. All these materials shall be demonstrated to be free from interferences under the conditions of analysis by analyzing method blanks.
6.3 Interferences from phthalate esters may pose a major problem in Aroclor determinations when using ECD. Phthalates generally appear in the chromatogram as broad late eluting peaks. Since phthalates are commonly used as plasticizers and are easily extracted from plastic, all contact of samples and extracts with plastic should be avoided.
6.4 While general clean-up techniques are provided as part of this test method, some samples may require additional clean-up beyond the scope of this test method before proper instrumental analysis may be performed.
