METHOD 8082 POLYCHLORINATED BIPHENYLS (PCBs) BY GAS CHROMATOGRAPHY
3.0 INTERFERENCES
3.1 Refer to Methods 3500 (Sec. 3.0, in particular), 3600, and 8000 for a discussion of interferences.
3.2 Interferences co-extracted from the samples will vary considerably from matrix to matrix. While general cleanup techniques are referenced or provided as part of this method, unique samples may require additional cleanup approaches to achieve desired degrees of discrimination and quantitation. Sources of interference in this method can be grouped into three broad categories.
3.2.1 Contaminated solvents, reagents, or sample processing hardware.
3.2.2 Contaminated GC carrier gas, parts, column surfaces, or detector surfaces.
3.2.3 Compounds extracted from the sample matrix to which the detector will respond.
3.3 Interferences by phthalate esters introduced during sample preparation can pose a major problem in PCB determinations.
3.3.1 Common flexible plastics contain varying amounts of phthalate esters which are easily extracted or leached from such materials during laboratory operations. Interferences from phthalate esters can best be minimized by avoiding contact with any plastic materials and checking all solvents and reagents for phthalate contamination.
3.3.2 Exhaustive cleanup of solvents, reagents and glassware may be required to eliminate background phthalate ester contamination.
3.3.3 These materials can be removed through the use of Method 3665 (sulfuric acid/permanganate cleanup).
3.4 Cross-contamination of clean glassware routinely occurs when plastics are handled during extraction steps, especially when solvent-wetted surfaces are handled. Glassware must be scrupulously cleaned.
Clean all glassware as soon as possible after use by rinsing with the last solvent used. This should be followed by detergent washing with hot water, and rinses with tap water and organic-free reagent water. Drain the glassware, and dry it in an oven at 130EC for several hours, or rinse with methanol and drain. Store dry glassware in a clean environment.
NOTE:
Oven-drying of glassware used for PCB analysis can increase contamination because PCBs are readily volatilized in the oven and spread to other glassware. Therefore, exercise caution, and do not dry glassware from samples containing high concentrations of PCBs with glassware that may be used for trace analyses.
3.5 Elemental sulfur (S8) is readily extracted from soil samples and may cause chromatographic interferences in the determination of PCBs. Sulfur can be removed through the use of Method 3660.
