EPA-NERL: 505:  Pesticides and PCBs in Water GC-ECD

(A) Glassware contamination: Thoroughly clean glassware, including baking or solvent rinse.

(B) Reagent contamination: Use high purity reagents.

(C) Contamination from sample carryover: Rinsing apparatus with hexane and purging equipment between analyses can minimize contamination.

(D) Extracted interferences: Interference from extracted non-target compounds, with retention times similar to target compounds, can be reduced by cleaning the extract or using confirmation analysis.

(E) Variable solvents: Use the same solvent for each analysis.

(F) Endrin degradation: The splitless injector may cause endrin degradation. Endrin can break down by reacting with the active sites on the port sleeve.

(G) PCBs loss to glass surfaces: Rinse glass and minimize sample contact with glass to prevent adsorption loss of PCBs.

(H) Oxidation of target compounds: Oxidation of compounds (specifically easily-oxidized aldrin, hexachlorocyclopentadiene, and methoxychlor) can be prevented by adding sodium thiosulfate at collection.

(I) Phthalate interference: An unknown interference (possibly dibutyl phthalate) appears in heptachlors retention window.

Initial demonstration of laboratory capability, followed by analysis of laboratory reagent blanks (LRB), laboratory fortified blanks (LFB), laboratory fortified sample matrix (LFM), and quality control samples (QCS). A MDL for each analyte must also be determined.

All samples should be collected in 40 mL bottles containing 3 mg of sodium thiosulfate crystals added just prior to shipping the bottles to the sampling site or 75 ug/L of freshly prepared sodium thiosulfate solution (0.04 g/mL) may be added to empty 40 mL bottles just prior to sample collection. Samples must be chilled to 4^oC at the time of collection and maintained at that temperature until analysis.

14 days before extraction, except for heptachlor (7 days). Extracts up to 24 hours.