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Organochlorine Pesticides from Tap Water

Matrix: Tap Water, 2mL; buffered to pH 2 or 12

Extracting Phase: Trifluoropropyl (25µL ILE Cap)

Compounds: Organochlorine Pesticides, 500ng/mL

Two series of 2mL tap water samples were spiked with a variety of organochlorine pesticides at a concentration of 500ng/mL in 40mL VOA vials. The first series of samples were buffered to pH 2, while the other set of samples had their pH adjusted to 12. Each series of samples was further subdivided into two groups. First, those which were salted with 10% potassium carbonate, and second, those which which had methanol added to a concentration of 10%. Sample vessels were sealed with 25µL Trifluoropropylmethylsiloxane ILE Caps, inverted, and agitated by a mechanical wrist shaker for 1 hour to allow analytes to partition from the sample into the immobilized solvent phase.

The ILE Caps were removed from the sample vessels and placed on high-recovery vials containing 150µL acetone. These vials were inverted and agitated for 20 minutes to allow analytes to partition from the immobilized phase into the acetone. The resulting extracts were analyzed by an HP-5971 GC/MS in SIM mode with a 30m x 0.25mm i.d. x 0.25µm VB-5 column. The following table displays the efficiency, and conditions (pH, salting, methanol) which gave the best results for each compound:

Phase: Fluoro Matrix: Water

Compound Log P Efficiency Conditions
Etridiazole 3.37 86.7% pH 12, Salt
Chloroned 3.44 96.8% pH 12, Salt
a-BHC 3.8 98.2% pH 2, Methanol
Atrazine 2.61 50.2% pH 12, Salt
b-BHC 3.78 85.7% pH 12, Salt
g-BHC 3.72 75.7% pH 2, Methanol
Alachlor 3.52 82.0% pH 12, Salt
Heptachlor 6.1 67.9% pH 12, Methanol
Aldrin 6.5 57.9% pH 12, Methanol
Dacthal 4.4 99.2% pH 2, Methanol
Heptachlor Epoxide 5.4 81.3% pH 12, Methanol
1-Chlordane 6.1 63.6% pH 12, Methanol
Endosulfan I 3.83 89.9% pH 2, Methanol
g-Chlordane 7 72.5% pH 2, Methanol
trans-Nonachlor 6.2 58.7% pH 12, Methanol
Dieldrin 5.4 79.2% pH 2, Methanol
Endrin 5.2 88.7% pH 2, Methanol
Chlorobenzilate 4.74 84.1% pH 2, Methanol
4,4-DDD 6.02 66.7% pH 2, Methanol
Endrin Aldehyde 4.8 77.7% pH 2, Methanol
Endosulfan Sulfate 3.66 99.3% pH 2, Methanol
Methoxychlor 5.08 70.8% pH 2, Methanol