Analysis of Drinking Waters for a Suite of Pesticides Using GC with Dual ECD (US EPA Method 508.1) after SPE Concentration

Pesticides, including insecticides, herbicides, and fungicides are used extensively to increase agricultural yields. US EPA Method 508.1 is a sensitive method to detect chlorinated pesticides in drinking water using solid phase extraction (SPE) and gas chromatography (GC) coupled with ECD detection. Method 508 includes 29 chlorinated pesticides, three herbicides, and four organohalides that can be determined in drinking water in any stage of treatment, and groundwater. EPA Method 508 is a good method for measurement of regulated levels and for screening of other pesticides that may be present. This work will demonstrate the performance of method 508 using solid phase extraction with an automated system.

Table I: Lab fortified blank, four runs, selected analytes

Drinking water samples from the county are obtained using usual tap collection procedures. Table I lists a selection of analytes and their recoveries from lab-fortified blank samples and duplicates, fortified at 100 µg/L. The recoveries are excellent and the precision between runs is very good. Table II shows the lab fortified blank and lab-fortified blank duplicate for selected analytes. The agreement is well within the 20% relative percent difference limit specified in the method.

Table II: Relative percent difference (RPD) between

Conclusion

Solid phase extraction has become well established and most of the US EPA drinking water methods include SPE as the primary extraction technique or as an alternative. This work demonstrates the good performance of automated SPE for a wide suite of chlorinated pesticides, herbicides, and organic compounds. Recoveries are good and agreement between duplicates is well within the method requirements of 20%. In addition to good reproducibility, automation of the technique requires less attention than a manual extraction technique

Reference

(1) Analysis of Drinking Waters for a Suite of Pesticides using GC with dual ECD (US EPA Method 508.1) after SPE Concentration, AN1031602_01, available from Horizon technology at www.horizontechinc.com (2016).

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