ASTM D7645 Determination of Insecticides in Water by Liquid Chromatography

Scope:

The U.S. Environmental Protection Agency (EPA) has identified the N-methyl carbamate (NMC) insecticides, such as aldicarb, carbofuran, methomyl, oxamyl, and thiofanox as having an influence on the human neurological system as they lower enzyme activity. The principal toxicological consequence of the regulatory concern of the EPA in analyzing the NMC’s food, and drinking water, and responding to residential concerns was enzyme inhibition. The breakdown products of aldicarb, aldicarb sulfone, and aldicarb sulfoxide, should be monitored owing to their toxicological consequences. ASTM D7645 has been evaluated for usage with reagents, surface, and drinking water for the specified carbamates.

Procedure:

In ASTM D7645 testing, the samples that are delivered to the lab are acidified between 0°C and 6°C and examined for carbamate assay within 14 days of collection. The samples are spiked with surrogates in the lab, filtered using syringe-driven filter equipment, and LC/MS/MS examined directly. Retention time and two SRM transitions distinguish the carbamates, methomyl-¹³C₂, 15N (surrogate), and carbofuran-¹³C₆ (surrogate). Using an external calibration, the major SRM transitions quantify the target analytes and surrogates.

Specimen size:

For ASTM D7645 testing, the specimen should be conditioned between 0°C and 6°C in an acidified environment. 

Data:

Percent recovery of the spike (P) is calculated as follows for ASTM D7645 testing:

P = 100   |A (V_s ̶ V) ̶ BV_s|/CV

Where:

A = concentration found in the spiked sample 

B = concentration found in the unspiked sample

C = concentration of analyte in the spiking solution

V_s= volume of the sample used

V = volume of the spiking solution added

P = percent recovery

Conclusion:

The measurement of aldicarb, aldicarb sulfone, aldicarb sulfoxide, carbofuran, methomyl, oxamyl, and thiofanox in water by liquid chromatography (LC) and tandem mass spectrometry (MS/MS) is covered by ASTM D7645.