ASTM D7645-14 Determination of Insectides  in Water by Liquid Chromatography

Scope:

The U.S. Environmental Protection Agency (EPA) has identified the N-methyl carbamate (NMC) insecticides aldicarb, carbofuran, methomyl, oxamyl, and thiofanox as having a similar mode of action. These influence the neurological system via lowering enzyme activity. The principal toxicological consequence of regulatory concern for the EPA in analyzing the NMC’s food, drinking water, and 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 reagent, surface, and drinking water for the specified carbamates.

Procedure:

Samples are delivered to the lab 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:

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:

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 spiking solution

V_s= volume of sample used

V = volume of spiking solution added

P = percent recovery