There are a number of carbamate pesticide compounds employed worldwide which are not included in the 10 compounds mandated by USEPA Method 531.1 and AOAC Protocol 29.A05. This Application Note describes methods for separating as many as 23 compounds, using a Pickering C8, 5µm silica, column with either Water/Acetonitrile or Water/Methanol gradients. Instruments, post-column derivatization and detection protocols, and reagents remain unchanged, as described Pickering’s brochure, Post-Column LC Systems for Environmental Pesticide Analysis (B-CA5) and User’s Manual 0101-0002. Although there are only two co-elutions in each of the solvent gradient protocols, the compounds were assigned to two separate test mixtures, A and B, in order to demonstrate the full range of separation. The differences in selectivity between the Acetonitrile and Methanol protocols enable the user to employ both solvent systems as a means of confirming peak identification. The following comparison of Acetonitrile to Methanol might be helpful in choosing which solvent system will be for used routinely, and which will be for confirmation:
- Acetonitrile generally exhibits higher sensitivity and baseline noise.
- It also costs more and its disposal is more restricted.
Eleven of the most widely occurring carbamate compounds and BDMC (internal standard) are supplied by Pickering Laboratories in its qualitative test mixtures, Cat. No. 1700-0063. These are designated by in the test mixture tables below. Other compounds may be purchased from suppliers of environmental standards. A few may vary considerably in homogeneity and availability.