Ionic liquid magnetic bar microextraction and HPLC determination of carbamate pesticides in real water samples

We have developed a simple method for the microextraction of the carbamate pesticides carbofuran, pirimicarb, and carbaryl. It is termed ionic liquid magnetic bar microextraction (ILMB-ME) and based on an ionic liquid deposited on a magnetic stirrer bar placed in a sealed short PCR tube into which microholes where pinned. When placed in a vial containing the aqueous sample solution, the ILMB tumbles freely in the aqueous solution and the carbamates are extracted into the ionic liquid phase which then was determined by HPLC. The enrichment factors for carbofuran, pirimicarb, and carbaryl are 107, 94, 95, respectively. The limits of detection, calculated as three times the signal-to-noise ratio (S/N), are 1.4 mu g L-1 for carbofuran, 3.4 mu g L-1 for pirimicarb, and 1.7 mu g L-1 for carbaryl. The repeatability, carried out by extracting water samples spiked with carbamate levels of 200 mu g L-1, yielded relative standard deviations between 2.9 and 6.0 %, (for n = 5). The recoveries of all the three fungicides from tap, lake and rain water samples at spiking levels of 5 and 50 mu g L-1 are in the range from 86 to 98 %, and from 80 to 96 %, respectively. We conclude that this is a simple, practical and efficient method for the determination of fungicide residues in real water samples.