Off-line Preconcentration Coupled With On-line Stacking Methods in Enhancing Detection of Selected Pesticides Using Capillary Electrophoresis
In this study, off-line preconcentration which involves the usage of solid phase disc extraction (SPDE) was used as an enrichment step in enhancing the detection of selected pesticides with capillary electrophoresis (CE). Micellar electrokinetic chromatography (MEKC) with stacking with reverse migrating micelles (SRMM) is the mode used in improving the limit of detection (LOD) of the analytes. The selected pesticides chosen are organophosphorous pesticides (OPPs) which
include dicrotophos, monocrotophos and phosphamidon. This study was carried out by spiking 1 μg and 0.5 μg of each pesticide into 250 mL of pond water before undergoing sample enrichment with SPDE thus achieving a concentration of 4 ppb and 2 ppb respectively. Recovery and repeatability studies of the SPDE method were also carried out as a means of method validation. From the results, the recovery for 1 μg of spiked pesticide was in the range of 96.2-132% while at 0.5 μg it was at 74-117%. The repeatability of the extraction was higher for lower concentrations in the range of 10-12%RSD as compared to higher concentration within 0.81-5.36%RSD. The LOD for the three analytes has been reduced by 250 times with dicrotophos (0.6 ppb), monocrotophos (1.56 ppb) and phosphamidon (0.88 ppb) when SPDE was coupled with on-line preconcentration technique that is SRMM.