Determination of organochlorine pesticides in propolis by gas chromatography-electron capture detection using double column series solid-phase extraction.

A rapid and reliable method was developed and applied for the simultaneous determination of 17 organochlorine pesticides (OCPs) in propolis. After extraction with hexane and acetone (1:1, v/v), four sorbents (florisil, silica, graphitized carbon, and tandem graphitized carbon plus florisil) were assayed for the clean-up step. The elution solvents hexane and ethyl acetate (1:1, v/v), hexane and dichloromethane (3:7, v/v), and ethyl acetate and hexane (2:8, v/v) were studied. The results showed that the combination of the tandem graphitized carbon and florisil cartridge with the elution solvent of 6 mL of ethyl acetate and hexane (2:8, v/v), which was capable of eliminating matrix interference and providing colorless eluates, was the most efficient clean-up procedure for propolis extracts when testing for OCPs. The analytical technique employed was gas chromatography with electron capture detection (GC-ECD). The correlation coefficients from linear regression for the analyzed concentrations (5 approximately 100 microg/kg) were >0.9961. The limits of detection (LODs) varied between 0.8 microg/kg for 4,4'-DDE and 11.4 microg/kg for endosulfan II, and the limits of quantitation (LOQs) ranged from 2.6 to 38.1 microg/kg. The average recoveries varied between 62.6 and 109.6%. Relative standard deviations (RSD%) ranged from 0.8 to 9.4%. Sample analysis indicated that 4,4'-DDE was detected more often in propolis than other pesticides, such as beta-HCH, delta-HCH and heptachlor.