Troubleshooting in the Analysis of Hexachlorocyclohexane Isomers in Agar-Agar Culture Media

A method to determine hexachlorocyclohexane isomers (HCHs) in agar-agar culture media was developed in order to study the bioremediation potential of these compounds. Spiked culture medium samples (0.5 g) were finely chopped and then extracted with 20 ml of hexane:ethyl acetate (80:20) in an ultrasonic bath during 30 min and analyzed by gas chromatography and electron capture detection (GC-ECD). Analytical recoveries were highly satisfactory, ranging between 84 and 101%, and relative standard deviations were lower than 5%. The method was applied to evaluate the stability of lindane (γ -hexachlorocyclohexane, γ-HCH) and isomers (α-, β- and δ -HCH) in agar-agar culture media at different temperatures. Our results showed a decrease on the recoveries of γ- and α-HCH, very important in the case of α-HCH, during the incubation period at room temperature and at 30°C, while the losses of β -HCH and δ-HCH were negligible.