Multiresidue pesticide analysis of the medicinal plant Origanum syriacum.

Origanum syriacum is a medicinal plant widely used in Jordan both as a folk remedy and in the food and beverage industry. As the plant can be treated with pesticides during commercial production, three different methods for pesticide multiresidue analysis of this plant have been evaluated. One method based on soxhlet extraction followed by acetonitrile/petroleum ether (PE) partitioning was found to be particularly suitable. Extracts were cleaned-up using a Florisil column. Mean recoveries of pesticides from spiked herbal samples were 74-119%, with coefficients of variation between 1.0 and 23.6%. The limits of detection were in the range 0.0008-0.5 mg kg(-1). The method was used for the determination of pesticide residues in O. syriacum samples purchased from the local market. Seven out of eight samples contained detectable levels of dichlorodiphenyltrichloroethane (DDT), folpet, dicofol, hexachlorobenzene (HCB), hecachlorocyclohexane (HCH), quintozene, transchlordane and vinclozolin.