Decontamination of Organochlorine Pesticides Residue and Heavy Metal in Rehmannia glutinosa Libosch by SFE

Abstract

A method involving the simultaneous extraction and decontamination of 12 organochlorine pesticides (OCPs) and seven heavy metals (HM) from Rehmannia glutinosa Libosch was established using supercritical fluid extraction (SFE). A gas chromatography (GC) method with electron capture detection was employed for the determination of the OCPs. The quantitative determination of active constituents (iridoid glycoside and catalpol) in Rehmannia glutinosa Libosch was detected by high-performance liquid chromatography (HPLC). An atomic absorption spectrometry (AAS) was designed for the determination of seven HM, including lead (Pb), cadmium (Cd), copper (Cu), iron (Fe), zinc (Zn), arsenic (As), and mercury (Hg) in Rehmannia glutinosa Libosch. Recovery of the determination of the 12 organochlorine pesticides in Rehmannia glutinosa Libosch sample was 85.9%-101.4% by GC, and relative standard deviation (RSD) was 1.9%-6.0%. Catalpol determination with HPLC in a Rehmannia glutinosa Libosch sample was 0.2486 and 0.2559 mg/mL before and after decontaminating OCPs by SFE, respectively. Those were 0.2486 and 0.2632 mg/mL before and after decontaminating HM by SFE, respectively. After a series of experiments to optimize the final SFE, the following conditions were used to determine the OCPs: pure CO(2), extraction pressure of 15 Mpa, extraction temperature of 60 degrees C, extraction time of 30 min, flow rate at 35 kg/h, and the final SFE conditions of HM was pure CO(2), extraction pressure of 18 Mpa, extraction temperature of 50 degrees C, extraction time of 20 min, modifier at 2.5 mL/50 g. The SFE was used to remove the 12 OCP residues and seven HM residues from Rehmannia glutinosa Libosch with less residue left and negligible loss of the active constituent catalpol.