The measurement of 23 organochlorine, organophosphorus, and pyrethroid pesticides in typical traditional Chinese medicine (TCM), flos lonicerae, was made using gel permeation chromatography (GPC) purification and gas chroma- tography-mass spectrometry (GC-MS) detection. The pesticides were extracted with ultrasonic device and 5.0 mL mixture of ethyl acetate and cyclohexane (1:1, v/v). Coextractants from sample matrices which may have interfere to the qualitative and quantitative analysis, such as pigments, were removed using GPC purification. Simultaneous full scan and selective ion monitor (scan/SIM) mode for GC-MS was used for qualitative and quantitative analysis, which pro- vided retention time and characteristic fragments ratio for each pesticide so as to positively identify each analyte. Rela- tive standard deviations (RSDs) were within 7.7% (5.0 - 22.5 μg/kg, n = 3). The recoveries of pesticide standards at the spiked concentration of 5.0 - 22.5 μg/kg were between 87.1% and 110.9%. Limits of detection (LODs) for the analytes were 0.16 - 3.2 μg/kg, which could meet the demand of routine analysis and TCM quality control.
Traditional Chinese Medicine (TCM) usually means medicinal plants. Herb water, mixed tablet, and powder from the extracts of herbs are the general styles in clinical practice. The usage of TCM in China has a very long history. The influence of TCM on health care system has been profound in Asia as well as in the West in recent years [1-3]. The concerning of contaminations of heavy metals [4-6] and pesticides [2,6-9], which may be introduced during the cultivation, transportation, preparation and preservation, has been increased as the popularity of TCM enlarged.
Pesticides using to control various insect pests all over the world have advanced agriculture to gain great productivity [10,11]. In the mean time, they contaminate the environment [
Typically, measurement of multi-residue in complex matrices comprises sample pre-treatment, separation and detection by gas chromatography-mass spectrometry (GCMS) [19,20]. The pre-treatment usually is time-consuming, which includes extraction, purification, and enhancement of the analytes to reduce or eliminate possible interference to the accurate detection. Soxhlet extraction [
The purpose of this study was to develop a novel method for accurately and simultaneously determination of organochlorine, organophosphorus, and pyrethroid pesticides in flos lonicerae. The advantage of GPC purification and good separation and high sensitivity of GC-MS was investigated in qualitative identification and quantitative detection of multi-pesticide in complex chemical matrices.
Acetone, acetonitrile, cyclohexane and ethyl acetate were all of HPLC grade and purchased from Thermal Fisher Co. (USA). The 23-pesticide standards were from Chem Service Co. (USA), which were of purity ≥ 98.1%.
1000 µg/mL stock solutions for each pesticide were prepared with acetone and stored in freezer at –18˚C. 10 µg/mL mixed standard solution for daily work were obtained by mixing and diluting stock solutions with acetone, and stored in a refrigerator at 4˚C.
Agilent 7890A gas chromatography, 5975C mass spectrometer, and 7683B auto sample injector was used (Agilent Technologies, USA). Data acquisition, data processing, and instrumental control were performed with Agilent Enhanced ChemStation (Agilent Technologies, USA). A DB-5 MS fused silica capillary column of 30 m × 0.25 mm with 0.25 µm film thickness from Agilent Technologies was used.
The GPC system (Vario, LC Tech, Germany) consisted of high pressure pump, auto-sampler with 24-sample vials (10 mL) and 5.0 mL sample loop, GPC column, and 24 fraction collected vials (100 mL). The clean-up GPC column was packed polystyrene-divinylbenzene (Bio-Beads S-X3, 400 mm × 25 mm I.D., 200 - 400 mesh).
MS2 mini-shaker (IKA, Germany), B5200S-OT ultrasonic extract device (Branson, USA), centrifuge (Shanghai, China), auto concentrating apparatus (EVA Ш, LC Tech, Germany), and laboratory-built nitrogen evaporator were used.
1.000 g of ~2 kg homogenized dry flos lonicerae sample was extracted with 5.0 mL mixed ethyl acetate and cyclohexane (1:1, v/v) for 10 min. The extraction was repeated for 3 times. Combine the extracts together, and then concentrated with a nitrogen stream to 10.0 mL. 5.0 mL of the extract solution was injected and separated on GPC with a mixed mobile phase of ethyl acetate and cyclohexane (1:1, v/v) at a flow rate of 5.0 mL/min. The fraction containing the analyzed pesticides was collected within the retention time of 17 to 36 min (totally 95.0 mL of eluant). The GPC fraction was evaporated and concentrated to 5.0 mL using EVA Ⅲ rotary evaporator at 40˚C, and further concentrated to near dry with nitrogen stream, re-dissolved with 0.5 mL mixture of ethyl acetate and cyclohexane (1:1, v/v) for GC-MS analysis.
Carrier gas was high purity of Helium (≥99.999%). The separation of all pesticides was performed with a constant pressure mode. The injection port of GC was 250˚C. 1.0 µL of pretreated sample solution was injected in splitless mode (split valve closed for 0.75 min). The retention time was locked by chlorpyrifos-methyl. Programmed temperature for GC oven was initially 50˚C for 1 min, increased to 125˚C at a rate of 25˚C/min, and then to 300˚C at 10˚C/min, and finally maintained at 300˚C for 10 min until all the analytes eluted.
Electron impact (EI) ionization source was used at 70 eV. The interface between the GC and mass detector was maintained at 280˚C. The temperature for EI source and quadrupole were set at 230˚C and 150˚C, respectively. The solvent delay time was set to 3.5 min. Full scan and selected ion mode (Scan/SIM) were used to qualitative identification and quantitative detection of multi-pesticide.