Tea Analysis with eXtreme|FV® by GC-MS

Introduction

This method investigates whether SPE is required for the analysis of pesticides in green tea leaves using GC-MS. To simplify the comparison, the method utilizes an existing validated ISO method for the analysis of pesticides in food and natural products. The method is comprised of two sections: first, the extraction of the pesticides from the sample; second, the sample clean-up required for GC/MS.

Experimental

Sample Preparation for Green Tea Leaves

  • Current method uses a salt extraction followed by SPE clean-up.
  • Improved method uses a salt extraction followed by Thomson eXtreme|FV® clean-up.
  • One large sample is extracted and then split in half. Half the sample goes through SPE and the other half through the eXtreme|FV®.
  • 2.0g of commercially available Green Tea is spiked with 0.2mL of 1.0 ppm pesticide standard mix containing 87 pesticides in a 40mL vial for a final concentration of 0.050 ppm.

SPE Cleanup Prior to Analysis - 6 mL Combo SPE Cartridge

  1. Wash one 6 mL Combo SPE Cartridge (packed with 200 mg CarboPrep 200 and 400mg PSA) with acetonitrile.
  2. Add the 10mL portion of the re-suspended residue from the flask labeled “for SPE” to the SPE cartridge.
  3. Elute the sample from the cartridge with 50mL of acetonitrile.
  4. Concentrate the eluted sample to 10mL using a Turbovap II concentrator.
  5. Filter sample with a syringe and syringe filter, PTFE 0.45μm and elute into autosampler vial

Thomson eXtreme|FV® Cleanup Prior to Analysis

  1. Add 400μL of the re-suspended residue from the flask labeled “for Thomson eXtreme|FV® to the shell of one Thomson eXtreme|FV® 0.45μm.
  2. Insert plunger completely.

Equipment Conditions

Samples were analyzed utilizing an Agilent Technologies GC/MS, 7000 Triple Quad system equipped with a 7890A GC system and 7693 auto sampler.

Results

pesticide concentration graph

fig.1Pesticides in Green Tea Comparison of SPE to eXtreme|FV®s.

The results for the green tea can be seen in Table 1, Pesticides in Green Tea Comparison of SPE to eXtreme|FV®s and Fig. 1, Pesticides in Green Tea Comparison of SPE to eXtreme|FV®s, below, shows the recoveries for both clean-up methods: SPE and syringe filter (PTFE 0.45µm) and Thomson eXtreme® Filter Vial. The results show Thomson eXtreme® Filter Vials offer a viable alternative with higher recovery and less preparation time compared to SPE for the sample clean-up of tea leaves and for the clean-up of samples prior to pesticide analysis.

Table.1Pesticides in Green Tea Comparison of SPE to eXtreme|FV®s
Compound/Sample NameSPE Clean-up Average ppmeXtreme|FV® Clean-up Average ppm
Azinphos-ethyl0.0310.033
BHC-alpha (benzene hexachloride)0.0370.037
Chlordane-oxy0.0370.039
Cyfluthrin I0.0330.082
Dimethoate0.0320.032
Endosulfan II (beta isomer)0.0320.036
Heptachlor0.0410.044
Hexachlorobenzene0.0380.039
Methacrifos0.0340.036
Pentachloroaniline0.0410.048
Pentachloroanisole0.0390.042
Permethrin I0.0660.069
Permethrin II (trans)0.0580.61
Prothiofos0.0310.032
Quintozene0.0310.032
Tetradifon0.0370.039

SPE -vs- eXtreme|FV®

urine analysis elements

Conclusion

The results clearly show Thomson eXtreme|FV®s, 0.45µm, PTFE Filter Vials (Thomson # 85540-500) offer a viable alternative with equivalent recovery and significantly less preparation time and solvent usage compared to sample clean-up with SPE for the preparation of green tea samples prior to pesticide analysis. Future testing is required to further streamline this method by re-evaluating the extraction procedure, specifically the need for the concentration/re-suspension steps.

Title

Tea Analysis with eXtreme|FV® by GC-MS

Description

This method investigates whether SPE is required for the analysis of pesticides in green tea leaves using GC-MS.

PDF Application

Product Used in Application

eXtreme|FV® - PTFE 0.45µm

Pre-Split Septum, Blue Cap

pn#85540-200

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