Cleanup of Peppermint and Black Tea Using Gel Permeation Chromatography (GPC) for The Analysis of Pesticides

Pickering Laboratories, Inc.

Gel permeation chromatography (GPC) is a very effective sample clean-up technique, key to an accurate and sensitive analysis of pesticide, PCBs, mycotoxin, PAHs, and other similar compounds. Using this technique, a laboratory can efficiently and reproducibly clean up a variety of herbal products, even those with extremely complex matrices containing oils, waxes, resins, and large color compounds. The resulting solution of the desired analytes is then analyzed with an appropriate instrument, such as a gas chromatograph with any number of detectors. This application note describes the highly effective cleanup of black tea and peppermint using the GPC Quattro, from LCTech GmbH.

Test 1 – Carry-over

Experimental Design

4 mL of a matrix solution containing 5 ppm of chlorpyrifos are run five times over the separation column of the GPC quattro. To check any carry-over into the subsequent eluates, pure elution solvent (ethyl acetate/cyclohexane (1+1)) is run after the runs with the high concentration of chlorpyrifos and collected in a new receptacle. This procedure is repeated. The two runs of solvent are analyzed via GC-FPD.

Result: Ret. Time (chlorpyrifos) = appr. at 12 min.

No measurable carry-over (see Figure 1).

Figure 1

Test 2 – Reproducibility

Experimental Design

A stock solution containing pesticides which elute over the entire parameterized collect phase (at the beginning, in the middle, and at the end) are added to two matrices (black tea Camellia sinensis and peppermint Mentha piperita), processed according to method §64 LFGB L 00.00-34 and cleaned-up consecutively 10 times via the GPC quattro. Overlay of 10 black tea samples is presented in Figure 2.

Figure 2

Pickering Laboratories, Inc.

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Website: www.pickeringlabs.com