Extraction and Cleanup of Pesticide Residues from Tea Prior to Analysis by LC/MS/MS and GC/MS/MS

Klaus Buckendahl, Merck/Sigma-Aldrich Chemie GmbH, Taufkirchen, Germany (klaus.buckendahl@merckgroup.com)
Katherine Stenerson, Milliporesigma, Bellefonte Pa, Usa
Olga Shimelis, Milliporesigma, Bellefonte Pa, Usa

The analysis of pesticide residues, particularly in dry foodstuffs such as spices and teas, is often challenging due to the presence of concentrated matrix interferences. If not removed, these oils and pigments can produce ion-suppression or matrix enhancement effects and also contaminate both GC/MS and LC/MS systems. To this end, implementation of an effective cleanup method prior to the injection of extracts onto chromatographic systems is necessary.

For such high background samples, standard QuEChERS methodology [1,2] often does not provide the required cleanup capacity. A novel adsorbent combination in a dual-layer solid phase extraction (SPE) cartridge was recently developed for an efficient cleanup of acetonitrile extracts from dry commodities and difficult matrices (spices, tea, etc.) prior to pesticide analysis. The top bed consists of a mixture of C18, primary-secondary amine (PSA), and a unique graphitized, spherical carbon. This specialized carbon was engineered to sufficiently remove pigments while allowing for better recoveries of planar pesticides without the use of toluene for elution. A zirconia-coated silica in the bottom layer of the cartridge aids in the removal of remaining oily matrix components and various pigments.

The analysis of a wide range of pesticides of different polarities and classes from spiked (5 ng/g and 50 ng/g) organic green tea matrices will be demonstrated by both GC/MS/MS and LC/MS/MS (using a polar embedded HPLC phase column). Specifically, analyte recovery, reproducibility, and background removal using a novel dual-layer SPE cartridge will be the focus and compared to a classical QuEChERS method approach.

 

References:

[1] Anastassiades M. Lehotay S.J. et al., J. AOAC International 86(22) (2003) 412-431

[2] EN15662:2008, Foods of plant origin - Determination of pesticide residues using GC-MS and/or LC-MS/MS following acetonitrile extraction/partitioning and cleanup by dispersive SPE – QuEChERS method.