Improved Cleanup for the LC/MS/MS and GC/MS/MS Analysis of Pesticides In Turmeric Powder Using a Novel Dual-Layer SPE Cartridge

Paul Rodwell, Merck/Sigma-Aldrich Company Ltd, Cambridge, United Kingdom
Katherine Stenerson, Milliporesigma/supelco, Bellefonte, Pa, U.s.a.
Olga Shimelis, Milliporesigma/supelco, Bellefonte, Pa, U.s.a.
Jennifer Claus, Milliporesigma/supelco, Bellefonte, Pa, U.s.a.
Michael Ye, Milliporesigma/supelco, Bellefonte, Pa, U.s.a.
Klaus Buckendahl, Merck/sigma-aldrich Chemie Gmbh, Traufkirchen, Germany

The complex composition of turmeric powder presents a challenge when performing chromatographic analysis of pesticides. Residual pigments and oils from the turmeric matrix can contaminate both GC/MS and LC/MS systems, and also result in significant matrix effects. Therefore, an effective cleanup method is needed prior to the injection of turmeric extracts. Standard QuEChERS methodology does not offer the cleanup capacity required for the analysis of high background samples such as turmeric. Dual-layer solid phase extraction (SPE) cartridges containing graphitized carbon black (GCB) and primary-secondary amine (PSA) are often used to improve matrix removal from complex samples; however, toluene is normally added to the elution solvent to improve recovery of planar pesticides. Recently, a novel dual-layer cartridge was designed for the cleanup of acetonitrile extracts from difficult matrices such as dry commodities (spices, tea, etc.) prior to pesticide residue analysis. The top bed consists of a mixture of PSA, C18 and a novel graphitized, spherical carbon. This carbon was engineered to remove sufficient pigmentation while allowing for better recoveries of planar compounds, without the need for toluene in the elution solvent. The bottom cartridge layer contains Z-Sep, a zirconia-coated silica. Z-Sep removes oily residues and provides additional retention of some pigments. This study demonstrates the use of this unique dual-layer SPE cartridge for the cleanup of turmeric powder extracts prior to pesticide analysis by GC/MS/MS and LC/MS/MS. Turmeric powder extracts were spiked at 100 ng/g with a wide range of pesticides of different polarities and classes. For the GC/MS/MS analysis, separation was performed on a SLB^®-5ms column. The LC/MS/MS analysis utilized a Ascentis^® Express C18 column for separation. Quantitation was performed against multi-point calibration curves prepared in unspiked turmeric extract (after cleanup). The recovery, reproducibility, and background removal for the analysis of 33 pesticides from turmeric extract will be discussed herein.