SPE for Pesticide Residue Analysis in Spices and Other Dry, Difficult Samples

A recent survey revealed that one out of three analytical chemists in the food industry has difficulty analyzing compounds in dry commodities such as herbs, spices, tea, and coffee. Although most analysts use the QuEChERS method for sample cleanup when performing pesticide residue analysis, the dispersive SPE cleanup method often does not have the capacity to remove the concentrated matrix interferences associated with these dry commodities. Cleanup performed with traditional dual-layer solid phase extraction (SPE) cartridges containing graphitized carbon black (GCB) often results in low recoveries of analytes with planar characteristics. Although toluene can be added to the elution solvent to recover these planar analytes, a solvent exchange must be performed prior to HPLC analysis, making the use of toluene unattractive to analytical chemists.

Recently, the Supelclean™ Ultra 2400, a new small-volume, dual -ayer SPE cartridge was developed for the cleanup of extracts of difficult, dry matrices prior to pesticide residue analysis performed by GC/MS/MS or LC/MS/MS. The top bed consists of a mixture of PSA/C18 and a graphitized, spherical carbon. PSA removes acidic interferences, C18 retains some hydrophobic interferences, and carbon removes pigments. The variety of carbon used in this cartridge was engineered to remove sufficient pigmentation while allowing for better recoveries of compounds with planar structures. The bottom bed of the cartridge contains Z-Sep, which is a zirconia-coated silica. Z-Sep removes oily residues and provides additional pigment removal.

With little solvent usage, the Ultra 2400 cartridge provides a cleaner extract over QuEChERS cleanup sorbents and traditional SPE cartridges without the use of toluene. By removing concentrated oil and pigment interferences from difficult samples, the Ultra cartridge makes it possible to achieve ppb levels of pesticides and attain improved recovery of even the most challenging planar pesticides. To see the use of the Ultra cartridge for the analysis of pesticide residues in turmeric, click here. To request a free sample of this product, please visit sigma-aldrich.com/spe-samples. For ordering information, please visit sigma-aldrich.com/supelcleanultra.