7.5-Min Screening Analysis of Multiresidue Pesticides in Brown Rice Flour

• 7.5-min analysis with complete analytical cycle time of less than 10 min.
• Over 90% of the 200+ residues analyzed exhibit recoveries between 70-120%.
• Compatible with both traditional HPLC and modern UHPLC instruments.

Analysis of multiresidue pesticides is no easy task, and it’s made even more difficult by complex sample matrices and the sophistication of the LC-MS/MS instrumentation commonly used for analysis. An LC-MS/MS can provide remarkable sensitivity, even allowing a degree of chromatographic coelutions to exist and still quantitatively monitor analytes of interest. However, too many coelutions can overwhelm the mass spectrometer, so a good chromatographic method is still essential. The optimized chromatographic method described here allows the analysis of hundreds of compounds in as little as 7.5 minutes with a total cycle time under 10 minutes, ensuring fast, accurate sample screening and increased lab productivity.

As detailed below, a sample of brown rice flour was fortified with all of the components included in the Restek LC multiresidue pesticide kit, extracted with Q-sep QuEChERS extraction salts, cleaned up using dSPE, and analyzed using a 2.7 µm Raptor ARC-18 column. The inherent efficiency of a 2.7 µm superficially porous particle column produces narrow peaks, which permits more compounds to be fit into a given unit of time. The selectivity of the Raptor ARC-18 stationary phase ensures that compounds elute throughout the entire length of the analysis, which avoids crowding compounds in time and potentially taxing the mass spectrometer’s ability to monitor all the relevant ions effectively. Note that it is important to keep internal system volume down to a minimum, so selecting narrow-bore LC tubing and avoiding excess lengths of tubing will help produce the narrowest peaks and achieve the quickest, most efficient chromatography. This analysis of multiresidue pesticides in brown rice flour uses straightforward mobile phases that are mass spec friendly and a flow rate that keeps the back pressure within the operating range of conventional HPLC instruments. These advantages make it possible to analyze over 200 pesticides, surrogates, and internal standards—even in such a challenging matrix—in a matter of minutes.