Assessment of Test Portion Sizes after Sample Comminution with Liquid Nitrogen in an Improved High-Throughput Method for Analysis of Pesticide Residues in Fruits and Vegetables

Abstract

The manufacturer of the sample processing device used in this study did not design nor test their product for use with liquid nitrogen. Appropriate care should be taken to avoid liquid nitrogen contact with skin and possible asphyxiation due to nitrogen displacement of oxygen in an enclosed breathing space.

High-Throughput Mega-Method for the Analysis of Pesticides, Veterinary Drugs, and Environmental Contaminants by Ultra-High-Performance Liquid Chromatography−Tandem Mass Spectrometry and Robotic Mini-Solid-Phase Extraction Cleanup + Low-Pressure Gas Chromatography−Tandem Mass Spectrometry, Part 1: Beef

“…Similarly, a comparison of constant carrier gas flow rates was made from 0.5 to 2.5 mL/min, and 1 mL/min was found to yield about double the peak heights versus 2 mL/min for nearly all analytes. Previous evaluations of flow rates in LPGC−MS­(/MS) used different instruments and ion source designs than the Agilent 7010 in this study. − The closed-source design of the 7010 instrument provides lower detection limits than previous models ,,,, but does not handle a higher flow rate as well as the previous open ion source designs. Unfortunately, the flow rate evaluation experiment was not performed in the previous studies using the 7010 instrument, ,,− and their use of the same 2 mL/min flow rate optimal in the 7000 models led to higher detection limits than possible at 1 mL/min in this case.…”

“…Previous evaluations of flow rates in LPGC−MS­(/MS) used different instruments and ion source designs than the Agilent 7010 in this study. − The closed-source design of the 7010 instrument provides lower detection limits than previous models ,,,, but does not handle a higher flow rate as well as the previous open ion source designs. Unfortunately, the flow rate evaluation experiment was not performed in the previous studies using the 7010 instrument, ,,− and their use of the same 2 mL/min flow rate optimal in the 7000 models led to higher detection limits than possible at 1 mL/min in this case. Even so, the 7010 instrument at the non-optimal 2 mL/min flow rate was ≈5-fold more sensitive than the 7000C system at its optimal flow rate.…”

“…Then, 1 mL of each upper layer was transferred to 2 mL amber glass vials, which were placed on the autosampler tray for ITSP cleanup + LPGC−MS/MS analysis (as in LC, seven aliquots of the matrix blank extract were taken for MM standards). ITSP was conducted as previously described, ,,− in that 300 μL of extract was added by the robotic autosampler to the mini-cartridges at 2 μL/s with an average of 220 μL passing into receiving vials containing glass inserts, to which 25 μL of AP/QC solution had been added. Similar to LC, 25 μL of MeCN or calibration preparation solutions was added to receiving vials for samples and MM standards, respectively.…”

“…Cleanup of extracts using automation conducted in parallel with the analysis step typically improves method accuracy while decreasing time and labor. One automation tool of particular note uses mini-SPE cartridges for Instrument Top Sample Preparation (ITSP) to provide better and easier cleanup than d-SPE just in time prior to injection of the final extracts. ,,− ITSP using cartridges containing 20 mg of anhydrous MgSO 4 , 12 mg of each of C18 and primary secondary amine (PSA) sorbent, and 1 mg of CarbonX has been shown to remove excess water, fatty acids and other lipids, and chlorophyll from quick, easy, cheap, effective, rugged, and safe (QuEChERS) extracts very well, including fatty matrices . The ITSP cleanup step is performed by a robotic autosampler already commonly used with liquid and/or gas chromatography instruments; therefore, it is not much more expensive or complicated than existing practices.…”

“…Subsequent to this validation study, the 7010 source was also found to respond differently to APs than the 7000 model. Some of the additional optimizations to the LPGC−MS/MS conditions were used in a later study, 10 and the details of those experiments will be reported separately.…”