Automation Used: Gerstel

The conventional analysis of pesticides in food products that are high in fat content is labor intensive and time consuming. The high concentration of fatty acids from extracts of these samples greatly interferes with chromatographic analysis. This study explores the use of dispersive pipette extraction technology for removing fatty acids and water from acetonitrile extracts of food samples. The sorbent used for the QuEChERS method is primary secondary amine, (PSA). XTR tips are compatible with automated liquid handlers making extractions easy to automate, and additional centrifugation steps are unnecessary. XTR tips contain loose or “dispersive” sorbent that is filtered to ensure solutions are free from particulate material.

Although the PSA used in QuEChERS products are effective for fatty acid removal from fruit and vegetable extracts, this sorbent lacks capacity to remove fatty acids from samples high in fat content, such as grains and beans. In a previous study, we found that a polyamino sorbent has approximately 5 times the capacity of PSA resulting in more effective removal of fatty acids during extraction of high fat content samples.

We examined the use of three different sorbents in the XTR tip to remove fatty acids from acetonitrile extracts of fatty foods. XTR tips containing weak anion exchange (WAX) sorbent showed the most effective removal of fatty acids from extracts of samples with as high as 50% fat content in as little as 60 seconds.

1Aspirate and Dispense sample solutions 2x with WAX XTR tips
2Dispense solution into a GC vial

Add 0.2 mL of acetonitrile into the top of tip and dispense into the same GC vial. (This removes residual analytes to obtain high recoveries.)

4 Inject onto GC/MS

Publication References for Pesticides in Food Products:

Journal Article
H Guan, W Brewer, S Morgan; New Approach to Multiresidue Pesticide Determination in Foods with High Fat Content using Disposable Pipette Extraction (DPX) and Gas Chromatography-Mass Spectrometry (GC-MS). Journal of Agricultural and Food Chemistry (2009) 57: 10531-10538.
Journal Article 
Z Li, Y Li, X Liu, X Li, L Zhou, C Pan; Multiresidue Analysis of 58 Pesticides in Bean Products by Disposable Pipette Extraction (DPX) Cleanup and Gas Chromatography-Mass Spectrometry Determination. Journal of Agricultural and Food Chemistry (2012) 60: 4788-4798.