Automating QuEChERS for Pesticide Residues

The QuEChERS workstation can be run on-line with LC-MS

I was recently at the European Pesticide Residues Workshop, held this year in Strasbourg. I was invited along by Gerstel to present a talk “Automating Dispersive Solid Phase Extraction Clean-Up (QuEChERS) for LC-QQQ & GC-MS” at their Vendor seminar and to help demonstrate the Automated QuEChERS clean-up workstation and talk to customers on their booth.

In the last couple of years I had been leading the development of a robot compatible centrifuge, to allow sedimentation of plant materials in an online Automated Derivatisation and Analysis system. This solution combined an automated MPS prep-station from Gerstel and the LECO Pegasus GC-TOFMS system and was used in Metabolomics studies. The Centrifuge worked great for this application which gave me the idea of utilising this new capability to automate the automation of dispersive solid phase clean up as used in the QuEChERS extraction and clean up technique for food pesticide analysis.

Paul carried out a short feasibility study extracting pesticides from Orange Juice automated on-line with HPLC, I used the results from this to discuss the potential with a number of experienced clients in this field of work and the Anatune Automated QuEChERS clean-up workstation was born.

We then approached our colleagues at Agilent to purchase the 6410 LC-MSMS instrument for the Anatune laboratory and once installed, Paul set about testing the system on a range of Pesticides in various food matrices. The results were excellent and it seemed there was likely to be some major advantages for an on-line ‘just in time’ preparative approach.

The Automated on-line approach could give the following advantages:

• Automation of all the Clean-Up preparative steps and injection to LC-MS MS or GC-MS on-line. Leaving less room for human error and the resulting improvement in reproducibility gained.
• Minimised contact time between the clean-up sorbents, sometimes including Carbon Black, which may potentially help to reduce the losses of certain classes of pesticides.
• Automated filtration of the final extract, making the sample compatible with UHPLC to allow faster separation times and reducing the likelihood of blockages.
• Automatically dilutes a portion of the extract with mobile phase ‘just in time’ so that peak shape and detection limits for early eluting pesticides are much improved. This ‘just in time’ dilution also reduces the possibility of dissolution and the resulting lower recovery associated with less polar pesticides being left in a more aqueous solution for longer periods of time, as might be the case with an off-line approach.
• Allows the scaling up of productivity with the 24/7 operation capability that an automated on-line approach brings to the laboratory.

The EPRW event was very successful for Gerstel, generating quite some interest in the automated workstation, but also for their Automated Liner EXchange (ALEX) system for GCMS, again a solution aimed at improving data consistency and productivity in pesticide residue analysis by automatically swapping out dirty liners for new, maintaining inlet, column and detector cleanliness and vastly reducing down time caused by the need for system maintenance.

If you want to know how these techniques or others might help for your analysis, please leave a blog entry or get in touch using bob.green@anatune.co.uk or call on 01954 212909.