One of the most important aspects of reducing pesticide exposure is monitoring of pesticide residues in foods. A number of analytical methods have been developed, many of them based on traditional liquid-liquid extraction in combination with GC-MS or LC-MS. The QuEChERS (quick, easy, cheap, effective, rugged, and safe) sample preparation methods have been developed to help monitor pesticides in a range of food samples. These methods, however, still require many manual steps, such as shaking, mixing, centrifugation, and dispersive SPE (dSPE), making them quite labor-intensive. There is a need for automating the dSPE technique to clean up QuEChERS type extracts in order to improve laboratory productivity for monitoring pesticide residue in foods.
This paper describes an automated dSPE cleanup method for QuEChERS extracts that is performed with commercially available kits from Agilent® Technologies. Extraction and clean-up is performed using a micro-scale version of this method and automation is achieved using a GERSTEL MPS autosampler equipped with an Anatune CF-100 centrifuge. The clean-up process is followed by automated injection of the cleaned extract to a GC/MS system. Analytical methodology for confirming the presence of a variety of pesticides in various food samples was developed using an Agilent 7890 GC with 5975 MSD. Samples were introduced into the gas chromatograph using a GERSTEL Thermal Desorption Unit (TDU) and MPS autosampler with Automated TDU-liner EXchange (ATEX) option. The sensitivity and selectivity of GC/MS combined with the described injection technique, results in method detection limits that meet acceptance criteria for reporting maximum residue levels (MRLs) as established by regulatory agencies.
The ability to automate the dSPE clean-up of QuEChERS extracts and to couple extraction and clean-up directly to GC-MS analysis, results in improved laboratory productivity by streamlining the complete analytical process.
