Phoenix Le

Grace Paragas

Chem 230


QuEChERS Homework Problems


1. What is QuEChERS used for?

Answer: QuEChERS is used for the effective analysis of pesticide residues in fruits and vegetables. It is a multi-residue method meaning several analytes in one sample can be analyzed. Additionally, QuEChERS can be easily modified to tailor to an analystís needs.


2. There are 2main methods of QuEChERS:the CEN method which utilizes a citrate buffer, and the AOAC method which utilizes an acetate buffer. Both methods have comparable results. When would you use one method over the other?

Answer: The acetate buffer will keep a sample solutionís pH at around 5. The citrate buffer will keep the pH at around 8. For base sensitive pesticides, the pH of the sample solution becomes critical. You would use the AOAC method for base sensitive pesticides. The CEN method has a more optimized pH for using d-SPE sorbents and the cleanliness of extract is improved.