QuEChERS A Mini-Multiresidue Method for the Analysis of Pesticide Residues in Low-Fat Products

QuEChERS
A Mini-Multiresidue Method for the Analysis of
Pesticide Residues in Low-Fat Products

1. Aim and Scope
This manuscript describes a method for the analysis of pesticide residues in produce
with a low fat content, such as fruits, vegetables, cereals as well as processed products
including dried fruit.
2. Short Description
The homogeneous and representative subsample is extracted in frozen condition
with the help of acetonitrile. After addition of magnesium sulfate, sodium chloride and
buffering citrate salts (pH 5-5.5), the mixture is shaken intensively and centrifuged for
phase separation. An aliquot of the organic phase is cleaned-up by dispersive SPE
employing bulk sorbents (e.g. PSA, GCB) as well as MgSO4 for the removal of residual
water. PSA treated extracts are acidified by adding a small amount of formic acid,
to improve the storage stability of certain base-sensitive pesticides. The final extract
can be directly employed for GC- and LC-based determinative analysis. Quantification
is performed using an internal standard, which is added to the extract after the
initial addition of acetonitrile. Samples with a low water content (<80%) require the
addition of water before the initial extraction to get a total of ca. 10 mL water. When
dealing with samples containing <25% water (e.g. cereals, dried fruit, honey, spices)
the size of the analytical sample may have to be reduced (e.g. 1-5 g) depending on
the load of matrix-co-extractives expected in the final extracts. A brief overview of
the method is shown in the flowchart at the end of this document.
...

 

http://www.mediafire.com/?fq1t7drx4d6ylbc