QuEChERS method and pre-mixesWithin a few years after its devleopment by Anastassiades et al. the QuEChERS method has gained a leading position for determination of pesticide residues in food by GC-MS or LC-MS allowing rapid and cheap clean-up of strong matrix-contaminated samples.
Standard clean-up of food samples10 g sample are homogenised with 10 ml acetonitrile. After adding the internal standard the sample is shaken with 4 g MgSO
4 and 1 g NaCI and afterwards centrifuged. 1 ml of the supernantant is spiked with 25 mg CHROMABOND
® Diamino and 150 mg MgSO
4 and shaken again. After centrifugation the supernatant is injected into the GC/MS.
Extraction mixtures for sample preparation for determination of pesticides in food samples.MACHEREY-NAGEL offers a number of individually weighed and pre-mixed buffers and extraction mixtures, specially composed for different sample matrices.
Mix I and Mix II are extraction mixtures, Mix III to Mix VI are clean-up mixtures.
The food samples will be extracted with either Mix I or Mix II.
Afterwards they will be purified with one of the following mixtures:
- Mix III (samples with low fat content; e.g. apples, strawberries),
- Mix IV (moderate content of chlorophyll and carotinoids; e. g. carrots, lettuce),
- Mix V (high content of chlorophyll and carotinoids; e. g. bell peppers, spinach),
- Mix VI (high fat content; e. g. avocados).
Every mix is prepacked in a 15 ml centrifuge tube. Pack of 50 pieces. 
