Why Use Acetonitrile as the Extraction Solvent during QuEChERS?
1. Advantages and disadvantages of commonly used extraction solvents
Acetonitrile: easy to salt out; compatible with LC/MS; difficult to concentrate
Acetone: not easy to salt out; easy to volatilize, concentrate
Ethyl acetate: immiscible with water; less extraction of impurities; more lipids are extracted
2. The cleanliness of the extract
The experimental results show that the sample is the cleanest when using acetonitrile as the extraction solvent, whether or not PSA purification is used. The extract of ethyl acetate and acetone is equivalent, but when purified by PSA, ethyl acetate provides a better purification effect than acetone.
3. In terms of recovery, there is no significant difference between acetonitrile and ethyl acetate for non-polar pesticides, but acetonitrile can provide more stable results (smaller RSD); for polar pesticides (methamidophos, acephate, etc.), the extraction efficiency of acetonitrile is much higher.
4. It is well known that mass spectrometry (especially ESI ionization source) is greatly affected by the cleanliness of the sample matrix; too dirty sample will have a great inhibited effect on the ionization of the target compound which ultimately leads to distortion of the results, so the selection of a suitable extraction solvent is essential.