Agriculture Reference
In-Depth Information
Figure 5.3.
The comparison of the extraction efficiencies of seven solvents for 77 environmental pollutants
in 5 g fat samples.
5.3.3 Comparison of Sample Extraction Methods
After the selection of acetonitrile as the extraction solvent, three extraction methods
were compared:
1.
Accelerated Solvent Extraction:
Accurately weigh 5 g sample into a mortar
containing 17 g diatomite, grind evenly and transfer to the sample cell, heat at
10.34MPa, 80
C for 5min, extract with acetonitrile for 3 min, repeat twice, and
purge with nitrogen for 100 s (to collect all acetonitrile from the sample
residues).
2.
Homogeneous Extraction:
Accurately weigh 5 g sample, add 35ml acetoni-
trile, homogenize at 12,000 rpm for 1min, and repeat twice.
3.
Oscillation Extraction:
Accurately weigh 5 g sample into a mortar containing
10 g anhydrous sodium sulfate, grind evenly and transfer to an 80ml centrifuge
tube, add 35ml acetonitrile, oscillation extract for 30 min, and repeat twice.
°
For each solvent, three standard added samples and one matrix standard are
prepared for calculating recoveries of 77 environmental pollutants. The results of
three standard forti
ed samples are averaged before the calculation of recoveries.
Different extraction methods are applied, and the extracts are collected. After
concentration and GPC cleanup, GC
-
MS/MS is used to detect the analytes, and
internal standard is used for quanti
cation.
In homogeneous extraction, the recoveries of 70 analytes are between 60 and
120%, accounting for 90.9% of the total; in oscillation extraction, the recoveries of 65
analytes are between 60 and 120%, accounting for 84.4% of the total; in ASE
extraction, the recoveries of 64 analytes are between 60 and 120%, accounting for
83.1% of the total. In homogeneous extraction, the RSDs of 74 analytes are less than
20%, accounting for 96.1% of the total; in oscillation extraction, the RSDs of 66
analytes are less than 20%, accounting for 85.7% of the total; in ASE extraction, the
RSDs of 69 analytes are less than 20%, accounting for 89.6% of the total. Overall,
