Application Note 20549
QuEChERS Dispersive Solid Phase
Extraction for the GC-MS Analysis of
Pesticides in Cucumber
Anila I Khan, Thermo Fisher Scientific, Runcorn, Cheshire, UK
Introduction
QuEChERS (Quick, Easy, Cheap, Effective, Rugged and
Safe) is a dispersive Solid Phase Extraction (SPE)
technique for extracting multi-residue pesticides from
fruits and vegetables. The advantages of this methodology
are speed, ease of execution, minimal solvent requirement
and cost. The QuEChERS methodology was developed by
Anastassiades et al
1
and has become widely used in food
safety analyses.
The method is:
•
Quick
– high sample throughput, typically 8 samples
can be prepared in under 30 min
•
Easy
– it requires less handling of extracts than other
techniques i.e. fewer steps are required
•
Cheap
– less sorbent material is needed and less time is
required to process samples compared to other techniques
•
Effective
– the simple technique gives high and accurate
recovery levels for a range of different compound types.
•
Rugged
– the method can detect a large number of
pesticides including charged and polar pesticides
•
Safe
– unlike other techniques, it does not require the
use of chlorinated solvents. Extraction is typically carried
out using acetonitrile, which is both GC and LC
compatible.
Key Words
QuEChERS, pesticide residue analysis, cucumber, food safety
Abstract
QuEChERS dispersive SPE is a simple, fast and quantitative sample
preparation method. This application demonstrates the effectiveness of this
technique in the GC/MS analysis of pesticides in cucumber, using a Thermo
Scientific TraceGOLD TG-5MS GC column for analysis.
The recoveries for the spiked pesticides in cucumber matrix at 50 ng/g were
between 75.2 to 119.6% with relative standard deviations ranging from
2.1 to 8.9% using the QuEChERS method described in EN15662.
The sample preparation approach described in the
European EN15662 QuEChERS procedure
2
was used for
extracting pesticides from cucumber. This is a two stage
process: sample extraction, followed by dispersive SPE.
In the sample extraction stage, the food sample is
homogenized to increase the available surface area of the
sample to provide optimal extraction efficiencies. The
homogenized sample is placed in the extraction tube
containing magnesium sulfate and salts (sodium chloride,
sodium citrate tribasic dihydrate, sodium citrate dibasic
sesquihydrate). Magnesium sulfate ensures that, upon
addition of acetonitrile, a phase separation is induced
between water and organic solvent with the pesticides of
interest being extracted into the organic phase. When
acetonitrile is poured into the extraction tube containing
the homogenized sample,
