www.rdmag.com January/February 2016 R&DMagazine 25
QuEChERS methodology developed
by Steven Lehotay and Michelangelo
Anastassiades was a significant improvement
in extraction and cleanup for analysis of
pesticides in foods over traditional methods.
This led to the development of AOAC
(2007.01) and European (EN 15662) methods
because they can use 95 percent less solvent
and 95 percent less consumables, and offer
a 90 percent reduction in preparation time.
Shown in Figure 2 is a schematic of typical
steps required for sample preparation,
extraction and cleanup using QuEChERS for a
spinach sample. Sample preparation time can
be up to 35 minutes.
Because of the increased selectivity of
SFE, the sample preparation and extraction
time can be reduced from 35 minutes to 5
minutes. A proprietary absorbent is used to
absorb the water.
After the extraction, traditionally the
next question is whether to use GCMS or
LCMS for analysis. Generally, GCMS is
used for low polarity and low molecular
weight compounds as shown in Figure 4. For
GCMS, ideally the compounds are volatile
and thermally stable regardless of the MS
detection design. For higher polarity and
higher molecular weight compounds, the
ideal choice is LCMS. ESI (electrospray
ionization) is typically used for higher
polarity and molecular weight compounds.
Shimadzu’s DUIS ionization source includes
both the ESI and APCI (atmospheric
pressure chemical ionization) sources.
SFC covers a wider range of polarities
compared to GCMS or LCMS. The molecular
weight of SFC is not as high as that of LCMS,
but many compounds such as pesticides are
not high molecular weight compounds.
During the SFE-SFC, methanol is added
to the mobile phase in order to solubilize
more of the polar compounds since the
supercritical fluid CO2 is non-polar. Thus,
SFE-SFC-MS/MS can analyze non-polar and
polar type compounds.
Coenzyme Q10 is a liable compound
which is oxidized during the traditional
solvent extraction process. The analyst
typically would assume the original content
in the dietary supplement was in the reduced
form. However, assumptions are not always
correct. By performing an online SFE-SFC
analysis, one can clearly see the extraction and
chromatography results differ, thus illustrating
the advantages of the online coupled technique.
Pharmaceutical Cleaning Validation
Clinical Biomarkers from Dried
The conventional analysis of biomarkers in
dried blood spots (DBS) requires a numbers
of steps such as cutting off the DBS, solvent
extraction, stirring/shaking, solvent soaking,
filtration and evaporation before analysis in
the LCMS. Online SFC-SFE-MS/MS only
requires placing the sample in the sample
vessel, placing the sample vessel inside the
instrument and selecting the start button.
Polymers with Trace Additives
Online SFE-SFC-MS/MS provides
several advantages over traditional sample
preparation and analysis of solid samples.
The advantages affect all areas of the analysis
workflow, including sample preparation,
chromatography and detection. Sample
preparation can be up to seven times faster,
chromatography up to three times faster,
and sensitivity up to five times higher when
compared to other techniques. In addition, it
offers a wider range of sample polarities then
GC-MS/MS or LC-MS/MS and protection of
— Robert H. Clifford, Ph.D., Alan Marks,
 K. Klesper, A.H. Corwin and D. A. Turner, J. Org. Chem., 27,
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Figure 2: Steps Used in QuEChERS for Extraction and Cleanup of Spinach – Up to 35 minutes.