Application
News
No.L502
Supercritical Fluid Extraction / Chromatography
Analysis of Residual Pesticides in Agricultural Products
Using Nexera UC Off-Line SFE-GC/MS System
LAAN-A-LC-E278
Since enforcement of the positive list system for residual
pesticides in foods in 2006 in Japan, over 800 pesticides
have been included in the system. Consequently, there
is now a strong demand for effective analytical methods
encompassing any sample pretreatment steps that are
capable of inspecting large numbers of pesticides.
Conventionally, analysis of residual pesticides in foods
has involved pesticide extraction by a solvent extraction
method before analysis by LC/MS or GC/MS. The
problem with solvent extraction methods is that sample
pretreatment requires a substantial amount of time and
effort, and large quantities of organic solvents are used.
Supercritical fluid extraction (SFE) that uses supercritical
carbon dioxide as the extraction solvent provides good
extraction efficiency, where the solvent is similar to gas
in terms of low viscosity and high diffusivity, and similar
to fluid in terms of high solubility. This allows for
extraction within a short period of time. This extraction
method is also less damaging to the environment since
it uses a smaller amount of organic solvent compared
to conventional solvent extraction methods.
We introduce an example GC/MS analysis of pesticides
extracted from an agricultural products using the
Nexera UC off-line SFE system.
Meanwhile, as shown in Fig. 2, sample preparation for
the Nexera UC off-line SFE system only involves mixing
1 g of agricultural product pulverized in a mixer with
1 g of dehydrating agent*, then filling the extraction
vessel with this mixture. This not only results in
improved productivity and a reduced environmental
burden, but also avoids human errors involved in the
sample pretreatment process. Using a specially designed
rack changer also allows for extraction of a maximum
of 48 samples consecutively.
* "Miyazaki Hydro-Protect" Patent No. 3645552
n Off-Line SFE System
n Sample Preparation
Fig. 1 shows the principle behind operation of the
Nexera UC off-line SFE system. An extraction vessel
filled with a sample is placed in the SFE unit, and is
heated to 40 °C (Fig. 1 A). The extraction vessel is then
filled with supercritical carbon dioxide, and the target
components are extracted statically without pumping
the liquid (Fig. 1 B). After static extraction, dynamic
extraction is performed by pumping supercritical carbon
dioxide through the extraction vessel (Fig. 1 C). After
trapping the extract material in the trap column, eluate
that contains the target components is then collected in
the fraction collector (Fig. 1 D).
The QuEChERS method that prioritizes simplicity and
speed is widely used to pretreat agricultural products
for residual pesticide analysis. While there is a special kit
available for the QuEChERS method, sample preparation
for this kit requires a large number of process steps
including reagent addition, solvent extraction,
purification by dispersive solid phase extraction, and
centrifugal separation.
Fig. 2 Sample Preparation
Fig. 1 Flow of Off-Line SFE Extraction
(A)
(B)
(C)
(D)
CO2
cylinder
Collection
tubes
Solvent
delivery pump
CO2 pump
SFE unit
Back pressure
regulator
Column oven
Fraction collector
Trap column
Pressure
control ON
Extraction vessel
15MPa Atmospheric
pressure
Modifier Eluate
CO2
cylinder
Collection
tubes
Solvent
delivery pump
CO2 pump
SFE unit
Back pressure
regulator
Column oven
Fraction collector
Trap column
Pressure
control ON
Extraction vessel
15MPa Atmospheric
pressure
Modifier Eluate
CO2
cylinder
Collection
tubes
Solvent
delivery pump
CO2 pump
SFE unit
Back pressure
regulator
Column oven
Fraction collector
Trap column
Pressure
control ON
Extraction vessel
15MPa Atmospheric
pressure
Modifier Eluate
CO2
cylinder
Collection
tubes
Solvent
delivery pump
CO2 pump
SFE unit
Back pressure
regulator
Column oven
Fraction collector
Trap column
Pressure
control OFF
Extraction vessel
Atmospheric
pressure
Atmospheric
pressure
Modifier Eluate
Homogenize Add absorbent Mix
Enclose in
extraction vessel
Homogenize Add solvent Stir Add reagent Stir Centrifuge Centrifuge Stir Add reagent
Transfer
supernatant
Conventional (QuEChERS) Pretreatment Method
Nexera UC Pretreatment Rack changer Mixing agricultural product with dehydrating agent