Page 44 - Application Handbook - Liquid Chromatography

LAAN-A-LC-E278

Application Supercritical Fluid Extraction / Chromatography

News Analysis of Residual Pesticides in Agricultural Products

Using Nexera UC Off-Line SFE-GC/MS System
No.L502

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