Page 29 - Application Handbook - Liquid Chromatography

LAAN-A-LC-E279

Application Supercritical Fluid Extraction / Chromatography

News Application of Nexera UC SFE Pretreatment System

for Extracting Pesticide Residues from Soil
No.L503

Evaluating the persistence of pesticides in environmental as shown in Fig. 2. This not only improves productivity
soil is an important criteria for evaluating the safety of and minimizes environmental impact, but also avoids
pesticides and analyzing pesticides in soil is extremely human errors involved in the sample pretreatment
important for initial evaluations or registration of process. Furthermore, a specially designed rack changer
pesticides. However, in most cases, analyzing pesticides can be used to perform extraction consecutively for up
in soil using liquid-liquid extraction to extract the to 48 samples.
pesticides is very time-consuming, requires special * "Miyazaki Hydro-Protect" Patent No. 3645552
equipment and reagents, and can cause problems, such
(A)
as metal ions or other introduced ionic substances (A) CO2 pump Back pressure
contaminating analytical instruments or the target SFE unit regulator Column oven Fraction collector
Pressure
substances being decomposed by oxidation, exothermic CO2 Solvent control ON
reactions, or other consequences of the extraction cylinder delivery pump Trap column
process. 15MPa Atmospheric
In contrast, supercritical fluid extraction (SFE) provides Extraction vessel pressure Collection
tubes
excellent extraction efficiency using supercritical carbon Modifier Eluent
(B)
dioxide as the extraction solvent, which offers the low (B) CO2 pump Back pressure
viscosity and high diffusivity of a gas and the high SFE unit regulator Column oven Fraction collector
Pressure
solubility of a fluid. Consequently, it extracts target CO2 Solvent control ON
substances quickly using smaller quantities of organic cylinder delivery pump Trap column
solvent than existing solvent extraction methods, 15MPa Atmospheric
pressure
making it a more environmentally-friendly method as Extraction vessel Collection
tubes
well. Modifier Eluent
This article describes an example of using the Nexera (C) CO2 pump Back pressure
(C)
UC SFE pretreatment system to extract residual SFE unit regulator Column oven Fraction collector
Pressure
pesticides from soil. CO2 control ON
Solvent
cylinder delivery pump
Trap column
15MPa Atmospheric
n Off-Line SFE System Extraction vessel pressure Collection
tubes
The operating principle of the Nexera UC SFE pretreatment Modifier Eluent
(D)
system is shown in Fig. 1. An extraction vessel filled with a (D) CO2 pump Back pressure
sample is placed in the SFE unit and heated to 40 °C SFE unit regulator Column oven Fraction collector
Pressure
control OFF
(Fig. 1 A). The extraction vessel is then filled with CO2 Solvent
supercritical carbon dioxide and the target components cylinder delivery pump Trap column
are extracted statically without pumping the liquid (Fig. 1 Atmospheric Atmospheric Collection
pressure
pressure
B). After static extraction, the target components are Extraction vessel tubes
extracted dynamically by pumping supercritical carbon Modifier Eluent
dioxide through the extraction vessel (Fig. 1 C). After Fig. 1 Process Flow of SFE Extraction
trapping the extract material in the trap column, the
eluate that contains the target components is then
collected in the fraction collector (Fig. 1 D).
n Sample Preparation
Liquid-liquid extraction is typically used to pretreat soil
samples for residual pesticide analysis. However, due to Mix soil and dehydrating agent
the extraction time and equipment required, throughput Fill extraction vessel
is low, limiting the number of samples that can be
processed in a day. It also requires using organic solvent
during extraction. Therefore, an alternative extraction
method to liquid-liquid extraction is desirable, in terms
of both the environment and cost.
In contrast, the Nexera UC SFE pretreatment system
requires only mixing 1 g of soil with 1 g of a dehydrating Rack changer
agent* and placing the mixture in the extraction vessel, Fig. 2 Sample Preparation