Commonly used sample pretreatment techniques for agricultural products

(1) Solid phase microextraction (SPME)

Solid phase microextraction is a new type of non-solvated sample preparation technology, which was first reported by Pawliszyn in 1989
.
In solid phase microextraction, specific solids (usually fibrous extraction materials) are used as solid phase extractors to immerse them in sample solutions or headspace extraction, and then directly perform gas chromatography (GC), high performance liquid chromatography (HPLC) and other analyses

The advantages of solid-phase microextraction are: it integrates sampling, extraction, concentration and sample injection, convenient operation, short time-consuming, fast and efficient determination; without any organic solvents, it is solid-phase extraction in the true sense and avoids environmental damage.
Secondary pollution; suitable for on-site analysis and easy to operate
.
The disadvantages are: the device is more expensive, the types of coatings are limited, the selectivity is poor, and the inorganic ion extraction technology is not yet mature

(2) Gel Permeation Chromatography (GPC)

Gel permeation chromatography extraction is an effective method commonly used in pesticide multi-residue analysis.
It is applicable to a wide range of samples, a wide variety of pesticides, and a high recovery rate
.
Not only the oil purification effect is good, but also the reproducibility is good, the column can be reused, and it has become a general purification method in the analysis of pesticide multi-residue

(3) Supercritical fluid extraction (SFE)

Supercritical fluid refers to a single phase formed when the pressure and temperature reach the critical point of a certain substance
.
It has special properties, neither a gas nor a liquid, but it has a density similar to that of liquids, and has a strong solubility similar to liquids; the diffusion coefficient of solutes in supercritical fluids is similar to that in gases, and the extraction time is short , Fast

(4) Microwave-assisted extraction technology (MAE)

Microwave assisted extraction (MAE) refers to the use of microwave energy to enhance the efficiency of solvent extraction, so that certain organic components (or organic pollutants) in a solid or semi-solid sample can be effectively separated from the matrix material
.
Microwave-assisted extraction technology has the following characteristics: ① Fast and efficient

Therefore, when the microwave-assisted extraction technology is used to extract the analyte from the biological matrix, the extraction efficiency can be improved
.
Avoid prolonged high temperature to cause the sample to decompose

(5) Membrane separation technology

Membrane separation technology refers to a technology that achieves selective separation of a mixture of molecules of different particle sizes at the molecular level when passing through a semi-permeable membrane
.
Also known semipermeable membrane or membrane separation, membrane wall covered with small holes, according to the pore size can be divided into microfiltration, ultrafiltration, nanofiltration, reverse osmosis membrane

The principle, applicability and characteristics of several pre-treatment methods are compared in Table 2-5

Table 2-5 Comparison of principles, applicability and characteristics of several pre-treatment methods

Related link: Dispersive solid phase extraction