1. Introduction to Solid Phase Extraction Technology
Solid phase extraction (SPE) technology, developed in the 1970s, because of its high efficiency, reliability, and low consumption of reagents, has replaced traditional liquid-liquid extraction in many fields and has become an effective method for sample pretreatment. .
Some traditional books on SPE attribute it to the principle of a liquid chromatography, which is actually one of the main causes of improper use. Considering the SPE cartridge as a liquid chromatography column, it is more appropriate to treat it as a pure extractant, because the focus of liquid chromatography is separation, and the focus of SPE is extraction.
The role of solid phase extraction technology in sample processing is divided into two types: one is purification, and the other is enrichment. These two functions may exist at the same time.
Compared with liquid-liquid extraction, the advantages of solid extraction are convenience and less reagent consumption. The disadvantage is that the repeatability between batches is difficult to guarantee. The reason for this is that the reproducibility of the liquid reagent is good, as long as its purity is reliable, the physical and chemical properties of products of different generations are reliable. Even if the solid extractant guarantees purity, there are also differences in particle size, shape and other liquid reagents that are not present and difficult to measure. The extraction properties of different batches in different years may vary greatly.
From the theoretical point of view and the propaganda of the manufacturer, solid phase extraction should be well applied in the pretreatment of chromatographic analysis: organic solvents are rarely used, and samples can be processed in batches, which can enrich and remove impurities The impression is the revolutionary progress of pre-processing. However, the actual situation is at least in China. Although it has been popularized for many years, its practical application is still quite limited.
SPE is not widely used, it is related to our usage and expectations, but also to its own limitations. For suppliers, starting from economic benefits, they have always ignored the limitations and deficiencies of solid phase extraction. Solid phase extraction can be used as a good supplement to the pretreatment method, but when using it, you must be aware of its advantages and disadvantages, pay attention to local conditions, and avoid weaknesses.
2. Application advantages of solid phase extraction
What kind of pre-treatment is suitable for the use of solid phase extraction technology, that is, solid phase extraction will be more ideal than ordinary solvent extraction, personally think that there are the following situations:
(1) Pretreatment of organic matter in water.
This type of conventional treatment is basically a shaking extraction with an organic solvent that is incompatible with water. The advantage of using solid phase extraction is that
(1) The pretreatment process can be repeated quantitatively.
The operation of solvent oscillation can generally only be controlled to the degree of time, but it cannot control the frequency, intensity, and movement of the oscillation. We know that the oscillation action of each person is different. Even the same person, it is difficult to guarantee a uniform movement. Therefore, the action of solution extraction is not quantitative and cannot be repeated.
When applying solid phase extraction, it is easier to maintain the uniformity and stability of the column and the elution rate. Therefore, the extraction process of solid phase extraction can be repeated and quantified.
(2) On-site treatment.
The analysis of organic matter in water has a bottleneck that has plagued us for a long time. That is, organic matter can remain relatively stable in environments such as ponds and reservoirs, but once it enters the small environment of the sampling bottle, it will change rapidly. Therefore, many water organic analysis methods require immediate analysis, which cannot exceed 4 hours at most. The general situation is that the time from taking water back to the laboratory is far more than 4 hours, the sample has changed, and the reliability of the analysis results can be imagined.
If the solid phase extraction technology is introduced, due to its simple equipment, small size, and easy to carry, it can be done while sampling at the site while pre-processing. The sampler brought back to the laboratory the solid phase extraction column, not the water sample. This will ensure that we are dealing with truly stable water samples.
In terms of practical application, there is still considerable work to be done to replace the traditional liquid-liquid extraction with solid-phase extraction technology in the detection of water. At present, it cannot be completely replaced, but its development prospects are worthy of optimism.
(3) Reduction in consumption of organic reagents.
When processing water samples, if solid phase extraction is used, only organic solvents need to be used during elution, and the amount is more than ten times less than traditional liquid-liquid extraction. It has positive significance for the personal protection and environmental protection of the experimenter.
(2) Extraction of pharmaceutical ingredients from bulk biological materials
This is a more successful example of solid phase extraction in practical applications, mainly referring to the pre-treatment work when testing blood and urine samples in hospitals. Because the adsorption of drug components is the advantage of solid phase extraction, plus the single sample Fixed, after determining the method, it is very suitable for large-scale batch purification operations.
(3) Immunoaffinity solid phase extraction.
The ideal state of extraction is specific enrichment or specific repulsion, but whether it is solution extraction or solid phase extraction, they are basically similar and miscible. A "level of extraction."
Adding immunoaffinity technology on the basis of solid phase extraction column can use its biological specificity selective adsorption, which can achieve near theoretical perfect extraction.
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