Solid phase extraction column or solid-phase extraction cartridges, SPE cartridges for short is a sample pretreatment device developed from a chromatography column for extraction, separation, and concentration.
It is a more popular and mature sample pretreatment method in recent years, including a solid phase (solid adsorbent with certain functional groups) and a liquid phase (sample and solvent). Because the extraction adsorbent has different functional groups, it can adsorb and retain specific compounds on the extraction column. The filler is a polymer resin formed by introducing anion exchange groups into a polymer with both hydrophilic and hydrophobic groups.
Concept and Basic Principle of SPE
Solid phase extraction (SPE) is a sample pretreatment technique developed in the mid-1980s. Developed by the combination of liquid-solid extraction and liquid chromatography.
Solid phase extraction cartridge is using solid adsorbent adsorption target compounds in liquid samples, matrix and interference with the sample of compound separation, next reoccupy eluent elution or heat desorption, reach the purpose of separation and enrichment of the target compounds (namely sample separation, purification, and concentration), the purpose is to reduce the sample matrix interference, improve the detection sensitivity, applied to all kinds of food safety testing, agricultural residue monitoring, medicine, health, environmental protection, commodity inspection, tap water, and chemical production laboratory.
Basic principles and methods of solid phase extraction
Solid phase extraction (SPE) is a physical extraction process including liquid phase and solid phase, which is based on the theory of liquid-solid chromatography and adopts the methods of selective adsorption and elution to concentrate, separate, and purify samples. It can also be approximated as a simple chromatographic process.
Solid phase extraction(SPE) is a separation principle by liquid chromatography using selective adsorption and elution. The more commonly used method is to make the liquid sample through an adsorbent, retain the measured substance, and then select the appropriate strength of the solvent to wash away the impurities, and then eluate the measured substance with a small amount of good solvent, so as to achieve the purpose of rapid separation and purification and concentration.
Can also selectively adsorb interference impurities, and let the measured substances out, Or adsorb both the impurity and the tested substance, and then elute the tested substance selectively with an appropriate solvent.
Advantages of SPE:
SPE has unparalleled advantages: no special equipment and materials. Simple operation, no special device. It is a method of sample enrichment and purification to improve detection sensitivity. Faster than liquid-liquid extraction, save solvent. Automatic batch processing, good reproducibility.
SPE devise and basic operation Steps
1. SPE cartridge
About SPE cartridge: The common SPE cartridge is divided into three parts: medical polypropylene cartridge tube, porous polypropylene sieve plate (20 m), and packing (mostly 40-60 m, 80-100 m).
Common specification: 100 mg/ml, 1200 mg/ml, 500 mg/ml, 1 g / 6 ml, etc. Take 100mg/1 ml as an example, in which 100mg is the mass of the filler and 1 ml is the volume of the empty cartridge tube.
The vacuum SPE device consists of a glass cylinder, vacuum pressure gauge, vacuum pump, vacuum buffer bottle, collecting tube holder, small cartridge connecting head, large volume sampler, and 12 or 24 positions anti-cross contamination device. Standard valve, precise control of flow rate. The height of the test-tube frame can be adjusted to meet the needs of different volumes. Pressure gauge vent valve side design, easy to use. The design is compact, durable, and cost-effective.
3. Basic operation steps
Here are the operation steps of the solid phase extraction cartridges:
The filler retains the target compound. The operation is slightly different depending on the packing retention mechanism (packing retention target compound or retention impurity). SPE operations typically involve four steps:
(1) Activation – Removing impurities from the cartridge and creating a solvent environment. (2) Sample loading – The sample is dissolved in a solvent, transferred into the cartridge, and the components are retained on the column. (3) Leaching – Degree of removal of interferences. (4) Elution – The substance is eluted and collected in a small volume of solvent. The filler retains impurities.
4. SPE generally operates in three steps
The filler retains impurities. The operation generally has three steps:
(1) Activation – Removing impurities from the cartridge and creating a solvent environment. (2) Sample loading – The sample is transferred into the cartridge, where most of the target compounds flow out with the sample base solution and the impurities are retained on the cartridge. So the steps start to collect. (3) Elution – The constituents are eluted and collected in a small volume of solvent. Combined collection fluid.
This kind of situation is mostly used to remove pigment in food or pesticide residue analysis.
The simple solid-phase extraction can be done manually, that is, a syringe is connected to the upper end of the solid-phase extraction column, and the liquid in the extraction column is squeezed out of the extraction column by squeezing the syringe. In addition, a positive or negative pressure solid-phase extraction device can also be used to perform solid-phase extraction operations on batch samples.
With the development of science and technology and the increase in the number of samples, more and more analytical laboratories are beginning to use automatic solid-phase extraction instruments, especially multi-channel solid-phase extraction instruments to process batches of samples.
SPE, many different kinds of SPE small cartridges, and specific experimental work must according to the analysis object, testing methods, and laboratory conditions reasonably choose appropriate packing and reasonable specifications of SPE solid phase extraction cartridge.
The extraction capacity of the SPE cartridge to the analyzed object, the volume of the sample solution, the final volume of eluted solution, and the total amount of measured and interferences in the sample solution should be considered. Generally, the total mass of the measured and interferences adsorbed by the adsorbent in the cartridge should not exceed 5% of the total mass of the adsorbent. Generally, the volume of eluent should be 2-5 times the volume of the extraction cartridge.