Commonly Used Solid Phase Extraction Procedure

SPE is a kind of sample production technology which is more and more useful in which many problems related to liquid and liquid extraction could be avoided, such as the incomplete separation, non-quantitative recycle, the use of expensive and fragile glass vessels, massive organic solvent and so on.

SPE is more efficient than liquid extraction, which is easy to execute, automatable quantitative extraction and time-saving on the use of solvent and laboratory. SPE is commonly applied in the preparation of the liquid sample, and the extraction of the semi-volatile or non-volatile analyte, which is the excellent sample extraction, concentration, and cleaning. It has a wide range of chemistries, adsorbents, and sizes so that the choices for APPs and examples could be much more.

SPE is a kind of digital chromatography which aims to extract, separate and absorb from the solvent sample. It extends the longevity of the chromatography system, which improves the qualitative and quantitative analysis so that the requirements of instrumental analysis would largely decrease. Generally, SPE has three key purposes which are analyte concentration, disturbed compounds removal and the change from analyte environment to a more simple matrix respectively.

1. Reversed phase packing – This type of packing includes the most widely used reversed-phase packing C18. In addition, C8, C2 cyclohexyl and phenyl bonded phases are also available and offer different selectivity. Generally, non-polar to moderately polar compounds remain on the reverse phase packing in a polar matrix. Such fillers require equilibrium adjustment with an organic solvent and subsequent aqueous solution prior to use. The elution of moderately polar compounds is usually methanol, and the elution of non-polar compounds requires less polar solvents.

Reverse SPE cartridge operation steps

A. Adjustment First rinses the packing with 3-5ml methanol. Rinse the packing with 3-5 ml of water or buffer. Do not allow the packing to drain before loading.
B. Loading The sample is applied to the top of the packed bed. The sample was pushed or pumped through the packing at a rate of 1-5 mL/min. If the desired sample is not retained, collect the sample for analysis.
C. Flush If the desired sample is retained, use a polar solvent to flush out the weakly retained interference.
D. Elution The desired compound was eluted using 1-2 mL of a non-polar solvent. Samples were collected for analysis.

Such as Reversed Phase C18 SPE Cartridge, Reversed Phase C8 SPE Cartridge.

2. Normal phase fillers – silica gel, Florisil, amino, cyano, diol, and alumina are available. The normal phase filler retains polar compounds that are soluble in the non-polar medium. The equilibrium is adjusted using a non-polar solvent and eluted with a more polar solvent. The basic compounds are retained on the silica gel filler, and very polar compounds such as carbohydrates are irreversibly retained in the silica filler. In this case, a diol or amino bonded phase is a better choice.

Normal phase SPE cartridge operation steps

A. Adjustment Flush the packing with 3-5mL of non-polar solvent.
B. Loading The sample is applied to the top of the packed bed. The sample was pushed or pumped through the packing at a rate of 1-5 mL/min. If the desired sample is not retained, collect the sample for analysis.
C. Flush If the desired sample is retained, use a non-polar solvent to flush out the weakly retained interference.
D. Elution The desired compound was eluted using 1-2 mL of a polar solvent. Samples were collected for analysis.

Such as Normal Phase Cyanopropyl (CN) SPE Cartridges, Normal Phase Silica SPE Cartridge.

3. Ion exchange packing – both strong anion (SAX) and strong cation (SCX) exchange groups are available. The anion/cation exchange in the sample with the anion/cation on the resin respectively causes the anion/cation to remain on the relevant resin. The elution uses a high ionic strength buffer (0.1M – 0.5M) or the compound in the sample is no longer charged by changing the pH of the eluent. The backbone of these resins is typically a styrene-divinylbenzene copolymer, and an increase in the organic solvent content of the sample will result in a decrease in exchange capacity.

Ion exchange SPE cartridge operation steps

A. Adjustment Wash the packing with 5mL deionized water or low ionic strength buffer solution (0.001M-0.01M).
B. Loading The sample is applied to the top of the packed bed. The sample was pushed or pumped through the packing at a rate of 1-2 mL/min. If the desired sample is not retained, collect the sample for analysis.
C. Flush If the desired sample is retained, rinse off the weakly retained interference with deionized water or a low ionic strength buffer solution.
D. Elution The desired compound is eluted using 1-5 mL of a high concentration of salt solution (0.1-0.5 M), or the pH of the elution buffer is changed so that the sample compound is no longer ionized. Samples were collected for analysis.

Such as Ion-Exchange PRS SPE Cartridges, Ion-Exchange SCX SPE Cartridge, Ion-Exchange Amino (NH2) SPE Cartridge.