Solid phase extraction (SPE) is one of the most used techniques in sample preparation. It is replacing the conventional time-consuming liquid-liquid extraction (LLE) method. The process of SPE is a miniature version of liquid column chromatography. SPE, utilizing the same type of stationary phases as used in liquid chromatography columns, are practiced in different mechanisms including normal phase, reversed phase, ion-exchange, affinity chromatography and mixed-mode in the fields of agricultural and food, bio-analytical, environmental, and forensic applications.
The Meizheng family of solid-phase extraction (SPE) products are designed to simplify and improve your sample preparation by combining the right sorbent chemistry, device format and methodology.
We provide PuriTestTM and PloyplusTM these series included bonded silica series sorbent, no-silica absorption sorbent and polymer sorbent which are designed to meet all your sample preparation needs.
Bonded Silica SPE: PuriTestTM
Silica based SPE series are made of high quality and low metal contents silica particles. Using the special surface modification methodology, the activity of silica surface is reduced, which will reduce the tailing of basic compounds and ensure high recovery and reproducibility. Such as C18, C8, NH2, and PSA etc.
No-silica Absorption SPE: PuriTestTM
Florisil, GCB, Alumina (Neutral, Acid, Basic).
They are commonly used to remove polar interference from non-polar samples. They are widely used in sample preparation for environmental and food analyses.
Polymer SPE: PloyplusTM
HLB, MAX, MCX, WAX, WCX and PS
Based on polystyrene/divinylbenzene, and each phase has different functionality and unique selectivity. They are highly recommended for the extraction of a wide
range of compounds in pharmaceutical, agricultural, food, and environmental industries.
III. General SPE process
Step 1: Conditioning
C18, C18-N, C8, HLB series, PS and Ph: condition cartridge with proper volume of acetonitrile or methanol, followed by proper volume of water or aqueous solution of similar pH and salt concentration to sample solution.
Silica, CN, Diol, NH2 and Alumina series; condition cartridge with proper volume of sample solvent. Ion-exchange phase
SAX, SCX, MAX, MCX, WAX, WCX, NH2, PRS
If the sample was dissolved in non-polar solvent such as hexane or methylene chloride, condition the cartridge with proper volume of sample solvent.
For aqueous sample solution, proper volume of methanol followed by proper volume of water is suggested. Additional solution could be applied to adjust pH value, organic solvent content and salt concentration according to the property of sample solution.
It is crucial to ensure cartridges NOT to be dried during conditioning or sample loading (especially for C18, C18- N and C8 cartridges). Re-condition the cartridge if it is dried over 5 minutes before sample loading.
Step 2: Loading Samples
(Reversed Phase, Normal Phase, Ion-exchange phase)
- To ensure proper retention of analytes or precipitation of unwanted compounds, pH, salt concentrationand
the content of organic solvent should be optimized. Filtration and centrifuging of sample may be required to avoid frit-clogging.
- Vacuum or positive pressure can be applied when necessary. Flow rate can affect retention of target compounds. In general, speed should not exceed 5mL/min.
Step 3: Washing
(Reversed Phase, Normal Phase, Ion-exchange phase)
- If compounds of interest are retained, use sample solution to wash the cartridge to get rid ofunwanted,
un-retained materials from cartridge. The volume of washing solution would be equal to the volume of one empty cartridge. To remove unwanted material, washing solution may be stronger than sample matrix but weaker than eluant in polarity. A typical solution may contain less organic solvent or less inorganic salt than final eluant.
- If interfering compounds, but not the target compounds are retained in the cartridge, adequate sample solvent should be used to ensure the recovery of the targets after sample loading. In this case, washing and elution are seen as the same step, all the solution out from SPE cartridge should be collected.
Depending on the size of cartridge, the amount of solvent used should be as small as possible to elute the compounds of interest. Elution speed impacts sample recovery. Generally, flow rate of elution should not exceed 5mL/min.
Cartridges stored in their original sealed pouch remain stable for long periods. Once opened, special care must be taken to ensure that the SPE cartridges are not exposed to the laboratory environment for long periods. The highly active sorbents will readily accumulate background contaminants from the environment and will affect the quality of the device. Meizheng recommends that you open and use only those cartridges that will be needed. If this is not possible, store the exposed cartridges in clean contaminant free container such as a desiccator.
Dispose of used cartridges safely in accordance with applicable government or local regulations.