Activation and Sample Loading of SPE Cartridge
Activation of Solid Phase Extraction Cartridge
The purpose of activation is to create an environment compatible with the sample solvent and to remove all impurities in the SPE cartridge. Two solvents are usually needed to accomplish the above task, one solvent (initial solvent) is used to purify the stationary phase, the other solvent (final solvent) is used to establish a suitable stationary phase environment for the sample analyte to be properly retained. and the amount of each activated solvent is about 1-2 ml/100mg stationary phase. The final solvent should not be stronger than the sample solvent.
If too strong a solvent is used, the recovery rate will be reduced. There is usually no problem using a solvent weaker than the sample solution. it is worth noting that the stationary phase can not be drained during and at the end of the activation process, because this will lead to cracks in the packed bed, resulting in low recovery and reproducibility, and the sample is not purified as it should be. If dry cracking occurs in the activation step, all activation steps must be repeated.
Sample-loading of Solid Phase Extraction Cartridge
The upper sample step refers to the process of adding the sample to the SPE cartridge and forcing the sample solvent to pass through the stationary phase when the analyte and the batch sample interferences are retained on the stationary phase. The key market of this step is to ensure that the target sample is adsorbed on the stationary phase, so if the manual sample is taken, the sample speed should be slowed down as much as possible to avoid leakage.
For retention analysis The solvent of the dissolved sample is weak. If the solvent is too strong, the analyte will not be retained, and the recovery rate will be very low, which is called leakage (breakthrough).
As far as possible, the use of weak sample solvents can make the solute strong retention or narrow band. As long as there is no leakage, large volume samples are allowed (0.5-1 L). Sometimes solid samples are extracted with a strong solvent, such an extraction solution can not be directly sampled.
So the extract should be diluted with a weak solvent to obtain a suitable total solvent strength. such as a soil sample, extracted with 50% methanol to obtain 2 ml of extraction solution, diluted with 8 ml of water to obtain 10% methanol solution, so that the reverse phase solid phase extraction column can be directly mounted without leakage problem.