Overview: Sample preparation is arguably the most critical step within the analytical process. Studies have reported that sample preparation can represent up to 60 % of a laboratory technicians timetable and also forms one of the principal sources of error. Sample preparation undoubtedly has a fundamental impact on the subsequent quality of analysis affecting a wide range of analytical parameters. A variety of proven techniques, such as filtration, dialysis, liquid/liquid extraction and Solid Phase Extraction (SPE), are routinely adopted in today's analytical laboratories to resolve the vast array of sample preparation demands. SPE has established itself as one of the most popular and flexible tools within the analytical laboratory; providing effective, efficient sample concentration and purification prior to HPLC, LC/MS, GC or GC/MS and adaptation to automated techniques such as combinatory chemistry. The resultant SPE product range provides unparalleled performances and satisfies the clients demand for Recovery, Reliability and Reproducibility. SPE methods consist of several steps:
- Conditioning: Condition the absorbent with an organic solvent such as MeOH or a solvent mix to eliminate contaminants and activate the media. The absorbent should not be allowed to dry before adding the sample.
- Sample introduction: Into the top part of the absorbent bed and either push or pull the sample through the bed at a low flow rate.
- Wash: Rinse to remove all interfering agents with a solvent or suitable solvent mixture (0 % affinity for the compound of interest 100 % for interfering agent. A number of washing phases with different solvents may be required. This being usually dependent upon the nature of interfering substances. (Only necessary if your compounds of interest has been absorbed onto the bed).
- Elution: The absorbed sample must be eluted with a solvent or a solvent mixture that has 100 % affinity for the sample and 0 affinities for any potential interfering agents.
- Dry: (If necessary), elute with anhydrous sodium sulfate to remove all traces of water
- Concentration: (If necessary), concentrate the compound of interest by an evaporating step and retake it with the analysis mobile phase before injection for analysis.