Contaminants and Residues
Liquid- Liquid Extraction (aqueous samples)
A measured volume of sample at a specific pH and solvent are added to a separatory funnel, the funnel is shaken to mix the liquids with venting intervals to release the pressure buildup. Depending on the method, this procedure can be repeated several times with new solvent addition. In the end, the solvent aliquots are collected, cleaned up (if required), dried and concentrated. Depending on the determinative method used, they may also be transferred to a different solvent for injection. There are also continuous liquid-liquid extractor set up that allow the sample to be extracted over longer periods of time without human intervention. Essentially, the glassware apparatus allows for a solvent to be heated and condensed back down through the sample continuously for a set period of time. Again, drying, clean up, and concentration can be performed as required.
Solid Phase Extraction (aqueous samples)
An aqueous sample is passed through a disk or cartridge containing a solid sorbent specific to the analytes of interest, the sorbent is eluted with a specific solvent to allow for the analytes to be transferred from the sorbent to the solvent. This can be done manually or automatically with commercially available systems. The extract is again collected, filtered, cleaned and concentrated as required.
Soxhlet Extraction (solids)
A dried sample is placed in a thimble or between two glass wool plugs and placed into the Soxhlet extractor. The extractor consists of a round bottom flask containing solvent, connected to piece of glassware with a solvent bypass arm and a reflux arm, connected to a condenser. The round bottom flask rests in a heating mantle that is temperature controlled. The heated solvent bypasses the sample is condensed and dripped back down through the sample, via the reflux arm, for a defined period of time. Once the extract is collected, it can be dried, cleaned up and concentrated if required.
Sonication Extraction (solids)
A dried sample is extracted by using a solvent and a commercially available sonicator with pulsed intervals. The Inert sonicator horn is placed in the solvent and above the sample for varied operation times. Typically the extraction is repeated with fresh solvent. Once complete, the extracts are filtered and again cleaned up and concentrated as required.
Pressurized Liquid Extraction (solids)
A dried sample is ground to a 100-200 mesh powder (150 to 75um) and placed into a solvent extraction cell. The cell is heated to specific set point and pressurized with an appropriate solvent for a predetermined amount of time. The extract is allowed to cool and can then be cleaned up, and concentrated as required.
Supercritical Fluid Extraction (solids)
A known amount of sample is transferred to an extraction vessel and is extracted with supercritical carbon dioxide at 340 atm, 80c, and a gas flow rate between 500-1000 mL/min. After depressurization, the extract can be collected in a solvent for the determinative method, or on a solid sorbent which is rinsed with an appropriate solvent for the determinative method.
As the name implies, the sample is extracted using microwave energy which will cause a rise in temperature and pressure to perform the solvent based extraction. Once the extract is collected it can then be cleaned and concentrated as required.
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Volatile Organic Compounds (VOC)
Total Organic Carbon (TOC)
Semi-Volatile Organic Compounds (SVOC)
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