The use of solid phase extraction (SPE) has been developed and improved over the years since its introduction into organic extraction and has been included in US EPA Method 1664 since its start in the 1990’s. In addition, the automation of the method is facilitated by the use of SPE. Automation can reduce the variability that comes from human intervention and error. Table 1 compares the results of SPE with automation (SPE-DEX® 3000 Extractor or SPE-DEX 4790 and SpeedVap® IV, Horizon Technology) to conventional liquid-liquid extraction (LLE) without automation for simple distilled water samples spiked with standards, an initial demonstration of capability. It can be seen that the recoveries are better and the standard deviations more tightly controlled using the automated process for hexane extractable material (HEM) and silica gel treated HEM (SGT-HEM).
|Effluent Replicate||LLE Recovery (%)||SPE Recovery (47-mm disks) (%)|
Comparing results with the requirements in method 1664B, it can be seen that the recoveries using SPE are well within the limits of 83-101% for HEM and 83-116% for SGT-HEM. The precision requirements are standard deviation of 11 for HEM and 28 for SGT-HEM. In both cases the standard deviation was much better than the criteria.
Additional benefits of using the SPE-DEX extractor are that it uses less solvent than LLE, it is an automated procedure, and sample process times are more rapid relative to LLE. In this case, SPE methods average 50 minutes per sample versus 2.5 hours for the LLE methods on a collected treatment plant sample. Since labor costs are often the most expensive part of an analysis this can significantly reduce the labor required and improve turnaround time.
The SpeedVap® IV is a newly updated, CE- marked evaporator that provides optimal evaporation for oil & grease extracted from water or soil or food fat extracts. It is decoupled from the extraction process to provide additional flexibility. Samples will often evaporate differently and this allows them to be easily removed for observation when approaching dryness.
Please contact Horizon Technology for more information on modern oil and grease analysis.
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