Reduction of contamination levels in on-line supercritical fluid extraction systems

Supercritical Fluid Chromatography and Extraction

“…However, there is some interest in exploring the use of organic solventmodified CO2, alternative fluids, or chemical derivatization, particularly for the extraction of increasingly polar compounds. Wallace et al reported a method to reduce the levels of contaminants in pure CO2 (365). They carefully heated the head of their syringe pump to extractively remove contaminants due to the seals and valves of the SFE system.…”

Optimization of SFE for the Determination of Chlorinated Hydrocarbons at the Part-per-Trillion Level

“…The active carbon powder was cleaned in this way for ∼12 h. The cell was then connected to the SF transfer line, between the syringe pump and the first valve, so that the pressurized extraction fluid flowed through the adsorption device. Because the pump of a SF system might be a contamination source, this position of the adsorption device ensures the best cleaning effect. The pathway of the SF is shown schematically in Figure .…”

“…Several researchers reported that the above-mentioned analytical techniques for the determination of environmentally relevant compounds are not applicable because of impurities inherent in the sample preparation process. , Nielen et al evaluated several grades of CO 2 and tried to purify the gas by means of sorbent resins (Tenaxc GC) and a molecular sieve (5 Å). They concluded that the purity of carbon dioxide is the limiting factor of SFE (on-line) because “impurities present in supercritical carbon dioxide make trace analysis, especially when applied to environmental studies, at the part-per-billion level problematic.” Later, Wallace and co-workers found the source of the impurities mainly in the SFE system itself, because the seals of pumps and valves in high-pressure systems consist of high-density polymers which contain byproducts and other contaminants .…”

Computer-Controlled Low-Volume Air Sampler for the Measurement of Semivolatile Organic Compounds

“…The factory-installed graphite-filled Teflon piston and wiper seals of the pump were replaced with ultrahigh molecular weight polyethylene seals (ISCO, Lincoln, NE). Prior to the start of this experiment, the pump was dynamically extracted with supercritical C02 as described previously (18).…”