A two-step supercritical fluid extraction of polycyclic aromatic hydrocarbons from roadside soil samples

A two-step procedure for the supercritical fluid extraction (SFE) of polycyclic aromatic hydrocarbons from soil samples was developed. The procedure consists of a static supercritical fluid treatment in a closed extraction cell at a high temperature (T=250 or 340degreesC for 20 min) and an SFE with a solvent trapping. During the static phase, the sample is exposed to a supercritical organic solvent (methanol, toluene, dichloromethane, ACN, acetone, and hexane). The solvent penetrates particles of the matrix to substitute strongly bonded molecules and dissolves the analytes in the supercritical phase. At ambient temperature, supercritical fluids became liquid and lost their solvation abilities. Most of the analytes condense on the surface of the particles or on the extraction cell walls without forming strong bonds or penetrating deep into the matrix. Thus, the pretreatment liberates the analytes and they behave similar to those in freshly spiked samples. The common SFE with toluene-modified CO2 as an extraction fluid follows the static phase. With the use of the most suitable extraction phases (toluene, ACN), the extraction efficiency of the combined procedure is much higher (approximately100%). The results of the combined procedure are compared to the SFE procedure of the same untreated sample (difference less than 5%) and to the Soxhlet extraction. The extracts were analyzed using a GC with the flame ionization detection.

Utilization of fat retainers in supercritical fluid extraction for the selective extraction of polychlorinated biphenyls from a model fat sample

Two common fat retainers used in supercritical fluid extraction--basic alumina and the silica based adsorbent Florisil--were investigated using lard fat as model material. With a fat retainer in the extraction cell it was possible to obtain fat-free time windows. Activation by heating did not influence the length of the time windows, while deactivation of the retainers with 10% water (w/w) drastically decreased the fat retaining capabilities. The influence of modifier addition was also investigated. Finally, a method was developed, where basic alumina was utilized to selectively extract polychlorinated biphenyls (PCBs) from a model fat sample, containing PCBs, triglycerides and phospholipids. The PCBs could be quantitatively extracted in a totally fat-free time window.

Instrumentation of biotechnological processes

Modern bioprocesses are monitored by on-line sensing devices mounted either in situ or externally. In addition to sensor probes, more and more analytical subsystems are being exploited to monitor the state of a bioprocess on-line and in real time. Some of these subsystems deliver signals that are useful for documentation only, other, less delayed systems generate signals useful for closed loop process control. Various conventional and non-conventional monitoring instruments are evaluated; their usefulness, benefits and associated pitfalls are discussed.

Development of a supercritical fluid extraction method for determination of lipid classes and total fat in meats and its comparison with conventional methods

A method has been developed for the determination of total fat and lipid classes in meat using supercritical fluid extraction (SFE). The results agreed well with results from the conventional Bligh and Dyer and Schmid, Bondzynski and Ratzlaff extraction methods. SFE has advantages compared to the latter methods of a low consumption of hazardous organic solvents and shorter extraction time. After investigation of several different conditions, the most rapid extraction was achieved by adding 1 ml of cyclohexane to a 0.5-g sample mixed with 1 g Hydromatrix in a 7-ml thimble. The optimized SFE parameters were: 370 bar, 50 degrees C, 8% ethanol modifier, 4 ml/min dynamic flow for 30 min and collection with a tube leading to a vial.

Supercritical fluid extraction of PCBs from human adipose tissue for HRGC/LRMS analysis

Supercritical fluid extraction (SFE) of 36 PCBs from human adipose is presented. Selective extraction of the PCBs is achieved using supercritical CO2 with a density of 0.9 g/ml (281 bar) at 40 degrees C and with AlOx as a fat retainer. Compared to the traditional liquid extraction method followed by further sample clean up, SFE is not only faster (2 hours compared to three days) but also utilises lower amounts of organic solvents (4 ml compared to over 500 ml). The recoveries of 7 added 13C labelled PCBs are 83-106%. The repeatability in the analysis of 36 PCBs in 6 identical samples is excellent, with an average R.S.D. of less than 10%.