Supercritical fluid extraction method development

Roston DA, Sun JJ. Supercritical fluid extraction method development for extraction of an experimental HIV protease inhibitor drug from animal feed. J Pharm Biomed Anal 1997 15 461-468. 

Scott KS, Oliver JS. Development of a supercritical fluid extraction method for the determination of temazapam in whole blood. J Anal Toxicol 1997 21 297-300. 

Castells, P., Santos, F. J., and Galceran, M. T., Development of a sequential supercritical fluid extraction method for the analysis of nitrated and oxygenated derivatives of polycyclic aromatic hydrocarhons in urhan aerosols, J. Chromatogr. A, 1010, 141-151, 2003. 

This paper describes various analytical supercritical fluid extraction methodologies developed in the authors laboratory and summarizes selected investigations conducted to evaluate the applicability and efficiency of these methods for a range of applications. Described methodologies include off-line... 

Lopez-Avila et al. [86] have considered validation of analytical supercritical fluid extraction methods. When developing an SEE method, various critical factors need to be considered (i) solubility of the analyte in the supercritical fluid (SF) (ii) diffusion of the analyte from the solid matrix into the bulk fluid or displacement of the analyte by the SF that diffused into the matrix and (Hi) the matrix itself, which can be very adsorptive. Poor SEE recoveries may be attributed to matrix effects (e.g., not all of the analyte may be extractable), to inefficient retention of the analyte in the collection solvent or on the sorbent trap, or to inefficient desorption from the sorbent trap. Once an SEE procedure has been developed and tested with real matrices, the next step... 

The concern by consumers about cholesterol has stimulated the development of methods for its removal. Three principal approaches are in the pilot-plant stages use of enzymes, supercritical fluid extraction, and steam distillation. Using known techniques, it is not possible to remove all cholesterol from milk. Therefore, FDA guidelines identify cholesterol-free foods as containing less than 2 mg cholesterol per serving, and low cholesterol foods as containing from 2 to 20 mg (37). 

The development of methods of analysis of tria2ines and thek hydroxy metabohtes in humic soil samples with combined chromatographic and ms techniques has been described (78). A two-way approach was used for separating interfering humic substances and for performing stmctural elucidation of the herbicide traces. Humic samples were extracted by supercritical fluid extraction and analy2ed by both hplc/particle beam ms and a new ms/ms method. The new ms /ms unit was of the tandem sector field-time-of-flight/ms type. 

Although on-line sample preparation cannot be regarded as being traditional multidimensional chromatography, the principles of the latter have been employed in the development of many on-line sample preparation techniques, including supercritical fluid extraction (SFE)-GC, SPME, thermal desorption and other on-line extraction methods. As with multidimensional chromatography, the principle is to obtain a portion of the required selectivity by using an additional separation device prior to the main analytical column. 

The coupling of supercritical fluid extraction (SEE) with gas chromatography (SEE-GC) provides an excellent example of the application of multidimensional chromatography principles to a sample preparation method. In SEE, the analytical matrix is packed into an extraction vessel and a supercritical fluid, usually carbon dioxide, is passed through it. The analyte matrix may be viewed as the stationary phase, while the supercritical fluid can be viewed as the mobile phase. In order to obtain an effective extraction, the solubility of the analyte in the supercritical fluid mobile phase must be considered, along with its affinity to the matrix stationary phase. The effluent from the extraction is then collected and transferred to a gas chromatograph. In his comprehensive text, Taylor provides an excellent description of the principles and applications of SEE (44), while Pawliszyn presents a description of the supercritical fluid as the mobile phase in his development of a kinetic model for the extraction process (45). 

Acrylonitrile metabolites have been measured in blood and urine, but, except for measurement of thiocyanate, these methods have not been developed for routine monitoring of exposed humans. Supercritical fluid extraction/chromatography and immunoassay analysis are two areas of intense current activity from which substantial advances in the determination of acrylonitrile and its metabolites in biological samples can be anticipated. The two techniques are complementary because supercritical fluid extraction is especially promising for the removal of analytes from sample material and immunoassay is very analyte-selective and sensitive (Vanderlaan et al. 1988). 

On-going studies to improve analytical methods for hexachloroethane and related compounds include the EPA "Master Analytical Scheme" being developed for organic compounds in water (Michael et al. 1988) and the research in supercritical fluid extraction (Lopez-Avila et al. 1991 Wieboldt et al. 1988). Research continues on improving extraction, concentration, and elution techniques, and detection devices (Eichelberger et al. 

On-line supercritical fluid extraction/GC methods combine the ability of liquid solvent extraction to extract efficiently a broad range of analytes with the ability of gas-phase extraction methods to rapidly and efficiently transfer the extracted analytes to the gas chromatograph. The characteristics of supercritical fluids make them ideal for the development of on-line sample extraction/gas chromatographic (SFE-GQ techniques. SFE has the ability to extract many analytes from a variety of matrices with recoveries that rival liquid solvent extraction, but with much shorter extraction times. Additionally, since most supercritical fluids are converted to the gas phase upon depressurization to ambient conditions, SFE has the potential to introduce extracted analytes to the GC in the gas phase. As shown in Fig. 13.8, the required instrumentation to perform direct coupling SFE-GC includes suitable transfer lines and a conventional gas chromatograph [162,163]. 

The objective of this panel was to develop protocols that could be used today with a minimum of methods development. The panel members recognized that promising research is currently underway to develop new techniques for sample preparation. However, procedures such as supercritical fluid extractions or preparative ion chromatographic separation of polar fractions are still considered to be in a research phase and not yet ready for general laboratory application. The procedures presented will be periodically reviewed and updated as the state of available technology improves. 

Niobium and titanium incorporation in a molecular sieve can be achieved either by hydrothermal synthesis (direct synthesis) or by post-synthesis modification (secondary synthesis). The grafting method has shown promise for developing active oxidation catalyst in a simple and convenient way. Recently, the grafting of metallocene complexes onto mesoporous silica has been reported as alternate route to the synthesis of an active epoxidation catalyst [21]. Further the control of active sites, the specific removal of organic material (template or surfactant) occluded within mesoporous molecular sieves during synthesis can also be important and useful to develop an active epoxidation catalyst. Thermal method is quite often used to eliminate organic species from porous materials. However, several techniques such as supercritical fluid extraction (SFE) and plasma [22], ozone treatment [23], ion exchange [24-26] are also reported. 

Supercritical fluid extraction (SFE) is a new and promising technique for sample preparation. Because SFE is so new, and there are so many control parameters available to the scientist, it can be difficult to know how to proceed when developing an SFE method. This paper discusses two samples and describes a systematic approach for evaluating SFE extraction parameters for methods development. The effects of modifiers are investigated. 

Sample preparation is a key step in all environmental analyses. Two major areas of development in this area have been solid phase extraction and supercritical fluid extraction. Both techniques have made the extraction of pollutants from aqueous and nonaqueous matrices relatively simple, fast, and less expensive. These processes, along with gel permeable chromatography, provide efficient methods of removing interferences. 

Sato et al. (1999) developed a rapid quantitative method for estimating capsai-cinoids in placentas of Capsicum. This was achieved by employing a direct connection of supercritical fluid extraction and supercritical fluid chromatography. They suggested this method was useful as a rapid (20 min) and safe screening test for the pungency of C. annuum fruits. 

In our institute a novel method is under development to integrate mediated electrooxidation and supercritical fluid extraction for synthesis of organic compounds. Figure 2 shows the principle of this combination... 

Supercritical fluid extraction has been focused for the deterpenation of citrus oil as a lower temperature process [1-6]. Coppella and Barton [4], Stahl and Gerard [5], and Temelli et al. [6] studied the extraction process for the removal of terpenes in citrus oil. However, the simple extraction process does not give sufficient selectivity and yield A continuous countercurrent extraction process is one of the method to achieve higher selectivity between terpenes and oxygenated compounds. Perre et al. [7] and Sato et al. [8] succesfully developed the continuous extraction process. 

Supercritical fluid extraction has now found a lot of applications in different fields (polymers, aromas and essential oils, fats, natural products, soil decontamination...) and several production units are operated in agroalimentary (coffee, hop...) and pharmaceutical industries. In order to estimate the economical interest of these applications, technical and economical extrapolation methods have been developed. These methods are dependent of the nature of the extraction and are based on experimental results obtained on pilot plant units. We describe here a general extrapolation procedure, and a case study is presented to illustrate an economical estimation of a supercritical fluid extraction. 

Preparing the sample is a key step in all biological analyses, and hair analysis is no exception to this rule. Over the last ten years, there has been an ever increasing interest in the use of supercritical fluid extraction (SFE) as an alternative to traditional methods of preparing samples. The driving force behind this development is, without doubt, the need for a simple, rapid, automated, and selective method which should also be environmentally friendly. In this context, the use of supercritical fluids fulfills these conditions, due to their unique physicochemical properties. The following is a list of advantages ... 

Morrison, J.F., MacCrehan, W.A., Selavka, C.M., Evaluation of supercritical fluid extraction for the selective recovery of drugs of abuse from hair, 2nd International Meeting on Clinical and Forensic Aspects of Hair Analysis, National Institute on Drug Abuse. Special Publication, submitted, 1995. Welch, M.J., Sniegoski, L.T., Allgood, C.C., Habram M., Hair analysis for drugs of abuse evaluation of analytical methods, environmental issues, and development of reference materials, /. Anal. Toxicol, 17(6), 389-398, 1993. 

Roston, D.A. Sun, J.J. Collins, P.W. Perkins, W.E. Tremont, S.J. Supercritical fluid extraction-liquid chromatography method development for a polymeric controlled-release drug formulation. J. Pharm. Biomed. Anal. 1995, 13 (12), 1513-1520. 

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