Static extraction method

Resins and parts have been extracted with acids, such as nitric, hydrofluoric, and hydrochloric, and ultra-pure water at room or elevated temperatures for a period of a few hours to several days by both static and dynamic methods. A solvent such as/-propanol is usually added to the aqueous phase to improve the wetting of the fluoropolymer surface. Anions and TOC are extracted in ultra-pure water. Most of the available data are based on the static extraction method. 

The effect of different pai ameters such as temperature, pressure, modifier volume, dynamic and static extraction time on the SFE of the plant were investigated. The orthogonal array experimental design method was chosen to determine experimental plan, (5 ). In this design the effect of five parameters and each at five levels were investigated on the extraction efficiency and selectivity [4]. 

SFE can be carried out in three different ways. In a static extraction (no flow-rate), the extraction vessel is pressurised to the desired pressure with the extracting fluid and then simply left for a certain length of time. The main benefit of this method is that the fluid has time to penetrate the matrix. It is most applicable when the analyte has a high affinity for the solvent and a low affinity for the matrix and also when the solubility limit of the analyte in the fluid is much higher than the actual level reached during the extraction [89]. This method was popular in early SFE experiments but has declined in favour of dynamic SFE. Here, fresh SCF is continuously passed over the sample, extracting soluble compounds and depositing them in a suitable solvent or on a solid trap. The dynamic mode is particularly useful when the concentration of the solute... 

The principles behind MAP liquid-phase and gas-phase extractions are fundamentally similar and rely on the use of microwaves to selectively apply energy to a matrix rather than to the environment surrounding it. MAP gas-phase extractions (MAP-HS) give better sensitivity than the conventional static headspace extraction method. MAP-HS may also be applied in dynamic applications. This allows the application of a prolonged, low-power irradiation, or of a multi-pulse irradiation of the sample, thus providing a means to extract all of the volatile analytes from the matrix [477]. 

The ability of SFE-FTIR to perform a variety of extraction methods is a definite advantage, especially for the study of complex mixtures containing analytes of varying solubility. For analytes which are readily solubilised in C02, direct dynamic and direct static-dynamic SFE-FTIR methods are quite successful. Elimination of the trapping process reduces both analysis time and potential analyte loss arising from... 

Shang et al. [5] used ASE for the extraction of NP and NPEO from estuarine sediments. A sample of 15-25 g was extracted three times using hexane/acetone at 100°C and 103 atm. This was followed by a clean-up step using CN-SPE. A blank sample was extracted between all samples to avoid contamination. Hexane/acetone was also used in the ASE method for alkylphenols and NPEO by Heemken et al. [12]. Extraction conditions for samples of 0.5-1 g were 100°C, 150 atm, with a static extraction step of 15 min, and a rinse step with 20 mL solvent. After a clean-up by HPLC, the analytes were derivatised with heptafluorobutyric acid anhydride for GC analysis. 

A novel pressurised-liquid extraction method was studied (concentration of the solvent, temperature, static time, pressure, extraction steps, particle size, diato-maceous/sample ratio and fiush volume) to carry out sample pretreatment... 

When a continuous flow of 5% methanol modified C02 was used for extraction at 60°C/5000psi, an 85% recovery of atrazine was observed, an increase of 38% over the static modifier method and a recovery very close to that observed with a spiked sample. 

A study compared ASE and SFE to Soxhlet and sonication in the determination of long-chain trialkylamines (TAMs) in marine sediments and primary sewage sludge [89], The recoveries of these compounds by SFE at 50°C and 30 MPa with CO2 (modified dynamically with methanol or statically with triethylamine) were 10 to 77% higher than those by Soxhlet or soni-cation with dichloromethane methanol (2 1). ASE at 150°C and 17 MPa with the same solvent mixture as Soxhlet showed the highest extraction efficiency among the extraction methods evaluated. SFE exhibited the best precision because no cleanup was needed, whereas Soxhlet, sonication, and ASE extracts required an alumina column cleanup prior to analysis. SFE and ASE used less solvent and reduced the extraction time by a factor of 3 and a factor of 20 compared to sonication and Soxhlet, respectively. 

As shown in Section 7.4, the sample size-to-cell volume ratio is one of the variables to be optimized in every SF extraction method. Its effect depends on the particular matrix-analyte couple and on the extraction mode (static or dynamic) to be used. 

A. Frank Seibert, Ph.D., P.E. Technical Manager, Separations Research Program, The University of Texas at Austin Member, American Institute of Chemical Engineers (Liquid-Liquid ITispersion Fundamentals, Process Fundamentals and Basic Calculation Methods, Hydrodynamics of Column Extractors, Static Extraction Columns, Process Control Considerations, Membrane-Based Processes)... 

Krieger, 1991) and Liquid-Liquid Extraction Equipment, Godfrey and Slater, eds. (Wiley, 1994). The method used by Becker [Chem. Eng. Technol. 26(1), pp. 35-41 (2003)] is discussed in Static Extraction Columns. ... 

Dankers J, Groenenboom M, Scholtis LHA, et al. 1993. High-speed supercritical fluid extraction method for routine measurement of polycyclic aromatic hydrocarbons in environmental soils with dichloromethane as a static modifier. J Chromatogr 641 357-362. 

Supercritical fluid extraction is also a suitable technique for enhancing the quality of essential oils obtained by conventional extraction methods, by means of fractionation and deterpenation. Thus, the separation of citrus oils into different clssses of substances by supercritical CO2 has been widely investigated. Temelli et al. reported a method for the extraction of terpene hydrocarbons from cold-pressed Valencia orange oil with supercritical CO2, using both static and dynamic flow approaches (65). Another article has reported the SFE of terpenes from cold-pressed orange oil in a temperature range from 40°C to 70°C and pressures from 83 to 124 bar (66). The determination and elimination of psoralens from lemon peel oil by SFE has also been conducted (67). The procedure included the increase of CO2 density in successive steps. 

Figure 14 (On previous page) An approach to SFE method development. In Phase 1 the density and composition of the extraction fluid are varied for the extraction step while the packing composition (of a solid trap having a porous packing material) and the reconstitution solvent composition are varied for the reconstitution part of the process. In Phase 2 the extraction and reconstitution temperatures are explored. In Phase 3 the extraction fluid flow rate and dynamic and static extraction times are optimised for the extraction step the reconstitution solvent flow rate and number of reconstitution fractions (or rinses of the sohd trap) are adjusted to minimise reconstitution time. Reprinted with permission from Reference [13] copyright 1993, Hewlett-Packard Company.

The most common extraction techniques for semivolatile and nonvolatile compounds from solid samples that can be coupled on-line with chromatography are liquid-solid extractions enhanced by microwaves, ultrasound sonication or with elevated temperature and pressures, and extraction with supercritical fluid. Elevated temperatures and the associated high mass-transfer rates are often essential when the goal is quantitative and reproducible extraction. In the case of volatile compounds, the sample pretreatment is typically easier, and solvent-free extraction methods, such as head-space extraction and thermal desorption/extraction cmi be applied. In on-line systems, the extraction can be performed in either static or dynamic mode, as long as the extraction system allows the on-line transfer of the extract to the chromatographic system. Most applications utilize dynamic extraction. However, dynamic extraction is advantageous in many respects, since the analytes are removed as soon as they are transferred from the sample to the extractant (solvent, fluid or gas) and the sample is continuously exposed to fresh solvent favouring further transfer of analytes from the sample matrix to the solvent. 

Enrichment techniques described in the literature for organic sulfur compounds include liquid/liquid extraction, static and dynamic gas extraction methods, trapping, solid-phase microextraction (SPME), and solid-phase extraction. 

The headspace technique, a static gas extraction method, is particularly suitable for the enrichment of volatile compounds. It enables the analysis of solid and liquid samples by direct sampling from the gas phase, and can be directly combined with gas chromatography. This principle is based on the distribution of analyte between the matrix and gas phase. It has been used successfully to determine volatile sulfur compounds from various matrices, such as wastewater, body fluids, plants, and animal fatty tissue. 

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