Pressurised solvent extraction

Diffusive sampler Membrane extraction (MESI) Liquid-liquid extraction (LLE) Solid-phase extraction (SPE) SPE-PTV-GC Solid-phase microextraction (SPME) Headspace GC (SHS, DHS) Large-volume injection (LVI) Coupled HPLC-GC Membrane extraction (MESI) Difficult matrix introduction (DMI) Conventional solvent extraction methods 1 Pressurised solvent extraction methods Headspace GC (SHS, DHS) Thermal desorption (TD, DTD) Pyrolysis (Py) Photolysis Photon extraction (LD) Difficult matrix introduction (DMI)... 

PSE Pressurised solvent extraction RLVI Rapid large-volume injection... 

H.Fr. Schroder, Determination of Fluorinated Surfactants and their Metabolites in Sewage Sludge Samples by Liquid Chromatography-Mass Spectrometry and -Tandem Mass Spectrometry after Pressurised Solvent Extraction and Separation on Fluorine Modified RP-Phases, J. Chromatogr. A, in press. 

Marclc, C., Lespes, G., Potln-Gautier, M. Pressurised solvent extraction for organotin speciation in vegetable matrices. Anal. Bioanal. Chem. 382, 1574-1583 (2005)... 

Chee KK, Wong MK, Lee HK (1997) Microwave-assisted solvent extraction of air particulates for the determination of PAHs. Environ Monit Assess 44 391 08 Christensen A, Ostman C, Westerholm R (2005) Ultrasound-assisted extraction and on-line LC-GC-MS for determination of polycyclic aromatic hydrocarbons (PAH) in urban dust and diesel particulate matter. Anal Bioanal Chem 381 1206-1216 Cortazar E, Bartolome L, Delgado A, Etxebarria N, Fernandez LA, Usobiaga A, Zuloaga O (2005) Optimisation of microwave-assisted extraction for the determination of nonylphenols and phfhalate esters in sediment samples and comparison with pressurised solvent extraction. Anal Chim Acta 534 247-254... 

Lenicek J, Sekyra M, Bednarkova K, Benes I, Sipek F (2000) Short term temperature dependent air-surface exchange and atmospheric concentrations of polychlorinated naphthalenes and organochlorine pesticides. Environ Sci Technol 34 393-398 Li K, Landriault M, Fingas M, Llompart M (1998) Pressurised solvent extraction of environmental organic compounds in soils using a supercritical fluid extractor. Analusis 26 365-369... 

Kaufinann B, Christen P (2002) Recent extraction techniques for natural products micro-wave assisted extraction and pressurised solvent extraction. Phytochem Anal 13(2) 105-113... 

In liquid-solid extraction (LSE) the analyte is extracted from the solid by a liquid, which is separated by filtration. Numerous extraction processes, representing various types and levels of energy, have been described steam distillation, simultaneous steam distillation-solvent extraction (SDE), passive hot solvent extraction, forced-flow leaching, (automated) Soxh-let extraction, shake-flask method, mechanically agitated reflux extraction, ultrasound-assisted extraction, y -ray-assisted extraction, microwave-assisted extraction (MAE), microwave-enhanced extraction (Soxwave ), microwave-assisted process (MAP ), gas-phase MAE, enhanced fluidity extraction, hot (subcritical) water extraction, supercritical fluid extraction (SFE), supercritical assisted liquid extraction, pressurised hot water extraction, enhanced solvent extraction (ESE ), solu-tion/precipitation, etc. The most successful systems are described in Sections 3.3.3-3.4.6. Other, less frequently... 

More recently, some novel pressurised procedures for extraction of additives from polymers have been developed (Table 3.3). The principal objectives of all these techniques, such as SEE [89], MAE [90] and pressurised fluid extraction (PEE), is to replace the conventional extraction methods by shortening the extraction time, reduction in solvent use and automation. 

A single SFE/ESE instrument may perform (i) pressurised C02 (SFE), (ii) pressurised C02/modifier and (iii) pressurised modifier (i.e. ASE /ESE , organic solvent) extractions. The division between SFE and ASE /ESE blurs when high percentages of modifier are used. Each method has its own unique advantages and applications. ESE is a viable method to conduct matrix/analyte extraction provided a solvent with good solvating power for the analyte is selected. Sample clean-up is necessary for certain matrix/analyte combinations. In some circumstances studied [498], SFE may offer a better choice since recoveries are comparable but the clean-up step is not necessary. 

Boundaries in chromatography and extraction are blurring, as evident from the relation between GC, SFC and HPLC, the use of superheated/subcritical water for extraction and chromatography, and the role of enhanced fluidity solvents and pressurised fluid extractions [2]. Extraction is an extreme form of chromatography. Separation science recognises that there is unity in the... 

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... 

Pressurised hot water extraction has been used to isolate polycyclic aromatic hydrocarbons from soil [104,105]. Ramos et al. [106] reported an rapid (ten minutes) miniaturised pressurised liquid extraction method using only 100 pi solvent for extracting polycyclic aromatic hydrocarbons from soil. 

Williams JR, Morgan ED, Law B. Comparison of supercritical, subcritical, hot, pressurised and cold solvent extraction of four drugs from rodent food. Anal Commun 1996 33 15-17. 

The techniques used in the certification involved solvent extraction (MeHg) or acid digestion, either pressurised, under reflux or -based (total Hg), derivatisation (e.g. NaBH4), separation by capillary gas chromatography (CGC) and various methods of final detection (e.g AAS, ECD, MIP). Table 7.6 gives an account of the techniques used by each laboratory in the certification for methylmercury in the case of total mercury, the final determination techniques were CVAAS, CVAFS, ICPMS and RNAA. More details on the method description can be found in the certification report [7], including also important precautions taken in the certification to avoid sources of error. 

A pressurised liquid extraction device and hydride generation system were coupled. The design was used to investigate the dependence of extraction time, temperature and solvent on the recovery. 

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... 

For the analysis of organic additives in polymeric materials, in most cases, prior extraction will be necessary. Depending on the nature of the additive, many different approaches are employed. These include soxhlet extraction with organic solvent or aqueous media, total sample dissolution followed by selective precipitation of the polymer leaving the additive in solution, assisted extraction using pressurised systems, ultrasonic agitation and the use of supercritical fluids. In trace analysis, solid phase extraction (SPME) from solution or solvent partition may be required to increase the analyte concentration. 

An alternative to supercritical fluid extraction is to use a classical solvent combined with microwaves. In a pressurised environment, this can be an efficient and rapid process for the treatment of samples. 

For low solvent ratios and very fast extractions, e.g. if the raw material contains only 1 % of essential oil to be removed, it should be considered that the exchange of spent vs. new material including de- and re-pressurisation takes 45-90 minutes depending on the size of the extractor even if baskets are used for material handling. In such cases were the extraction time is shorter than the handling time the gas flow can be reduced for energy savings. 

Gaseous samples can either be pumped into a gas sampling valve or introduced from a pressurised container. Liquid and solid samples can be introduced directly but are often contained in solution, which may be made up directly or obtained from an extraction process. The solvent needs to be carefully chosen to avoid problems in the chromatography. Some of the solvent requirements are... 

---