Partitioning solid-phase

Liquid-liquid partitioning Solid-phase extraction Column chromatography... 

In most published methods, the primary sample extracts are subjected to various types of cleanup procedures including conventional liquid-liquid partitioning, solid-phase extraction, matrix solid-phase dispersion, and online trace enrichment. In many cases, some of these procedures are used in combination in order to help obtaining highly purified extracts. 

Using mentioned extraction/deproteinization procedures, the obtained aqueous or organic extracts often represent very dilute solutions of the analyte(s). These extracts may also contain coextractives that, if not efficiently separated prior to analysis of the final extract, will increase the background noise of the detector making it impossible to determine the analyte(s) at the trace residue levels likely to occur in the analyzed samples. Hence, to reduce potential interferences and concentrate the analyte(s), the primary sample extracts are often subjected to some kind of additional sample cleanup such as liquid-liquid partitioning, solid-phase extraction, or online trace enrichment and liquid chromatography. In many instances, more than one of these cleanup procedures may be applied in combination to allow higher purification of the analyte(s). 

The primary sample extract is subsequently subjected to cleanup using several different approaches including conventional liquid-liquid partitioning, solid-phase extraction, liquid chromatography, immunoaffinity chromatography, and supercritical fluid extraction cleanup. In some instances, more than one of these purification procedures can be applied in combination for better results. 

Extraction Shaking, ultrasonication, Soxhlet, liquid-liquid partitioning, solid-phase extraction To extract analytes from sample matrix into solution... 

Acid/base partition Acid/base partition Solid phase extraction Acid/base partition Acid/base partition Ion exchange Solid phase extraction... 

Extraction Solvent partition Solid phase, e.g., Lipidex, etc, Immunoadsorption Dialysis to remove inorganic salts... 

Determination of Controlling Rate Factor The most important physical variables determining the controlhng dispersion factor are particle size and structure, flow rate, fluid- and solid-phase diffu-sivities, partition ratio, and fluid viscosity. When multiple resistances and axial dispersion can potentially affect the rate, the spreading of a concentration wave in a fixed bed can be represented approximately... 

Both liquid and vapor phases are totally miscible. Conventional vapor/liqiiid eqiiilihriiim. Neither phase is pure. Separation factors are moderate and decrease as purity increases. Ultrahigh purity is difficult to achieve. No theoretical limit on recovery. Liquid phases are totally miscible solid phases are not. Eutectic system. Sohd phase is pure, except at eutectic point. Partition coefficients are very high (theoretically, they can be infinite). Ultrahigh purity is easy to achieve. Recovery is hmited by eutectic composition. 

The proposed proeedure are detailed next eaeh SPMD was mierowave-assisted extraeted twiee with 30 mL hexane aeetone, and irradiated with 250 W power output, until 90°C in 10 minutes, being this temperature held for another 10 minutes. Clean-up of extraet was performed by aeetonitrile-hexane partitioning eoupled by a solid-phase extraetion with a eombined eartridge of 2 g basie-alumina (deaetivated with 5% water) and 0.5 g C. ... 

A recent method, still in development, for determining total 4-nitrophenol in the urine of persons exposed to methyl parathion is based on solid phase microextraction (SPME) and GC/MS previously, the method has been used in the analysis of food and environmental samples (Guidotti et al. 1999). The method uses a solid phase microextraction fiber, is inserted into the urine sample that has been hydrolyzed with HCl at 50° C prior to mixing with distilled water and NaCl and then stirred (1,000 rpm). The fiber is left in the liquid for 30 minutes until a partitioning equilibrium is achieved, and then placed into the GC injector port to desorb. The method shows promise for use in determining exposures at low doses, as it is very sensitive. There is a need for additional development of this method, as the measurement of acetylcholinesterase, the enzyme inhibited by exposure to organophosphates such as methyl parathion, is not an effective indicator of low-dose exposures. 

Solid phase micro extraction (SPME) is a techniques in which a silica fiber coated with a thin film of polymer is brought into contact with an aqueous matrix where the organics in solution partition onto the fiber. The fiber is subsequently placed into the injector of a GC where the heat causes the release of analyte onto the column. This has been applied to endosulfan (a- and (3-) and endosulfan sulfate in water with limits of detection of less than 0.3 pg/L reported (Magdic and Pawliszyn 1996). 

Deposition of adamantane from petroleum streams is associated with phase transitions resulting from changes in temperature, pressure, and/or composition of reservoir fluid. Generally, these phase transitions result in a solid phase from a gas or a liquid petroleum fluid. Deposition problems are particularly cumbersome when the fluid stream is dry (i.e., low LPG content in the stream). Phase segregation of solids takes place when the fluid is cooled and/or depressurized. In a wet reservoir fluid (i.e., high LPG content in the stream) the diamondoids partition into the LPG-rich phase and the gas phase. Deposition of diamondoids from a wet reservoir fluid is not as problematic as in the case of dry streams [74, 75]. 

Water solubility, dissociation constant(s) and n-octanol/water partition coefficients allow one to predict how an analyte may behave on normal-phase (NP), reversed-phase (RP), or ion-exchange solid-phase extraction (SPE) for sample enrichment and cleanup. 

The extent of cleanup needed depends on the target analyte, the quality of the sample extract, the method of detection and sensitivity. Liquid-liquid partition (LLP) and solid-phase extraction (SPE) columns such as the Cig cartridge and macroporous diatomaceous column are the cleanup method of choice. 

Analytical methods for parent chloroacetanilide herbicides in soil typically involve extraction of the soil with solvent, followed by solid-phase extraction (SPE), and analysis by gas chromatography/electron capture detection (GC/ECD) or gas chromatog-raphy/mass spectrometry (GC/MS). Analytical methods for parent chloroacetanilides in water are similarly based on extraction followed by GC with various detection techniques. Many of the water methods, such as the Environmental Protection Agency (EPA) official methods, are multi-residue methods that include other compound classes in addition to chloroacetanilides. While liquid-liquid partitioning was used initially to extract acetanilides from water samples, SPE using... 

A soil sample (10 g) was extracted by mechanically shaking with methanol-deionized water. This mixture was filtered and a portion was removed for partitioning into toluene-hexane. A phenyl solid-phase extraction (SPE) cartridge was employed... 

Ion-exchange solid-phase extractions are used for ionic compounds. The pH of the extracts is adjusted to ionize the target analytes so that they are preferentially retained by the stationary bonded phase. Selection of the bonded phase depends on the pK or pA b of the target analytes. Sample cleanup using ion exchange is highly selective and can separate polar ionic compounds that are difficult to extract by the liquid-liquid partition technique. 

The extent of the cleanup depends on the sample matrix to be analyzed, the extraction procedure, the method of detection and the desired sensitivity. Generally, the cleanup method is liquid-liquid partitioning (LLP), but recently it has become simpler and more reliable to use solid-phase extraction (SPE) columns. 

A cleanup procedure is usually carried out to remove co-extracted matrix components that may interfere in the chromatographic analysis or be detrimental to the analytical instrument. The cleanup procedure is dependent on the nature of the analyte, the type of sample to be analyzed, and the selectivity and sensitivity of the analytical instrument used in the analysis. Preliminary purification of the sample extracts prior to chromatographic separation involves liquid-liquid partitioning and/or solid-phase extraction (SPE) using charcoal/Celite, Elorisil, carbon black, silica, or aminopropyl-silica based adsorbents or gel permeation chromatography (GPC). 

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