Clean up methods

The use of hot gas clean-up methods to remove the sulfur and particulates from the gasified fuel increases turbine performance by a few percentage points over the cold clean-up systems. Hot gas clean-up permits use of the sensible heat and enables retention of the carbon dioxide and water vapor in the... 

The application of automated GPC for the clean-up of various matrices has been demonstrated by other authors (58, 59). As well as organophosphorus pesticides, conventional methods for the analysis of organochlorine pesticides (OPCs) in fatty samples may involve various clean-up methods, such as LC or GPC. The main... 

Figure 13,12 Illusti ation of the clean-up method, showing the analysis of an air sample (a) with and (b) without column switching. Details of the analytical conditions are given in the text. Reprinted from Journal of Chromatography, A 697, R R. Kootsti a and H. A. Herbold, Automated solid-phase exti action and coupled-column reversed-phase liquid cltromatogra-phy for the trace-level determination of low-molecular-mass carbonyl compounds in ak , pp. 203-211, copyright 1995, with permission from Elsevier Science.

P. De Voogt, Cliromatographic clean-up methods for the determination of persistent organic compounds in aqueous environmental samples . Trends. Anal. Chem. 13 389-397(1994). 

For the same reason it is also possible to use Over Pressure Layer Chromatography (OPLC) on-line for prefractionation or as a clean-up method for HPLC [13,14] A group separation according to polarity is followed by a differentiation of the substances according to their differing lipophilicities (Fig. 5). 

The on-line principle has also been extended into the field of detection (Fig. 8). Thus, it is now possible to record FTIR [27-31] and Raman spectra in situ [32, 33], and there have been considerable advances in the on-line coupling of thin-layer chromatography with mass spectrometry. Here it has been, above all, the research groups of Wilson [34-36] and Busch [37-40] that have made the necessary instrumental and methodological advances, so that TLC must no longer be viewed as merely a clean-up method. Rather it forms the essential central point for all these on-line coupling techniques. 

Solid phase extraction (SPE) is fast and can work as a clean-up method when combined with capillary electrophoresis or used prior to HPLC/MS.34-37 Kerns et al.35 described an online alternating parallel SPE column with MS/MS detection and a turn-around time of 1.1 min. 

The herbicides are estimated in the extract by electron capture gas chromatography. Both of the clean-up methods used are capable of giving good results at the lpg g 1 level but XAD-2 is inadequate for smaller amounts of herbicides in soil. This poor clean-up and the higher variability in recovery shows XAD-2 to be unsuitable for residue determinations. 

Mirex can be extracted from tissues using hexane, hexane-acetone, hexane-ethyl ether, or petroleum ether (Caille et al. 1987 EPA 1980e Head and Burse 1987 Kutz et al. 1985 LeBel and Williams 1986). Clean-up methods include liquid-liquid partitioning (adipose tissue) (Kutz et al. 

Gas clean up methods can be classified into two distinct routes wet low temperature cleaning and dry high temperature cleaning. 

Gross contamination can overload the HPLC or GC columns with obvious and usually rapid deterioration of chromatographic performance. This can occur with so called rapid techniques where the detector is used as a filter, e.g., selected ion monitoring (SIM) MS, or where the clean-up method has been overloaded (e.g., excess of lipid). This problem can be overcome by using and monitoring more selective clean-up techniques. 

The extraction and clean-up methods used for the recovery of organophosphorus derivatives do not differ basically from those applied to other groups of substances. However, because of the high toxicity of the compounds involved, the techniques must be extremely sensitive and able to detect sub-nanogram amounts. A number of reviews have been published on the subject164-171. As previously mentioned, the compounds to be analysed may be found in living matter as well as in soil, sediments, water and air the experimental methods vary accordingly. 

A Patey, M Sharman, J Gilbert. Liquid chromatographic determination of aflatoxins level in peanut butter using an immunoaffinity columns clean-up. method international collaborative trials. J Ass Off Anal Chem 74(1) 76-81, 1991. 

For the determination of the individual fluoroquinolones the authors developed a MISPE clean-up method followed by HPLC-UV on a C18 column. Figure 3 (Fig. 7 of the original) shows the substantial clean-up effect due to MISPE. Recoveries for five fluoroquinolones tested were around 80%. The selectivity of the MISPE clean-up... 

K. Tsuji, S. Naito, F. Kondo, M.F. Watanabe, S. Suzuki, H. Nakazawa, M. Suzuki, T. Shimada and K.-I. Harada, A clean-up method for analysis of trace amounts of microcystins in lake waters, Toxicon, 32 (1994) 1251-1259. 

Solid-phase extraction (SPE) it is widely accepted as an alternative extraction/clean up method [39]. SPE has been used for the extraction of PCBs in various types of human milk. Milk powder and evaporated milk were constituted with water prior to extraction. The milk sample was mixed with 5mL of water and 10 mL of methanol and sonicated, followed by passing the sample through the column. 

For OTA detection, the optimized immunosensors and the protocol that was implemented on the electrochemical device allowed the detection of 0.4 pg/kg, with within- and between-assay variability less than 5% and 10%, respectively. The method was evaluated with respect to a reference instrumental method (HPLC/immunoaffinity clean-up method based on the AOAC Official Method 2000.03) obtaining good agreement (r — 0.9992). 

The sensitivity of invertase toward methyl mercury using the clean-up method can be improved using the low amount of invertase (0.05 pg/mL) with 10 min of incubation time and kipping the hydrolysis reaction time for more than 10 min. 

The principle of combination of electrochemical glucose oxidase biosensor with the clean-up method for direct extraction and determination of methyl mercury has been successfully demonstrated. The extraction of methyl mercury from the organic solvent has been based on invertase enzyme inhibition. The combination of very low concentration of invertase enzyme and 10 min of incubation time allows the detection of methyl mercury at 5 ppb level. Our method permits the detection of this inhibitor below the legal limit given by the European Union with good recoveries when fish samples were measured. 

Kaupp and Sklarz [50] reported a clean-up method for the determination of polyaromatic hydrocarbons in plant samples including maize leaves. The two-step clean-up consisted of gel permeation chromatography on a porous styrene-divinylbenzene copolymer, followed by further clean-up on silica gel. 

Food chemical safety Part 3 clean-up methods... 

TABLE 5.1 Some Clean-Up Methods for Different Molecules... 

As the speed of the impacting electrons is still further increased no new processes are observed by the positive ray or clean-up methods. Some experimenters have observed additional ionization setting in at about thirty volts. Of more importance, however, are the results of Franck and Blackett, who showed that the emission of Balmer lines was a primary result of impact of thirty volt or higher speed electrons. In other words, they showed dissociation may occur with excitation of one (or perhaps both) atoms. 

Kleinveld AJ, Verhoeve P, Nielen MWF. 1989. Evaluation of clean-up methods for the determination of chlorinated aromatic hydrocarbons in fly ash by capillary gas chromatography and mass selective detection. Chemosphere 18 1401-1412. 

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