Cleanup methods

The most important aspect in planning this production run, therefore, may be to make Ae processing campaign as long as is practicable in order to reduce the number of times file equipment must be cleaned. The bar chart below shows a t)q)ical sequence for the above example. 

Cleanup methods may be either chemical or mechanical. Chemical cleaning consists of adding a substance into an apparatus or onto its surfaces which helps to remove any residues of process materials by dissolution or chemical reaction. Mechanical cleaning is the physical removal of such residues, which may be performed manually or with the aid of mechanical devices. Some cleaning processes combine the two methods. 

While cleaning mettiods must be selected on a case-by-case basis, some general guidelines can be applied to specific situations. Some of these are  

Clean manually with solvents or reagents, in combination with mechanical means if necessary. Waste production should be kept to a minimum. Provide adequate personnel protection and ventilation consistent wifii hazards associated with cleaning reagents and waste products. 

Avoid physical entry where possible. Use in-situ chemical cleaning. If physical entry is unavoidable, use chemical or mechanical cleaning as required. Waste 

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Sample Cleanup. The recoveries from a quick cleanup method for waste solvents based on sample filtration through a Elorisd and sodium sulfate column are given in Table 2 (40). This method offers an alternative for analysts who need to confirm the presence or absence of pesticides or PCBs. 

Analysis of methyl parathion in sediments, soils, foods, and plant and animal tissues poses problems with extraction from the sample matrix, cleanup of samples, and selective detection. Sediments and soils have been analyzed primarily by GC/ECD or GC/FPD. Food, plant, and animal tissues have been analyzed primarily by GC/thermionic detector or GC/FPD, the recommended methods of the Association of Official Analytical Chemists (AOAC). Various extraction and cleanup methods (AOAC 1984 Belisle and Swineford 1988 Capriel et al. 1986 Kadoum 1968) and separation and detection techniques (Alak and Vo-Dinh 1987 Betowski and Jones 1988 Clark et al. 1985 Gillespie and Walters 1986 Koen and Huber 1970 Stan 1989 Stan and Mrowetz 1983 Udaya and Nanda 1981) have been used in an attempt to simplify sample preparation and improve sensitivity, reliability, and selectivity. A detection limit in the low-ppb range and recoveries of 100% were achieved in soil and plant and animal tissue by Kadoum (1968). GC/ECD analysis following extraction, cleanup, and partitioning with a hexane-acetonitrile system was used. 

Using established extraction and cleanup methods, followed by GC/FPD and GC/thermionic detection, Carey et al. (1979) obtained detection limits in the ppb range and recoveries of 80-110% in soil and 70-100% in plant tissue. Good sensitivity and recovery were maintained in a simplified extraction procedure of sediments followed by GC/FPD analysis (Belisle and Swineford 1988). Bound methyl parathion residues that were not extracted with the usual methods were extracted using supercritical methanol by Capriel et al. (1986). They were able to remove 38% of the methyl parathion residues bound to soil, but 34% remained unextractable, and 28% could not be accounted for. 

Shibata Y, Oyama M, Sato H, et al. 1998. Simultaneous cleanup method for multi pesticide residue analysis by GC and HPLC. J Food Hyg Soc Jpn 39(4) 241-250. 

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. 

Consistent with other analytical methods, immunoassays must be validated to ensure that assay results are accurate. Initial validation involves an evaluation of the sensitivity and specificity of the immunoassay, while later validation includes comparison with a reference method. Because a goal of immunoassays is to minimize sample preparation, validation also includes testing the effects of sample matrices and(or) sample cleanup methods on results. The final steps in validation involve testing a limited number of samples containing incurred residues to determine if the method provides reliable data. 

Two general approaches have been used to overcome matrix effects (1) partial purification of the analyte prior to analysis by immunoassay ( cleanup methods) and (2) the use of a matrix blank when preparing the calibration curve. Both options are widely used, but each has its individual limitations. 

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. 

Whereas SPE is a sample cleanup method, SPME is essentially a solvent-free sampling method. Stir bars in hyphenated SBSE-TDS-CGC configuration for product control analysis are a powerful tool for the extraction and analysis of organic compounds in aqueous matrices. 

Linking TLC with a tandem instrument differs from combining GC or LC with an appropriate spectrometer. Hyphenation of planar chromatographic techniques represents a niche application compared to HPLC-based methods. Due to the nature of the development process in TLC, the combination is often considered as an off-line in situ procedure rather than a truly hyphenated system. True in-line TLC tandem systems are not actually possible, as the TLC separation must be developed before the spots can be monitored. It follows that all TLC tandem instruments operate as either fraction collectors or off-line monitoring devices. Various elaborate plate extraction procedures have been developed. In all cases, TLC serves as a cleanup method. 

Overpressure layer chromatography (OPLC) can be employed as a cleanup method for HPLC, or used for prefractionation. OPLC-HPLC coupling has been described by ref. [1003],... 

Fracturing is a way to crack rock or very dense soil, like clay, below ground. It is not necessarily a cleanup method in itself. Rather, fracturing is used to break up the ground to help other cleanup methods work better. The cracks, which are called fractures, create paths through which harmful chemicals can be removed or destroyed.1746 84... 

MNA works best where the source of pollution has been removed. For instance, buried waste must be dug up and disposed of properly. Or it can be removed using other available cleanup methods. After the source is removed, the natural processes get rid of the small amount of pollution that remains in the soil and groundwater. The soil and groundwater are monitored regularly to make sure they are cleaned up. 

Marble LK, Delfino JJ. 1988. Extraction and solid phase cleanup methods for pesticides in sediment and fish. American Laboratory 23-32. 

Two approaches are generally used to develop methods with lower detection and quantitation limits for target compounds. One approach involves the use of sample cleanup methods such as size exclusion chromatography (SEC) for the... 

There are two noncolumn cleanup methods, one of which uses acid partition (EPA SW-846 3650) to separate the base/neutral and acid components by adjusting pH. This method is often used before alumina column cleanup to remove acid components. The other method (EPA SW-846 3660) is used for sulfur removal and uses copper, mercury, and tetrabutylammonium sulfite as desulfurization compounds. Sulfur is a common interfering compound for petroleum hydrocarbon analysis, particularly for sediments. Sulfur-containing compounds are very common in crude oil and heavy fuel oil. Elemental sulfur is often present in anaerobically biodegraded fuels. Thus, abnormally high levels of sulfur may be... 

Identification and quantification is obtained by combined high-resolution gas chromatography/mass spectrometry (GC/MS) methods after special cleanup procedures of the matrix, as shown later for sediments (see Figure 8.2). The cleanup methods for other matrices are similar. Quantification is obtained by addition of 13-C labeled standards before the cleanup procedure. In general, only the toxic isomers are identified and quantified. 

Figure 8.2 Scheme for the cleanup method of PCDD/F in sediments. 

Cost of GasificatUm-Tiased Power Systems Comparing power options is complicated by the many different parameters that must be considered in making a cost determination coal cost coal properties, inclnding sulfur and moisture contents ambient temperature degree of process integration gas turbine model and gas cleanup method. These, and many other factors, have a significant impact on cost. 

Wastewater generation can be reduced by general good housekeeping procedures such as substituting dry cleanup methods for water washdowns of equipment and floors. This is especially applicable for situations where liquid or solid materials have been spilled. Flow measuring devices and pH sensors with automatic alarms to detect process upsets are two of many ways to effect reductions in water use. Prompt repair and replacement of faulty equipment can also reduce wastewater losses. 

P14 The most common cleanup methods are as follows shaking the extract with concentrated sulfuric acid, Florisil, alumina,and silica gel and using size exclusion chromatography (SEC). (From Llompart et ah, 2001)... 

ChemPete, Inc., bioremediation is an effective and continuous cleanup method for transforming gasoline, diesel fuel, fuel oil, kerosene, and chlorinated solvents to nonhazardous organic matter, carbon dioxide, and water, according to the vendor. ChemPete uses bacteria, nutrients, and a catalyst developed by Alpha Environmental Biosystems, Inc. ChemPete was the first company to achieve closure of both gasoline and fuel oil sites in situ in accordance with Illinois rigorous closure guidelines (5 parts per billion benzene). RIMS was unable to contact the vendor, and the commercial availability is unknown. 

A three-phase liquid-liquid partitioning consisting of hexane, acetonitrile, and dichloromethane has also proven to be a preferred cleanup method for diethylstilbestrol and zeranol (455), trenbolone and epitrenbolone (445), trenbolone and nortestosterone (446), and melengestrol residues (456) in tissues. Following adjustment of the initial aqueous acetonitrile sample extract at pH 13, most of the polar and ionic acidic matrix components were directed into the aqueous layer during the partitioning process, while the low-polarity components were extracted... 

Therefore, pH 12 was chosen to minimize base hydrolysis of organic compounds. The 10 1 volume ratio was used to assure sufficient recovery of the ether phase from a larger volume ratio, and only one extraction step was used to minimize loss of volatiles during the cleanup method. 

Until very recently, explosives-contaminated soils have been remediated by incineration, a process whose high cost has stimulated the search for a more economical cleanup method (Roberts et al., 1993). Microbially mediated degradation of explosives is a promising technology. Many researchers have studied microbial consortia and various pure cultures for their ability to degrade TNT and other nitroaromatic compounds (for a review see Crawford, 1995), bringing about the development of bioremediation processes that can remove TNT and other explosives from contaminated soil and water (Funk etal., 1995 Williams a/., 1992). 

If necessary, select a sample cleanup method. Cleanup could be required if resolution is poor, if the salt content is high, or if the capillary fouls. Cleanup might involve solid-phase extraction (Section 28-3), protein precipitation, or dialysis (Demonstration 27-1). 

TABLE 7.1 PERCENT PESTICIDE RECOVERY WITH VARIOUS CLEANUP METHODS 1 (9)... 

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