Extraction and preparation of samples

ANALYSIS OF PCBs IN WATER Extraction and preparation of samples... 

Table 4.15 fists the many possibilities for solid sampling for GC analysis. In general, sample preparation should be considered in close conjunction with injection. Robotic sample processors have been introduced for automatic preparation, solvent extraction and injection of samples for GC and GC-MS analyses. Usually, facilities are included for solvent, reagent, and standard additions and for derivatisation of samples. 

The tissue of interest should be removed from the animals using equipment that has been treated to ensure that it is RNase-free. The surface hair of the animals can be soaked in 70% ethanol to minimize the inclusion of hair or dander in the isolated tissues. A sterile disposable Petri plate, placed on top of a bed of crushed ice, is a suitable RNase-free surface for microdissection. Immediately after isolation from the animal, individual samples of tissue can be flash frozen by immersion in liquid nitrogen and stored in cryovials in liquid nitrogen or at -70°C until all samples from an experimental set have been obtained. RNA extraction and preparation of single-stranded cDNA can then be performed simultaneously on all samples. This will minimize differences between RNA populations that result from differences in sample preparation. 

Determination of CholesteroL For meat extraction, the procedures for determining the cholesterol of extracted lipid samples were described Chao et al. (2i). For edible beef tallow extraction, the preparation of samples for cholesterol content was based on the AOAC (22) method Section 28.110. The prepared sample was then injected into a Supelco SPB-1 fused silica capillary column of 30 meters x 032 mm i.d. in a Varian Model 3700 gas chromatograph equipped with dual flame ionization detectors. The initial holdup time was 4 min at 270°C and then programmed to a temperature of 300°C at a ramp rate of 10°C/min. Helium flow rate and split ratio were 13 ml and 50 1, respectively, while the injector/detector temperature was 310°C. 

Procedures for isolation and measurement of lipids in foods include exhaustive Soxhlet extraction with hexane or petroleum ether (AOAC, 1995 see Basic Protocol 1), chloro-form/methanol (Hanson and Olley, 1963 Ambrose, 1969), chloroform/methanol/water (Folch et al., 1957 Bligh and Dyer, 1959 see Basic Protocol 2 and Alternate Protocol 2), acid digestion followed by extraction (see Basic Protocol 4), or, for starchy material, extraction with n-propanol-water (e.g., Vasanthan and Hoover, 1992 see Basic Protocol 3). Each method has its own advantages and disadvantages and successful measurement of lipid content is often dictated by the type of sample and extraction medium employed. Commercial extraction and preparation of edible oils are explained in the literature (Williams, 1997). 

Dialysis, ultrafiltration and lyophilisation are processes that are used to change the composition of the medium in which macromolecules are dissolved. The focus of our discussion is on proteins, and we consider methods that can be applied widely, from the processing of cell extracts to preparation of samples for experiments. 

The most simple and common workstations are those for dilution and/or reagent addition to a number of samples in a simultaneous manner, either to all samples in a rack or to a line with a slide z-axis (as in the Biomex" 2000 model from Beckman). Most workstations are designed to operate with liquid samples such is the case with those from Cyberlab, Gilson, Zymark, SciLog, Sagian, Beckman and Hamilton, which manufacture specific equipment for liquid handling, solid-phase extraction and preparation of liquid... 

Extraction and Preparation of Culture Medium Samples for Dot-Blot Hybridization... 

Yeast biomass was freeze-dried and grounded. Fatty acid extraction and preparation of methyl esters were carried out according to Lepage and Roy [25]. Samples (100 mg) were transmethylated with 5 ml of methanol/acetyl chloride (95 5 v/v). The mixture was sealed in a light-protected Teflon-lined vial under nitrogen atmosphere and heated at 80 °C for 1 h. The vial contents were then cooled, diluted with 1 ml water, and extracted with 2 ml of n-heptane. The heptane layer was dried over Na2S04, evaporated to dryness under nitrogen atmosphere and redissolved in heptane, which contained the methyl esters. 

Miyake et al. (1991) found that extraction of neutral limonoids from Natsudaidai seeds depended upon the solvents used, time of extraction, and methods of sample preparation prior to extraction. Since the seeds contain high concentrations of both dilactones and monolactones with dilactones dominating, direct organic solvent extraction method yields lower values than extraction with the Hasegawa method mentioned above. The optimum extraction method was determined to be grinding the seeds in 0.1 M Tris buffer at pH 7.0 and incubating the mixture for at least 20 h at room temperature. It was followed by acidification and extraction with methylene chloride. The organic phases can then be evaporated off to concentrate the samples for analysis. 

Pesce, G.L.A., Ball, R., Quarta, G., Calcagnile, L. (2012). Identification, extraction and preparation of reliable lime samples for the dating of plasters and mortars with the method of "pure lime lumps". Proceeding of the 6 International Symposium on Radiocarbon and Archaeometry, Cyprus, April 2011... 

Theoretical and applied aspects of microwave heating, as well as the advantages of its application are discussed for the individual analytical processes and also for the sample preparation procedures. Special attention is paid to the various preconcentration techniques, in part, sorption and extraction. Improvement of microwave-assisted solution preconcentration is shown on the example of separation of noble metals from matrix components by complexing sorbents. Advantages of microwave-assisted extraction and principles of choice of appropriate solvent are considered for the extraction of organic contaminants from solutions and solid samples by alcohols and room-temperature ionic liquids (RTILs). 

Determination of Na " and Na" ions in raw cosmetic materials was conducted with the developed method of flame photometry. A necessity of development of method of samples preparation arose up in the work process, as this spicily-aromatic raw material contained pectin in amount 0.1-0.5% and that prevented preparation of samples by standard method of extracts dilution and required incineration of analyzed sample, time of analysis was increased in 60 times. It was established that CaCl, solution with the concentration 0,4 % caused destmctions of the carbopol gel. It was established that the addition of 0,1% CaCl, and 0,1% NaCl salts solutions into the system intensified the effect of negative action of these salts onto the gel stmcture and the gel destmcted completely. 

Brain et al. [137] reported a tandem mass spectrometry (MS-MS) procedure by which a direct measurement from an n-pentane extract of a surfactant is possible. This procedure is excellent from the standpoint of sensitivity and simplicity of sample preparation but is not commonly applied because of the need of an MS-MS instrument. 

Solid samples are generally treated in one of two ways. If completely soluble, they can be dissolved directly and completely in a suitable solvent. Alternatively, if the samples contain insoluble materials that are of no interest, then they can be extracted with a selected solvent to obtain the relevant compounds in solution. The extract can be subsequently filtered or centrifuged to remove any unwanted substances that make up the sample matrix. The procedure will differ, depending on the amount of the substances present that are germane to the analysis. The preparation of samples for LC analysis from solid... 

Kennedy et al. developed a lasalocid immunoassay for application to residues in chicken meat and liver samples. The antibody was specific and did not cross-react with salinomycin, maduramicin, or monensin. Sample preparation consisted of homogenization in aqueous acetonitrile, removal of fat from an aliquot of the aqueous acetonitrile by hexane extraction, and evaporation of acetonitrile. The sample was then reconstituted with assay buffer. Liver required an additional solid phase extraction step. The LOQ was 0.02 xgkg for muscle and 0.15 agkg for liver. These workers were able to use the system to determine the half-life of lasalocid in the tissues. 

Table 3.4 summarises the main characteristics of a variety of sample preparation modes for in-polymer additive analysis. Table 3.5 is a short literature evaluation of various extraction techniques. Majors [91] has recently reviewed the changing role of extraction in preparation of solid samples. Vandenburg and Clifford [4] and others [6,91-95] have reviewed several sample preparation techniques, including polymer dissolution, LSE and SEE, microwave dissolution, ultra-sonication and accelerated solvent extraction. 

SFC has played an important role in the extraction and isolation of fatty acids [355,356]. Underivatised fatty acids and methyl esters of fatty acids are surprisingly easy to elute using a bonded phase or a silica based packed column and pure C02, probably due to the long hydrocarbon tails on the molecules [357]. On the other hand, most aromatic and polysubstituted acids will not elute. Triglycerides with saturated fatty acids can be analysed faster with pSCF-ELSD than with GC-FID and do not require sample preparation [358]. Using... 

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