Isolation/extraction techniques

At present, soil derived humic matter and fulvic acids extracted from freshwater are available commercially and are commonly used to test techniques for DOM detection and also used as model compounds for trace metal chelation studies. The results obtained using these model compounds are frequently extrapolated to the natural environment and measurements on "real" samples provide evidence that this DOM is a good model compound. In the past, some investigators also made available organic matter isolated from marine environments using C18 resins. While these compounds come from aquatic sources, this isolation technique is chemically selective and isolates only a small percentage of oceanic DOM. Reference materials are not currently available for these compounds, which inhibits study of the role they play in a variety of oceanographic processes. 

T2. Titus, E. 0-, Isolation procedures—liquid extraction and isolation techniques. In Fundamentals of Drug Metabolism and Drug Disposition (B. N. LaDu, H. G. Mandel, and E. L. Way, eds.), pp. 419-436. Williams Wilkins, Baltimore, Maryland, 1971. 

These analytical dilemmas interfere with the methods of alkaloid analysis. Each group of alkaloids has its own methods of extraction, isolation and crystallization, as well as detection in structure, molecule and dynamicity. Not all these stages are still possible in the majority of alkaloids. In recent years, many techniques have been used in alkaloid detection. There are atomic and molecular electronic spectroscopy, vibration spectroscopy and electron and nuclear spin orientation in magnetic fields, mass spectroscopy, chromatography, radioisotope and electrochemical techniques. Although important developments in methodology and... 

The analyses of the flavour composition of yellow passion fruits were performed by four dilferent isolation techniques, namely vacuum headspace sampling (VHS), the dynamic headspace method, simultaneous distillation and extraction at atmospheric pressure, and simultaneous distillation and extraction under reduced pressure [62]. Significant differences were found not only in the chemical composition of the resultant extracts but also in their sensory properties. The most representative and typical extract was obtained by VHS. 

Not recognizing the need for special media or isolation techniques (eg, charcoal yeast extract agar for isolation of legionella species, shell-vial tissue culture system for rapid isolation of cytomegalovirus)... 

For example, in eel, high concentrations of polychlorinated biphenyls can be present and can interfere in the cleanup procedure. Fly ash is difficult to extract. Drastic concentration and cleanup procedures such as saponification can convert some isomers. Oc-tachlorodibenzo-p-dioxin can easily be broken down during the cleanup procedure. For each matrix a specific isolation technique is necessary. The method has to be validated for all the isomers of the analytical program (24). 

Application of the MAS to drinking water should considerably broaden the scope of organic compounds detected and measured, relative to previously available analytical methods. This conclusion is especially true for the polar compounds of relatively low MW (<500) however, a few of these compounds are not recovered well by the MAS extraction and isolation techniques or are not gas chromatographable, even after derivatization. HPLC methods offer the most promise for separation and analysis of these compounds as well as those of high molecular weight. 

In this study, a factorial experiment was set up to evaluate the effects of four variables at two levels on extraction efficiencies by using bonded-phase isolation techniques and a 27-component synthetic test mixture. The compounds studied and the respective mass ions used for quantitation are given in the box. The compounds in the mix vary greatly in water solubility and volatility and, in general, represent a wide class of organic compounds typical of those present in environmental samples. To maximize solute recoveries, the procedure was... 

Light hydrocarbons were extracted, isolated, and characterized chro-matographically following techniques of Dunton and Hunt (2). Sediment studies require no special modifications other than more stringent precautions to avoid contamination because of the lower concentrations in sediments than rocks. Figures 2 and 3 are both based on analyses from the same technique, but in Figure 3 the chromatograms were produced as part of a routine, automatic operation. Extracts are encapsulated in indium and then introduced into the heated injection block presentation is somewhat compressed, but results are comparable. 

Because SPA usually occur in foods at concentration levels up to 200 ppm, the appropriate extraction and isolation techniques for individual procedures depend on various factors ... 

A prerequisite for the calculation of OAVs are exact quantitative data. Aroma compounds, which are relatively stable and are present in food extracts in higher concentrations (>100 pg/kg food) are often quantified by using an internal standard containing a similar pattern of functional groups as the analyte. In a quantitative study on cherry odorants [63] it has been shown, that the results are significantly influenced by the isolation technique used and by the structure of the odorant. However, under appropriate conditions the values differed only between 7 % (benzaldehyde) and 26 % ((E,Z)-2,6-... 

The techniques of sample preparation, extraction (isolation), and/or preconcentration of analytes are usually applied in the analysis of trace components of gaseous, liquid, and solid samples. During this operation, transport of analytes from primary matrices (donors) to the secondary matrix (the acceptor) takes place. It should be remembered, however, that the extraction and preconcentration steps could be a source of environmental pollution. The techniques of sample preparation introduced in this chapter have the following advantages253 ... 

TECHNIQUES FOR THE EXTRACTION, ISOLATION, AND PURIFICATION OF NUCLEIC ACIDS... 

Since then much progress has been made in sample preparation techniques that reduce sample complexity. An overview of the sequence of extraction, isolation, and purification of nucleic acids is presented in Figure 8.1. It can be categorized in several unit steps beginning with the extraction of DNA until its sizing and sequencing. The different options within each step are listed in Table 8.1 and are described in this chapter. The technique best suited in a given application depends on ... 

Table 8.1. Techniques in Extraction, Isolation, and Purification of Nucleic Acids...

Upon employing the more rigorous simultaneous distillation-extraction (SDE) technique (100°C pH 3.7) to isolate the quince fruit volatiles, the resulting aroma composition distinctly differed from that obtained by HVD/SE. After SDE the hydrocarbon 5, the bicyclic alcohol 6 and 3,4-didehydro-(B-ionol (7) were identified as... 

Extraction and isolation techniques of tamarind xyloglucans and polyphenols... 

Vibrational spectroscopy is an important tool for the characterization of various chemical species. Valuable information regarding molecular structures as well as intra- and intermolecular forces can be extracted from vibrational spectral data. Recent advances, such as the introduction of laser sources to Raman spectroscopy, the commercial availability of Fourier transform infrared spectrometers, and the continuing development and application of the matrix-isolation technique to a variety of chemical systems, have greatly enhanced the utility of vibrational spectroscopy to chemists. 

A variety of extraction separation techniques has been applied to problems of isolation and radiochemical purification of nuclides. Most of the extractions employed in radiochemistry are based on previously developed conventional analytical extractions, and general Information of the technique can be found in the literature (89,185) ... 

---