Single-extraction method

As with most other drugs, no single extraction method will suffice for removing any barbiturate from any biological sample, and recovery will depend on technique. Generally, multiple solvent extraction under different pH conditions has been used. 

The partition coefficient for pentazocine has been measured between various organic and aqueous phases. The results of four studies are shown in Table 4. The first value was obtained by a single extraction using 50 mL of each phase while the second value is from a countercurrent distribution study with pentazocine added to the aqueous phase and extracted eight times into benzene. The third value was obtained by the single extraction method with the additional definition of a distribution ratio, DnOH for pentazocine using the partition coefficient k NOH) in the relation ... 

Application of single-extraction methods that concomitantly enable the simplification of operational protocols... 

Take a look at the results of this study in Table 5.9 below. As a result of these findings, the use of ammonium acetate was excluded as a suitable single extraction method. Why do you think this was ... 

The procedures for the extraction of metals using the two single extraction methods (0.05 moll-1 EDTA and 0.43 moll-1 acetic acid) are shown in Figures 5.17 and 5.18, respectively. 

Figure 5.17 Procedure adopted in the single extraction method for metals (employing EDTA), as applied to the analysis of soils and sediments.

Miller El, Wylie FM, Oliver JS. Simultaneous detection and quantification of amphetamines, diazepam and its metabolites, cocaine and its metabolites, and opiates in hair by LC-ESI-MS-MS using a single extraction method. J Anal Toxicol 2008 32(7) 457-69. 

The ether extraction method (B) is quicker, especially when several runs are to be made. Mandelic acid is obtained in the same yield by this method. The benzene extraction may be better for small preparations, or when a single run is to be made. 

On the other hand, single-residue methods developed by the applicants give basic information about appropriate cleanup steps and specific determination procedures. In addition, not many laboratories other than those from the applicants are able to test the real solvent extraction efficiency. The reason is that extraction studies need radio-labeled incurred residues instead of fortified samples. Hence enforcement methods provided by the manufacturers accelerate the development of methods which meet the needs of (official) food control laboratories. 

Most modern methods of analysis to determine pesticide residues in food commodities, whether a multi-residue method (MRM) or a single-residue method (SRM), can be broken down into three or four basic steps sample processing, sample extraction, extract cleanup (optional) and instrumental determination. 

B. Richter, J. EzzeU, and D. Felix, Single Laboratory Method Validation Report Extraction of Organo-phosphorus Agrochemicals, Chlorinated Herbicides and Polychlorinated Biphenyls Using Accelerated Solvent Extraction (ASE) with Analytical Validation by GC/NPD and GC/ECD, Document 101124, Dionex Sunnyvale, CA (1994). 

One of the attractive features of SFE with CO2 as the extracting fluid is the ability to directly couple the extraction method with subsequent analytical methods (both chromatographic and spectroscopic). Various modes of on-line analyses have been reported, and include continuous monitoring of the total SFE effluent by MS [6,7], SFE-GC [8-11], SFE-HPLC [12,13], SFE-SFC [14,15] and SFE-TLC [16]. However, interfacing of SFE with other techniques is not without problems. The required purity of the CO2 for extraction depends entirely on the analytical technique used. In the off-line mode SFE takes place as a separate and isolated process to chromatography extracted solutes are trapped or collected, often in a suitable solvent for later injection on to chromatographic instrumentation. Off-line SFE is inherently simpler to perform, since only the extraction parameters need to be understood, and several analyses can be performed on a single extract. Off-line SFE still dominates over on-line determinations of additives-an... 

Unlu, M., Morgan, M.E., Minden, J.S. (1997). Difference gel electrophoresis a single gel method for detecting changes in protein extracts. Electrophoresis 18, 2071-2077. 

Rajagopalan et al. [72] described an electron-capture gas chromatographic assay method for the determination of primaquine in blood. The method involves deriva-tization with heptafluorobutyric anhydride to form the diheptafluorobutyramide derivative after a single extraction at alkaline pH. The derivatives are quantitated by electron-capture gas chromatography. Blood levels of primaquine as low as 8 ng/mL can be measured with good precision. 

Chu W-S, Liang Q, Liu J, et al. A nondestructive molecule extraction method allowing morphological and molecular analyses using a single tissue section. Lab. Invest. 2005 85 1416-1428. 

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