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Sample preparation medicine

One important practical aspect of PLS is that it takes into account errors both in the concentration estimates and spectra. A method such as PCR will assume that the concentration estimates are error free. Much traditional statistics rest on this assumption, that all errors are in the dependent variables (spectra). If in medicine it is decided to determine the concentration of a compound in the urine of patients as a function of age, it is assumed that age can be estimated exactly, the statistical variation being in the concentration of a compound and the nature of the urine sample. Yet in chemistry there are often significant errors in sample preparation, for example, accuracy of weighings and dilutions and so the independent variable (c) in itself also contains errors. With modem spectrometers, these are sometimes larger than spectroscopic errors. One way of overcoming this difficulty is to try to minimise the covariance between both types of variables, namely the x (spectroscopic) and c (concentration) variables. [Pg.13]

It is tempting to draw analogy with the development of other analytical technologies (NMR, FAB-MS) and conclude that protein crystallography will soon leave the incubator of "big machine physics" to become an everyday, routine tool used in the medicinal chemistry laboratory. Hopefully, this chapter has shown some of the subtle complexities of sample preparation and handling, data collection, and refinement, etc. that temper this vision and will likely keep this a specialized field for some time. [Pg.496]

Most papers dealing with phenolic acid HPLC analysis in herbs describe only simple liquid extraction without the hydrolysis step. Acetone, methanol, or alcoholic-water or acetone-water mixtures are applied. Very rarely, pure water is used as the extraction solvent. " It was found that the extraction recoveries for water extracts are often lower in comparison to alcoholic-water mixtures, especially when the simultaneous separation of polar and less polar phenolic acids has been performed. Sometimes, the control of pH can improve the recovery. If necessary, n-hexane, chloroform, diethyl ether, benzene-acetone, petroleum ether, or other less polar solvents are recommended for removing interfering compounds. The extraction is usually performed by refluxing the samples for a specific time in a Soxhlet apparatus, with simple mechanical or magnetic stirring of the sample with the extraction solvent, or by plant sample maceration. The application of an ultrasonic bath for the liquid extraction has also become popular in recent years. The hydrolysis steps have also been recommended for medicinal species preparation, especially when other phenolic compounds are also analyzed simultaneously with phenolic acids in herbs. [Pg.1171]

Advances in herbal medicines have hastened the need for high-throughput CE methods that can effectively screen and resolve numerous compounds in a short period of time. Chemometric experimental design and optimization techniques will continue to increase as new developments in sample preparation, method optimization, and data processing in (3E analysis of herbal medicines occur. [Pg.238]

In the TLC analysis of dry extracts prepared from medicinal plants, the sample preparation is performed in a different way from that prescribed in the monographs for the drugs in the pharmacopoeias. Also, there is no binder in the recommended solvent system, and in these cases a validation of the new in-house method is certainly necessary. [Pg.224]

G. D. Christian and F. J. Feldman, Atomic Absorption Spectroscopy. Applications in Agriculture, Biology, and Medicine. New York Wiley-Interscience, 1970. Describes sample preparation procedures. [Pg.540]

Behne, D. (1981). Sources of error in sampling and sample preparation for trace element analysis in medicine. J. Clin. Chem. Clin. Biochem., 19,115. [Pg.14]

D PAGE Sample Preparation and Fractionation, Volume 2, edited by Anton Posch, 2008 2D PAGE Sample Preparation and Fractionation, Volume I, edited by Posch, 2008 Electroporation Protocols Preclinical and Clinical Gene Medicine, edited by Shulin Li. 2008 Phylogenomics edited by William J. Murphy, 2008 Affinity Chromatc raphy Methods and Protocols, Second Edition, edited by Michael Zachariou, 2008 Drosophila Methods and Protocols, edited by Christian Dahmann, 2008... [Pg.228]

Whether the ionization is positive or negative, TIMS requires careful sample preparation, often involving considerable chemical processing to separate and purify the element of interest. TIMS finds applications in geoscience, environmental analysis, cosmochemistry, biosciences, medicine, material science, and physics. Samples generally include soil, minerals, meteorites, and biological tissue. More information on the specifics of the TIMS technique and its applications is in the monograph by De Laeter (2001). [Pg.394]


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