Colorimetry biology

National Institute of Standards and Technology (NIST). The NIST is the source of many of the standards used in chemical and physical analyses in the United States and throughout the world. The standards prepared and distributed by the NIST are used to caUbrate measurement systems and to provide a central basis for uniformity and accuracy of measurement. At present, over 1200 Standard Reference Materials (SRMs) are available and are described by the NIST (15). Included are many steels, nonferrous alloys, high purity metals, primary standards for use in volumetric analysis, microchemical standards, clinical laboratory standards, biological material certified for trace elements, environmental standards, trace element standards, ion-activity standards (for pH and ion-selective electrodes), freezing and melting point standards, colorimetry standards, optical standards, radioactivity standards, particle-size standards, and density standards. Certificates are issued with the standard reference materials showing values for the parameters that have been determined. 

Many biologically interesting molecules, for instance hormones, can be determined using any of a number of analytical methods, such as GC, GC-MS, and RIA. In blood serum and similarly complex matrices, the more traditional methods (colorimetry, titration, TLC) suffer from interference and/or lack of sensitivity. 

An improved HPLC-photohydrolysis-colorimetry method was validated for twenty-eight reference nitrosamines. These were separated by HPLC and photolytically cleaved by UV radiation. The resulting nitric oxide was oxidized and hydrolyzed to nitrite ions, which were derivatized into an azo dye with Griess reagent and measured spectrophoto-metrically. The method was applied to separate and detect hitherto unknown nonvolatile nitrosamines in biological fluids and food extracts591. 

Methods of Analysis of Pesticides. The extracted residue obtained after isolation from tissues and other biological materials is subjected to qualitative and quantitative determination of the pesticides. Sometimes, the amount of material available is so small that the colorimetric and other allied methods cannot be successfully applied as some of the residue is likely to be lost during the purification technique. Furthermore, these purification techniques required for spectrophotometry, colorimetry, and other sophisticated instrumental methods are appreciably time consuming. Therefore, other techniques were sought for the quantitative determination of pesticides. Thin layer chromatographic (TLC) techniques were found to be most suitable for toxicological analysis of pesticides. Randerath(16j stated that... 

V4. Van Sumere, C. P., Cottenie, J., and Teuchy, H., Purification and quantitative determination of amino acids in biological mixtures, by means of multiple elimination thin layer chromatography (METC) and colorimetry. Arch. Int. Physiol. Biochim. 76, 967-968 (1968). 

Numerous methods for determining macro concentrations of molybdenum are available. Optical emission spectroscopy has been used in survey-type analyses (2), but it does not have adequate sensitivity to measure part-per-billion levels. X-ray fluorescence has been applied for part-per-million levels but cannot be readily extended to the lower levels of interest to the Project. Kinetic methods (3) and colorimetry with suitable pre-concentration (4) are capable of measuring part-per-billion levels of molybdenum but have not been applied to petroleum analysis. Molybdenum has been determined by atomic absorption techniques in such materials as sea water, biological tissue, and soils (5,6,7), Although a procedure for determining metals including molybdenum in petroleum by atomic absorption has been reported (8), no actual data are given for molybdenum. Flame and heated vaporization atomic absorption of aqueous solutions of ashed samples were selected by the Project for concurrent study in two separate laboratories. 

BIOLOGICAL PROPERTIES not likely to migrate to groundwater uptake by plants is generally low chromium compounds are very persistent in water, half-life >200 days most in surface waters may be present in particulate form as sediment Cr (IV) is the major stable form in seawater can be detected in water by digestion followed by atomic absorption or by colorimetry analysis or by Inductively Coupled Plasma Optical Emission Spectrometry chromium (IV) can be detected by extraction and atomic adsorption or colorimetry dissolved forms can be detected by 0.45 p filtration followed by the previous methods... 

The Allen-Doisy test was a biological test for E., in which the response of ovarectomized mice to urinary or plasma E. was observed. It was replaced in clinical practice by a colorimetrie test, the Korber method, in which the E. are treated with HjSOj and hydroqui-none to produce intensely fluorescing derivatives. However, the development of Immunoassays (see) for the steroid hormones has made the Korber method obsolete for routine clinical assays. 

In the 1985 edition of this book, TLC received the credit of occupying an important position among analytical methods in the vitamin E field. Before the advent of modern liquid chromatography and given the inability of the older GC systems to separate P- and y-tocopherol, assays aiming at the differentiation of positional isomers nearly exclusively relied on TLC. Furthermore, TLC was frequently used as a lipid prefractionation step for complex biological samples prior to the quantitation of the E vitamers by colorimetry or GC. However, due to the poor resolving... 

Colorimetry and Spectrophotometry Protein and Amino Acid Analyses Biological Analyses Digestibility Trials Nutrient-Deficient Animals Microbiological Assays Microscopic Analyses for Filth and other Adulterants or Contaminants Physical Methods of Analyses Use of Food Composition Data for Planning Menus and Diets... 

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