Additives, determination mass spectroscopy

Visual examination of crystals using a light microscope does not indicate whether the crystals consist of only the protein or the protein-DNA complex. Therefore, the crystals are washed free of any uncrystallized DNA and protein several times with a solution containing the precipitant and any additives, etc. at the concentration and pH used for growing crystals (mother liquor). Finally, the crystals are separated from the mother liquor by microcentrifugation, dissolved in a suitable buffer, and analysed biochemically. The protein content is determined by SDS polyacrylamide gel electrophoresis, the protein concentration by BIO-RAD assay, and amino acid composition by mass-spectroscopy. The DNA can be detected by staining the gel with ethidium bromide or methylene blue (Jordan et al., 1985), whereas... 

Analysis. Be can be quantitatively determined by colorimetry down to 40 ppb using eriochrome cyanine R or acetylacetone. The sensitivity may be improved by electrothermal absorption spectroscopy (ETAS) to 1 ppb and to 0.1 ppb by inductively-coupled plasma emission spectroscopy (ICPES) or inductively-coupled plasma mass spectroscopy (ICPMS). A simple spot test for qualitative detection of Be is one with quinalizarin in alcoholic NaOH which can detect 3 ppm. The color is produced by both Be and Mg. If the color persists after the addition of Br2 water. Be is present. If the color is bleached. Mg is indicated. 

The minor and trace elements in coals are currently determined by several techniques, the most popular of which are optical emission and atomic absorption spectroscopy. Neutron activation analysis is also an excellent technique for determining many elements, but it requires a neutron source, usually an atomic reactor. In addition, x-ray fluorescence spectroscopy, electron spectroscopy for chemical analyses (ESCA), and spark source mass spectroscopy have been successfully applied to the analyses of some minor and trace elements in coal. 

Mass spectrometry is also applied in the control of pesticides and other contaminants (e.g., 2,4,6-trichloroanisole), detection of compounds formed by yeast and bacteria, determination of illegal additions to the wine. Liquid chromatography/mass spectroscopy (LC/MS) methods for determination of toxins in the wine (e.g., ochratoxin A) have been proposed (Zollner et al., 2000 Flamini and Panighel, 2006 Flamini et al., 2007). 

Biomarkers of Exposure and Effect. There are no studies available to determine specific biomarkers of exposure or effect. Components of Stoddard solvent can be measured in the blood, fat, and breath. Fat appears to be the best compartment to sample for chronic exposure, since Stoddard solvent is extremely lipid soluble (Pedersen et al. 1984, 1987). However, these chemicals can be found in many types of petroleum distillates and are not specific to Stoddard solvent. Additional research that identifies Stoddard solvent exposure using currently available breathalizer techniques with mass spectroscopy would also be useful. 

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