Fluorescence contamination

MP-suspension by automated ASTM-bulb Magnetization current by Hall-Sensor Magnetization time UV-Light intensity All Liquids (fluorescence, contamination) Process times and temperatures Function of spraying nozzles, Level of tanks Flow rates (e.g. washing, water recycling) UV-Light intensity... 

To correct for possible fluorescent contamination in the RNAase solution, place 3.0 mL of pH 7.5, ethidium bromide-Tris buffer in a cuvette. Add 15 fiL of Tris buffer I and 2 fxL of ribonuclease. Mix well and incubate at 37°C for 20 minutes. Record the fluorescence intensity, if any. If the fluorescence is significant (> 1 intensity unit), subtract from Adna x before calculation of unknown DNA. Calculate the concentration of DNA in your sample in units of /ag/mL. Was RNA present in your unknown DNA solution ... 

Bioassay procedures for the determination of gibberellic acid have been developed (2, 5), but more recent chemical fluorometric assay methods are equally specific. However, both assay methods show a low response with samples containing less than 10 /x/xg. of the gibberellins. Consequently, in determining residual amounts within the part per billion (p.p.b.) range, relatively large samples must be extracted and extracts partially purified to satisfy the assay conditions. These operations are usually accompanied by some material losses or degradation, which impair quantitative interpretation of the results. Natural inhibitors can influence the results in the bioassay method (2), and fluorescent contaminants can interfere with the spectrophotometric analysis. 

Fig. 2. Dermal contamination as revealed by fluorescence - contamination of a sheep-dipper who wore a woUen cardigan and woUen trousers, but no waterproofs (Roff 1997)...

Sample treatment prior to SPE was required to convert FMN and FAD to riboflavin using a hot acid extraction procedure followed by enzymatic digestion, as the HPLC method applied allows the determination of only riboflavin. In this case, the recovery of riboflavin from FAD in pork samples was 94-98% with 2-4 hours of incubation time prolonging the incubation time to 24 hours did not improve the recovery. Indeed, the SPE procedure allowed a concentration factor of two to four fold, with recoveries for samples in the range 96-108%. The method was applied to 21 food samples, providing comparable results to the AO AC method (modified) apart from the crispbread sample. This was justified by the presence of a fluorescent contaminant in this sample that caused an overestimation of the amount of riboflavin in the fluorimetric, non-separative method. 

Interference by other fluorescent contaminants in sample can occur... 

Standardizing the Method Equations 10.32 and 10.33 show that the intensity of fluorescent or phosphorescent emission is proportional to the concentration of the photoluminescent species, provided that the absorbance of radiation from the excitation source (A = ebC) is less than approximately 0.01. Quantitative methods are usually standardized using a set of external standards. Calibration curves are linear over as much as four to six orders of magnitude for fluorescence and two to four orders of magnitude for phosphorescence. Calibration curves become nonlinear for high concentrations of the photoluminescent species at which the intensity of emission is given by equation 10.31. Nonlinearity also may be observed at low concentrations due to the presence of fluorescent or phosphorescent contaminants. As discussed earlier, the quantum efficiency for emission is sensitive to temperature and sample matrix, both of which must be controlled if external standards are to be used. In addition, emission intensity depends on the molar absorptivity of the photoluminescent species, which is sensitive to the sample matrix. 

Post-column in-line photochemical derivatization permits fluorescence detection of the common aflatoxins Bl, B2, Gl, and G2 (60). Chromatographic evidence indicates that photolysis causes the hydration of the nonfluorescent Bl and Gl components to B2a and G2a components, respectively. Analysis of naturally contaminated com samples show no interfering peaks and permits the deterrnination of 1 and 0.25 ppb for Bl and B2, respectively. 

Barium can also be deterruined by x-ray fluorescence (XRF) spectroscopy, atomic absorption spectroscopy, and flame emission spectroscopy. Prior separation is not necessary. XRF can be appHed directly to samples of ore or products to yield analysis for barium and contaminants. AH crystalline barium compounds can be analy2ed by x-ray diffraction. 

The very low Hg concentration levels in ice core of remote glaciers require an ultra-sensitive analytical technique as well as a contamination-free sample preparation methodology. The potential of two analytical techniques for Hg determination - cold vapour inductively coupled plasma mass spectrometry (CV ICP-SFMS) and atomic fluorescence spectrometry (AFS) with gold amalgamation was studied. 

The performance of microwave-assisted decomposition of most difficult samples of organic and inorganic natures in combination with the microwave-assisted solution preconcentration is illustrated by sample preparation of carbon-containing matrices followed by atomic spectroscopy determination of noble metals. Microwave-assisted extraction of most dangerous contaminants, in particular, pesticides and polycyclic aromatic hydrocarbons, from soils have been developed and successfully used in combination with polarization fluoroimmunoassay (FPIA) and fluorescence detection. 

Other techniques to inspect bonding surfaces for contamination have also been proposed, including ultraviolet fluorescence [162], Pulsed ultraviolet light incident on the surface excites fluorescence of organic contamination, which can... 

Chelerythrine crystallises from alcohol in colourless, prismatic leaflets, m.p. 207°, containing one molecule of alcohol. The alkaloid absorbs carbon dioxide from the air, becoming yellow. The solutions fluoresce blue when the alkaloid is contaminated with its oxidation product, which is formed by mere exposure of solutions to air. The salts, which are quaternary, are intensely yellow. The hydrochloride, B. HCl. HjO, forms citron-yellow needles, and the sulphate, B. H2SO4.2HjO, golden-yellow needles, sparingly soluble in water the platinichloride, B2. HaPtCl. ... 

Filthy conditions, due to rodent or insect population, may be observed in a grain warehouse. The inspector notes rat-chewed flour sacks and sacks contaminated with rat excrement. He removes a sample of sacking and flour from such contaminated areas and submits them to the analyst. Urine fluoresces under ultraviolet light. Where rodent urine is to be confirmed, the xanthydrol test is one of several that may be used. Excreta pellets may be moistened with water or an appropriate clearing solution and crushed for observation under the compound microscope. The presence of striated hair fragments indicates rodent excrement. 

If flour or meal has become contaminated with storage insects after milling, the insect parts or larvae may be removed for identification by sieving or by a flotation procedure, but perhaps only excrement remains in the sample. This is about the same color as the material upon which the insects have fed and has generally the same appearance macroscopically. By means of the fluorescent light, however, pellets may be rendered more readily visible. If such flour is treated with clove oil, the pellets stand out distinctly and may be readily counted. 

New process technologies (Ref 53) such as jet mills (Fig 2) and co-precipitation (Ref 97) may allow safe compounding of sensitive or toxic formulations. New analytical tools such as neutron radiography (Ref 92) afford improved non-destructive testing of devices. X-ray fluorescence (Ref 93) and neutron activation (Ref 94) provide quantitative analysis of pyrotechnic compns and their trace contaminants... 

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