Nephelometry precipitates used

Description of Method. Adding BaC to an acidified sample precipitates S04 a BaS04. The concentration of S04 may be determined either by turbidimetry or nephelometry using an incident source of radiation of 420 nm. External standards containing known concentrations of S04 are used to standardize the method. 

APPL is determined by acid precipitation (12M HC1) using either turbidity measurements (nephelometry abs. at 600 nm) or gravimetry according to Crawford et al. (4). All experiments reported in this paper were carried out with uninoculated controls whose values were always substracted. 

Kinetic solubility This pragmatic approach starts with a concentrated compound solution in pure DM SO further diluted in a buffer medium. The amount of compound in solution is measured after a few minutes incubation either by recording its UV absorbance (with or without a chromatographic step) or precipitate formation using an optical method (turbidimetry, nephelometry or flow cytometry). This approach mimics the typical path of the compound in biochemical, cellular assays or in vivo animal models. Kinetic solubility usually serves as a quality filter prior to cell based assays (see paragraphs on solubility, permeability and cellular assays). 

Nephelometry, a technique that differs from colorimetry, also uses Beer Lambert s law. This method involves the formation of a precipitate and, based on the absorbed light at a given wavelength, allows the concentration of the precursor... 

Forerunners of nonisotopic immunoassay had already appeared before radioimmunoassay was developed. For example, nephelometry is based on precipitation, which is known as the classical immune reaction, and the ideas of particle immunoassay and viroimmunoassay seem to have developed from the hemagglutination test. The principles of enzyme and fluorescence immunoassay had already been used as enzyme and fluorescence antibody techniques in histochemical analysis. In 1971, two groups reported use of an enzyme immunoassay (E5, V2). Leute et al. reported spin immunoassay, which has spurred recent development of nonisotopic immunoassays (L5). 

These two optical techniques are particularly applicable to methods measuring the precipitate formation in antigen antibody reactions (see Chapter 9). Turbidimetry is used in several chemistry immunoassay systems for therapeutic drug monitoring and specific protein assays. Details of turbidimetry and nephelometry are discussed in Chapter 3. 

The alternative method to turbidimetric detection used for measuring solubility in early discovery is to quantify the aqueous supernatant directly via UV absorbance [13, 20, 21]. Typically, DMSO stock solution is added to aqueous buffer such that the final DMSO composition is kept to a minimum (5% or less) and the resulting precipitate is removed by filtration. A UV plate reader is then used to determine the aqueous solubility by comparing the filtrate absorbance against that of a calibration solution prepared in an identical solvent. It is important to match the sample and calibration solutions to prevent solvochromic effects. Care must also be taken in the selection of the filter plate since nonspecific binding of compound can occur with some filter materials leading to erroneously low solubility values [22], Like nephelometry, the plate-based UV detection approach is amenable to automation. 

Precipitate detection methods typically use light scattering techniques such as nephelometry, flow cytometry, and turbidity measurements to determine the amount of the precipitate formed during the incubation process. A major advantage with these types of techniques is the availability of particle size distribution and aggregation information. 

The ethanol test (Boulton etal., 1996) consists of adding a volume of absolute ethanol to the same volume of wine. The turbidity formed in the presence of alcohol, measured by nephelometry shortly after the substances are mixed, does not consist only of unstable proteins, as polysaccharides and particularly mannoprotein also precipitate. It is relatively common for wines that are perfectly thermostable to become turbid when subjected to this ethanol test, particularly if they have acquired a high mannoprotein content through aging on the lees. This test leads to the use of higher doses of bentonite than are truly necessary to achieve stability. 

Much of the theory and equipment used in spectrophotometry applies with little modification to nephelometry and turbidimetry. These fields involve the scattering of light by nontransparent particles suspended in a liquid examples of such particles include fine precipitates and colloidal... 

The phase transformations and phase compositions during interaction of dextran sulphate and proteins precipitating in the vicinity of their isoelectric points have been investigated using nephelometry and chemical analysis. Sodium dextran sulphate and chitosan solutions have been co-reacted under various experimental conditions to form a water-insoluble hydrous precipitate. ... 

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