Assay determination

The assay determination of sulfamic acid is made by titration of an accurately prepared sulfamic acid solution using sodium nitrite solution and an external potassium iodide starch-paste indicator. It is based on the reaction... 

Standard 1/10 N nitrite is used to titrate a solution prepared by dissolving 10—100 mg of sulfamic acid and about 6 mL of (1 + 1) H2SO4 in 300 mL of distilled water at 40—50°C. At the end point, the colorless external potassium iodide starch-paste indicator changes to blue. A 1-mL solution of 1/ION NaN02 is equivalent to 9.709 mg of sulfamic acid. The 1/10 N nitrite titrant solution is standardized using primary standard-grade sulfamic acid. For sulfamate assay determination, the same procedure is used as for sulfamic acid. 

Enzyme Assays. An enzyme assay determines the amount of enzyme present in sample. However, enzymes are usually not measured on a stoichiometric basis. Enzyme activity is usually determined from a rate assay and expressed in activity units. As mentioned above, a change in temperature, pH, and/or substrate concentration affects the reaction velocity. These parameters must therefore be carefully controlled in order to achieve reproducible results. 

Chiral or achiral assay and purity determinations are done according to an external calibration calculation procedure, either with or without internal standardization. The calibration is performed against a 10% w/w (compared to the nominal concentration of the sample solution at 100% w/w) reference standard solution. The sample solution for the purity determination remains at the 100% w/w level, while that of the assay determination is diluted 10 times. The reason for the difference in concentration levels is similar to the purity method. A suggested sample injection sequence can be... 

Sample solutions injections at 10% w/w level for assay determinations... 

Enantiomeric assay determinations are typically applied to characterize racemic mixtures using the normalized peak area (area%) calculation procedure. The selectivity solution is utilized to demonstrate the separation capability in the method and to allow peak identification. A suggested sample injection sequence can be... 

Due to the lower injection precision of CE, it is not the method of first choice for the assay determination because the methods with higher precision are competing (HPLC, titration). However, a few examples in literature can be found and as a rule of thumb a well-developed CE method including internal standards should be able to obtain a repeatability of injections around 1% while values below 0.5% are generally expected for HPLC. 

In general, several doses are tested in genotoxicity assays. Determination of experimental dose-response relationships may be used to assess the genotoxic potential of a substance, as indicated below (EC 2003) ... 

The work that follows pertains primarily to actin networks. Many proteins within a cell are known to associate with actin. Among these are molecules which can initiate or terminate polymerization, intercalate with and cut chains, crosslink or bundle filaments, or induce network contraction (i.e., myosin) (A,11,12). The central concern of this paper is an exploration of the way that such molecular species interact to form complex networks. Ultimately we wish to elucidate the biophysical linkages between molecular properties and cellular function (like locomotion and shape differentiation) in which cytoskeletal structures are essential attributes. Here, however, we examine the iri vitro formation of cytoplasmic gels, with an emphasis on delineating quantitative assays for network constituents. Specific attention is given to gel volume assays, determinations of gelation times, and elasticity measurements. 

In cases like this, assay determination of hydrogen peroxide concentration would be the most sensitive metric. Titrametric determination will give a reliable measure of the specific ingredient that is most crucial to the polishing process. Assay by titration of low-concentration ingredients, such as hydrogen peroxide or ammonium hydroxide, both of which degrade over... 

Single-compound potencies in the standard 12-mL hlAlv2 assay determined using data of Durant et al. (1996). Units are induced mutant fraction x 10f /ng of PAH or PAC tested. ND, not detected but included for reference. 

Procedure. The site was developed on a five-spot pattern about 25 ft square, as shown in Figure 2. The wells were rotary drilled with water and completed with 50 ft of 7-in. casing and cemented to the surface. A 6%-in. hole was drilled below the casing to a total depth of 100 ft in the oil shale. Two additional wells were drilled off pattern as observation wells. A Fischer assay determined the oil yield of the section as 19.0-26.5 gal/ton. Two sand-propped hydraulic fracture treatments were applied for emplacing NG1 in the formation. 

Values are averages of two assays determined in duplicate. R designates irradiated culture UI, unirradiated. 

Sterility. This assay determines the absence of bacterial or fungal organisms. 

A typical chromatogram obtained using this method is shown in Figure 12, and the retention times (Rt) and the relative retention time (Rrt) for pantoprazole sodium and some of its related compounds are shown in Table 6. The calibration curve for the assay determination, obtained over a concentration range of228-670 pg/mL, was found to be linear with a correlation coefficient of0.999. The recovery and relative standard deviation for various assays were 97.3-101.5 and 1.1, respectively. A calibration curve was also developed for pantoprazole sodium related compounds, covering a concentration range of 1 to 3 pg/mL, and which was found to be linear with a correlation coefficient of more than 0.999. The limits of detection and limits of quantitation were calculated as 0.15 pg/mL and 0.49 pg/mL, respectively. 

Choose method for bound/free separation Optimize assay conditions Develop standard curve Characterize assay Determine assay reliability... 

Assay Determine as directed under Alginates Assay, Appendix IIIC. Each milliliter of 0.25 A sodium hydroxide consumed in the assay is equivalent to 25 mg of (CgHgOg), (equiv wt 200.00). 

Assay Determine the total color strength as the weight percent of the sample taken using Methods I and II in Total Color under Colors, Appendix IIIC. Express the Total Color as the average of the two results. 

Assay Determine as directed under Aldehydes, Appendix VI, using about 1 mL of sample, accurately weighed, and 53.05 as the equivalence factor (e) in the calculation. 

Assay Determine as directed under Phenols, Appendix VI. Angular Rotation Determine as directed under Optical (Specific) Rotation, Appendix IIB, using in a 100-mm tube. Refractive Index Determine as directed under Refractive Index, Appendix IIB, using an Abbe or other refractometer of equal or greater accuracy. 

Assay Determine as directed under Solidification Point, Appendix IIIB. The sample s solidification point is not lower than 140°, indicating a purity of not less than 98.0%, by weight, of Q5H24O2. 

Assay Determine as directed in the monograph for Calcium Pantothenate. 

Assay Determine as directed in the monograph for Calcium Phosphate, Dibasic, using a 150-mg sample, accurately weighed. Each milliliter of 0.05 M disodium EDTA is equivalent to 2.004 mg of Ca. 

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