Homogeneity determination

PiOMde yourself with a yood book of leference, or chemist s pocket book which contains tables of physical constants. Homogeneity.—Determine if thesubstanceishomogeneous A Liquid.—If it is a hciuid, distil a few c.c. from a miniature distilling flask with a long side-tube, but no condenser, or with... 

The homogeneity determinations are performed to confirm that the variations between units (bottles, ampoules) are neither statistically nor practically significant compared to the certified uncertainty so that an appropriate result about the level of homogeneity is obtained. 

In the meantime, SS-ZAAS has gained in popularity in numerous apphcations, and has become of increasing importance for analyte homogeneity determination in the production and use of reference materials. Examples are Pb, Cd, Hg, Zn, and Fe in codfish candidate RM, Hg in copper metal, Zn in mussel tissue, Cd, Pb, Hg,... 

Another improvement that will allow quick simultaneous oligoelement homogeneity determinations in milligram samples can be expected by the use of solid sampling ETV-ICP-MS/AES and laser ablation ICP-MS which are now being studied in detail (Moens et al. 1995 Schiffer and Krivan 1999 Dobney et al. 2000). 

Extraction procedures combined with GC, GC-MS, HPLC, and HPLC-MS etc. are commonly applied for homogeneity determination of PAHs, PCBs and other organic compounds see Section 3.4. For these approaches sample sizes up to 10 g and even more are often needed for reliable results (Schantz et al. 1995). 

The sampling variance of the material determined at a certain mass and the number of repetitive analyses can be used for the calculation of a sampling constant, K, a homogeneity factor, Hg or a statistical tolerance interval (m A) which will cover at least a 95 % probability at a probability level of r - a = 0.95 to obtain the expected result in the certified range (Pauwels et al. 1994). The value of A is computed as A = k 2R-s, a multiple of Rj, where is the standard deviation of the homogeneity determination,. The value of fe 2 depends on the number of measurements, n, the proportion, P, of the total population to be covered (95 %) and the probability level i - a (0.95). These factors for two-sided tolerance limits for normal distribution fe 2 can be found in various statistical textbooks (Owen 1962). The overall standard deviation S = (s/s/n) as determined from a series of replicate samples of approximately equal masses is composed of the analytical error, R , and an error due to sample inhomogeneity, Rj. As the variances are additive, one can write (Equation 4.2) ... 

Homogeneity Determinations with Solid Sampling Atomic Absorption Spectrometry... 

Homogeneity Determinations with Instrumental Neutron Activation Analysis (INAA)... 

The homogeneity determination of the bacteria in the materials is performed by viable count followed by statistical evaluation of the cormts of sub-samples from the same capsule solution and of total counts of different capsules of one batch. An example for the homogeneity determination for a batch of capsules containing Enterococcus faecium is also presented in (Janning et al. 1995). 

LA-ICP-MS allows quick simultaneous oligo-element homogeneity determinations in mg samples of polymeric material. Coupling of ICP-MS to chromatographic techniques provides element speciation capabilities, especially as a detector for LC. Kingston et al. [417] have described a speciated technique for the determination of Cr(III) and Cr (VI) by HPLC-ICP-MS. 

G. T. Carter, R.E. Schiesswohl, H. Burke, and R. Young, Peak homogeneity determination for the validation of high-performance liquid chromatography assay methods, J. Pharm. Sci., 77 317 (1982). 

In many cases, sample preparation is mandatory prior to lipid extraction. This crucial process might include tissue homogenization, determination of dry weights, cell numbers, protein content, or DNA content for normalization purposes. The addition of internal standards is not only used to control extraction efficiency, but also is required for lipid quantification by mass spectrometric analysis, in which an ion current is translated into a lipid concentration. Many standard lipids that can be distinguished from endogenously occurring lipids by using rare... 

Quaternary structure. A protein was purified to homogeneity. Determination of the molecular weight by molecular exclusion chromatography yields 60 kd. Chromatography in the presence of 6 M urea yields a 30-kd species. When the chromatography is repeated in the presence of 6 M urea and 10 mM P-mercaptoethanol, a single molecular species of 15 kd results. Describe the structure of the molecule. 

Altria, K.D. Dave, Y.K. Peak homogeneity determination and micro-preparative fraction collection by capillary... 

The mix preparation is checked by means of grain size and homogeneity determinations. Oversize on a mesh of 10 000 openings per cm is usually determined in fine ceramics slips. 

The use of NIR for homogeneity determination requires no calibration. The method could be applied to any mixture without the extensive preliminary work of building a quantitative calibration as required for most near-IR work. On the other hand, homogeneity determinations could be carried out by using either quantitative or qualitative calibrations. Quantitative calibrations involve prediction of the drug level at various locations or times with an appropriate calibration using spectra collected in one of the methods named previously. The... 

The nozzle can be positioned centrally in the tank just under the liquid surface and operated by the liquid contents of the tank, so that the jet streams perpendicularly downwards and sets the liquid contents of the tank in circulation. Experiments [174] were carried out, in which 3% of the vessel contents was utilised and the mixing time, which is necessary for attaining 99% homogeneity, determined. 

Al Material and it defines the kind of material used with four feasible values steel, concrete, wood, and plastic. The second attribute A2 Shape is also symbolic. It describes the shape of our object with the three feasible values of cube, cuboid, and cone. The last symbolic attribute, A3 Homogeneity, determines if our object is solid or hollow. The attribute A4 Height is a numerical attribute with three specific numerical values. Obviously, more specific values could be used for the individual attributes, depending on our needs (Table 4.1). 

CCD—microprobe 206.5- 830 Trace Fast-medium Microscope Research lab to process 1-4 cm" accuracy Low concentration Qualitative visualization Failure analysis Homogeneity determination... 

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