Powder mixtures analysis

The theoretical basis of the quantitative analysis of powder mixtures was developed by Alexander and Klug [1,45]. When an x-ray beam passes through any homogenous substance, the fractional decrease in the intensity, I, is proportional to the distance traveled, b. This relationship is given by... 

H. Martens, J.P. Nielsen and S.B. Engelsen, Light scattering and light absorbance separated by extended multiplicative signal correction. Application to near-infrared transmission analysis of powder mixtures, Anal Chem., 75, 394 (2003). 

A.D. Patel, P.E. Luner and M.S. Kemper, Quantitative analysis of polymorphs in binary and multi-component powder mixtures by near-infrared reflectance spectroscopy, Int. J. Pharm. 206, 63-74. Erratum in Int. J. Pharm., 212, 295 (2000). 

Scholz F, Lange B, Jaworski A, Pelzer J (1991) Analysis of powder mixtures with the help of abrasive stripping voltammetry and coulometry. Fresenius J Anal Chem 340 140-144. 

Alexander LE, Klug HP. 1948. Basic aspects of X-ray absorption in quantitative diffraction analysis of powder mixtures. Anal. Chem. 20 886-894. 

The powder XRD analysis of the components present in a mixture was one of the first applications carried out with this methodology. In fact, in 1919, Hull was the first to apply the XRD methodology in chemical analysis [43], However, Klug and Alexander [36] gave a big impetus to the development of the XRD phase analysis method. 

AIM sodium methoxide solution was prepared by adding Na (12.5 mmol) to 12.5 ml methyl alcohol with cooling, tosyl hydrazone (12.25 mmol) added, and the mixture stirred until all solids were dissolved. After stirring an additional 15 minutes the mixture was concentrated and the product ground to a fine powder. Elemental analysis, IR, and H-NMR provided. 

Some comparisons of production costs by SHS and conventional processes have been reported. Analysis for SisNa, AIN, and SiC materials has shown that combustion synthesis is economically favorable to existing technologies, as shown in Tables XIII, XIV, and XV (Golubjamikov et al, 1993). For all materials, the total cost per kilogram of material produced is lower for SHS-based processing than for conventional methods, with a major contribution to savings from reduced fixed costs (i.e., capital equipment costs). The significant difference in the raw material cost for SiC tiles occurs due to the use of Si+C powder mixtures in the SHS case, compared with SiC powder for conventional methods. 

York, P. Analysis of moisture sorption hysteresis in hard gelatin capsules, maize starch, and maize starch drug powder mixtures. J. Pharm. Sci. 1981, 33, 269-273. 

A profile analysis method of fitting has been used to determine the relative amounts of prazosin hydrochloride polymorphs (the a and S forms) in powdered mixtures.23 The method was calibrated over 5-prazosin levels of 0.5-10% using a series of calibration samples, and it was found that the limit of detection was equal to 0.5%. The favorable limit was attainable owing to significant regions of non-overlap in the powder patterns of the two forms. 

In order to explain the structure of the LiF-B203 melts, the composition of the quenched samples was determined by means of X-ray powder diffraction analysis and IR spectroscopy. Both methods eliminated the presence of LiBp4 in the mixtures. On the other hand, the presence of LiB02 up to 5 mole % B2O3 and of 0126407 at higher... 

The proper selection of sampling techniques or sampling devices affects the calculation value of the relative standard deviation of a powder mixture, the indication of homogeneity. With the use of conventional side slit thief for sampling for blend uniformity analysis, discrepancy between the two values (blend uniformity versus content uniformity) can be determined. In the manufacture of some tablets, the relative standard deviation of the blend uniformity of a lot of bulk powder mix was found to be unacceptable and should have been rejected, whereas the tablets prepared with that powder blend unexpectedly met the content uniformity test. The noncorrelated relative standard deviation values of these two tests required clarification. 

In a paper dealing with the analysis of the continuity of one phase in a powder mixture of two phases, Forscher presents another approach to the use of the concept of a random mixture as a criterion of mixing. 

His mathematical analysis deals with the problem of determining how much of one powder A, must be added to another powder B, to obtain continuity of powder A in a random mixture of the two. When more than the minimum is added, more continuity will result. Continuity is expressed as the probability that pairs of particles of powder A have radii, the sum of which just equals the distance between their centers. Forscher s mathematical analysis leads him to conclude that for an aggregate of equal-size spheres A is probably discontinuous if the ratio of A to B is below Both A and B are continuous when A/B exceeds this ratio and eventually B becomes discontinuous if B/A falls below In the discussion given, powder A is a good conductor of electricity, and powder B, a poor conductor. The degree of continuity of powder A was assumed proportional to the over-all conductivity of the compound powder mixture. 

Flow of ethane at 275 bar was commenced and almost immediately, water-white liquid began to collect in the U-tube. It is presumed that this was excess aminopropyl disiloxane that was originally in the vessel and that had dissolved in the ethane, not the product of the reverse reaction. After collecting —90% of the disiloxane that was charged, an opaque semisolid began to collect and finally a white powder. IR analysis and titration of the semisolid indicated that this sample was a mixture of disiloxane (whether it is strictly the... 

The electron microscopic analysis revealed that the hexaaluminate powder prepared by hydrolysis of the alkoxides crystallized in plate-like microcrystals.The size of the powder is 30 nm in thickness and 200 nm in diameter. The plate-like crystal was also observed for the sample derived from powder mixture however, the sample contains granular-shaped crystals and amorphous regions. The plate-like shape is characteristic of the hexaaluminate microcrystals due to their hexagonal layered structure. The granular crystals and amorphous regions observed in the calcined powder mixture are the unreacted particle or the intermediate phases. The composition of each microcrystal is not uniform in the sample from the powder mixture. This means that the bulk diffusion significantly limits the phase formation of hexaaluminate in the case of powder mixing. 

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