X-RAY DIFFRACTION A N A L Y S I S OF THIN CLAY FILMS FROM DILUTE SUSPENSIONS USING G L A N C I N G INCIDENCE DIFFRACTION
-X-ray diffraction (XRD) analysis of small quantities of clay mounted on glass slides using conventional Bragg-Brentano geometry generally produces unsatisfactory low-intensity reflections masked by amorphous substrate scatter. Glancing-incidence asymmetric Bragg diffraction, an alternative uncoupled geometry, uses a fixed low-incidence angle and parallel-beam optics to increase path length through the sample and decrease X-ray penetration into the substrate. To evaluate this technique on thin soil clay films, results from conventional Bragg-Brentano and glancing-incidence diffraction (GID) were compared for progressively diluted clay suspensions separated from 2 southeastern soils with typical mineral assemblages. Patterns produced by GID showed overall higher reflection intensities and reduced substrate scatter, especially at higher 20 angles within the amorphous glass region, Using GID, positive identification of clay minerals was obtained from sample quantities as small as 0.005 mg cm 2 and suspensions as dilute as 29 mg L 1. Key Words--GID, Thin Films, XRD.
X-ray Diffraction and the Identification and Analysis of Clay Minerals
Instructor: Dr. W. Crawford Elliott, Associate Professor, Department Chair Office: 331 Kell Hall Office Phone: (404) 413-5756 E-mail: wcelliott@gsu.edu Primary Texts: X-ray Diffraction and the Identification and Analysis of Clay Minerals, by D.M. Moore and Robert C. Reynolds, Jr. (2nd Edition), 1997, Oxford University Press. Office Hours: 4-5 pm M, anytime the door is open, or by appointment. Lectures: M, W, 5:30pm – 7:10 pm, Kell 314. Laboratory: By arrangement, see below.
On the fractionation of β-lactoglobulin and α-lactalbumin
Abstract Existing methods for the preparation of α-lactalbumin and β-lactoglobulin are examined critically. It is proposed that the most satisfactory method for the preparation of the whey protein fraction from bovine milk is (NH 4 ) 2 SO 4 fractionation. A number of new gentle procedures for the fractionation of the whey proteins are compared with some existing methods. The distribution of total protein at various stages is determined by total Kjeldahl nitrogen and the kind of protein by starch-gel electrophoresis. The effect of variables, such as pH, salt concentration and temperature on the separation of α-lactalbumin and serum albumin from β-lactoglobulin is studied. Differences in the behavior ( e.g. solubility) of genetic variants of β-lactoglobulin are noted. The solubility of each of the major whey proteins, under similar conditions to those used in the fractionation, is compared with its solubility in the whey protein mixture. The understanding gained of factors important in the fractionation is used in recommending new procedures for α-lactalbumin and β-lactoglobulin isolation.