Download X-Ray Powder DiffractionStudy

was suggested
(Perkin-Elmer
by Schmidt and Slavin
Corp.) in their compa-
ny’s Chromatography
1978).
Newsletter
(6: 22,
References
I. Soldin, S. J., and Hill, J. G., Rapid micro
method for measuring anticonvulsant
drugs
in serum by high-pressure
liquid chromatography. Clin. Chem. 22,856-859 (1976).
2. Kabra, P. M., Stafford, B. E., and Marton,
L. J., Simultaneous
measurement of phenobarbital,
phenytoin, primidone, ethosuximide, and carbamazepine
by high-pressure
liquid chromatography.
Clin. Chem. 23,
1284-1288
(1977).
3. Fairinotti, R., Pfaff, M. C., and Mahuzier,
C., Simultaneous
determination of phenobarbital and valproic acid in plasma using
high performance
liquid chromatography.
Ann. Biol. Clin. 36, 347-353 (1978).
4. Gupta, R. N., Eng, F., and Gupta, M. L.,
Gas-chromatographic
analysis of vaiproic
acid as phenacyl esters.
Clin. Chem. 25,
1303-1305 (1979).
5. Borch, R. F., Separation of long chain fatty
acids as phenacyl esters by high pressure
liquid chromatography.
Anal. Chem. 47,
2437-2439 (1975).
Ram N. Gupta
Paul M. Keane
Mohan L. Gupta
Clinical Chemistry
Laboratory
St. Joseph’s
Hospital
50 Charlton
Avenue East
Hamilton,
Ontario,
Canada
L8N 1 Y4
Simple Technique for the Camera
X-Ray Powder DiffractionStudy
of Urinary Calculi
To the Editor:
Determination
of the composition
of
the nucleus and individual layers of a
urinary calculus is of vital importance
in
establishing the pathogenesis of urinary
stone formation. This information cannot be obtained by conventional
wet
chemical techniques,
especially in the
case of small calculi. We describe an
easy,
accurate
method
based
on the
classical Debye-Scherrer
camera x-ray
powder diffraction
technique
(1-4),
which overcomes this problem.
After being crushed slightly with a
glass slide, the urinary calculus is examined in a Petri dish under a binocular
stereoscopic microscope with approximately 40X magnification, to determine
whether it is a simple or a mixed calculus. In the case of large or extremely
hard calculi, a dental-extraction
forceps
or a pair of long-nosed pliers may be
used to crush the calculus. Most stones
are of mixed composition and consist of
several concentric layers, including a
nucleus, so it is desirable to separate
these and examine them individually. It
must be noted, however, that a difference in appearance
between two consecutive layers often, but not always,
means a difference in composition. In
many calculi, the nucleus consists of a
substance
different from that of the
outer shell.
The carefully selected grain of microscopic size, which may weigh less
than 5 g or measure less than 0.1 mm in
diameter, is transferred to a clean glass
slide with a thin, sharp biological dissecting needle. By means of a needle, the
grain is then covered with a small drop
of rubber solution (such as can be obtained in a bicycle repair kit), diluted
with benzene. The grain is ground into
the solution between this slide and another, without losing any material. Short
strokes will prevent the powder from
spreading
too much. By inspection
under the stereoscopic microscope, one
can ascertain when the material is fine
enough. The slides are separated from
one another for a few seconds to allow
the benzene to evaporate. Each slide will
show a circular area of clear, sticky
rubber, with the calculus powder confined to the center of each. The two
slides are again opposed and with a circular motion the powder-rich solution is
rubbed into a small ball, about 0.2 mm
in diameter. This ball is mounted on the
tip of a stiff hair, which has previously
been wetted with rubber solution and
mounted
in a Debye-Scherrer
x-ray
powder camera, with the ball centered
in the middle of the monochromatic
x-ray beam. Ni-filtered Cu ka radiation,
produced
at 40 kV and 20 mA, and x-ray
cameras of 57.3 mm diameter are used.
To obtain x-ray photographs
of good
resolution, an exposure time of 2 h is
required.
Because every crystalline substance,
whether organic or inorganic, has a
unique and characteristic
powder diffraction pattern, the x-ray diffraction
spacing data obtained from the photograph of the urinary calculus can be
compared
with information
in the
J.C.P.D.S. (Joint Committee for Powder
Diffraction Standards) powder data file
to determine
the composition
of the
unknown substance by means of its internal atomic arrangement.
The x-ray
powder patterns may also be identified
by directly comparing
the unknown
patterns
with previously
prepared
standard
x-ray powder patterns
of
known substances. This physical analytical method provides a powerful tool
in the routine study of calculi. Although
most clinical chemistry laboratories do
not have their own facilities for camera
x-ray powder diffraction,
such equipment is available at most universities.
The technique described here is relatively simple in the hands of a skilled
operator and yields much information
as to the detailed structure of the calculus.
References
1. Klug, H. P., and Alexander, L. E., X-Ray
Diffraction Procedures. John Wiley, New
York, NY, 1954, p 716.
2. Az#{225}roff,
L. V., and Buerger,
M. J., The
Powder Method. McGraw-Hill, New York,
NY, 1958, p 342.
3. Nuffield,
E. W., X-Ray
Diffraction
Methods. John Wiley, New York, NY, 1966,
p 409.
4. Flutchison, C. S., ,Laboratory Handbook
of Petrographic
Techniques.
John Wiley,
New York, NY, 1974, pp 132-179.
G. J. Beukes’
A. De Waal2
Depts. of Geochemistry’
and
Chemical
Pathology2
University
of the Orange Free State
Bloemfontein,
R.S.A.
CLINICAL CHEMISTRY, Vol. 25, No. 11, 1979
1985