LABORATORY
OF THE MONTH
Cornell Trace Analysis Laboratory Aids Materials Research T.1AR
ABOVE
CAYUGA'S
WATERS
is
-Γ located one of the most modern re search facilities devoted to trace analy sis. A t Cornell University's Baker Chemical L a b o r a t o r y in Ithaca, New York, both research and service for theanalysis of high p u r i t y solid state materials a r e being performed under the direction of Professor George II. Morrison. The analytical facility is p a r t of Cornell's Materials Science Center, an interdisciplinary laboratory for re search in t h e field of materials spon sored b y the Advanced Research Pro jects Agency. T h e Center, which was established to foster graduate education and research in this field, is a free association of professors interested in the materials area, a n d represents various disciplines in the D e p a r t m e n t s of Chemistry, Physics, Engineering Physics a n d Materials Science, a n d Electrical Engineering. A n u m b e r of central technical facilities, of which analytical chemistry is one, provide not only technical assistance, b u t also permit research t o b e conducted on a more sophisticated technical level and give t h e students t h e o p p o r t u n i t y to familiarize themselves, under expert guidance, with the latest techniques.
Spark source mass spectrograph, recently developed by Nuclide Corporation, provides maximum versatility for research at the Cornell Trace Analysis Lab oratory. The instrument is equipped with both photographic and electron multiplier detectors and is used for comprehensive determination of im purities in metals, semiconductors, and other solids in the parts per billion range. To ensure flexibility, additional ports and electrical leads are provided at various strategic places. Ion pumps supply extremely high vacuum
T h e analytical service facility is m a n n e d b y g r a d u a t e chemists. R e search in materials analysis is per formed by graduate students and post doctoral associates. I n order t o keep pace with advances in materials re search, a n u m b e r of the modern trace analytical techniques a r e u n d e r i n vestigation. I n t h e area of neutron activation analysis, the Cornell M a r k I I T R I G A reactor with a thermal n e u t r o n flux of 2 Χ 10 12 n / c m . 2 sec. is used t o ir radiate high p u r i t y samples. Both radiochemical separations a n d non destructive analyses using gamma spec t r o m e t r y are employed in the measure ment of trace elements. A specially designed Flexo R a b b i t rapidly t r a n s fers irradiated samples from a n y posi tion in the reactor t o the detector of the R I D L 400-channel analyzer for the measurement of short lived radio isotopes. A magnetic t a p e t e m p o r a r y storage device, I B M electric typewriter digital readout, Mosely x-y point plot-
ter, a n d Tally tape punch provide rapid and versatile processing of data. In order t o achieve increased selec tivity in instrumental activation analy sis, a computer program h a s been developed which rapidly determines the optimum times of irradiation and decay before counting for activation analysis of any element in any matrix regardless of its complexity. Students perform all operations themselves a t the Reactor Laboratory a n d at t h e C o m p u t i n g Center on t h e Cornell campus. For t h e comprehensive analysis of high purity materials, b o t h emission spectroscopy a n d spark source mass spectroscopy a r e employed. Direct, methods using atmospheres, as well as chemical preeoncentration methods, are being developed t o increase the sensi tivity of emission spectroscopy. A complete emission spectrographic lab o r a t o r y is equipped with a separate
p r e p a r a t o r y laboratory, dark room, and instrument laboratory containing a Jarrell-Ash E b e r t spectrograph with a 22-channel direct reader and a console recording mierophotometer. A separate radioactive tracer a n d high purity laboratory is provided for the development of chemical methods of preeoncentration of samples, a n d methods of purification of reagents. Novel ion exchange techniques have been developed which rapidly separate the matrix from t h e trace elements with minimum contamination, thereby permitting increased sensitivity for emission spectrographic, flame photo metric, and other methods of estima tion. T h e recently developed Nuclide G R A F - 2 double focusing spark source mass spectrograph is used t o analyze various solids for trace impurities in the parts p e r billion concentration (Continued on page 103 A)
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A
LABORATORY OF THE MONTH
Computer is used by members of the analytical facility for designing experiments and processing data from instrumental analyses. The Control Data 1604 computer shown is housed in the Cornell Computer Center Neutron activation analysis, carried out with a Flexo Rabbit between a TRIGA reactor and an RIDL 4 0 0 channel gamma spectrometer, permits the nondestructive determination of submicrogram amounts of elements in high purity materials
Emission spectroscopy using novel methods of excitation provides rapid and comprehensive trace analyses of a large variety of materials in the low parts per million range. The instrument shown is an Ebert 3.4-meter spectrograph. It is equipped with a 22-channel direct reader 102 A
•
ANALYTICAL CHEMISTRY
Flame photometry with the ORNL Model VI flame photometer employing a 0.5-meter Ebert monochromator permits the convenient determination of many elements at the trace level. Prior removal of matrix by ion exchange eliminates interference
WACO . . . f o r Karl
TITRATOR Fischer
Moistures
Neutron capture gamma spectrometry of samples irradiated in a neutron beam from the TRIGA reactor is being explored to augment activation analysis
range. The instrument was designed to provide maximum versatility in research and is equipped for both photographic and electron multiplier detection of ions. Special sampling equipment to minimize contamination of solid materials is provided in the laboratory and includes a lathe, cutting wheels, and ultrasonic cleaners. Mass spectrometry is an excellent survey method for determining impurities in high purity metals, semiconductors, and other solids. In addition to the above trace techniques, facilities exist for flame pho-
tometry, atomic absorption, absorption spectrophotometry, x-ray fluorescence spectrometry, as well as the more classical methods of analysis. All facilities except the reactor and computer are housed in newly renovated air conditioned laboratories in the Chemistry Building at Cornell. The large assortment of analytical instruments available and the variety of techniques under investigation at the Trace Analysis Laboratory provide the Cornell student with a thorough grounding in all the modern analytical techniques.
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