5 0 MM. P R E S S U R E
-I/
4 MM. P R E S S U R E OQ
v
*Y
la5
II.0
me
*'
NORMAL SCAN
IQ
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I MM. P R E S S U R E
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11.5
NORMAL S C A N
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IP
Figure 3.
expansion from less than 1X to greater than 5OX. The cost of components is less than $40 if a conventional potentiometric recorder is available. The unit provides maximum information on
Application of scale expansion
spectra whirh contain both \Teak and strong bands, since expanded and un-
and moved to other instruments as the need arises.
Automatic Sample Changer for Routine Infrared Analyses J. W. Carrels,
E. G. Brame, and
C. E. Day, Polychemicalr Department, E. I. du Pont d e Nemourr and Co., Inc., Wilmington 98,
Del.
o INCREASE efficiencyof operation in Troutine infrared analyses, a method was developed to change film samples automatically on an infrared spectrophotometer. This development permits a series of scans to be obtained without operator attention. An automatic 35-mm. slide changer (Airequipt Manufacturing Co., Electrochanger) was adapted for use with a Perkin-Elmer Model 21 infrared spectrophotometer. The end of the slide channel was cut open and the shutter and shutter spring were removed. The catch at the end of the changer arm was also removed to eliminate the returning of the film sample to the cartridge. A 22.5-volt d.c. solenoid was mounted on side of the slide changer to actuate the manual triggering mechanism for changing samples. The changer was mounted on the side of the monochromator housing as shown in Figure 1. During operation, each film sample in its cardboard mount was pushed into position in the sample beam by the following sample. Upon completion of the scan, the sample was ejected onto the bottom of the sample compartment of the instrument. Two cartridges were joined together to increase to 70 the number of routin? scans that could be obtained during R
single unattended operation. This is equivalent to 24 hours of operation for a 20-minute scan cycle. Automatic Scanning. The scanning control switch is turned to the cycle position and the speed and the suppression control switches are adjusted appropriately. The scan is begun in the forward direction at the speed determined by the position of the speed control. The scanning continues until the riveme microswitch is aotuated by a cam located on the light side of thc drum. Immediately,
the scan is changed to reverse direction. At the same time the electrical circuit through the solenoid is closed and a new film sample is pushed into position. The reverse scan continues at maximum speed until a second microswitch is actuated. Then, the scan is changed to the forward direction and the entire process is repeated. Each scan is recorded in sequence on a strip-chart slave recorder. This recorder is coupled to the pen wedge system of the infrared speetrophotomctrr as describrd b; W(&Icat [ANAL. CHEM.33.812 (1961)'
Figure 1. Adoptotion of slide changer to Perkin-Elmer Model 21 infrared spectrophotometer
r 1
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VOL. 33. NO 6. MAY 1961
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