INSTRUMENTATION
instrument abstracts Applied Physics
Corporation/Pasadena/California
At R i k e r L a b o r a t o r i e s
Cary Model 14 Spectrophotometer leads to discovery of new alkaloid in Rauwolfia series C. Howard Stimmel, Analytical Chemist at Riker Laboratories, says: "With the Cary Model 14 we detected structure in the spectra of crude Reserpine samples which was not revealed with our manual spectrophotometer. Further research led Figure 5.
to the discovery of Canescine, a pre v i o u s l y u n i d e n t i f i e d m e m b e r of t h e Rauwolfia series. Differing only slightly from Reserpine, Canescine has notable therapeutic properties of its own."
Typical isodose plot
self-bias in t h e cathode of this stage. T h e time constants in t h e above cir cuits were chosen t o achieve a rea sonably clean d.c. grid bias, y e t main tain a sufficiently quick response t o large changes in t h e input signal. Sensitivity of t h e 4 0 X amplifier can be adjusted t o produce m o t o r drive from signals much less t h a n 1.2 μν. B u t t h e small fluctuations in probe o u t p u t m a k e it undesirable t o operate t h e amplifier a t a n y greater sensitivity in this application. W i t h t h e addition of t h e A.G.C. circuit t o t h e amplifier, full speed of t h e operation of t h e balancing m o t o r can be obtained with i n p u t signals t h a t range from 60 μν. to a t least 1.5 volts (Figure 3). T h e motor speed is proportional t o t h e i n p u t voltage a t values below 60-μν. Below 100-μν. input, there is no A . G . C . action while above this value, t h e A.G.C. functions excellently as observed both b y oscilloscope exam ination a n d actual performance. T h e complete isodose plotter is shown in Figure 4 with t h e control center on t h e right a n d recorder on t h e left. A typical record is shown in Figure 5. I n this record, vertical a n d horizontal distances on t h e c h a r t rec ord correspond t o t h e same distances in t h e p h a n t o m . I n related techniques—for example, in t h e location of administered I 1 3 1 in t h e thyroid g l a n d — t h e m a p p i n g h a s been achieved b y a mechanical scanner combined with photographic techniques. I n this m e t h o d , t h e scanner carries a Geiger t u b e or scintillator, t h e o u t p u t of which triggers a flash lamp which prints images on photographic film or paper. W i t h proper mechanical syn chronization, a contour m a p results. These a r e techniques which serve t h e u n r e m i t t i n g search for more d a t a a n d their precise delineation.
Investigation of unusual features in crude Reserpine absorption spectra obtained by Riker Laboratories with the Cary Model 14 led to the discovery of the important new alkaloid Canescine (left), a relative of Reserpine (right). Riker chemists particularly appreciate the speed and accuracy of the Model 14, according to Stimmel. He says: "Our reasons for buying the Cary Model 14 were two-fold. One, the automatic scan ning feature enables us to get more spec tra in a given time; and two, we get more information from the spectra because of the instrument's greater inherent accu racy. Our laboratories are using the
Riker Laboratories, an ethical pharmaceutical specialties house with main offices in Los Angeles, California, is primarily engaged in pro ducing hypotensive agents, including alkaloids in pure and mixed form.
Model 14 eight hours per day, five days per week, for both production control and research. Since purchasing the Model 14, we have been able to quadruple our output of spectra." "Before," Stimmel continues, "we were selective as to what we analyzed because of time limitations. Our research depart ment now sends through anything they are even vaguely interested in analyzing. We feel the performance of the Cary Model 14 justifies o u r reading signifi cance into every 'wiggle' of the spectra." Resolving power of the Cary Model 14 is better than 1A in most of the ultra-, violet visible region and better than 3 A in the near-infrared. Stray light is en tirely negligible for most applications — less than 0.001% between 2100A and 1.8 microns, and less than 0 . 1 % at 1860A and 2.6 microns. Wavelength scale of the Model 14 is linear, and accurate to bet ter than 4A throughout most of its range: reproducibility is better than 0.5Â. W h y don't you consider the advantages of the Model 14's greater resolving power and speed? Write to Applied Physics Corporation, 362 W. Colorado Street, Pasadena, Calif., for bulletinAC-27.
For further information, circle number 55 A on Readers' Service Card, page 73 A
VOL. 29, NO. 7 , JULY 1957 ·
55 A
