Programming System for the Automatic Amino Acid Analyzer
POWER -~
SHUT-DOWN TIMER UICROSIITC*ES
TO WlHHIDRlN PUYP
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TO RECORDER
Wesley C. Starbuck and Harris Busch, Department of Pharmacology, Baylor University College of Medicine, Houston, Tex.
automatic determination amino acids [Spackman, D. H., Stein, W. E., Moore, S., ANAL.CHEM.30, 1150 (1958)] has been accelerated markedly by the development of commercial models for this purpose. One of the problems attending the use of such an instrument is the need for manna1 changes in the systems used for separation of amino acids. It seemed probable that a programming system could be designed which could make possible a complete amino acid analysis with a single setting of the instrument. The available commercial instruments for the automatic determination of amino acids employ an interval timer (shutdown timer) for automatically stopping the ninhydrin pump and recorder, flushing the column for 1 hour, and stopping the buffer Bump a t the end of a given analysis. This paper descrihes the incorporation of a programming unit which would automatically complete the following: turnon the ninhydrin pump and/or the recorder after a preset interval, turn off the long column pnmp after equilibration while a short column run is in progress; begin a long column run a t the end of a short column run (or vice versa); and s h r t or stop a fraction collector (or other external device) a t the end of a preset time or a t the end of a rnn when fractions are being collected from the analyzer. HE USE OF
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Materials. The interval timer used was a Gralah Model 176 (DimcoGray Co., Dayton, Ohio). This has been designated as the program timer to differentiate it from the interval timers of the amino acid analyzer. I n addition, as shown in Figure 1, we used one single pole, triple throw, three position (no off position) switch (S,); one single pole, double throw, three position center off toggle switch (S?); five double pole, double throw, three position center off toggle switches (S, to S6); and one pilot lamp and two receptacles. Switches Sa to SIS are already present in the amino acid analyzer. The program timer unit can be mounted in a panel of the analyzer or in a box (6 X 8 X 3'/2 inches) which can be connected externally to obviate the need for modification of the existing instrument (Figure 2). Operation of the program timer unit for several functions is shown in Table I. When all of the switches of the program timer system are in the center position, the analyzer can
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TURNOFF
TURNON
Figure I . Schematic diagram of fhe program timer unit and its incorporation into the wiring of the automatic amino acid analyzer (Spinco Model 120 Amino Acid Analyzer)
Figure 2. Photograph of program timer unit mounted on a Model 120 Spinca Amino Acid Analyzer underneath the existing control panel (It may also be set on the work bench and Connected only b y a ten wire cable) VOL. 34, NO. 7, JUNE 1962
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ANALYTICAL CHEMISTRY
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be operated as though the program timer system mas completely absent. The ninhydrin pump and/or the recorder may be set to turn on after a preset interval following the initiation of a run on any column of the analyzer. It is important that the program timer power switch (S,)be set to the controlled position so that a t the end of the run the ninhydrin will be turned off and the reaction coil will then be flushed. By setting the proper switches, a run on the short column can be stopped while another is initiated on the long column (Table I). The reverse is also possible. It is necessary that the effluent selector valves for both the short column and the long column to be used be set in the coil (colorimeter) position. The design of the valve systems is such that no mixing occurs when the effluent selector valves for both the long and short columns are set to the coil position a t the same time, although a back pressure of about 6 pounds will appear on the pressure gage for the column opposite to that column which will be in operation. This pressure will go back no farther than the valves of the pumps and has not been found to affect the columns or the resolution obtained. Caution should be exercised not to remove the buffer line from the top of the opposite column during such an operation without first closing the respective effluent buffer valve. By setting the program timer power switch (S,) to the controlled position, the long (or short) column pump, which is intiated by the program timer, will be shut off as usual at the end of the flush period by the shut-down timer. The ninhydrin pump should be controlled continuously throughout such a procedure by the ninhydrin pump power switch (SI2) and will thus be shut off properly by the shut-down timer. The shutdown timer should be preset for the interval required for the second run and will be activated a t the end of the first run. The buffer change timer should be set for the proper interval plus the time left for the first run. If a fraction collector is used to collect effluent fractions from the analyzer, it may be stopped automatically a t the end of a run or other desired interval by setting the program timer and connecting the fraction collector to the proper receptacle in the program timer system. Automatic equilibration of a long column with the long column pump while a short column run is in progress may be effected by setting the program timer for the proper interval required and the long column control switch (Sz) to turn off position. The program system described above has been used in this laboratory for several months on a n amino acid analyzer which has been in almost continuous use The experimental results have been completely satisfactory by comparison to results obtained by a competent technician. Studies supported in part by grants from the U. S. Public Health Service, the American Cancer Society, and the Jane Coffin Childs Fund for Medical Research.
