acid is an atomic oxygen preservative, an antipoison for the walls. However, droplets will char the paper very badly, so that the tubes must have only a thin coating. The condition of greatest attack is a t high current density and high pressure, a t which condition the so-called auroral green line of atomic oxygen is observed. This condition will produce charring if put directly on the paper. A hole must first be burned slowly and then the pressure and current raised so that the edge of the oxygen stream performs the burning. The red nebular line appears a t a lotl-er pressure than the green line and the two are excellent measures of
the operating conditions. There is an induction period in the destruction. It appears that the process is to some extent self-catalyzed-i.e., formation of some partly destroyed cellulose promotes the destruction of fresh cellulose. Temperature measurements were made inside the bell jar during oxidation of a paper. Under the exit slit the temperatures a t the thermocouple reached 280" to 290" C. under maximum burning. The temperature a t the outer edge of the paper, well removed from the slit, was approximately 80" C. Six units identical to Figure 1 and two very small units were constructed to handle the Hardtack papers.
Almost all of the radioactivity remains in the dish or on the grid; contamination of the vacuum line was negligible and only traces were detected on traps cooled to liquid-nitrogen temperature. The papers burned in 1 to 16 hours, depending on the amount of particulate matter collected. Most papers required 2 to 6 hours. Although the amount of unburned fiber seemed to increase with particle loading, it always was less than 1% of the total residue. WOREperformed under the auspices of the U. S. Atomic Energy Commission.
Automatic Device for Changing Solutions in Column Chromatography John H. Kreisher and John H. McClendon, Department of Agricultural Biochemistry and Food Technology, University of Delaware, Newark, Del.
work and preliminary fractionations of fungal pectolytic enzymes (S), along with the work of Rhodes, Parvis, and Feeny (5) using various substituted cellulose ion exchange materials, have shown that stepwise elution is often advantageous Manual change-over has proved tedious, inefficient, and difficult t o reproduce from run to run. Hamilton and Anderson (2) described a device for changing solutions in amino acid ion exchange chromatography utilizing a motorized stopcock system. An automatic changeover device has been developed whereby elutant buffers going into ion exchange columns are automatically changed on a reproducible schedule utilizing solenoid-actuated glass valves. EXPLORATORY
A
-INLET
FROM
RESERVOlR
ROUND G L A S S
O U T L E T TO PUMP
AND
COLUMN
Figure 1 . Diagram of solenoid actuated glass valves
-
PROCEDURES
Eluting solutions drawn from reservoir botttles are drawn through solenoidactuated glass valves (Figure 1) (glass check valve M40510, H. S. Martin & Co., Evanston, Ill.) into a constant volume per unit time peristaltic type pump equipped with a vernier for accurate flow adjustment (Model T-8 with vernier, Sigmamotor, Inc., 3 North Main St., Middleport, N. Y.). The solutions then are pumped through the ion exchange column of substituted cellulose (1, 4 ) exchanger to which the protein material to be separated had previously been applied. Fractions are collected on a time basis by a fraction collector (automatic fraction collector with constant timing unit, Research Specialties Co., 2005 Hopkins St., Berkeley, Calif.). A stop (Figure 2) made of appropriately cut glass tubing is fitted and held in place by rubber bands over a test tube on the fraction collector table corresponding to the time a solution
890
ANALYTICAL CHEMISTRY
DELIVERY A R
TABLE
Figure 2. Delivery arm switch and positioned glass stops
change is desired. These stops actuate, on passing, a switch, SW-1 (3-ampere, 125-volt Acro Switch, Acro Switch Co., Columbus, Ohio), attached to the delivery arm of the fraction collector. This switch actuates a 21-position stepping relay with electrical reset (Figure 3) (M.E.R. 115-volt, 21-position electrical reset stepper, Guardian Electric
Manufacturing Co.. Chicago, Ill.). The panel for the stepping relay contacts (Figure 3) is set up so that by means of patch cords various mixing motors or other types of equipment may be operated by 12-volt relays for one step, along with any selected solenoid valve. This would be a useful accessory in the case of ammonia or carbonate buffers in a step and gradient system where evaporation might result if the stirrer were allowed t o heat the mixing chamber for long periods of time before utilization. The stepping relay can be stepped and reset using momentary contact switches, SlV-3 and STT7-2,respectively. The stepping relay is connected with a make-before-break relay with continuous duty coil (Series 610 make-beforebreak relay, Guardian Electric Manufacturing Co.) such that the noncontinuous duty coil of the stepping relay will not stay actuated when the stop switch on the fraction collector table (Figure 2) remains closed for a long time. This occurs in slow-flow separations or after the automatic shutoff step a t the end of a run. The solenoid coils, l'/z x 1 inches, wound of 325 feet of magnet !?ire (No. 28 HNC Syclad magnet wire. Bpldin Manufacturing Co., Chicago, Ill.) on a spool '2 inch in diameter, are operated by a 12.6-volt, 2-ampere transformer (Stancor Type P8130, Allied Radio Catalog No. 140142). The coils fit tightly around the glass valves. Ballseated joints tended to leak more than the standard taper. Also, the glass valves worked better if a number of small iron rods were used in their manufacture rather than a single solid bar. A small fan is adequate to prevent the coils from overheating at room temperature. Probably no fan would be needed in a cold room. At the end of a run, an appropriately located glass stop actuates the stepping
The chief advantages of this automatic change-over system over mechanically operated stopcocks are simplicity, low cost, ease of operation, and, above all, versatility. Up to 20 steps may be made within one column run. Gradients may be used along with linear steps. This system has several possible uses in routine amino acid separations and various other column procedures where solution changes are required. ACKNOWLEDGMENT
Figure 3. Schematic diagram of automatic device for changing solutions in column chromatography
relay, connected by a patch cord to a double pole-double throw on-off ratchet relay (Series IR-RC-100-115 GR ratchet relay, Guardian Electric hlanufacturing Co.). This on-off ratchet relay, which also can be operated manually by a momentary contact mitch, STT'-4,12volt on-off relay combination (Series 200, Guardian Electric llanufacturing Co.), autoniatically shuts off the pump, fraction collector, etc. The on-off ratchet should not be actuated nianually when the ratchet is on the off position at the end of a run. The stepping relay must be reset first or the 110-volt on-off ratchet mill energize and ulti-
mately burn out the coil on the associated 12-volt relay. In practice, the glass valve system is filled in reverse order, using a technique similar to that of Hamilton and Anderson ( 2 ) . After filling, the stepper relay is manually placed in the number 1 solenoid valve position. The changes can be followed visually by white, high resistance lights (18-volt) on the front panel. To start the pump and fraction collector, the on-off relay is actuated manually, STV-2. As the collection table rotates, the appropriately placed glass stops actuate the stepping relay, resulting in the required solution changes.
The authors thank Paul Hamilton, Alfred I. du Pont Institute, Wilmington, Del., for helpful discussion and P. V. Avizonis for suggesting the use of glass valves. LITERATURE CITED
(1) Ellis, S., Simpson, J., J . Bid. Chem.
220,939 (1956). (2) Hamilton, P. B., Anderson, R. X., ANAL.CHEM.3, 1504-12 (1959). (3) McClendon, J. H., Kreisher, J. H.,
IXth Intpmational Botanical Congress, Montreal, Canada, Aug. 1929, 1959, Vol. 11, Bbstracts, p. 239. (4) Peterson, E. A., Sober, H. A., J . Am. Pror.
_...
~
~
Chem. Sac. 78, 751 (1956). (5) Rhodes, bI. B., Parvis, R. A , Feeny, R. E., J . Biol. Chem. 230, 399-408 (1958).
PUBLISHED as Miscellaneous Paper S o . 354, with the approyal of the Director of the Delaware Agricultural Experiment Station.
Heated Cell for Quantitative Infrared Spectrophotometry Frederic J. Linnig and James
E. Stewart,'
cell for quantitative infrared studies is shown in a diagrammatic cross~sectiona~ view. ~t employs cell windows inch in diameter and is designed for use with Perkin-Elmer or Beckman equipment. Modification may make it applicable to other instruments. The rectangular front and back plates, I and A , are made of l/d-inch stainless steel stock, with a circular hole and flare, G, sufficient to accommodate the cone of infrared rays from the source housing. A is flanged along the sides to allow for insertion into the ways of the instrument. The heating units, B. are made of aluminum for easy machining, and contain circular spaces, L , in which the heating coils are placed. The roil cavities are covered by thin aluminum plates, M , attached to the aluminum blocks by small screws. The heating coils are identical in reAHEATED
1 Present address, Beckman Instruments Inc., Fullerton, Calif.
National Bureau of Standards, Washington 25, D. C.
sistance and are made of glass-insulated resistance wire that is in turn insulated from the aluminum cavity on all sides by glass paper held in place with sodium
P
silicate. The coil wires emerge through two holes, K , in each of the heating units. The four stainless steel posts, c, may be friction-mounted in -4 and are provided with holes a t the other end threaded to accommodate an 8-32 screw. The lead sparers, AT, about 0.1 mm. thick, are cut as shown in the front view of the cell proper. .4 nell, 0, is drilled in the inner sides of the cell window, F . The heaters, the cell windows, and spacer are mounted on posts C as shown and a circular Phosphor bronze spring, E, is placed over the outer heating unit. I is held in place with four 8-32 Allen-head cap screws, D. The Phosphor bronze spring should be made so that it will provide a constant adequate tension on the whole assembly TT ithout the screws being completely tightened. It will also prevent the assembly from becoming loose when used, and thus help to maintain constancy of cell thickness. The length of the coils may be varied to suit individual temperature requirements, and if the resistance in both coils VOL. 32, NO. 7, JUNE 1960
891
