Small Dry Box for Sampling E. C. Fiebig, E.
L.
Spencer, and R. N. McCoy, Shell Development Co., Emeryville, Calif.
o w analytical laboratories are "periodically called upon to analyze air- or mater-sensitive materials. Standard coinmercial dry boxes generally consist of large boxlike structures fitted with various accessories and are intended for a variety of operations which are conducted by means of rubber gloves attached to the box. They are expensive, require an excessive amount of laboratory space, and consume large volumes of inert gas for purging, and the gloves make delicate handling operations difficult. I n addition, they are difficult to clean if a noxious material is spilled. Franklin and V o h [ANAL.C H E x 27, 865 (1955)] recently described a small low-cost plastic bag which overcomes most of these disadvantages. For the limited purpose of sampling materials for analysis the authors have devised a small, compact dry box based upon use of an inverted 150-mm. glass funnel. All operations are conducted through an open 16 x 50 mm. slot cut in the side of the funnel. The entrance of significant amounts of air or water vapor is prevented by a continuous outflow of inert gas through the same slot. The dry box is illustrated in Figure 1. The funnel, A , is a common glass funnel which has had a slot cut in the side by drilling two holes and making connecting cuts between them with a Carborundum cutting wheel. The hollow stainless steel base, B, has twelve 0.03-inch holes drilled in a &inchdiameter circle t o facilitate purging with inert gas. It is fitted with two rubber and two threaded feet (to enable the entire box to be tilted), a gas inlet fitting, C, and four small metal blocks glued to the top in such a manner that the funnel can be slid from front to rear without uncovering any of the holes. The sample vial holder, D, is solid metal and is held from sliding by two short metal pins set in the base. The front face is beveled a t an angle of 45" to enable the sample to be seen clearly. An oversize hole (0.75 inch for 2-dram vials) is drilled almost through the block from the front at an angle of 20" from the horizontal to hold sample vials. This angle is such that liquid in nearly empty vials is accessible while nearly full vials do not overflow. A sheet metal table, E, is fitted over the sample vial holder as shonm. The clips hold horizontal-type weighing bottles which contain boats or other open sample containers during m-eighing and handling operations outside the dry box. The front space on the table provides a working area when the sample is being transferred to boats or other sample containers.
The cap remover, F , has metal fingers which grip the vial cap by spring tension as shown. A screw-type pinch clamp is placed on the rubber tubing, G, at point H and used for proportioning the gas flow between the top and bottom of the dry box. In use, the funnel is removed and the sample vial is placed in the block and !\-edged securely in place with a rubber wedge. Appropriate sample receivers are placed on the table and the funnel is replaced. Inert gas is passed into the box a t a rate of about 5 liters per minute. After 2 minutes of purging, the cap remover is inserted through the slot and slipped over the vial cap, and the cap is unscrewed and placed to one side inside the dry box. The entire dry box is tilted, if necessary, to make the contents of the vial accessible, and the desired quantity of sample is transferred by reaching through the slot with a spatula, eye dropper, hypodermic syringe, or other sampling aid. Liquid samples can be sucked into glass bulbs having capillary stems by inserting the stem into the sample while the bulb is outside the dry box where it can be heated and cooled. Sampling equipment such as eye droppers and bulbs which contain air must always be filled xith inert gas before use. Boats or other open sample containers are placed inside a suitable container which is closed before the dry box is opened.
materials, the initial cost might be lorn enough to permit damaged parts to be discarded. Satisfactory use of this box requires some coordination with the ' ~ m p l e makers" to ensure that the sample is furnished in a suitable container. The authors have found that coworkers making sensitive materials are usually aware of the sampling problem and will cooperate. Experience in routine use has shown that the dry box is convenient, useful, efficient. and easily stored. Hygroscopic, n-ater- and oxygen-sensitive, and even pyrophoric organic boron compounds prepared by Buls, Davis, and Thomas [ J . Am. Clzem. SOC. 79, 337 (1957)] have been sampled in it and successfully analyzed. Commercial purified nitrogen (99.901,) was sufficiently dry and inert to be used as the purge gas M ithout further treatment.
Device for Monitoring Absorbance of Column Eluates in a Spectrophotometer J. B. Stark, Roy Teranishi, and G. F. Bailey, Western Utilization Research Branch, Agricultural Research Service, United States Department of Agriculture, Albany 10, Calif. DEVICE
for continuous or manual
A monitoring of chromatographic-col-
Figure 1. Sampling dry box
The prototype model of this box was constructed by using wooden blocks and a perforated section of copper tubing for the bottom inert gas distribution system. However, the wooden blocks absorbed spilled materials and could not be readily cleaned. The recommended design can be subjected to drastic cleaning measures if necessary. Other materials, such as plastics, could also be used for most of the parts involved. While plastics might absorb or be attacked by spilled
umn eluates offers certain advantages in circuit simplicity and ease of operation over others previously described ( I ) . Automatic monitoring avoids circuit complexity by the use of commercially available automatic recycling timing devices of the type used to control reflux ratio in distillation columns. The ease of operation is illustrated by the routiiie manual determination of absorbance a t any set w,ve length for 50 samples in about 30 minutes. Khen desired, the spectrum can be scanned on a. sample before proceeding to the nest,
In Figure 1 the machined aluminum plate, A , 6j/8 X 5'/, X inches, serves as a lid and cell holder to cover the sample compartment. The lower edge of the plate is milled inch in and inch deep (Figure 2). The wooden block, B , fastened to the metal plate with screws, positions the cell in the path of the light beam. The 2-em. path cell, C, is made from a Teflon plug 2.15 em. in diameter with a 4-mm. VOL. 29,
NO. 5 , M A Y 1957
861
can be used for a reference cell or a standard cell 2 em. in diameter can be used in conjunction with a metal disk diaphragm having a 4-mm. aperture.
Figure 1. device
Disassembled monitoring
The tendency of the pen to dig through the paper a t slow chart speeds is eliminated by recording intermittently in a manner that consists of a closure of the “master” switch for a short period a t predetermined intervals. The “power,” “slit,” (‘pen;’ “chart,” and “lamp” switches remain on during the entire column run, while contact from the master switch is made by a program timer of the general class used for reflux ratio control. The most usual operating conditions were 7 seconds of recording a t 6minute intervals, with a chart speed of 1 inch per minute. Under these conditions continuous column operation has been satisfactorily maintained for 5 days. The spectrophotometer timer and fraction collector were usually synchronized to give three observations per time-controlled fraction with a column flow rate of 1 ml. per minute. 4UAL OPERATION
_”..-__
A.. operation, the switches are counected to operate in the regular manner. The apparatus is assembled as shown in Figure 2. The sample is loaded into the funnel and a t the same time drawn through the cell with the syringe. A solution with an absorbance of 2 can he washed out completely with 4 to 5 ml. of solvent nr replaced by the same volume of new solution. I
Figure 2. Assembled monitoring device
clear aperture (8). The ends are threaded to hold the quartz disks, D, 11 mm. in diameter and 2 mm. thick. The cell is held to block B with two springs, E. The holes in the top of the cell are tapered to fit a 5/20 standardtaper inner joint. The inlet and outlet tubes, F, of the cell are made of 2-mm. capillary tubing joined to a 5/20 inner joint. The tip of the ground joint is cut off so that it will not extend into the light beam through the cell. The tubes are positioned and held in the cell with the aid of two springs, E, attached to the ears on the tubes &s shown in Figure 2. The tubes are aligned in the plate by means of screws and washers as shown in Figure 1. The stopcock is 2-mm. bore. The funnel has a capacity of 5 to 10 ml., and the syringe a capacity of 10 ml. CONTINUOUS MONlTORlNG
To operate the device for continuously monitoring a column effluent, the funnel stopcock and syringe shown in Figure 2 are removed. The outlet of the column is attached to a tube, F, entering the Teflon cell. An outlet tube leading to a fraction cutter or other collector is a b tached to the other tube F. Filling the cell with alcohol aids in preventing airbubble formation. Another Teflon cell 862
ANALYTICAL CHEMISTRY
LITERATURE CITED
J. E., Boucher, E. G., Robinson, A. E., Wiebe, A. K., ANAL. CHEM. 27, 1888 (1955). Irk, P. L., Rosenfels, R. S., Hanahan, KD. F., Ibid., 19,355 (1947).
(1) Kenyon, W. C., McCarley,
(’)
MENTIONof products by commercial name does not imply recommendation by the Department of Agriculture over others of a similar nature not mentioned.
Warburg Manometer Flask for Increased Sensitivity in Ethylene Determinations Harlan K. Pratt, University of California, Davis, Calif., and Curt W. Greiner, Greiner Glassblowing Laboratory, 3604 East Medford St., Lor Angeler 63, Calif.
of ethylene by the method of Young, Pratt, and Biale (3). In this strictly chemical determination, the flask volume is critical only in its effect on the accuracy of the physical measurement. By using flasks with the small-
Figure 1. Manometer flask
est possible gas space aboye a given volume of liquid, sensitivity IS increased because the amount of gas released in an analysis gives a larger pressure reading in the constant-volume, variable-pressure manometric system. The flask here depicted (Greiner Catalog No. 23-500) is conical, with a 17/20 standard-taper ground joint, and with elass . . . a~ o~~ ~ nartition dividing the bodv of the flask into^ two equar compare ments. Each side of the flask will accommodate 3 ml. of sample or reagent. The hooks are placed so that shaking IS in a plane a t a-right angle to the partition; if shaking is parallel to the partition, premature mixing is likely. Total volumes of the flasks average about 10 ml., and the vessel constants of one set averaged 0.66, compared to 1.80 for the two-chamber vessels previously used or to standard 15-ml. Warburg vessels. ~~
~~
~~
Warburg manometers can be read to the nearest 0.5 mm. Assuming that the total available volume of one sample of mercuric perchlorate solution is 20 ml., and 3-ml. aliquots are taken for analysis (S), a minimum of 120 pl. of ethylene could be determined with the standard vessels, or 44 pl. with the type described (allowing *5% as satisfactory accuracy). Further increase in sensitivity might he obtained using the hydraulic leverage principle recently described by Burk and Hobby (1). The special flask of Stanley and Tracewell (8)does not appear to meet the desired standard of high fluid volume coupled with low gas volume. LITERATURE CITED
Burk, D., Hobby, G., Science 120, 640-8 (1954). Stanley, R. G., Tracewell, T., Ibid., 122.7R-7 _._, .. . (1955). ...,. ~~
A
m m o v m flask has been designed for the manometric determination
N
Young, R. E., Pratt, H. K., Bide, J. B., ANAL.G E M .24,551-5 (1952).
