APPARATUS
Connector. The connector shown in Figure l,a, is used with Bmalldiameter Teflon tubing (Pennsylvania Fluorocarbon Co.). Some dificulties are usunlly encountered in connecting such tubing, especially to glass, because of lack of elasticity and poor adhesive properties. I n the present case, watertightness and mechanical resistaneo are obtained by paasing the Teflon tubing through a sleeve, 1, of thick-walled, silicone rubber capillar tubing. Centering of the Teflon capil Iary, 2, is easier when it protrudes slightly from the silicone sleeve and when a small lodging, 3, is provided for it in the socket, 4, of the connector. A perfectly tight joint which will resist pressures of a t least 100 p.6.i. is obtained by tightening the cap, 5 . The connector, which may be assembled or disassembled as often as necessary, may be used to connect Teflon tubing to a chromatographic column (Figure 1,c), a microvalve (Figure 2) or any similar device, or to another piece of Teflon tubing. The socket part may be fixed to any piece of equipmmt, either by screwing (Figure 1,b) or by sealing with a synthetic resin, as in the case of chromatographic columns (Figure 1,c). The present connector has proved superior to ball or socket joints, because of watertight-
ness and higher mechanical resistance. Except for the silicone sleeves, all parts are made of Lucite or Teflon. Microvalve. The microvalve (Figures 2 and 3) was initially designed for use with a n automatic analyzer, of the type described by Spackman et al. (4, to replace the glass stopcock manifold which stuck easily. To reduce the over-all dimensions of the microvalve the several inlet slides, 1, are placed concentrically around the outlets, 2, 2'. Depending on their position the liquid will either be stopped or run through one of the outlets (Figure 3). The inlet is positioned in front of one of the outlets by pulling or pushing the slide a t full stroke. The slides are actuated by means of brass rods, 6, in which. a notch locates the median dead point position. Watertightness is ensured by neoprene O-rings, of 4-mm. i.d., for which a groove is provided around each opening facing the slides. Spring blades, 4, adjust the pressure. No lubricating agent is required for smooth operation. The microvalve is centered in the middle of a Lucite ring, 7, which is attached to the back side of the control panel by means of shafts, 6; the actuating rods, 6, emerge through it on the front side. The dotted parts in Figures 2 and 3 are made of Teflon, the hatched parts of stainless steel, and all others of Lucite. Inlet slides may ,be replaced easily if necessary.
APPLICATIONS
In addition to its use in the automatic analyzer of Spackman et i d . , Teflon capillary tubing may also prove useful whenever chromatographic effluents must be 'transferred without mixing between two distant points. For iostance, before being analyzed by chemical reagents the effluent liquid may be sent through a radioactivity (a, 3) or ultraviolet recorder. Or, when fraction collectors are used, the chromatographic columns may remain on a stand aside, so that, particularly for large columns, handling is facilitated. ACKNOWLEDGMENT
The authors express their thanks to Louis Ockum for his skillful cooperation in machining the equipment described. LITERATURE CITED
(1) Moore, S., Spackman, D. H., Stein, W. H., Fea'eratm Proc. 17,1107 (1958). (2) Schram, E., Lombaert, R., Anal. Chim. A c h 17, 417 (1957). (3). Schram, E., Lombaert, R., Arch. zntern. ahusiol. el biochim. 68, 845 (1960). (4) Spackman, D. H., Stein, W. H., Moore, S., ANAL. CHEM. 30, 1190 (1958). S
I
Modifications to an Ionization Detector Chromatograph for High Temperature Gas-liquid Chromatography Exploratory Studies B. J. Gudzinowicz and W. R. Smith, Special Projects Department, Research and Engineering Division, Monsanto Chemical Co., Everett, Mass. N INITIAL high temperature gasIliquid chromatography studies using an ionization detector chromatograph, hydrocarbons of lower molecular weight and complex aromatic mixtures, with some components having boiling points above 500" C., were resolved and determined by the authors. Preliminary quantitative investigations have been completed using microgram quantities of organics with accuracy and precision comparable to these obtained with conventional instruments [Gudzinowicz,
B. J., Smith, W. R., ANAL.CHEM.32, 1767 (1960)).
With continuous operation at or above 300" c., the silicone rubber con-
nectors (used with the Barber-Colman Model 10 argon ionization detector chromatograph) between the column and detector and the rubber septum in
0
b Figure 1. Schematic of modified introduction, column,, and detection systems
I
A. Stainless steel In/octlon block B. Detector Samplo-injection fitting 0.d. stainless steel tube) Water-coollng coil ('/&ch E. Sllicone rubber septum F. '/pinch 0.d. stolnless steel column G. Cartridge heater H. l/4-inch tube to '/&ch pipe stalnless stee' Swagelok Atting 1. Detector exlt J. Stoinless steel Swagelok fltting for l/le-lnch 0.d. caplllary K. l/l&ch 0.d. stainless steel capillary L Stainless steel ball ioint, 12/3 M. Glass elbow with ball lointi, 12/2 C.
D.
VOL. 33,
NO. 8, JULY 1961
1135
Figure 2.
Gas chromatograms of known aromatic mixture
Biphenyl 5. Trlphenylene o-Terphenyl 6. m-Quaterphenyl 3. rn-Terphenyl 7. p-Quaterphenyl 4. p-Terphenyl 8. rn-Quinquephenyl Chromatogram at 3 0 3 ' C. Chromatogram from temperature programming (160" to 3 3 7 " C.)
1. 2.
---
the introduction system became brittle and necessitated frequent replacement. The introduction system, the column, and the inlet to the detection system were therefore modified to eliminate these undesirable features and to provide a more extensive range of operation. Figure 1 is a schematic drawing of those parts of tho instrument in which a new stainless steel introduction system with water cooling incorporated waa in-
stalled to prolong the useful life of the septum and ball and socket joints were substituted for the rubber seals. The inclusion of Swagelok fittings (Crawford Fitting Co., Cleveland, Ohio) in the new introduction system haa permitted the use of metal columns, which heretofore waa impossible. After the completion of these modifications, the performance of ,the instrument was checked during an evalua-
tion wtudy of several silicone comlmiindq as possible high temperature stationnry phases for the separation of polyphenyls. A gas chromatographic 0.d. by &foot column packed with 5% by weight dimethyl silicone polymcr (General Elcctric SE-30 silicone gum rubber) impregnated on SO-to 100-mesh Chromosorb W was found to be a suitable liquid stationary phase for the separation of aromatic hydrocarbons a t column temperatures as high as 375" C. Recently, Vanden Heuvel et al. [J,Am. C h m . Soc. 82, 3481 (1960)l also reported excellent chromatographic separations of steroids at column temperatures as high as 260" C. using the SE-30 polymeric compound. At temperatures exceeding 375" C.,bleeding of the silicone occurred. Although a methylphenyl silicone polymer proved satisfactory at lower operating temperatures, this material was thermally unstable between 300" and 350" C. During the evaluation of thrse stationary phases, the advantages derived by temperature programming were evident, as noted in Figure 2 by the superimposed chromatograms of n complex aromatic mixture. WORKmpported in part by tbe United Stake Atomic Energy Commission under Contract No. AT(It-1)-705.
Device for Increasing Efficiency for large-Volume Gas Samples in Chromatography Fred Sicilio, James A. Knight, and
E. 1. Alexander,'
QAB chromatography, aa the size of a sample is increased, the resulting peak will broaden and eventually become flat-topped. Figure 1 compares the penks obtained from two identical samples from two columns that were operakd under similar conditions and that, wcre identical with one exception.
Radioisotopes Laboratory, Georgia Institute of Technology, Atlanta, Ga.
columns with a hypodermic syringe, through rubber septums, as ra idly m possible to simulate slug-type ckarging.
100-
IN
0 75 W VI
z
0
a
v, E W
One column consisted of 12 feet of copper tubing, of 1/4-inch uniform outside diameter, packed with 30/60 mesh acid -washed Chromosorb coated with trh-cresyl phosphate (20% by weight). The second column was identical to the first, except that a 4*/&nch length of */*-inch outside diameter copper tubing with the same packing, was connected to the forefront of the column. Retention times appear to be shortened by use of expandcd-section columns. This is not indicated in the figure. Helium at an exit flow rate of 30 ml. per minute was uscd as a carrier gas in thcse studies. The temperature of the columns and the thermal conductivit detector ivm maintained a t 40" All samplcs were injected into the
6
Present address, Industrial Reactor Laboratoriea, Plainaboro, N. J.
1136
ANALYTICAL CHEMISTRY
,050-
2
5 W
K
~
Z.0 -LITION TIME (MINUTES)
Figure 1. Elution curves for equalvolume samples on normal and expanded-section columns
- - -40 ml. ethane on expanded-section column __ 40 mi. ethane on normal uniform-diameter column
The effect of the expanded section iS dramatic. As yet, very little work has been performed on studying the effects of varying diameters on the efficiency of a column. The expanded section used in this work evidently acts as a sample collector, effcctively compressing the sample into a shorter plug. The increased efficiency, or enhanced peaking, is also evident when the expanded section is placed next to the detector as is the case when it is placed a t the sample-injection end. The compression of the peak width is probably due to increased lateral diffusion in the enlarged section. This type of device should be very useful for handling samples of large volume containing only small quantities of material to be analyzed and for work with preparative columns for which large-volume samples are employed. Thc device described in this paper has hem used in this laboratory to enhance the peaking of srtmples with long retention times.
