Joseph A. Caputo
State University College at Buffalo 14222 BU~~N OeIwOYork ,
Device for the Preparation of Wall-Coated Open Tubular Columns
Wall-coated open tubular (capillary) columns' have been excluded far too long from the typical undergraduate organic and analytical laboratories and even from many research lab~ratories.~ This unfortunate loss of higher column efficiency and peak resolution, to students and researchers alike, has been due in part to the greater complexity of capillary systems as compared to conventional packed columns as well as to their greater cost. The former consideration is of ever decreasing significance due to the increasing availability of flame ionization detectors, essential to capillary work, in relatively inexpensive chromatographs, and the optional capillary accessories available from the manufacturers. An average packed column (e.g., 5 X in., SS, SE-30, Chromosorb W60/80) can be purchased for about $25, while a capillary column (e.g., 100 f t X 0.01 in., SS, Apiezon 1,) will cost a t least $150 or roughly $50 plus $1 per foot. We have found the discussion of the greater efficiency of capillary versus packed columns pertinent to our introductory organic course as well as a potentially useful demonstration in our instrumental laboratory. I n addition, the high-resolutidu analysis afforded by use of capillary columns has been extremely helpful to both our undergraduate and graduate students in their respective researchprojects. A convenient and relatively inexpensive method for preparing capillary (wall-coated) columns using a homemade loading device3 has been developed. The column "loader" (see figure) is made from a &9-in. length of a/rin. or '/,-in. brass pipe, threaded at both ends, two i n . brass female adapters, one I/4-in. brass union tee, one brass '/rin. plug, and one stainless steel to - i u reducing union, assembled as shown. Stainless steel is chosen for the reducing union because it is a t this fitting that columns are repeatedly connected and disconnected as they are cleaned and loaded, and wear on a brass fitting may be excessive, necessitating replacement of this part. The total cost of the loader is less than $9. Suitable stainless steel capillary tubing is available4 a t less than $45 per Acknowledgement is made to the Joint Awards Council/Univemitv Awards Committee of the State Universitv of New York/ ~ e s e & c hFoundation for a grant-in-aid in supp&t of this work. 1 McNnm, H. M., AND BONELLI, E. J., '(Ba~icGas ChromatogL. S., "OpenTubular Columns," raphy" (5th ed.), 1969. ETTRE, Plenum Press, New York, 1965. ETTRE,L. S., AND ZLATKIS, A,, "The Practice of Gas Chromatogrsphy," Wiley-Interscience, ~ e York, w 1967. 'All rights to the manufacture of capillary wlumns are held bv the Perkin-Elmer Coro. 3 Anv number of oridnal variations in oractical desim are
100 ft, in quantities of 300 ft or more. With this device it is a routine matter to prepare columns for onethird, or less, of the commercial price. In a typical dynamic coating operation a 50-ft length of 0.01-in. i.d. stainless steel capillary tubing is fitted brass tube fittings and then connected with '/I& to the base of the column loader. Several milliliters of a 10% solution of the desired liquid phase in an appropriate solvent is introduced through the top of the union tee by means of a syringe or capillary pipet and the plug is then replaced. A pressure of 30 psi of nitrogen is applied to the system by means of '/,-in. Nylon tubing at the tee side-arm. When the solution has completely passed through the column the pressure is reduced to 10 psi, and a slow flow is maintained for several hours as a preliminary drying step. After conditioning by standard procedures, the column is ready for use. It is normally a good practice first to flush the column with pet ether, chloroform, and then acetone before actually beginning the loading procedure. The complete preparation of these columns has been well described,=and can be routinely accomplished in a 24-hr period, including an overnight column conditioning. For those who may choose to employ "low dead volume" tube fittings specifically designated by the manufacturer for use in gas chromatography, the loading device must be modified somewhat in order to accommodate the male nut used to connect the capillary column to this specialized fitting. This is accomplished by attaching a stainless steel "low dead volume" female union to the reducing union of the loader by means of a 1-in. length of 0.d. stainless steel tubing, preferably not itself of capillary bore. The reducing union need no longer be of stainless steel, but brass, thus reducing @ the cost somewhat. Unfortunately, the stainless steel female union is fairly expensive, raising the final cost of the loader to about $14. g
'0
a
nosaihle. 4 Handy and Harmon Tube Co., Inc., P.O. Box ,549, Norristown, Pa. 19404. 6 See second and third references in footnote 1.
486
/ Journal of
Chemical Educofion
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Looding device for wall-mated columns.
B
'Ir-in. Nvlon tube
E
'/,-in. nut '/
