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Ion Exchange Filter Paper Holder for X-Ray Spectrometry Stanford L. Tackett Department of Chemistry, Indiana Unirersity of Pennsyluania, Indiana, Pa. 15701 A RECENT IMPORTANT ADVANCE in X-ray spectrometric analysis has been the introduction of ion exchange resinloaded filter papers for sample collection. Trace amounts of samples can be collected onto small filter paper disks from relatively large volumes. Campbell, Spano, and Green reported the micro and trace analysis of numerous metals and nonmetals in both the cationic and anionic form using Reeve Angel ion exchange resin-loaded filter paper ( I ) . Hakkila, Hurley, and Waterbury reported the determination of scandium in plutonium by a similar technique (2). Campbell, Green, and Law have recently discussed both the sampling and measurement techniques for ion exchangeX-ray spectrometry (3). Numerous other specific applications have been reported (4-6). Previous workers have cut the paper disks to fit their instrument sample holders (1-3). This necessitated the construction of a filtering apparatus of the appropriate dimensions. We purchased the Reeve Angel resin-loaded papers already cut in circular disks of 3.2-cm diameter to fit the sample holder of our Picker X-ray equipment. We built a filtration apparatus similar to that described by Campbell and coworkers ( I , 2). While the filter holder worked satisfactorily, we found the plastic-to-glass bonding and the glass parts themselves not rugged enough for prolonged use on a routine basis. This report describes a Plexiglas filtration apparatus which we have found to be both rugged and effective. The filtration apparatus is shown in Figure 1. The completed unit consists of two parts, a length of 3.2-cm 0.d. Plexiglas tubing; and a machined Plexiglas block. The 3.2-cm tubing was machined flat on each end, and was left approximately 20 cm long to facilitate sampling relatively large volumes of solution. The Plexiglas block was machined as indicated in Figure 1. The upper portion of the block was drilled to a depth of 3.5 cm, and with a diameter of just slightly less than 3.2 cm which allowed the 3.2-cm tube to fit snugly. The best fit between the tube and block occurred when the inside diameter of the block was approximately 0.0005 inch less than the diameter of the tube. Next, the disk seat was machined flat, and the remainder of the block was drilled as shown. A filter stem was provided by cementing a length of 8-mm 0.d. Plexiglas tubing into the bottom of the block. The distance from the disk seat to the tip of the stem was 13 cm. The combination of the snug fit between the 3.2-cm 0.d. tube and the block, and the flat machined surfaces of the (1) W. J. Campbell, E. F. Spano, and T. E. Green, ANAL.CHEM., 38, 987, (1966). (2) E. A. Hakkila, R. G. Hurley, and G. R. Waterbury, ibid.,41, 665 (1969). (3) W. J. Campbell, T. E. Green, and S. L. Law, Amer. Lab., June 1970, p 28. (4) E. F. Spano and T. E. Green, ANAL.CHEM., 38, 1341 (1966). (5) J. G. Bergman, C. H. Ehrhardt, L. Granatelli, and J. L. Janik, ibid.,39, 1258 (1967). ( 6 ) J. A. Hayden, Tuluntu, 14, 721 (1967). 972
ANALYTICAL CHEMISTRY, VOL. 43, NO. 7, J U N E 1971
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Cutaway View of Plexiglas Block
8 m m 0.D. Plexiglas Tubing (13 cm from filter seat to tip of tubing)
I Figure 1. Filtration apparatus disk seat and end of the tube allowed the filter paper disk to be held firmly without any leakage around its edges. Although the fit between the tubing and the block was firm enough to hold the disk tightly, the apparatus was easy to manipulate. Machining a large chunk of Plexiglas can be tedious because of its expansion with heat. Construction of a Plexiglas filtering apparatus such as this could be simplified if several sizes of Plexiglas tubing are available. The outer portion of the block could be constructed from 3.2-cm i.d. tubing, and the paper disk seat could be a short length of 3.2-cm 0.d. tubing cemented inside the larger tube. A small funnel would complete the apparatus. We have found our filter to be reliable and easy to use, inert to acids, and durable. ACKNOWLEDGMENT
The author is grateful to David L. Ramsey, Physics Department, Indiana University of Pennsylvania, for constructing the apparatus, and to Miss Linda Illig for the drawing. RECEIVED for review February 12, 1971. Accepted April 6. 1971.
