tained, the problem of making matrix corrections for fission fragment ranges in the various minerals would have remained. (This would require a knowledge of the approximate composition of each mineral.) T o bring each raw fission track uranium measurement to the “accepted” probe/ ACP value, requires a considerable correction factor-e.g., ~ 0 . for 4 thorianite, -0.6 for thorite, and -0.7 for samarskite. Theoretical correction terms can be calculated by a t least four different approaches due to Bohr (32);Lindhard, Scharff, and Schiott (33);Kahn and Forgue (34);and Kleeman (3Ei)based on Mory, De Guillebon, and Delsarte (36). These theoretical approaches have been tested (with varying degrees of success) for only a few of the heavier metallic elements and not for compounds. I t was hoped to derive accurate empirical fission track range correction factors in the present work and to test each of the above theoretical approaches. However, for the reasons given earlier, publication of this must be delayed even though there is a need for such correction factors in current work on lunar (37) and meteorite (38) samples where uranium invariably is found to reside in complex, non-silicate minerals. As with other solid state analytical methods, the considerable difficulty in coping with matrix correction terms for the determination of uranium in complex minerals is evidenced with fission track analysis. None of the above should, however, be taken as a general criticism of the fission track techniques, which for silicates (and in the absence of the exceptional circumstances of the very high Gd etc. content) usually yields excellent results without any dissolution or chemical separation (39-42).
CONCLUSIONS The technique of high frequency ac polarography has the required specificity for undertaking the determination of uranium in extremely complex minerals. The present work demonstrates that matrix efforts are minimal, particularly if the method of standard additions is used. However, as a close to reversible charge transfer step is being utilized in the determination, the presence of interference, if it were (32) N. Bohr, Kgl. Dan. Vidensk. Selsk., Mat-fys. Medd., 18, 8 (1948). (33) J. Lindhard, M. Scharff and H. E. Schiott, Kgl. Dan. Vidensk. Selsk.. Mat.Fys. Medd., 33, 14 (1963). (34) S. Kahn and V. Forgue, Phys. Rev., 163, 290 (1967). (35) J. D. Kleeman, Fission Track Studies and the Geochemistry of Uranium in Rocks from the Crust and Upper Mantle, Ph.D. Thesis, Aust. National Univ.. Canberra, 1969. (36) J. Mory, D. De Guillebon, and G. Delsarte, Radiat. Effects, 5, 37 (1970). (37) J. F. Lovering and D. A. Wark, Geochim. Cosmochim. Acta, Suppl. 2, 1, 151 (1971). (38) J. F. Lovering, D. K. S. Sewell, and D. A. Wark in “Uranium-Enriched phases in the Allende Meteorite,” In preparation. (39) Nat. Bur. Stand. (U.S.), Tech. Note, 548, 88 (1970). (40) Geol. Survey of Japan, Geochem. J., 5, 151 (1971). (41) D. E. Fisher, Anal. Chem., 42, 414 (1970). (42) W. G. Cross and L. Tommassino, Radiat. E f f , ,5, 85 (1970).
1558
to occur, should readily be detected as a change in either peak potential, or wave shape (half-width) of the ac polarogram. Thus, the method also has the desirable attributes of having several easily used, inbuilt checks on interference. RECEIVEDfor review December 14, 1973. Accepted April 10, 1974. The Australian Research Grants Committee is gratefully acknowledged for funding the Polarographic Instrumentation. Part of the work was also carried out under grants to J. F. Lovering from the Australian Research Grants Committee and the Australian Institute of Nuclear Science and Engineering, to all of whom we express our thanks. CORRECTION Separations on Heavily Loaded Small Particle Columns in High Speed Liquid Chromatography
In our paper [Heinz Engelhardt, Jurgen Asshauer, Uwe Neue, and Norbert Weigand, Anal. Chem., 46, 336 (1974)l we neglected to cite an earlier paper that described a similar method for coating of active silica in prepacked columns [C. Y. Wu, S. Siggia, and R. D. Waskiewicz, Anal. Chim. Acta, 63, 393 (1973)l. Those authors found that by varying the concentration of polyethylene glycol (PEG) in the mobile liquid, different loadings could be obtained on various substrates. The substrates exercised an adsorptive effect on the alkaloids being separated and the PEG leaned more to a partition separation. Controlling the concentration of PEG led to columns with controllable contents of PEG stationary phase which resulted in a wide range of adsorptive to partition ratios; each ratio is able to be reproduced easily. The term “dynamic coating” used in our paper was first used by Wu et al. CORRECTION New Methods for the Preparation of Perchlorate Ion-Selective Electrodes
In a paper by T. J. Rohm and G. G. Guilbault, Anal. Chem., 46, 590 (1974) perchlorate ion-selective electrodes for the determination of perchlorate were described using a solid membrane and a coated wire electrode. This paper did not refer to the previously described studies of a coated wire electrode for perchlorate and many other anions, by H. James, G. Carmack, and H. Freiser, “Coated Wire IonSelective Electrodes,” Anal. Chem., 44, 856 (1952). This paper describes preparation, response characteristics, selectivity, and electrode life of an electrode prepared using Aliquat 336s-Decanol in a PVC membrane.
ANALYTICAL CHEMISTRY, VOL. 46, NO. 11, SEPTEMBER 1974
