obtained. For some detertors, this voltage might not be uaed for routine analysis because other voltages might yield a wider linear dynamic range. The lower limit of detection can often be lowered by operating the column a t a lower temperature or by changing the temperature of the detector. S o attempt was made to determine whether the conditions used in this study were optimum.
LITERATURE CITED
(1) Barney, J . E., 11, Stanley, C. W.> Cook, C. E., AKAL.CHEM.35, 2206-8
i 1963). ( 2 j Carey, W. F., J . dssoc. O$c. A g r . Chemists 46,876-8 (1963). (3) Clark, S. J., 140th Meeting, ACS, Chicago, Ill., September 1961. (4)Clark. S. J., Residue Reviews 5 , 32-44 (1964). (5) Dimick, K. P., Hartmann, H., Ibid., 4, 150-72 (1963).
16) Eean. H.. Hammond. E. W..Thomson,J.,’Anulyst 89, 175-8 (1964). ( 7 ) Goodwin, E. S., Goulden, R., Reynolds, J. G., Ibtd., 86, 697-709 (1961). (8) Gutenmann, W. H., Lisk, U. J., J . d g r . Food Chem. 11, 301-3 (1963). (9) , . Gutenmann. W. H.. Hardee. D. D.. Holland, R . F., Lisk, 11. J., j. Dairy Sci. 46, 1287-8 (1963). (10) Klein, A. K., Watts, J. O., Damico, J. Pi., J . A4ssoc. Ofic. .Igr. Chemists 46, 165-71 (1963). (11) LandoFne, R. A., Lipsky, S. R., ANAL.CHEW34,726-30 (1962). (12) Lovelock, J. E., Zbid., 33, 162-78 (1961). (13) Lovelock, J. E., .Vatwe 189, 729-32 (1961). (14) Lovelock, J. E., AXAL. CHEM.35, 474-81 (1963). (15) Lovelock, J. E., Lipsky, S. R., J . Am. Chem. Soc. 82, 431-3 (1960). 16) Lovelock, J. E., Simmonds, P. G., Yanden Heuvel, W. J. A., .Vature 197, 249-51 (1963). 17) Lovelock, J. E., Zlatkis, A., Becker, R. S.,Ibid., 193, 540-1 (1962). 18) Mattick, L. R., Barry, D. L., Antenucci, F. M., Avens, A. W., J . A g r . Food Chem. 11,34-5 (1963).
(19) >Tinyard, J. P., Jackson, E. R., J . Assoc. Ofic. ilgr. Chemists 46, 843-59 f 19631. \ - - - - ,
(20) Moore, A D., J . Ecun. Entomology 55,271-2 (1962). (21) O’Brien, It. D., “Toxic Phosphmm Esters,” Chapter 1, Academic Press, New York. 1960. (22) Petitjean, D. L., Lantz, C. D., J . Gas Chromatog. 1, ( 2 ) 23 (1963). (23) Schafer, ?J.L., Busch, K. A., Campbell, J. E., J . Dairy Set. 46, 1025-32 (1963). (24) Shuman, H., Collie, J. R., J . ilssoc. Ofic.Agr. Chemists 46, 992-5 (1963). (25) Watts, J. O., Klein, A. K., Ibid., 45, 102-8 (1962).
c. E. COOK C. W. STAXLEY J. E. BARNEY I1 lfidwest Research Institute Kansas City, Mo. 64110 Presented in part at Sixteenth Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, Pittsburgh, Pa., March 1964.
Spectrophotometric Determination of Trace Amounts of Zirconium, Titanium, and Molybdenum in Tungsten
SIR: Ken F. Sugawara in his paper [AXAL.CHEM.36, 1373 (1964)l points out correctly that elut,ion of the titanium and zirconium with 831 HC1 [Wilkins D. H., Tulantu 2 , 355 (1959)] leads to some tungsten contamination. We have had a very similar esperience with this particular eluent which is very effective for eluting titanium, zirconium, and hafnium, but which adversely affects the elution characteristics of all elements that normally follow in the analytical scheme (W, 110,S b , Ta). For instance, we have found some niobium in the 8N HC1 fraction when the sample contains more than 150 nip. of niobium, and found even more niobium in the 60-10 and 25-20 fractions., even though these eluents normally hold back niobium to a con.siderable estent [Hague et al., .Vat. Bur. Std. 53, 261 (1954)j. The lorn molybdenum results reported in this paljer by Sugawara are obviously not, caused by any tailing of the molybdenum (He uses 1000 ml. of 5% HF-25% HCI! This eluent and others such as 25% HC1--2070 HF are very effect’ive for eluting molybdenum), but can similarly be blamed on the use of the 8.11 HCl eluent for titanium and zirconium, with [)art of the nio1yl)denuni prohably being lost in the tungstm fraction. 2358
ANALYTICAL CHEMISTRY
(?\Tote that all of Sugawara’s molybdenum results are somewhat low while the titanium and zirconium results show a normal distribution.) One does not, have to look far for a reason for this “irregular” behavior of the elements following titanium and zirconium (W, 110,Xb, Ta). Before the use of 8.11 HC1 eluent, the column is in the HF form and contains approximately 35 ml. of free 4 to 5% (v./v.) of HF. When the 851 HC1 is used, the front edge of this eluent therefore consists of 8.11 HC1 to 1 to 1.5.11 HF and not just of 8JI HCl. In this medium tungsten, niobium, and, to a lesser extent, molybdenum move a t an accelerated rate through the resin bed and appear prematurely in every subsequent eluate. Work carried out in our laboratory indicates that a considerable iniprovement can be achieved by replacing the free HF in the column with either ethanol or methanol prior to using the 8 X HCl. The best method, however, consists of eluting tungsten, titanium, and zirconium together with the 6010 eluent and separnting the titanium and zirconium from the tungsten (after evaporation of the acids) on a second column by the method of Wilkins (2oc. cit.) with the additional alcohol re1)lacement step mentioned above. I n this way, the subsequent elution
on the first column of molybdenum, niobium, and tantalum can be achieved without the adverse effects cited above. SILVEKALLMANN Ledoux & Co., Inc. Teaneck, S . J.
Monitoring Countercurrent Distribution with a Recording Refractometer SIR: Subsequent to this article [ANAL.CHEM.36, 903 (1964)], a new Teflon and glass pump has become available and has been used to transport solvents in place of the modified Toepler pump used originally. Because chemical inertness, elimination of mercury, and a simpler control system are made possible, much improvement in reliability has been achieved. h revised wiring diagram and other pertinent details are available to the reader upon request. R. 0 . BUTTERFIELD H. J. DUTTBN Northern Regional Research Laboratory Peoria, 111.
