Table III. Hg12
Table I. HgC12 Standard sample, ng 20 40 60 80 100
Peak area weight, mg 43 134 215 289 352
Relative standard deviation, 5.1 3.9 6.3 7.5 13.6
z
Standard sample, ng 10 20 40 60 80
100
Peak area weight, mg 218 468 832 1298 1629 2057
Relative standard deviation, 4.5 9.5 9.9 5.9 6.1 4.9
z
Table 11. HgBr2 Standard sample, ng 10
20 40 60
Peak area weight, mg 122 276 461
753
Relative standard deviation, 3.0 1.7 6.0 2.6
number of fragments was small. Hg has seven naturallyoccurring isotopes, but only six of the seven have a significant abundance; Br and C1 have two and I has one. The cluster of peaks resulted from the various combinations of isotopes. The parent peak of highest intensity (base peak) was used for the quantitative determination of the substance, namely m/e 272, 360, and 456, respectively, for HgClz+, HgBrz+, and HgI2+. The mass spectrum of HgIz was the simplest for the samples studied. All three mass spectra were simpler than the mass spectra normally obtained for organometallic compounds.
In Tables 1-111, the results are given. The first column lists the amount of the standard sample, the second column the weight of the peaks (mg), and the third column the relative standard deviation for five determinations. For the most sensitive determination of mercury, the iodide should be used. Thus, as given in Tables 1-111, the peak areas for HgI2 in the 0- to 100-ng region ranged from 0 to 2000, while HgBr? and HgC12 showed significantly lower peak areas in this range of concentration; for example, at the concentration of 60 ng, the peak areas were 215, 753, and 1298 for HgC12, HgBr?, and Hg12, respectively. It is considered that the larger the molecule is, the better the sensitivity of the photomultiplier becomes, in homogeneous compounds. It is not clear why the 12’ peak appears in the mass spectrum of HgIz.
RECEIVED for review April 17, 1972. Accepted June 19, 1972.
Reaction of Tetraethy lammonium FIuoride-Water-Pro pylene Carbonate Solutions with Molecular Sieves John C. Synnott and David R. Cogley Tyco Laboratories, Inc., Waltham, Mass. 02154
James N. Butler Division of Engineering and Applied Physics, Harvard University, Cambridge, Mass. 02138 MOLECULAR SIEVES have been widely used to dry nonaqueous solvents and salt solutions with relatively little contamination or ion exchange ( I , 2). In order to determine whether such a procedure would be effective for drying fluoride-containing solutions, the experiments described here were carried out. EXPERIMENTAL
Reagents. Propylene carbonate [4-methyl-1,3-dioxolan-2one; 172-propanediol cyclic carbonate ester] was distilled and dried with Linde 4A molecular sieves (3). It (1) J. N. Butler, Advan. Electrochem. Electrochem. Eng., 7, 77-175 (1970). (2) J. N. Butler, R. J. Jasinski, D. R., Cogley, H. L. Jones, J. C. Synnott, and S . Carroll, “Purification and Analysis of Organic Nonaqueous Solvents,” Final Rept., Contract No. F19628-68C-0052. U.S. Dept. of Commerce A D 718109 (1970). (3) R. J. Jasinski and S . Kirkland, ANAL.CHEM., 39, 1663 (1967;.
contained less than 10 ppm water or organic impurities. Tetraethylammonium fluoride (Pfaltz and Bauer) was analyzed for chloride by potentiometric titration with aqUeOUS AgN03, and for fluoride by potentiometric titration with La(N03)a using a LaF3 membrane electrode (4-6). The salt was found to be 76.3% Et4NF, 1.5% Et4NC1,and 22.2% H20. Procedure. A 0.523M solution of Et4NF in propylene carbonate was prepared with approximately 1.1 hexafluoroacetone hydrate (K and K Labs.) added as an internal reference standard. Nuclear magnetic resonance (l9F) measurements were made at 56.4 MHz and 36.4 “ C using a Varian T-60 spectrometer. Half of the solution was placed over Linde Type 4A molecular sieves (25 ml sieves in 50 ml solution) and sampled periodically over a 1-week period. (4) M. Frant and J. W. Ross, Jr.. Science, 154, 1553 (1966). (5) J. J. Lingane, ANAL.CHEM., 39, 881 (1967). ( 6 ) Zbid., 40, 935 (1968).
ANALYTICAL CHEMISTRY, VOL. 44, NO. 13, NOVEMBER 1972
2247
Table I. NMR
19F
Resonance Peak Area for EtJVF-PC Solutions Treated with Molecular Sieves. Peak area
Time over, sieves (day) Oh 3.67 5.67 7.71
Total I(HFA) 75 75 73 75 0
2(F) 218 129 88 56 +75
3
