The optimum concentration of 1 in the assay is found to be a to 3.3 X 10-3M range. 10-3M for acetone i n the 5 x Higher concentrations of 1 led to decreased rates of fluorescence formation, perhaps due to further reactions with 2 (Table IV). Secondary alcohols, convertible to methyl ketones by oxidation, e.g., isopropanol, may be determined by the assay. Thus isopropanol vapor, passed over silica gel impregnated
with chromic acid and held at 80 "C,was qualitatively determined as acetone. Similarly 1, impregnated on silica gel and treated with dilute acetone vapors and then 0.1N alkali rapidly yielded the fluorescent indoxyl. No attempts were made to quantitate this method.
RECEIVED for review September 27, 1971. Accepted June 22, 1972.
Direct Determination of Mercury Halides by Electron Impact Mass Spectrometry Kozo Matsumoto, Yasuhisa Sasaki, and Tsugio Takeuchi Department of Synthetic Chemistry, Faculty of Engineering, Nagoya University, Nagoya, Japan
ATOMICABSORPTION, atomic emission, radio isotope analysis, and spark source mass spectrometry have been used to determine metals quantitatively. To obtain mass spectra of metals with a conventional electron impact mass spectrometer, it has been necessary to change metals to organometallic compounds. In an earlier paper ( I ) , we reported mass spectra of metal halide compounds. In this work we report the quantitative determination of mercury using mercury halides. Calibration curves were obtained by the ion current method ( 2 ) in the nanograms region. T. L. Isenhour et ai. (3, 4 ) have changed metals to chelate compounds to obtain their mass spectra. They reported calibration curves of metal chelate compounds in the picogram region, using the ion current method. We have succeeded in obtaining mass spectra of mercury from halogenated mercury compounds. This paper describes the quantitative determination of HgC12, HgBr2, and Hg12. EXPERIMENTAL The mass spectrometer used in this study was an RMS-4 (Hitachi Co. Ltd.). The operation conditions were as follows: Acceleration voltage, 1.5 keV; ionization voltage, 80 eV; emission current, 80 pA; collector slit, 200 pm (fixed); Torr; chamber temVacuum (in the ion source), 1 X perature, 250 "C. The recorder was set to run at 0.4 cm per second. The samples, HgC12, HgBr2, and HgIy, were dissolved in pure ethanol. Standard solutions for the calibration containing 10, 20, 40, 60, 80, and 100 ng of metal halides per p1 were prepared. A sample solution containing 1 pl was put into the sample container tube with a Hamilton 10-p1 microsyringe. After cooling in dry ice, the sample container tube was placed on the probe, evacuated for 8 sec, and introduced into the ion source. The repeat scans were started. The peak areas obtained on the photosensitive paper by the ion current method were cut out and weighed for the quantitative determination. RESULTS AND DISCUSSION Figures 1-3 show the mass spectra of the three mercury halides. Each compound has only three atoms and the
Kozo Matsumoto, Nobutoshi Kiba, and Tsugio Takeuchi, ANAL.CHEM.. 43. 1691 (1971). (2) A. E. Jenkins and J. R . Majer, Talanta, 14,777 (1967). (3) James L. Booker, T. L. Isenhour, and R. E. Sievers, ANAL. CHEM., 41, 1705 (1969). (4) B. R. Kowalski. T. L. Isenhour, and R. E. Sievers, ibid., p 998. (1)
2246
I
HpCI;
200
100
m/e
Figure 1. Mass spectrum of mercury chloride; sample temperature: 120 "C
200
100
ugBr+ 400
300
w e Figure 2. Mass spectrum of mercury bromide; sample temperature: 135 "C
i
3 ' 1 100
200
I'
I
300
400
m/e
Figure 3. Mass spectrum of mercury iodide; sample temperature: 160 "C
ANALYTICAL CHEMISTRY, VOL. 44, NO. 13, NOVEMBER 1972
Standard sample, ng 20 40 60 80 100
Table I. HgC12 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 Standard sample, ng 10
20 40 60
Table 11. HgBr2 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.
Table III. Hg12 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
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
