Anal. Chem. 1986, 58, 2591-2592 (3) Peterson, D. W.; Hayes, J. M. "Signal-to-Noise Ratios in Mass Spectroscoplc Ion-Current-Measurement Systems". I n Contemporary Topics in Ana/ytica/ and C/inica/Chemistry; Hercules, David M.,HiefJe, Gary M., Snyder, Lloyd R., Evenson, Merle A,, Ed$.; Plenum Press; New York, 1978; Vol. 3. (4) Wiley, J. F.; Taylor, J. W. Anal. Chem. 1978, 5 0 , 1930. (5) Jackson, M. C.; Young, W. A. Rev. Sci. Instrum. 1973,4 4 , 32. (6) Halas, S.;Skorzynsky, 2. J . Phys. E 1981, 1 4 , 509.
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(7) Halas, S.; Skorzynsky, 2 . J . Phsy. E 1980, 13, 346. (8) Miller, A. Basic Programs for Scientists and Engineers; Sybex: Berkeley, 1981; pp. 115-140. (9) Dixon, W. J. Biometrics 1953, 9, 74.
RECEIVED for review April 7,1986. Accepted June 12, 1986.
Evaluation of Alumina Furnace in Vacuum Fusion Determinations of Gases in High-Temperature Materials
-
Edward K. Pang
GTE Electrical Products, Lighting Research and Engineering, Syluania Lighting Center, Danuers, Massachusetts 01923 Knowledge of the outgassing characteristics of materials and the determinations of gases in materials used in a hightemperature and high-vacuum environment is important. Pang ( I ) recently reported a system for fast mass spectrometric characterizations and quantifications of high-temperature outgassing, but the quartz used in the system has a relatively low softening temperature. It has been noted that there is a substantial carbon monoxide background associated with the high-temperature reaction between the graphite insulation and the quartz furnace ( 2 ) . Dallmann ( 2 )suggested using a pyrolytic boron nitride furnace, but the nitrogen background is quite significant and can interfere with the carbon monoxide peak a t rnlz 28. A general program has been undertaken to design and evaluate different systems for vacuum fusion determinations of gases in high-temperature materials used in lighting products. This paper describes a high-purity alumina furnace for such application. The vacuum integrity and the outgassing properties of the assembly are reported.
EXPERIMENTAL SECTION The mass spectrometer and inlet systems have been described by Pang and co-workers ( I , 3) elsewhere. The modified furnace assembly using high-purity alumina is shown in Figure 1. The alumina tube (Omegatite, Omega Engineering, Inc., Stamford, CT) was connected to the glass inlet system by applying a very low vapor pressure resin (Torr Seal, Varian Associates, Palo Alto, CA), but the resin has to be maintained at temperatures below 100 "C by air cooling. The furnace system is attached to the all-glass inlet system by glass blowing. The experimental system is shown in Figure 2. The alumina is of high purity and typical analysis supplied by manufacturer shows 99.8% alumina, 0.07% silica, 0.05% magnesia, 0.05% calcium oxide, and 0.03% iron(II1) oxide. The electric furnace is microprocessor-based and programmable with a maximum temperature of 1650 "C (Applied Test Systems, Inc., Butler, PA). The tube temperature was measured with chromel-alumel and Pt/Pt-13% Rh thermocouples which were held against the alumina furnace tube. Pressure rise during measurement was monitored by a thoria-coated iridium ionization gauge (Fil Tech, Boston, MA) and a MKS Baratron capacitance manometer (10 mmHg full scale with ranges X l , 0.1, 0.01). Characterization of the gas was made possible by opening an all-metal variable leak valve that maintains a constant inlet preasure for mass spectrometric analysis. The as-received alumina tubes were stored in an inert atmosphere at room temperature before experiments. Before measurements were made, the asreceived tube assembly was baked at 1600 "C under a vacuum of 8 X lo4 mmHg for 200 h to detect any sign of deterioration. mmHg after the alumina tube The pressure dropped to 3 x
WRMGLASS
O.D. = 20 MM
1,l
12MM
ALUMINA FURNACE I.D. = 25.5 MM O.D. = 31.8 MM LENGTH = 305 MM
I
Figure 1. Design of alumina furnace. TO W A D R U W C E MASS SPECTROMETER AND "*C"UU SYSTEM
+
I l l CALIBRATED
TO
.
ffi ICU OAUGE CM .CAPACITANCE MANOMETER ABSQLUTE OR MFFERENiUL
LEAK VALYF
VACON PUMP
I
-
TGRBOMOLECIJLAR PUMP
AlummdTube
Figure 2. Schematics of experlmentai system. cooled to room temperature. Pressures during experiments were typically 4 X lo-' mmHg.
RESULTS AND DISCUSSION Figure 3 shows the quantity to gas with various temperatures of the alumina tube (volume, 0.57 L; inside geometric surface area, 244 cm2). Each measurement takes place in 30 min. Because of the minute quantity of the gases evolved a t high temperatures, the tube assembly is suitable for micro-
0003-2700/86/0358-259 1$01.50/0 0 1986 American chemical Society
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ANALYTICAL CHEMISTRY, VOL. 58, NO. 12, OCTOBER 1986
*O
X
.-8
e
-I
om
1
Table I. Results for the Composition (in % and Torr Liter) of Gas at 1600 OC
mo 0
I 0
species detected
70
Hz CH,
7.40
composition torr L
1.40 91.2
co
5.9 x 10-7 1.1 x 10-7
7.3 x 10‘8
propriate sample furnace for high-temperature outgassing investigations and vacuum fusion determinations of gases in high-temperature materials.
ACKNOWLEDGMENT 0
1000
The author thanks Vincent D. Meyer for many helpful comments on the manuscript and Lloyd E. Hall for carbon analysis.
2000
Temperature (Degree C)
Figure 3. Quantity of gas vs. tube temperature.
Registry No. Alumina, 1344-28-1
determinations of gases in high-temperature materials. Table I shows the gas analysis at 1600 “C. The total quantity is 8.0 X lo4 torr L. The gas is mainly CO with small amounts of CH, and H,. The presence of CO at high temperatures indicates the carbon impurities in the alumina. Subsequent carbon analysis reveals that the as-received alumina tube contains 175 ppm carbon, and the one after heating at 1600 “C, 50 ppm. The alumina tube assembly described can serve as an ap-
LITERATURE CITED (1) Fortucci, P. L.: Meyer, V. D.: Pang, E. K. Anal. Chem. 1985, 57, 2995-2996. (2) Dallmann, W. E.; Fassel, V. A. Anal. Chem. 1866, 38, 662-663. (3) Pang, E. K.: Keeffe, W. M. Presented at the 33rd Annual Conference on Mass Spectrometry and Allied Topics; San Dlego. CA, May 1985.
RECEIVED for review April 9, 1986. Accepted June 6, 1986.
CORRECTION Construction and Performance of Plastic-Embedded Controlled-Pore Glass Open Tubular Reactors for Use in Continuous-Flow Systems Matthew C. Gosnell, Ricky E. Snelling, and Horacio A. Mottola (Anal. Chem. 1986, 58, 1585-1587). Page 1586, first column, second line from bottom, should read “compared to 0.012 f 0.004” instead of “compared to 0.012 f 0.04”.
