has been shown not to catalyze the reaction of methane and oxygen to a t least 800 "C in solid-electrolyte oxygen gauges ( I 7). Gold also has a greatly reduced catalytic behavior as compared to platinum (18). Therefore silver or possibly gold electrodes might be used if the oxygen content of nonequilibrium gas mixtures of oxygen in the presence of combustible gases is desired. Studies of this nature are in progress.
(5) D. A. J. Swinkels, J . Electrochem. Soc., 117, 1267 (1970). (6) J. Fouletier, H. Seinera. and M. Kleitz, J . Appl. Electrochem., 5 , 177 ( 1975). (7) G. S. Snow and P. D. Wilcox, U.S. Patent 3,951,327, April 20, 1976. (8) G. S. Snow and P. D. Wilcox, SAND76-0329. July 1976. (9) R. J. Brook, W. L. Pelzmann, and F. A. Kroger, J . Electrochem. Soc., 118, 185 (1971). (10) J. Fouletier, G. Vitter, and M. Kleitz, J . Appl. Electrochem., 5 , 11 1 (1975). f 1 1) Y. K . Aarawal. D. W. Short. R. Gruenke. and R. A. RaDD. J . Nectrochem. Soc., i21, 354 (1974). (12) D. W. Strickler and W. G. Carlsson, J . Am. Ceram. Soc., 48, 286 (1965). (13) W. M. Boorstein, R . A. Rapp, and G R. St. Pierre, Tech. Rept., AFML-TR-73-67, April 1973. (14) H. Yanagida, R. J. Brook, and F. A. Kroger, J , Electrochem. Soc., 117, 593 (1970). (15) T. H. Etsel!,and S. N. Flengas, J . Nectrochem. Soc., 118, 1890(1971). (16) L. Heyne, Mass Transport in Oxides", J. B. Wachtman. Ed., Natl. Bur. Stand. ( U . S . ) , Spec. Pub/.. 296, 149-164 (1968). (17) Y. L. Sandier, J . Electrochem. Soc., 118, 1378 (1971). (18) J. O'M Bockris and A. K. N. Reddy, "Modern Electrochemistry", Vol. 2, Plenum Press, New York, N.Y., 1973, p 1161.
..
~I
ACKNOWLEDGMENT T h e author acknowledges the very valuable assistance of James M. Freese in the physical design and construction of the oxygen sensors as well as the electronics used in this work. H e also aided in acquiring experimental data and along with G. S. Snow developed the platinum-zirconia seals. In addition, thanks are given to E. E. Komarek, Jr., for preparing the sputtered platinum electrodes used in this work.
RECEIVED for review May 31, 1977. '4ccepted ,July 18, 1977. This work was supported by the U S . Energy Research and Development Administration and was presented in part a t the 173rd National Meeting, Americam Chemical Society, New Orleans, La., March 20-25, 1977, Analytical Division, Paper 173.
LITERATURE CITED (1) M. %to, "Research Techniques For High Pressure and High Temperature". G. C. Ulmer, Ed.. Springer Verlag, Berlin-New York, 1971, Chap. 3. (2) K. S . Goto and W. Pluschkell. "Physics of Electrolytes", Vol. 2, J. Hladik, Ed., Academic Press, London-New York, 1972, Chap. 13. (3) H. Schmalzried. Z . Elektrochem., 66, 572 (1962). (4) R. Baker and J. M. West, J . Iron Steel Ind.. 204, 212 (1966).
On-Column Reaction Gas Chromatography for Determination of Chloromethyl Methyl Ether at One Part-per-Billion Level in Ambient Air G. J. Kallos" Analytical Laboratories, Dow Chemical U.S.A., Midland, Michigan 48640
W. R. Albe Instrument Applications and Communications, Dow Chemical
U.S.A.,
Midland, Michigan 48640
R. A. Solomon Hydroscience Associates, Inc., 904 1 Executive Park Drive, Knoxville. Tennessee 379 19
A gas chromatographic method capable of selectively measuring one part-per-billion (v/v) or better of chloromethyl methyl ether (CMME) in air has been developed. This method utilizes the direct derivatiration of CMME as a vapor with an alkali salt of 2,4,6-trichlorophenoI. Subsequent analysis is performed without any enrichment. The volatile 2,4,6-trichlorophenoxy methoxy methane derivative is determined by gas chromatography with an electron capture detector. The cycle time per determination is 90 s.
Chloromethyl methyl ether ( C M M E ) used as a reaction intermediate in chloromethylation reactions has been identified ( I ) as a suspected carcinogen. Recent reports have implicated C M M E as an alleged carcinogen because of the development of lung cancers to workers who were occupationally exposed ( 2 , 3 ) . Although C M M E is not stable in aqueous solutions (4,it has been found to be significantly stable ( 5 ) in humid air and consequently becomes a major concern. All these implications clearly dictate the need to
measure airborne concentrations of C M M E a t very low parts-per-billion levels. T h e determination of CMME by the colorimetric technique (6) is tedious and not highly specific. Solomon and Kallos (7) reported a derivative procedure for the determination of C M M E a t levels less than 1 ppb. This method utilizes the derivatization of C M M E in a trichlorophenate solution to a more stable derivative, extracting the derivative with hexane and subsequent analysis by gas chromatography using an electron capture detector. A new gas chromatographic procedure is described which stabilizes C M M E as a vapor through derivatization on column with a n alkali metal salt of 2,4,6-trichlorophenol and immediately determined by gas chromatography using a n electron capture detector.
EXPERIMENTAL Reagents. Sodium hydroxide and potassium hydroxide, Baker analyzed reagents, were obtained from the J. T. Baker Chemical Company, Phillipsburg, N.J. 2,4,6-Trichlorophenol, mp 67-68 "C, was obtained from the Eastman Kodak Company, Rochester, N.Y. Methanol, distilled in glass, was obtained from Burdick and Jackson Laboratories, Muskegon, Mich. Chloromethyl methyl A N A L Y T I C A L CHEMISTRY, VOL. 4 9 , NO 12, OCTOBER 1 9 7 7
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Chromosorb 101
....
Dummy Reaction column
@ I
Bi
SeDaration column Vent
R
Figure 1. Block diagram of gas chromatographic analyzer
ether, bp 55-58 "C, was distilled Dow ether. P r e p a r a t i o n of Reaction Packings. S o d i u m Salt of 2,4,6-TrichlorophenoL. 2,4,6-Trichloropheno10.068 g, and sodium methoxide, 0.024 g, were dissolved in 40 mL of methanol. This mixture was poured in a dish containing 2.24 g of 0.1% OV-275 on GLC-100 120/140 textured glass beads. After continuous mild stirring and evaporation of the methanol on the steam bath, a free flowing reaction packing was obtained. Potassium Hydroxide o n OV-275. Potassium hydroxide, 0.091 g, was dissolved in 50 mL of methanol. Twenty mL of this solution is mixed with 4 g 0.1% OV-275 on GLC-100 120/140 textured glass beads. A free flowing packing was obtained after continuous mild stirring on the steam bath and evaporation of the methanol. Potassium Salt of 2,4,6-TrichLorophenol. Potassium hydroxide, 0.27 g, was dissolved in 40 mL of methanol and 0.12 g of 2,4,6-trichlorophenol in 15 mL of methanol. Then 5 mL of the potassium hydroxide solution were pipetted into an evaporating dish containing the 15-mL trichlorophenol solution and 9 g of 0.1% OV-275 on GLC-100 120/140 textured glass beads. A new reaction packing was obtained after mild stirring and evaporation of the methanol on the steam bath. C h r o m a t o g r a p h i c Conditions. All columns used in this system were '/s-inch o.d. stainless steel tubing that were rinsed internally with water, methanol, acetone, methylene chloride, and 170OV-3 in acetone and air dried before packing. The precolumn was 17 inches in length and packed with 8 O / l O O mesh chromosorb 101 (Johns-Manville). The reaction column was 4 inches in length packed with 120/140 mesh textured glass beads (GLC 100) coated with 0.1% OV-275 and sodium salt of 2,4,6-trichlorophenol. The scrubber or KOH column was 4 inches in length packed with 120/140 mesh textured glass beads (GLC 100) that had been coated with 0 . 1 7 ~OV-275 and potassium hydroxide. The separation column was 5 feet in length and packed with 120/140 mesh textured glass beads (GLC 100) coated with 0.1% OV-101. The flow rate of the prepurified nitrogen carrier was set at 60 mL/min. The oven temperature was 130 "C and that of the detector was 280 "C. Sample size was 2 cm3. The columns were preconditioned a t 175 "C overnight before being connected with the electron capture detector. Chromatographic System. A Beckman GC-Process Analyzer Model was used for this study. A block diagram of the gas chromatographic analyzer is shown in Figure 1. This system contains all columns, sample valve, and column switching valve 1818
ANALYTICAL CHEMISTRY, VOL. 49, NO. 12, OCTOBER 1977
in a well thermostated oven compartment. Temperature control, carrier gas flow regulators, valve controls, detector, detector electronics, recorder, and other accessories are also located in this analyzer. The programmer in this analyzer uses mechanical cam timers with 1 cam per function. Total time cycle in this programmer was 90 s. The sample injection valve A is a six-port slider Beckman valve while a four-port Valco valve B was installed for column switching. A predetermined volume of air, such as 2 cm.j, is injected on the Chromosorb 101 column for 10 s and then the sampling valve is switched back to its normal operation. Air, water, and other organic vapors preceding CMME are vented via ports a-b, while prepurified nitrogen carrier gas is led through ports c-d to the detector. At an exact time, which is determined from the retention time of CMME through the Chromosorb 101 (65-80 s ) , valve B is actuated to allow passage of CMME through ports a-d to the reaction, potassium hydroxide, and separation columns while prepurified nitrogen carrier is led through ports c-b to the vent. A4fterall the CMME has been eluted through the Chromosorb 101 to the derivatizing column (15 s), the four-port valve B is switched back t o its normal operation of bypassing flow from the Chromosorb 101 column to the vent and nitrogen carrier gas flow through ports c-d to the reaction and separation columns to the detector. The effluent from the OV-101 column is monitored by the electron capture detector and its output fed into a recorder. The entire cycle for the total analysis is set a t 90 s. Although 2 min and 5 s are required for complete analysis of a single CMME injection, there are no overlapping problems encountered when injecting a new sample in 90-s cycles. It will require another 65 s before the Chromosorb 101 column is put in series with other columns for 15 s to introduce a new CMME sample. A program sequence for automated system is shown in Figure 2. Detector. The detector employed in this study was an ATC model-140A wide-range electron capture detector (Analog Technology Corporation, 3410 East Foothill Boulevard, Pasadena, Calif. 91107). This detector provides a tritiated scandium source with a maximum temperature limit of 325 "C. A baseline current of a t least 2 X A can be achieved, and consequently high sensitivity and a broad dynamic range are realized. This detector can be operated with either argon/methane or pure nitrogen gas. Prepurified nitrogen gas (pulse 0.6 p s ) has been used throughout our study. Several standards of authentic CMME derivative of
< ,u
90 Sec.
1 Sec.
Valve
90 sec.
Purge Inject Sample
sw
rresenfafion Figure 2. Program sequence for automated system
h 10 Litersimin
Sampling Rotameter 1 Iiterimin VA
I
I
I
Vacuum Regulator
u n
'Vent
Air I n
Room Air or External Calibration Line
&
D U
50 ccimin Charcoal
V a c u u m Pump
Thermometer
Permeator Tube
Figure 3. Permeator calibration flow diagram 2,4,6-trichlorophenoxy methoxy methane that were prepared in hexane provided a linear response (0.006-3.56 ng range). Calibration. The CEA UP-37 permeator (CEA Instruments 555 Madison Avenue, New York, N.Y. 10022) designed to function as a dynamic calibration source was used for the calibration of the automated system. The source of the calibration gas is a permeation tube, a 3-in. X 1/4-in.Teflon tube, filled with liquid CMME. The CMME permeation tube was available from Metronics, Inc. The material will permeate out from the tube a t a rate which is extremely temperature dependent. Figure 3 shows the permeator calibration flow diagram and external sampling line. The CMME eluting from the tube is directed out of the permeator apparatus with a constant nitrogen flow (50 cm3/min) that is further diluted with room air (10 L/min) and then directed to the analyzer which is to be calibrated. The UP-37 permeator
provides a very accurate temperature condition for the permeation tube to be regulated to i=O.l%. A special glass apparatus was designed as shown in Figure 3 to replace the combination flow indicator-tube holder. This was done to avoid any contamination of the CMME from the permeator. The permeation tube is held in position inside this glass tube with the prepurified nitrogen flow connected to the bottom of this tube in order to sweep the permeated CMME through a flow meter installed at the outlet of this device. An external line was installed in the calibration system through a 3-way valve so that a known standard from a Saran bag could be used to calibrate the rate of the permeator tube. The temperature of the permeator apparatus was held at 35 O C . The permeation rate of CMME through the permeation tube was calculated to be approximately 330 ng/min a t 35 O C . Repeated injections showed a 33% reproducibility. A 19-ppb (v/v) standard of CMME provided 70% ANALYTICAL CHEMISTRY, VOL. 49, NO. 12, OCTOBER 1977
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Table I. Linearity of CMME in 40% Relative Humid Air" ppb ( v / v ) CMME
3 6 15
30 150 450 900
Response ( m m ) , Attenuation ( X 3 2 ) 14 k 1 281 2
68 i 6 1 5 0 1 15
780
1
70
2 2 4 0 t 200 4420 3 4 0 0
Sample size, 2 c m 3 .
would be derivatized and detected. Among several porous polymer packings investigated for this purpose, Chromosorb 101 was found t o be t h e best choice because of minimum amount of tailing for water a n d sharp elution of CMME. Preliminary experiments indicated t h a t the sodium salt of 2,4,6-trichlorophenol coated on top of a liquid-coated support would provide the CMME derivative with adequate sensitivity. T h e derivative was confirmed as t h e 2,4,6-trichlorophenoxy methoxy methane (I) compared t o our authentic standard and retention time. T h e overall reaction would be presented as follows:
of full recorder response at 192 attenuation. Sensitivity at sub parts-per-billion level is easily attained through this system.
RESULTS AND DISCUSSION Several gas chromatographic procedures t h a t would be suitable for a process monitor were investigated in an attempt t o determine C M M E a t the parts-per-billion level in ambient air. T h e direct determination of C M M E using an electron capture detector did not give adequate sensitivity t o be applicable at t h e level of interest. Gas phase enrichment of C M M E on a solid support and subsequent thermal elution into a gas chromatograph using a n electron capture detector or flame ionization detector did not seem feasible because of t h e instability of C M M E on different packings and surfaces. T h e derivatization in trichlorophenoxide methanolic solution required several liters of air, handling of solvents, and it could not be adapted conveniently t o a continuous monitoring system. However, adequate sensitivity a t the sub partsper-billion level was obtained through the derivative technique when a n aliquot of t h e solvent is injected into t h e gas chromatograph using a n electron capture detector. T h u s it was apparent t h a t direct derivatization of C M M E on a gas chromatographic column would a d d another dimension of flexibility. I n solution derivatization, a 10-L volume of air containing 1ppb (v/v) CMME corresponds to 32 ng of that material that would be extracted into 2 m L of hexane. One microliter injection of this hexane extract corresponds t o 16 pg of CMME. With column derivatization, assuming the formation of t h e same derivative, an electron capture detector should provide comparable sensitivity with 5 cm3 of ambient air. In this case, gas chromatography combined with chemical reaction possibilities provide a powerful technique t o be explored. T h e main requirements for on column derivatization of C M M E are (1)Derivative must have sufficient sensitivity t o electron capture detector, (2) Derivative must elute from gas chromatographic column a t reasonable temperatures, (3) Air a n d water must not be introduced into t h e detector system, (4) Reactant must have long life stability and not affect the detector, (5) T h e electron capture detector must have a long t e r m stability t h a t is necessary for a continuous monitoring operation. T h e presence of water and oxygen within t h e electron capture detector would have a significant effect on t h e sensitivity and linearity range of the detector response. I t was necessary t o preseparate those components before C M M E
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ANALYTICAL CHEMISTRY, VOL. 49, NO. 12, OCTOBER 1977
CI
Yci (1)
Differential thermal analysis of t h e sodium salt of 2,4,6trichlorophenol shows an endotherm from 125 to 175 "C and a strong exotherm a t approximately 400 "C. T h e endotherm has been interpreted as t h e loss of water since infrared d a t a shows one water of hydration. T h e higher temperature exotherm would not have any effect since gas chromatographic conditions are employed at much lower temperatures for long-term stability of t h e reactant salt. T h e potassium hydroxide packing was used t o react with any free 2,4,6-trichlorophenol that may be released as a result of an equilibrium when possible trace amounts of water enter the reaction zone. Linearity of C M M E concentration through derivatization t o electron capture response was found t o be excellent over a wide range of concentration. Table I clearly demonstrates t h e linear response of C M M E standards from 2 p p b t o 900 p p b (v/v) levels in 40% relative humidity.
ACKNOWLEDGMENT The authors thank W. Blaser, R. White, and L. Shadoff for consultations and valuable discussions. This project would have never been accomplished without the encouragement, consultation and understanding of L. Westover, H. Gill, and W. Crummett.
LITERATURE CITED (1) Occupational Safety B Health Standards, Pt. 11, Department of Labor, Occupational Safety and Health Administrations, Fed. Regist., 39, 23554-23556, (June 27, 1974). (2) W. G. Figueroa, R. Raszkowski, and W. Weiss. "Lung Cancer in Chloromethyl Methyl Ether Workers", N. Eng. J . Med.,288, 1096-1097 (1973). (3) R. E. Albert, B. S. Pasternack, R. E. Shore, M. Lippmann, N. Nelson, and B. Ferris, Environ. Health Perspectives, 11, 209 (1975). ( 4 ) T. C. Jones and E. R. Thornton, J . Am. Chem. Soc., 89, 4863 (1967). (5) J. C. Tou and G. J. Kallos. Anal. Chem., 46, 1866 (1974). (6) J. Epstein. R. W. Rostenthan,and R. J. Ess, Anal. Chem., 27, 1435 (1955). (7) R. A. Solomon and G. J. Kallos, Anal. Chem., 47, 955 (1975).
RECEIVED for review April 22, 1977. Accepted July 20,1977.
