1829
Anal. Chem. 1983, 55, 1829-1830
lands) for assistance in the 14Cactivity measurements and H. Th. Rijnten (AKZO, The Netherlands) for providing the alumina and silica samples. Registry No. BaP, 50-32-8; 14C-BaP,85976-68-7; PTFE, 9002-84-0; alumina, 1344-f!H-l;silica, 7631-86-9; Fe oxide, 133237-2; methyl laurate, 111-82-0; carbon, 74401-44-0.
(2) Grlest, W. H.; Yeatts, L. 6.; Caton, E. Anal. Chem. 1980, 52, 199-201. (3) Mlguel, A. H.; Korfmacher, W. A.; Wehry, E. L.; Mamamtov, G.; Natusch, D. F. S. Envlron. Scl. Techno/. 1979, 13, 1229-1232. (4) Janssen, F.; Kanlj, J. Int. J . Mvlron. Anal. Chem. 1982, 13, 37-54. (5) May, W. E.; Brown, J. M.; Chesler, S. N.; Guenther, F.; Hllpert, L. H.; Hertz, H. S.;Wise, S. A. "Polynuclear Aromatic Hydrocarbons"; Jones, P. W., Leber, P., Eds.; Ann Arbor, MI, 1979; pp 411-418. (6) Dalal, R. C. Analyst (London) 1979, 104, 151-154.
LITERATURE CITE11 (1) White, C. M.; Sharkey, A. G., Jr.; Lee, M. L.; Vassllaros, D. L. "Polynuclear Aromatic Hydrocarbons"; Jones, P. W., Leber, P., Eds.; Ann Arbor: MI, 1979; pp 281-275.
for review December 137 1982* Accepted
279
1983.
Determination of Carbon Monoxide wlth Tetrachloropalladate( II)-Cacotheline Reagent J a c k L. Lambert*
Department of Chemistry, Kansas State University, Manhattan, Kansas 66506 Y u a n C. Chiang
Department of Chemistry, Kansas Wesleyan University, Salina, Kansas 67401 Colorimetric methods for carbon monoxide include the reference method which employs silver p-sulfaminobenzoate complex in alkaline aqueous solution to produce a colored silver sol (1). The method described here is the third to be reporhd in which a soluble colored compound is formed. The first was a method which employed tetrachloropalladate(II), ethylenediaminetetraacetoferrate(III), a n d 1,lOphenanthroline in aqueous solution at 1pH 7.0 to produce red-orange 1,lO-phenanthrolineiron(I1)(i!). The second method used tetrachloropalladate(II),iodate, and leuco crystal violet in aqueous solution a t pH 3.1 to prloduce crystal violet (3). All of the above methods and the teitrachloropalladate(11)-cacotheline method described here suffer interference from gases such as hydrogen sulfide or sulfur dioxide which precipitate or reduce paJladium(I1). Normally, such gases are present in much lower concentration than carbon monoxide and do not affect the analyses. The method described here has the advantage over previously reported methods in using only oine reagent solution, which is stable on storage. Yellow cacotheline, obtained by the nitric acid oxidation of brucine, is reduced to violet dihydrocacotheline by atomic palladium produced by the reduction of the tetrachlalropalladate(I1) complex by carbon monoxide. EXPERIMENTAL SECTION All compounds used were analytical grade or the purest grade available. Solutions were prepared with deionized water. Stock Solutions. Cacotheline, 4 X IM, in 60% acetic acid solution was prepared by adding 10.94 g of cacotheline (Gallard-SchlesingerChemical Co., Carle Place, NY), 200 mL of water, and 200 mL of glacial acetic acid to a 500-imL volumetric flask. The solution was shaken for 10 min or until a clear solution was obtained. Glacial acetic acid was added slowly with shaking to volume. Tetrachloropalladate(I1) solution, 1 X M, was prepared by adding 0.443 g (0.0250 mol) of palladiunn(I1)chloride, PdCX2, 200 mL of water, and 5.00 mL of concentrated hydrochloric acid (12.1 M) to a 250-mL volumetric flask. The solution was shaken until a clear solution was obtained and water was added, with shaking, to volume. Reagent Solution. 'The following were added, slowly with shaking, in sequence to a 1-L volumetric flask 30.00 mL of water, 50.0 mL of cacotheline stock solution, and 50.00 mL of tetrachloropalladate(I1) stock solution. After glacial acetic acid was added slowly with shaking to volume, the reagent solution was
2X M in cacotheline, 5 X M in H2PdC14,and 1 X M in hydrochloric acid-all dissolved in 90:lO acetic acid-water solution. Calibration Curve. Single-neck500-mL round bottom flasks were fitted with T 24/40 Teflon standard thermometer adaptors (Ace Scientific Co., catalog no. 14-6920-08) fitted with 1/2 in. X 3 mm blue silicone septa (P. J. Cobert Associates, catalog no. 977774). The total volume (with thermometer adaptor in place) and the net volume after addition of 50.0 mL of reagent solution were determined for each of the five flasks. To establish the calibration curve, 50.0 mL of reagent solution was added to each flask, the flasks were sealed with the modified thermometer adaptors fitted with septa, and measured volumes of carbon monoxide were injected with a gastight microsyringe. Five determinationswere made at each concentration of carbon monoxide as shown in Figure 1 by shaking the flasks for 30 min in a wrist-action shaker. Absorbances were determined in 1-cm cuvettes at 520 nm with a Coleman Model 124 spectrophotometer (Perkin-Elmer Corp.).
RESULTS AND DISCUSSION The average, range, and standard deviation of five determinations at each concentration of carbon monoxide are shown in Figure 1. The plot is rectilinear from 0 to 600 ppm carbon monoxide, above which the reagent apparently became depleted. The chemical structures of cacotheline (I, yellow) and dihydrocacotheline (11,violet) are 1
COOH L
r
i
0003-2700/83/0355-1829$01.50/00 1983 American Chemical Society
r-7
1830
Anal. Chem. 1983, 55,1830-1832 0.6 r
The intercept on the absorbance axis is due to tetrachloropalladic(I1) acid and cacotheline. The tetrachloropalladic(I1) acid concentration remains constant but the concentration of cacotheline decreases as part of it is converted to dihydrocacotheline in proportion to the concentration of carbon monoxide. The calibration curve is a straight line, however, as demonstrated by the following:
‘t3.CIO ‘+O.CO?
AAtotal
=
AAH2[PdC141
+ (eCaco(0)2ACCaco(0)z1) 4(e for each substance at 520 nm)
(tCaco(OH)zACCaco(OH)z~)
-ACCaco(O)n
=
-
ACC~CO(OH)~
C C ~ ~ ~ (assuming ( ~ H ) ~stoichiometric reduction) AAtotal 3
0
200
400
I
500
I
I
BOO
CONCENTRATION,
I
I
I000
I
ppm
Figure 1. Calibration curve for absorbance vs. concentration of carbon monoxide. Average and range of values for five determinations are shown, with standard deviations listed beside each set of data.
Tetrachloropalladic(I1) acid has nearly the same yellow hue in solution as cacotheline. Cacotheline probably is protonated a t the amine groups in the reagent solution. The reactions for the reduction of tetrachloropalladate(I1) and subsequent reduction of cacotheline are as follows (Caco(0)z= cacotheline; Caco(OH)z = dihydrocacotheline):
-
+ H20 Pd + COz + 4H+ + 4C1Pd + Caco(0)2 + 2H+ Pd2++ Caco(OH)2 Pd2++ 4C1- + 2H+ H2[PdCl4] +
HZ[PdCl4] CO
CO
-
-
+ H20+ Cac0(0)~
HzLPdCI,I
C 0 2 + Caco(OH),
=
[(ECaco(OH)z - ~Caco(0)z)CCaco(OH)~~l = kCCaco(OH)z
The method described here is unique in using a stable one-solution reagent. In acetic acid solution substantially less than 90%, the violet dihydrocacotheline produced by reaction with carbon monoxide fades, probably due to oxidation of the dihydrocacotheline by atmospheric oxygen. In the 90% acetic acid media, the dihydrocacotheline color is stable indefinitely. Thus, both the reagent solution before use and the solution containing the reaction products are stable on storage. Registry No. I, 561-20-6;CO, 630-08-0; PdCld2-,14349-67-8. LITERATURE CITED ( 1 ) Smith, R. G.; Bryan, R. J.; Feldstein, M.; Levadie, B.; Miller, F. A.; Stephens, E. R.; Whlte, N. G. (Subcommlttee 4 of the Intersoclety Committee) Health Lab. Sci. 1970, 7 , (January Supplement) 75. (2) Lambert, J. L.; Hamlln, P. A. Anal. Lett. 1971, 4 , 745. (3) Lambert, J. L.; Wiens, R. E. Anal. Chem. 1974, 4 6 , 929.
RECEIVED for review December 30,1982. Accepted May 26, 1983. This research was supported in part by National Science Foundation Grant CHE-7915217 and by NSF Grant SPI8013291 to Yuan C. Chiang.
Portable Piezoelectric Crystal Detector for Field Monitoring of Environmental Pollutants Mat H. Ho and George G. Guilbault*
Department of Chemistry, University of New Orleans, New Orleans, Louisiana 70122 Bernd Rietz
National Institute of Working Environment, DK-2900 Hellerup, Denmark In general, there are two types of toxic chemicals in the atmosphere we breathe: acute toxins and cumulative toxins. Many acute toxins can be tolerated at sublethal concentrations. Cumulative toxins, on the other hand, may cause a harmful effect even upon exposure to minute amounts over long periods. Toxins in the atmosphere, either acute or cumulative, need to be monitored. For acute toxins, a continuous monitoring device is required to ensure rapid detection of the lethal concentrations. For cumulative toxins, a cumulative dosimeter is required to measure the time-weight-average (TWA) exposure. Most of present monitoring systems involve a sampling step, using activated charcoal, silica gel, Tenax GC, or passive sampling devices (1,2),and transport of the sample back to the laboratory for subsequent analysis. The results of an air sample taken one day are usually not known until the next day and a worker in the field may be poisoned before the harmful level is identified. Direct monitoring devices are preferred, but they are either bulky, high power consuming, complicated to operate, or expensive or lack sensitivity and selectivity. There is, therefore, a need for a direct monitor
that is portable for field use, lightweight, low power consuming, inexpensive, rugged, and simple to operate and yet is reliable, sensitive, and selective. It appears that the piezoelectric crystal can be developed as such a device. In an attempt to demonstrate this concept, a portable field monitor was constructed by using a coated piezoelectric crystal for direct monitoring of toluene in a Danish printing plant. The principle of the detector is that the frequency of vibration of an oscillating crystal is decreased by the adsorption of a foreign material on its coated surface (3). Toluene is adsorbed on the coating, thereby increasing the mass on the crystal and decreasing the frequency. This change in frequency is proportional to the concentration of toluene in the atmosphere. EXPERIMENTAL SECTION Apparatus. The detector, which is 20 X 14 X 9 cm in dimensions and weighs 2.5 kg, was developed for field use. Figure 1shows the schematic diagram of the detector. The device consists of two crystals, one as a sensor and the other as a reference (9 MHz, AT-cut piezoelectric quartz crystals from International Crystal Mfg. Co., Oklahoma City, OK). Only the sensor crystal was coated with Pluronic F-68. Two oscillators were employed
0003-2700/83/0355-1830$01.50/00 lg83 American Chemical Society
