Anal. Chem. 1986, 58, 1527-1529
of the previously reported chemiluminescent method (10) for the determination of chlorine dioxide has a detection limit around 50 ppb. The selectivity of this prior method was not quantitatively discussed, but the results reported here using luminol in the presence of hydrogen peroxide with gas diffusion indicate that our method using luminol only is more selective vs. chlorine and other interfering ions. It is shown that this method has a detection limit of 5 ppb, which is an order of magnitude lower. The selectivity of this method is excellent giving no interference from any ions tested and a selectivity factor of over 1500 for chlorine dioxide vs. chlorine (or monochloramine) on a mole-to-mole ratio. Therefore, the method presented here offers significant improvements for the selective determination of chlorine dioxide and can be used to reliably monitor the SNARL level recommended by the National Research Council. Registry No. CIOz, 10049-04-4;C1, 7782-50-5; luminol, 52131-3.
LITERATURE CITED (1) Masschelein, W. J. CHLORINE DIOXIDE: Chemlstry and Environmental Impact of Oxychlorjne Compounds; Ann Arbor Sci-
1527
ence: Ann Arbor, M I , 1979 Chapter 14. Hollowell, D. A.; Pacey, G. E.; Gordon, G. Anal. Chem. 1985, 5 7 , 2851. Drinking Wafer and Health; National Research Council, National Academy Press: Washington, DC, 1980 (Voi. 3), 1982 (Vol. 4). Hodgden, H. W.; Ingols, R. S. Anal. Chem. 1954, 26, 1224. Masscheleln, W. Anal. Chem 1966, 38, 1839. Palin, A. T. J . Am. Water Works Assoc. 1975, 6 7 , 32. Post, M. A,; Moore, W. A. Anal. Chem. 1959, 31, 1872. Smart, R. 6.; Freese, J. W. J . Am. Water Works Assoc. 1982, 7 4 , 530. Haller, J. F.; Lister, S. S. Anal. Chem. 1948, 2 0 , 639. Isacsson, U.; Wettermark, G. Anal. Chlm. Acta 1976, 8 3 , 227. Isacsson, U.; Wettermark, G. Anal. Lett. Part A 1978, A I I ( I), 13. Smart, R. 6. Anal. Lett. Part A 1981, A 14(3), 189. Marino, D. F.; Ingle, J. D. Anal. Chem. 1881, 53, 455. Marino, D. F.; Ingle, J. D. Anal. Chim. Acta 1981, 123, 247. W. E. van der Linden Anal. Chim. Acta 1983, 151, 359. Rosenbiatt, D. H.; Hayes, A. J., Jr.; Harrison, 6. L.; Streaty, R. A.; Moore, K. A. J . Org. Chem. 1963, 28, 2790. Kieffer, R. G.; Gordon, G. Inorg. Chem. 1968, 7 , 235. Gordon, G.; Kieffer, R. G.; Rosenblatt, D. H. The Chemistry of Chlorine Dioxide, Progress In Inorganic Chemlstry; Llppard, S . J., Ed.; Wiley: New York, 1972; Vol. 15, p 201. Standard Methods for the Examination of Water and Wastewater, 15th ed.; American Public Health Association: Washington, DC, 1980; 304.
RECEIVED for review September 3, 1985. Resubmitted February 3, 1986. Accepted February 3, 1986.
Air Sampling of N-Methylmorpholine on Solid Sorbent and Determination by Capillary Gas Chromatography and a Nitrogen-Phosphorus Detector Barbro Andersson* and Kurt Anderss'on National Board of Occupational Safety and Health, Research Department, Chemical Unit in Umea, Box 6104, S-900 06 Umea, Sweden
A method for sampling and determination of N-methylmorpholine In workroom air is presented. Sampling was performed on the adsorbent Amberilte XAD-7 at air levels of 2-100 mg/m3 methylmorpholine, and desorptlon was effected by solvent extraction with ethyl acetate. Analysls of the free amine was carried out by means of capillary gas chromatography with flame lonizatlon or nitrogen-phosphorus detection (FID and NPD, respectively). The recovery tests were performed at 20 % and 85 % relative alr humldlty, giving recoveries of 90-96% with a relatlve standard devlatlon of 2-5%. Afler 6 weeks of storage in a deep freezer at -20 OC, the recovery was even higher than 90%. The gas chromatographic detection limits of methylmorphoiine were 0.5 ng (FID) and 0.05 ng (NPD). The method was applled to the polyurethane industry.
Tertiary aliphatic amines, including N-methylmorpholine, find applications in a variety of industries: as corrosion inhibitors in steam boiler systems and as starting materials and solvents in organic synthesis. The main use of these compounds is, however, as catalysts in polyurethane production. In the vapor phase, methylmorpholine causes irritation in the eyes and the respiratory system. The occurrence of asthma among workers in the polyurethane industry has generally been ascribed to the isocyanates, but methylmorpholine and some other tertiary amines are now suspected as having similar 0003-2700/86/0358-1527$01.50/0
effects (1, 2). Moreover, the amines are present in 10-fold higher concentrations. Air sampling of tertiary amines has been performed on solid sorbents, such as silica gel, as recommended by the National Institute for Occupational Safety and Health for N-ethylmorpholine (3),acid-treated silica gel (4), Chromosorb 103 (5), and acid-treated Tenax (6). The amines are desorbed by solvent extraction except in the case of Chromosorb 103, where thermal desorption has been used (5). The amines are also trapped in impingers containing an acidic water solution (4, 7-10), which can then be analyzed directly. Analysis of tertiary amines has been performed by gas chromatography,usually on special base-treated columns, with flame ionization (4) or nitrogen-selective detection (7-9). Electron capture detection has also been used after derivatization of the amine (11). The opportunity has also been taken of utilizing the bonded-phase capillary columns in amine analysis. Analysis of tertiary amines by liquid chromatography with precolumn (12) or postcolumn (13) derivatization, with UV and fluorescence detection, respectively, has also been reported. An isotachophoretic method was reported recently (10). Some of the references above pertain to N-methylmorpholine (5, 8, 9). In the industrial hygiene sector, air sampling is usually carried out by a safety engineer stationed within the industry. The collected samples are sent to a laboratory for analysis. Accordingly, special procedures have to be observed in collection, transport, and storage of the samples prior to analysis. 0 1986 American Chemical Society
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ANALYTICAL CHEMISTRY, VOL. 58, NO. 7, JUNE
1986
We now present a convenient sampling method for Nmethylmorpholine on a solid sorbent glass tube, with desorption by solvent extraction and final determination of the free amine by capillary gas chromatography and nitrogenselective detection.
EXPERIMENTAL SECTION Collection of Samples. In the recovery tests, a system producing air with a known flow rate and relative humidity (RH) was used (14).After passage through a dust/oil filter, pressurized air was humidified in gas bottles and diluted with unsaturated air in chambers. The air stream was then divided into seven equal parts, which were respectively passed through seven parallel 10-cm application glass tubes, followed by XAD-7 tubes (one being used as blank) and an air humidity indicator (14). This system enables small adjustments to be made to both flow rate and humidity. Aliquots (10 pL) of N-methylmorpholine in ethyl acetate were injected into a glass wool plug in the application tube. Sampling was performed at 20% and 85% RH, with an air flow of 100 mL/min and a sample volume of 5 L collected over 50 min. The temperature was 20 "C. Breakthrough volumes were determined at 20 mg/m3 air level and 85% RH. In a field study, 12 stationary samples were collected at six different localities within a polyurethane industry. SKC 222-3 pumps, with sampling rate and sampling time as above, were used. The temperature and RH at the sampling localities were 18-22 "C and 65-90%. Desorption of the Amine. The XAD-7 adsorbent was transferred to 3.5-mL glass vials with screw caps and carefully agitated in 1.0 mL of ethyl acetate for 30 min (Ika Vibrax-VXR vibrator). The recovery samples were analyzed immediately after collection and the field samples within 1week (2 days of storage at 20 "C and darkness, thereafter at -20 OC). The sample solution was diluted 10 times before GC-NPD analysis. Gas Chromatography Equipment. GC analysis was carried out on a Hewlett-Packard Model 5880A gas chromatograph with flame ionization (FID) and nitrogen-phosphorus (NPD) detectors. The chromatograph was equipped with an automatic liquid sampler (Hewlett-Packard Model 7671A) and a 25-m X 0.20mm-i.d. fused silica capillary column with a 0.33 Mm film thickness (Ultra A2 cross-linked 5% phenyl methyl silicone, HewlettPackard). Two other columns were tested: a column similar t o that above (high-performance J 5% phenyl methyl silicone, 25 m, Hewlett-Packard), but with 0.32 mm i.d. and 1.05 ym film thickness, and a 25-m X 0.20-mm4.d. fused silica WCOT capillary column for amines with 0.20 mm film thickness (CP Wax 51, Chrompack). The injector glass tube was filled with silylated glass wool. The injector temperature was 200 "C, and the detector temperatures were 250 "C (FID) and 300 "C (NPD). Nitrogen (FID) or helium (NPD) was used as carrier gas, at a column flow rate of 1 mL/min. The samples were injected in the split mode (2 pL, splitting ratio 1:30). The column temperature was held at 70 "C for 7 min and then subsequently increased by 15 "C/min to 230 "C, which was held for 10 min. N-Methylmorpholine had a retention time of 4.3 min under these conditions. Gas Chromatography-Mass Spectrometry System (GCMS). The determination of N-methylmorpholine in the field samples was confirmed by GC-MS. The equipment consisted of a Finnigan Model 4021 mass spectrometer system supplied with a Hewlett-Packard capillary injector in the gas chromatograph. Helium was used as carrier gas, and the column and the other GC parameters were as above. The temperature of the mass spectrometer separator oven and ion source was held at 250 "C. Spectra were recorded at 70 eV, with an electron multiplier voltage of 1800 V and a preamplifier setting of lo-'. Reagents. The following were used Amberlite XAD-7 sorbent tubes (glass tubes with two sections of 80 and 40 mg; SKC, Inc., lot 164),Amberlite XAD-2 and XAD-4 tubes (SKC, Inc., lot 128 and 146, respectively), Tenax TA tubes, 50-mm X 4-mm4.d. glass tubes, packed with 50 mg of Tenax TA (Chrompack, 35-60 mesh), N-methylmorpholine (purum, Fluka), and ethyl acetate (LiChrosolv, Merck). RESULTS AND DISCUSSION The threshold limit value for N-methylmorpholine in workplace air in Sweden is 20 mg/m3. Accordingly, recovery
Table I. Recovery of N-Methylmorpholine on Amberlite XAD-7 air level
recovery," R ( R re1
std dev)
amt added, rug
in 5-L sample, mg/m3
20% RHb
500
100
93 (2)
50OC
100
5OOd 100 10 1Or 1Od
100 20 2 2 2
96 (2) 96 ( 5 )
85% RH 90 90 91 96 96
(3)
(4) (2) (3) (5) 92 ( 5 ) 86 (3)
"Six replicates. * R H = relative humidity. 'Six weeks of storage O C . d T ~ weeks o of storage at 20 "C and darkness.
at -20
tests were performed a t air levels of 2, 20, and 100 mg/m3. Several adsorbents were tested for trapping N-methylmorpholine: the Amberlites XAD-2, XAD-4, and XAD-7 and Tenax TA. Desorption was effected in all cases by solvent extraction with ethyl acetate. All adsorbents except Amberlite XAD-7 have too low sampling capacity for methylmorpholine. The influence of air humidity on the sampling capacity of Amberlite XAD-7 was tested a t two levels, 20 and 85% RH (Table I). The recoveries were 90-96%, and after 6 weeks of sample storage at -20 "C the recoveries were 90-92%. Storage tests were also made as above for 2 weeks a t room temperature (20 "C) and darkness. The recoveries were 86-91%. The higher RH level had no influence on the recovery not even a t 100 mg/m3 air level, which is consistent with our earlier studies of Amberlite XAD-7 (14,15). At this level about 1% of the methylmorpholine was found in the backup trap (second section of sorbent). The influence of pumped air volumes on the XAD-7 sorbent, and thereby the recovery, was determined at 5 L (92%), 10 L (84%), 15 L (81%), 20 L (77%), 25 L (72%), and 30 L (67%). However, no distinct breakthrough volume could be detected a t air volumes relevant for industrial hygiene sampling. Capillary columns with greater phase thickness have been produced for use in gas chromatography. These have proved to be suitable for chromatography of polar compounds with column adsorption problems. From the three columns tested, a phenyl methyl silicone column with a phase thickness of 0.33 pm was chosen. An increase in phase thickness to 1.05 Mm did not improve the column properties for analysis of methylmorpholine. Gas chromatographic analysis of the test samples was performed with a FID (split mode 1/30 injection), which afforded a detection limit of 0.5 ng for a standard methylmorpholine solution (signal-to-noise ratio, 4:l). The corresponding limit for the NPD was 0.05 ng. This detector was used in the analysis of the industrial samples. Application of an NPD increases sensitivity and facilitates identification of relevant compounds in complex mixtures. The current method was evaluated with authentic workplace samples from a company manufacturing polyurethane. The company manufactures interial fittings for automobiles, such as headrests and armrests, by compression molding cold foam. Polyurethanes are produced by the reaction between hexamethylene diisocyanate and a polyalcohol. Various tertiary amines are used as catalysts. On the occasion of sampling the company was only using N-methylmorpholine. The air samples were collected at places where the levels of interfering chemicals might be high. Figure 1 shows gas chromatograms (NPD) of standard methylmorpholine and of airborne contaminants in a factory producing polyurethanes. The small peak on the shoulder of the standard peak is an impurity in the solvent (ethyl acetate). This impurity, however, does not interfere even at the low levels studied here.
Anal. Chem. 1986, 58, 1529-1532
/
1529
The current method complies with the requirements for sampling and analyzing airborne compounds in the industrial hygiene sector. The high separation efficiency of the capillary column, in combinatioawith selective detection of nitrogen compounds, permits this method to be used in various kinds of industrial environments. Registry No. Amberlite XAD-7, 37380-43-1; N-methylmorpholine, 109-02-4.
LITERATURE CITED (1) Balin, L.; Wass, U.; Aundunsson, G.; Mathiasson, L. Br. J. Ind. Med.
+L-/
IF1
+'I-
*
1983, 40, 251. (2) Candura, F.; Moscato, G. Br. J. Ind. Med. 1984, 4 7 , 552. (3) NIOSH Manual of Analytical Methods, 2nd ed.; National Institute for Occupational Safety and Health: Clncinnati, OH, 1977; Vol. 3, method S 146. (4) Ferrari, P.; Guenier, J. P.; Muller, J. Chromafographia 1985, 20, 5. (5) Lovkvist, P.; Jonsson, J. A. J. Chromatogr. 1984, 266,279. ( 6 ) Fltzpatrick, M. R.; Warner, P. 0.; Thiel, D. P.; Lubs, P. L.; Kerfoot, E. J. Am. Ind. Hyg. Assoc. J . 1983, 4 4 , 425. (7) Dalene, M.; Mathiasson, L.; Jonsson, P. A. J. Chromatogr. 1981, 207, 37. (8) Audunsson, G.; Mathiasson, L. J. Chromatogr. 1983, 267, 253. (9) Audunsson, G.;Mathiasson, L. J. Chromatogr. 1984, 375, 299. (10) Hans&, L.; Sollenberg, J.; Uggla, C. Scand. J. Work. Environ. Heaffh 1985, 7 1 , 307. (11) Ahnfelt, N. 0.; Hartvig, P.; Karisson, K. E. Chromatographia 1982, 76, 60. (12) Gubitz, G.;Wlntersteiger, R.; Hartinger, A. J. Chromatogr. 1981, 278,
51.
No interfering compounds from the factory were detected in the analysis of methylmorpholine, neither by GC/FID nor by GC/NPD. The identity of methylmorpholine in the workplace samples was confirmed by GC-MS, and the air level range was 8-20 mg/m3.
(13) Kudoh, M.; Matoh, I.; Fudano, S. J. Chromatogr. 1983, 267, 293. (14) Andersson, K.; Levin, J.-0.; Lindahl, R.; Nilsson, C.-A. Chemosphere 1984, 73, 437. (15) Andersson, E.; Andersson, K.; Nilsson, C.-A. J. Chromatogr. 1984, 297, 257.
RECEIVED for review November 7,1985. Accepted February 3, 1986.
Continuous Monitoring Device for the Collection of 23 Volatile Organic Priority Pollutants Roger D. Blanchard and James K. Hardy*
Department of Chemistry, University of Akron, Akron, Ohio 44325
A method that allows for continuous monltorlng or single-point analysis of volatlle organic prlorlty pollutants has been developed. The method Is based on permeation of volatlle organlc compounds through a slllcone polycarbonate membrane, from a sample water matrix, Into an Inert gas stream. The volatlle organlc compounds are collected In a sampling loop connected to a six-port valve and then directed Into a caplllary column of a gas chromatograph. The procedure has the advantages of being simple and not requiring tlme-consumlng preconcentratlon steps and It can be used either In the field or In the laboratory. Detection llmlts are in the low parts-per-bllllon range. Llnear results of response vs. concentratlon are obtained from the low parts-per-billion to the low parts-per-mllllon range. Permeation rates increase In a nearly llnear manner with temperature. Preclslon Is comparable to present methods of analysis.
Federal regulations, which include the Federal Water Pollution Control Act of 1972 (1)and the Clean Water Act
of 1977 ( 2 ) ,require monitoring of effluent streams for hazardous pollutants. A list classified as the Priority Pollutant List contains 129 compounds that are to be regulated. Contained within the list are a group of compounds designated as volatile or purgeable organics consisting of 31 compounds. The present Federal Environmental Protection Agency (EPA) approved method of collection and analysis of volatile organic priority pollutants involves obtaining a grab water sample from an effluent stream, transporting the sample to a laboratory, and analyzing the sample by a procedure called the purge and trap technique ( 3 , 4 ) . In this procedure, the water sample is placed in a purge vessel, and an inert gas is bubbled through the sample to remove the volatile components contained in the water. The volatile components are trapped on an adsorbing matrix and thermally desorbed for analysis by gas chromatography or GC/MS. This procedure is limited in that it only provides concentration values for a certain point in time at a specified location, it does not provide for a long-term stabilized sample prior to analysis, and the procedure contains difficulties inherent in the purge and trap technique such as incomplete desorption of volatile components from the ad-
0003-2700/86/0358- 1529$0 1.50/0 0 1986 American Chemlcal Society
