Anal. Chem. 1982, 5 4 , 810-817
810
Collection and Analysis of Hazardous Organic Emissions Kenneth J. Krost Environmental Protection Agency, National Envlronmental Research Center, Research Trlangie Park, North Carolina 27709
Edo D. Pellizzari" Research Triangle Institute, Research Triangle Park, North Carollna 27709
Stephen G. Walburn and Sarah A. Hubbard Northrop Servlces, Inc., Research Triangle Park, North Carolina 27709
Over the past 8 years, research has been conducted on developing the anaiytlcai capablllty to collect, characterize, and quantlfy volatlle organic compounds present in typical amblent alr environments. This paper summarizes the overall progress made on this development. The descrlbed analysis system encompasses the collectlon and concentratlon of organlc pollutants from amblent alr udng tubes packed with polymeric beads. After sampllng, the cartridges are thermally heated under a He flow, the compounds desorbed, cryofocused, and subsequently Introduced Into a hlgh-resolution glass or fused caplilary for characterlratlon and measurement by gas chromatography/mass spectrometry/computer (GWMSICOMP) technlques.
Hazardous vapors have been postulated to occur in the atmosphere (1-3). Until the present program was initiated, no serious or thorough endeavor had been made to collect and characterize these substances. The National Academy of Sciences panel in a study of the biological effects of atmospheric pollutants has concluded and recommended in their report on Particulate Polycyclic Organic Matter that "Research is needed on the chemistry and biological activity of air pollutant cocarcinogens and tumorpromoting agents, such as polyphenols and paraffin hydrocarbons, and on the oxidation products of airborne olefins and aromatic hydrocarbons, including the nature of the epoxides, hydroperoxides, peroxides, and lactones formed and their biological porperties" (4). Van Duuren (5-8) summarized a review on the biological properties of carcinogenic vapors with the statement that "in view of the obvious importance of these aliphatic compounds (epoxides, hydroperoxides and peroxides), it is imperative that studies be undertaken on the analysis of volatile organic air pollutants". Once the identities of the physiologically active vapors present in polluted atmospheres are known, then investigators can ascertain which substances need to be routinely analyzed, studied epidemiologically, and eventually controlled. The primary goal of this research program has been to develop methodology for the reliable and accurate collection and analysis of a multitude of hazardous vapors present simultaneously in the atmosphere down to nanogram per cubic meter amounts. Each step of the developed method, from field sampling to instrumental and data analysis, is discussed.
EXPERIMENTAL SECTION Materials. Tenax-GC (60/80 mesh), Chromosorb 101 (100/ 120), Chromosorb 104 (100/120), and Chromosorb W-HP (100/120) were purchased from Applied Science, State College, PA. A series of stationary phases chemically bonded to supports including Carbowax 400/Poracil C (loo/ 120),Oxopropionitrile/Poracil C (80/100), and Phenylisocyanate/Poracil C (80/100)
were also obtained from Applied Science. Stationary phases consisting of Carbowax 600, dodecyl phthalate, and tricresyl phosphate and the sorbent Porapak Q were from Supelco, Inc., Bellefonte, PA. Carbon derived from coke (PCB and BPL, 12/30) was acquired from Pittsburgh Activated Carbon Division of Calgon Corp., Pittsburgh, PA. Cocoanut derived carbons (SAL19190and 580-26) were purchased from Barneby Cheney, Columbus, OH. SKC Carbon wassobtained from SKC, Inc., Eighty Four, PA. Methyl methanesulfonate, P-propiolactone, N-nitrosodiethylamine, 1,2-dichloroethylethyl ether, nitromethane, methyl ethyl ketone, and aniline were from Fisher Chemicals,Pittsburgh, PA. Glycidaldehyde and sulfolane were obtained from Aldrich Chemicals, Milwaukee, WI. 1,2-Propane sultone, maleic anhydride, butadiene diepoxide, and propylene oxide were from Eastman Organic Chemicals, Rochester, NY. Styrene epoxide, bis(chloromethy1) ether, and bis(2-chloroethyl) ether were from K&K Labs., Plainview, NY. Other chemicals and solvents were analytical reagent grade from Fisher Chemicals. Apparatus. GCIMS/COMP. Figure 1 schematically illustrates the basic collection and analysis system. A Varian MAT CH-7 or an LKB 2091 GC/MS/COMP system was used to perform the analyses. Typically, the mass spectrometer was first set to operate in the repetitive scan mode. In this mode, the magnet was automatically scanned upward from a preset low mass to a high mass value. Although the scan range varied depending on the particular sample, typically the range was from m / z 28 to m / z 400. The scan was completed in 1.5 s. The instrument then reset itself to the low mass position in preparation for the next scan. The information was accumulated on disk by an on-line computer or was transferred to magentic tapes for archival storage. A continuous scan cyle of 2.3-3 s was maintained. Prior to running known samples, the system was calibrated with perfluorokerosene by determining the time of appearance of known mass ions in relation to the scanning magnetic field. The calibration curve was stored, and daily checks were made to assure validity of the original calibration. Samples were analyzed with a variety of capillary columns and analyses conditions as summarized in Table I. For analysis of nonpolar and semipolar organics (e.g., halogenated hydrocarbons, ethers, esters, etc.), SE-30 or DB-1 coated capillaries were employed. More polar substances were chromatographed on DEGS and Carbowax 20M phases coated as SCOT columns. A singlestage glass jet separation was maintained at 240 OC and interfaced with the capillary column to the mass spectrometer. Sampling System. A Nutech Model 221-A AC/DC sampler (Nutech Corp., Durham, NC) was used to draw ambient air through the Tenax cartridge (9). At times, a DuPont Model No. P125 personal sampler (E. I. du Pont de Nemours, Wilmington, DE) was also used for long-term sampling (8 h or greater). Cartridges used to concentrate organic vapors consisted of 1.5 X 6.0 cm bed of Tenax GC (35/60). All sampling cartridges were preconditioned by heating to 275 "C for a period of 20 min under a helium purge of 20-30 mL/min. After samples were cooled in precleaned Kimax culture tubes, the containers were sealed to prevent contamination during transportation and storage. Sampling cartridges prepared in this manner were carried by automobile or air freight to the sampling site. Two to three cartridges
0003-2700/82/0354-0810$01.25/00 1982 American Chemical Soclety
ANALYTICAL CHEMISTRY, VOL. 54, NO. 4, APRIL 1982 FLOW METER
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GASMETLR
VAPOR COLLECTION SYSTEM PUREE
IOESORPTION CHAMBER CURRENT RECORDER
HLATEO BLOCKS( CARRIER 2 POSITION YALVE
I
CAPILLARY
COMPUTER
TAPE
CAPILLARY TRAP ICO.AXIALI
Flgure 1. Vapor collectiorl and analytical systems for analysis of organlc vapors in ambient air.
Table I. General Operating Parameters for GLC/MS/Compu%er-System parameter inlet manifold desorption chamber valve capillary trap: min max thermal desorption time He purge rate GLC SE-30 (1.0 pm film thickness) -glass WCOT (0.42 i.d. X 85 m) DB-1(1.0um film thickness) fuseh silica (0.32 mm i.d. x 60 rn) DEGS (0.8 pm film thickness) glass SCOT (0.42 i.d. X 55 m ) Carbowax 20M (0.8-1.0 pm film thickness glass SCOT (0.50 i.d. X 38M) MS single stage glass jet separator ion source vacuum filament current multiplier scan rate, automatic cyclic scan range
setting 265-270 "C 265 "C -195 "C 240 "C -8 min 1 5 mL/min 25-240 "C,4 "C/min, 1.2 mL/min 25-240 'C, 3 "C/min, 1.2 mL/min 70-205 OC, 4 "C/min, 2.5 mL/min 25-200 "C, 4 "C/min, 4 mL/min 240 "C -2 x l o m 6torr 300 pA 5.5 1 s/decade m/e 20-400
were designated as blankn for assessing the occurrence of any potential contamination. Inlet Manifold System. The manifold design used for thermal desorption evolved from a consideration of several criteria (9-12): (a) the heat transfer characteristics of cartridge samplers conMining sorbents of various physical bed dimensions, (b) the flow rate requirements for purging desorbed vapors from the cartridge sampler and for packed and GLC capillary columns, (c) the temperatures necessary for effecting thermal desorption of trapped vapors from sorbents, and Id) the ability to conveniently interchange and assemble on any standard GC or GC/MS instrument. Design. The fabricated inlet/manifold system consisted of four main components: a desorption chamber, a six-port two position high-temperature low-volume valve (Valco, Inc., Houston, TX),
811
a Ni capillary trap, and a temperature controller. The configuration of the chamber was designed to allow inert gas to enter through a side arm near the top. This permitted the purge gas to be preheated prior to entering the chamber and passing down through the sorbent bed. The overall chamber length was 13.3 cm which accommodated a Pyrex sampling cartrige of 1.6 cm 0.d. X 10.5 cm in length. An aluminum sandwich served as a heat sink for the desorption chamber and the valve. Two 150-W, 115-V heating cartridges were used to heat the aluminum sandwich, and the temperature was monitored and controlled via a platinum sensor probe. The desorbed vapors passed via a short Ni capillary line to the six-port two-position valve. Temperature control was f 2 "C. A nickel capillary (0.508 mm i.d. X 1.59 mm 0.d. X 0.75 m in length) constituted one loop of the valve proper which was cooled with liquid N2and served as a trap for collecting and concentrating desorbed vapors for their introduction into high-resoltion GLC columns. The vapors were released from the capillary trap by rapidly heating the trap to 250 "C using a 150-W, 115-V heating cartridge. The multiport valve was chosen for its polyimide internal stem to minimize the contact of desorbed trace vapors with reactive metal surfaces, therefore, minimizing contamination of decomposition of sample consituents. Operation. In a typical thermal desorption cycle, a sampling cartridge was placed in the preheated (ca. 270 "C) chamber, and He gas was purged through the cartridge (ca. 15 mL/min) to purge the vapors into the liquid N2cooled Ni capillary trap. After the thermal desorption step was complete (8 min), the six-port valve was rotated and the temperature on the capillary loop was rapidly raised (>lo0 "C/min) whereupon the carrier gas carried the vapors into a GLC column. As designed, the protoytpe thermal desorption chambers were easily interchangeable and accommodated cartridges of two different internal diameters with up to 8 cm of packing (sorbent) depth. Thus, comparisons of different cartridge sizes with respect to sorbent background during thermal desorption could be made. This inlet-manifoldconfigurationalso allowed the desorbed vapors from one or more cartridges to be accumulated in the capillary trap prior to analysis by GC or GC/MS. The capillary trap on the inlet-manifold was evaluated. Capillary traps were constructed of Ni tubing in lengths of 0.25,0.5, 1.0, and 1.5 m with an internal diameter of 0.508 mm. Two confiiations were examined. The f i t was a coaxial arrangement in which the tubing was wound around the axis of the exiting purge gas stream and the second was transaxial in which the tubing was parallel to the entrance and exit of the purge gas. Tenax Purification and Cartridge Preparation. Devices. The devices required for preparing and storing cartridges included (a) glass cartridge tubes, 16 mm 0.d. X 100 mm long, (b) glass culture tubes, 25 X 120 mm with Teflon-lined caps, (c) 1 qt metal paint cans, (d) vacuum oven bakeout chamber, and (e) GC equipped with an inlet manifold. Cleaning of Materials. Clean equipment was found to be crucial for overall cartridge cleanliness. The culture tubes and their caps (Teflon lined), the paint cans and their lids, and the glass cartridge tubes were all washed with nonionic soap and water. They were rinsed twice, first with tap water and then with deionized water, and allowed to air-dry. The Teflon liners were further washed with methanol and n-pentane and then air-dried. The glass wool was Soxhlet extracted for 3-4 h. Within 8 h before use, the glass wool, culture tubes, Teflon liners, and caps were baked in a vacuum oven (1h, 110 "C). The glass wool, Teflon liners, and culture tubes were baked simultaneously,but the caps had to be baked by themsleves due to their tendency to outgas at elevated temperatures. The Drierite, for the bottom of the culture tubes, was baked (400 "C) overnight the night before the cartridges were to be thermally conditioned. The paint cans were baked for 1 h at 270 "G in an oven continuously flushed with nitrogen, and all materials not used immediately after baking were stored in a clean paint can. The bakeout operations, both for the equipment and the cartridges, were carried out in an area of minimal organic solvent usage. The Tenax was cleaned by Soxhlet extractions to remove soluble contaminants. ? b o solvents were used, methanol followed by n-pentane. Fresh redistilled solvent was used for each batch
812
ANALYTICAL CHEMISTRY, VOL. 54, NO. 4, APRIL 1982
of Tenax. After extraction, the Tenax was removed from the thimble, placed in a large clean porcelain dish, and dried in a vacuum oven (3-5 h, 110 "C). Upon removal from the oven, the Tenax was sieved to obtain a particle size range of 35-60 mesh (250-500 pm). Since the sample would be recovered from the cartridge by thermal desorption, the cartridge was placed in the bakeout chamber and swept with filtered helium at a flow rate of 100 mL/min for 1 h at i70 OC. The helium was filled through a Drierite-charcoal or liquid N2trap to remove any contaminants in the gas stream. The cartridges were removed from the chamber while still hot and placed in a culture tube containing Drierite (-5 g) and a glass wool plug. The tube was immediately capped and placed in a paint can. The extent of impuritieson a typical cartridge after preparation and storage is less than 30 ng of equivalent C6Fe Since this quantity presents no problem in GC/MS analysis, the cartridge can be considered devoid of interfering contaminants. Estimation of Breakthrough. On the basis of results obtained in prior studies for collection efficiencies, thermal desorption, and pressure drop measurements, Tenax GC was selected for further study as a possible candidate material for collecting hazardous vapors (13). The method employed consisted of determining the elution volume for an organic vapor on a gas chromatographic column packed with the sorbent Tenax GC. A column with the dimensions of 2.5 mm i.d. X 1.76 m in length was used. After each vapor was injected, the elution volume was determined as the product of flow rate and elution time. A series of injections were made at vapor levels which obeyed Henry's law and at decreasing temperatures. A graph of log l / u , vs. T "C was constructed. By use of a linear regression analysis, the breakthrough volumes (50% loss) for several ambient temperatures were determined by extrapolation. At the end of the experiment, the volume of the chromatographic column occupied by the sorbent was determined and the breakthrough volume was expressed in L/7.96 mL of sorbent, which is the standard bed volume which has been employed in field sampling (13). Qualitative Analysis. Identification of the constituents in the samples was established by comparing the mass spectrum of the unknown to mass spectra in an eight-peak index (14) and a Wiley collection (15). In many cases the identification was confirmed by comparing the mass spectrum of an unknown compound run under identical conditions to that of the known. The relative elution times were also compared, based on the chromatography of the authentic compound under identical conditions to the unknown, as well as the boiling points for a homologous series. In some cases, identification was achieved with computer based mass spectral search systems and/or the PBM/Stirs system located at Cornel1 Univeristy. A scheme relating the degree of confidence of an identification to the information content employed has been reported (21). Quantitative Analysis. The concentrationof each substance was determined by utilizing either the total ion current monitor when the constituents were adequately resolved or selected mass ions in other cases. In order to eliminate the need to obtain complete calibration curves for each compound, we used the method of relative molar response factor, RMR (10, 16). The selected ions used for a number of compounds are shown in Table 11. Authentic standards were loaded onto Tenax GC sampling cartridges using a permeation system (10, 13) or solvent evaporation system. Instrument calibration involved the complete system, i.e., inlet manifold (recovery by thermal desorption), capillary, GC/MS/COMP. RESULTS AND DISCUSSION Tenax Cartridge Sampler. Design Specifications. The development of a cartridge containing Tenax material for the collection and analysis of hazardous vapors from ambient atmosphere required a study of the physicochemicalproperties (17). These investigations included: (a) the examination of collection efficiencies of several sorbents, (b) the relationship between cartridge dimension (length and diameter), sorbent particle size, sampling rate, and pressure differential, and (c)
Table 11. Mass Fragment Ions Selected for Quantification bv Mass Fragmentography chemical class
m/z (ion intens) first third second
Halogenated Hydrocarbons chloroprene 88 (50) 90 (17) 1,2-dichloroethane 62 (100) 64 (32) l,l,l-trichloroethane 117 (19) 119 (18) carbon tetrachloride 117 (100) 1 2 1 (30) trichloroethylene 130 (99) 132 (95) 1,2-dichlorobu tene 75 (100) 89 (43) tetrachloroethylene 166 (100) 168 (49) 1,2-dichlorobutane 55 (100) 62 (20) 2,3-dichloropropene-l 3,3-dichloropropene-l 110 (20) 75 (100) 1,3-dichloropropene methylene bromide 172 (52) 174 (100) 1,2-dichloropropane 6 3 (100) 62 (68) dibromochloro129 (100) 208 ( 1 2 ) methane 1,1,1,2131 (100) 133 (97) tetrachloroethane 1,1,2,2168 (18) 166 (13) tetrachloroethane bromoform 173 (100) 252 (10) bis(2-chloroisopropy1) 45 (100) 121 (17) ether hexachloro-l,3225 (100) 229 (22) butadiene 1,2-dibromopropane 123 (98) 202 (2) tetrachloropropane 178 (18) 180 ( 2 ) isomers vinylidene chloride 96 (61) 98 (38) phosgene 63 (100) 65 (32) 1,2,2-trichloropropane 111 (43) 61 (23) 1,1,2-trichloropropane 75 (100) 110 (32) l,l,l-trichloropropane 111 (100) 113 (80) pentachloroethane 202 (0) 167 (88) perchloroethane 234 ( 0 ) 201 (100) 1,l-dichloropropene-1 120 (100) 112 (64) Oxygenated Compounds isobutyl isobutyrate 89 (20) isobutyl n-butyrate 89 (12) 60 (23) isoamyl benzoate 123 (28) 70 (87) dimethyl phthalate 163 (100) butyl formate 56 (100) 73 (8) methyl methacrylate 69 (83) 100 (51) isobutyl methacrylate 69 (78) 87 (14) n-butyl methacrylate 69 (58) 87 (31) diethyl phthalate 177 (100) 149 (44) dipropyl phthalate 149 (100) 209 (9) dibutyl phthalate 149 (100) 223 ( 9 )
64 (100) 49 (51) 61 (59) 47 (41) 95 (100) 53 (50) 129 (63) 90 (22) 49 ( 2 0 ) 93 (72) 76 (30) 127 (80) 117 (82) 83 (100) 175 (49) 93 (8) 260 (38) 121 (100 143 (100 61 (100 44 (40 75 (20 61 (30 75 (60 165 (69 203 (63 49 (22
2 2 2 (10)
an estimation of the breakthrough volume for hazardous vapors. The effect (a) bed packing diameter, (b) bed length, (c) sampling rate, and (d) particle mesh range on the pressure differential developed across a sampling cartridge was examined (17).The total data taken collectively indicated that cartridge diameters of 0.5 cm and a mesh range >35/70 should be avoided in any studies which would require field sampling rates of 4 L/min or greater; likewise, mesh sizes of 100/120 and bed diameters of 1.056 cm would not be suitable (Figure 2). Consideration of calculated pressure drop (AP)curves for each mesh size allows for selecting the practical attainable flow rates for each mesh size and bed packing dimensions. Furthermore, large AP values are undesirable since vacuum desorption ("stripping") of vapors initially trapped on a sorbent may occur (Figure 2). Breakthrough Volumes. A determination of breakthrough volumes was performed for several organic compounds which have either been identified or are anticipated to be present
ANALYTICAL CHEMISTRY, VOL. 54, NO. 4, APRIL 1982 1400
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I
813
1
NUMBERS = FLOW A l I T E llmin
18 1000
P
B -J
0 ACROLEIN
0 OLYCIAOALOEHYOE A C V C L O H E X E N E OXIDE
ON NITROSOOIETHYLAMINE
'1
200
0
05
10
4 1
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V
'
-i
4
3 -PROPIOLACTONE
1
10
'
i0
7
k
L
U
i-10
TEMPERATURE OC
Figure 3. Linear regression of the elution volume vs. temperature for vapors on Tenax GC.
into the N-nitrosodimethylamine (to yield N-nitrosodiethylamine) produces a marked increase in the breakthrough volume. In fact, it increases by a factor of 9. An important relationship which can be extracted from the information presented in Figure 3, is the relationship between the breakthrough volumes a t seven different temperatures. The slopes of the linear regressions are parallel for compounds within a given chemical class. If the breakthrough volume a t one temperature is known, then the breakthrough at other temperatures for the unknown can be approximated. A series of mercaptans, thiophenes, and other sulfur-containing compounds were studied (13). Again a direct relationship was observed between an increase in the boiling point of each compound and its breakthrough volume. The inorganic gases tested (NO, NOz,Clz,Brz, 12, and SOJ exhibited rather low or no retention volume at all on Tenax GC. The low retention index for these inorganic gases is an important factor when considering the formation of artifacts during the concentration of organic pollutants from ambient air (13, 20, 21). For example, when high concentration of diimethylamine occur in ambient air, the possibility of artifact formation during sampling, with a cartridge sorbent such as Tenax GC, via a reaction between NO, (NO NOz) and dimethylamine is highly diminished since NO, does not accumulate (20). Of particular importance is the very low breakthrough volume for water on Tenax GC; water accumulating on the substrate may otherwise provide a medium for reactions such as hydrolysis of reactive species and/op formation of nitrous acid (20, 21). In view of the low retention volume of Tenax for highly volatile organics, the use of backup sorbent for Tenax GC was considered. The principal difficulty encountered with a backup sorbent for Tenax GC in the field has been the trapping of excessive quantities of water. Four requirements were deemed necessary for a material to be used as a backup sorbent: (a) the material must have a higher affinity than Tenax GC for the polar organic vapors, (b) even though it may have a greater affinity for water, water must have a finite elution volume a t ambient temperature, i.e., it must not be so strongly retained by the sorbent that the adsorption properties for other compounds are altered, (c) the sorbent material must allow the recovery of vapors by thermal desorption without producing decomposition products from the trapped constituents, and (d) during the thermal desorption cycle, the sorbent itself must not be decomposed with the formation of volatile background components or be altered such that its performance characteristics are also changed. Experiments indicated that it was feasible to desorb vinyl chloride from SKC Carbon and transfer it to Tenax cartridges for further analysis. We then investigated the breakthrough
+
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ANALYTICAL CHEMISTRY, VOL. 54, NO. 4, APRIL 1982
Table 111. Breakthrough Volumes for Several Atmospheric Pollutantsa (Liters)
chemical class acids alcohols aldehydes amines
aromatics esters ethers halogenated ethers halogenated hydrocarbon
compound n-butyric acid methanol 1-propanol acetaldehyde benzaldehyde dimethy lamine isobutylamine pyridine aniline benzene toluene ethylbenzene ethyl acetate methyl acrylate methyl methacrylate diethyl ether propylene oxide 2-chloroethyl ethyl ether bis(chloromethy1) ether methyl chloride methyl bromide vinyl chloride vinyl bromide methylene chloride chloroform carbon tetrachloride 1,2-dichloroethane 1,1,1-trichloroethane tetrachloroethylene trichloroethylene 1-chloro-2-methylpropene 3-chloro-2-methylpropene 1,2-dichloropropane l13-dichloropropane epichlorohydron (l-chloro-2,3-epoxypropane) epibromoh ydrin
bp, "C 162 64.7 97.4 20 179 7.4 69 115 184 80.1 110.6 136.2 77
breakthrough volumes at 50°F 70°F 90 OF (10 "C) (21.1 "C) (32.2 "C)
42 34 53 23 361 90 26 29 2 29 348 200
290 0.8 14 2 3507 4 34 189 3793 54 245 693 72 75 3 18 15 7 241 456 5 2 1.2 4 7 24 21 31 15 196 50 16 17 115 184 104
136 0.4 7 0.9 1622 2 16 95 1766 27 122 334 32 34 137 8 4 124 209 3 1 0.8 2 4 13 13
134-136
678
338
168
142-145 64 45 75 84 132 181 173 179 149 131 155 68.7 98.4
1130 19 21 47 146 899 1531 2393 2792 507 348 2144 32 143
6 56 12 12 27 77 47 3 867 1291 2520 294 188 1079 17 75
329 7 6 15 40 249 494 697 330 171 101 542 9 39
0 0
0 0 12 2 04 1330 25 2075 10 168 17 714 1153
0 0
80 100 34.6 35 108
-24 3.5 13 16 41 61 77 83 75 121 87 68 72 95 121 116
615 1
27 3 7586 9 71 378 8128 108 494 1393 162 164 736 29 13 468 995 8 3 2 8 11
18
9 106 28 9 10 58 97 54
est detection limit ngh3
4.1 1.0 2000 500 800 250 700 200 32 66 2.5 10.0
62 62
PPt
0.97 1.1 1000
135 333 57 2 00 4 20 8.1 12.4 0.3 1.9 21.5 21.5
9.6
2.5
0.30
0.0
(l-bromo-2,3-epoxypropnne)
hydrocarbons inorganic ketones nitrosamines nitrogenous hydrocarbons oxygenated hydrocarbons
trimethylene chlorobromide 3-chloro-1-butene allyl chloride 4-chloro-1-butene 1-chloro-2-butene chlorobenzene o-dichlorobenzene in-dichlorobenzene benzyl chloride bromoform ethylene dibromide bromobenzene n-hexane n-heptane nitric oxide nitrogen dioxide acetone N-nitrosodimethylamine N-nitrosod iethylam ine nitromethane aniline acrolein glycidaldehyde propylene oxide butadiene diepoxide cyclohexene oxide
56 151 177 101 184 53 34 132
25 38 5 25 29 5 3864 19
3 64 35 1426 2339
6 148 7 00 14 1114 6 77 5 358 570
83 83 38 13 2.1 1.0 0.7
28.8 28.8 13.2 4.5 0.47 0.06 0.01
0.34
0.03
0.10
0.02
5.0 3.0 8.0
3.0 100 59 60 20 10
1.6 0.7 2.4 0.7 56.5 19.5 25.5 6.7 2.5
ANALYTICAL CHEMISTRY, VOL. 54, NO. 4, APRIL 1982
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Table I11 (Continued)
breakthrough volumes at chemical class
compound
sulfur compounds a
bp, "C 194 183 202 57 20 8 86
styrene oxide phenol acetophenone 0-propiolactone diethyl sulfate ethyl methane sulfate
50°F (10 "C) 5370 2071 3191 721 40 5093
70°F (21.1 ?C) 2870 1072 1778 366 21 2564
90 OF (32.2 "C) 1531 554 991 186 11 1384
est detection limit ng/m3 2
PPt 0.41
2 3 50 5.0
0.41 1.2
Breakthrough volumes are based on 7.96 mL of Tenax GC. --
.___
Table 1V. Estimation of Breakthrough Volumes for Vinyl Chloride, Vinyl Bromide, Methyl Chloride, and Methyl Bromide on SKC Charcoal (104)n brleakthrough volume, L/g -~~ vinyl vinyl methyl vinyl chloride bromide chloride bromide
Table V. Performance of Coaxial and Transaxial Nickel Capillary Traps on Inlet-Manifold System
~
temp, "C 10 15.5 21.1 26.7 32.2 37.8 a
104 81
63 49 38 30
388 306 24 1 190 150
118
14.3 11.1 8.7 7.5 5.6 4.4
98 75 57 43 32 25
A 1.5 cm i.d. x 4.0 cm bed of charcoal weighed 2.52 g.
_ _ _ _ _ _ l l _ l -
volumes for vinyl chlorilde, vinyl bromide, methyl chloride, and methyl bromide on this SKC Carbon. For vinyl chloride the breakthrough volume increased from 0.9 L/g for Tenax to 105 L/g of SKC Carbon (Table IV, 10 O C ) . Similar results were observed from vinyl bromide, whereby the breakthrough volume on Tenax GC increased from 3.6 L/g to 388 L/g of SKC Carbon (Table IV, LO "C). On the basis of these results for breakthrough volumes for compounds on Tenax GC and SKC Carbon, it was concluded that the SKC carbon could serve in this limited capacity as a backup to Tenax GC where required (10). Inlet Manifold. Cryiofocusing Efficiency. Experiments were conducted to ascerlain the trap lengths and configurations which efficiently trap the organic vapors desorbed from Tenax GC cartridges. The percent trapping efficiency for capillary traps of 1m and 0.5 m lengths was 100% when the transaxial trap was 50% submerged into liquid nitrogen (Table V). In contrast, the percent trapping efficiency varied considerably for the coaxial trap which had been 100% submerged in liquid nitrogen i l m length), the lowest efficiency being that observed for n-hexane (811%). For a coaxial trap length of 0.5 m, n-hexane vapor was only trapped to an extent of 75%. Nonpolar compounds exhibited the lowest trapping efficiency while polar compounds or relatively nonvolatile substances exhibited the highest trapping efficiency (13, 22). One of the problems encountered in the use of a capillary trap with an internal diameter of 0.508 mm was icing and plugging in the trap during the introduction of vapors from a sampling cartridge containing a relatively high amount of water vapor (a result of sampling in areas with high humidity). This problem increased when the transaxial trap was 50% submerged in liquid nitrogen. In separate experiments, the use of a larger diameter capillary (1.016 mm) was examined. The trapping efficienciemi were repeated by using lengths of 0.25,0.5, and 0.75 m with an internal diameter of 1.016 mm. The trapping efficiency foJrthe transaxial remained unchanged when purge rates of 10 or 30 mL/min were used. High humidity sampling was conducted (go%, 90 O F ) and thermal desorption analysis was conducted utilizing these traps.
capillary trap dimensions 0.625 0.d. x 0.020 i.d. x 1m b
0.625 0.d. x 0.020 i.d. X 0.5 m b
0.625 0.d. x 0.020 i.d. x 0.25 m b
0.625 0.d. x 0.020 i.d. X 0.5 m c
test compd acetone n-hexane benzene n-heptane toluene chlorobenzene acetone n-hexane benzene n-heptane toluene chlorobenzene acetone n-hexane benzene n-heptane toluene chlorobenzene acetone n-hexane benzene n-heptane toluene chlorobenzene
% trapping efficiencya transcoaxial axial trap trap
90 81 86 84 95 100 89 75 84 85 95 100 84 72 81 80 93 100
100 100 100 100 100 100 100 100 100 100 100 100 97 89 95 96 99 100 97 87 90 98 99 100
a Inlet-manifold conditions were as follows: thermal desorption chamber, 265 "C; He purge rate, 30 mL/min. Coaxial and transaxial traps were completely and 50% submerged, respectively, in liquid N,. Transaxial traps were completely submerged in liquid N,.
Obstruction of gas flow or complete plugging was not observed in these cases. However, it was found that a minimum trap length of 0.5 m was still necessary in order to quantitatively recover all the vapors desorbed from the Tanax GC using thermal desorption periods of up to 15 min. The use of 0.5 m X 1.016 mm i.d. capillary traps with 100 m (0.42 mm i.d.) glass SCOT or 60 M fused silica (0.32 mm i.d.) capillaries coated with SE-30 indicated that no reduction in theoretical plates occurred when the larger inside diameter trap was employed (13, 22). Trap Inertness. A second study was conducted in order to determine whether any decomposition and/or elimination reactions might occur during desorption of organics into the Ni capillary trap or during the heating and injection step onto a gas chromatographic column. To test this possibility, we selected seveal compounds which were particularly prone to elimination reactions (dehydration or dehydrohalogenation) forming the corresponding olefin. The compounds tert-butyl alcohol, %bromopentane, and cyclohexyl iodide were used for this evaluation. These compounds were introduced into the
816
ANALYTICAL CHEMISTRY, V6L. 54, NO. 4, APRIL 1982
-_. Table VI. Sampling Accuracy and Precision for Common Pollutants Using Tenax GC Sampling Cartridgesa chemical
front
chloroform carbon tetrachloride benzene toluene chlorobenzene bromobenzene
93 i 77 c 95 f 93 f 86 f 80 t
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I _ . _ -
expt no. 1 expt no. 2 _ . I _ back front back
2 (2)b 13 (17) 3 (3) 2 (2) l(1) 6 (7)
7 f 3 (42) 23 +I 10 (43) 5 i 4 (80) 7 f 2 (28) 14 j. l(7) 20 t 9 (45)
7 i: 4 ( 4 1 ) 18 i t(6) 2-+O ( 0 ) 6 c 2 (33) 15 i 15 (100) 25 i 3 (12)
98 c 3 (3) 92t l ( 1 ) 98 t 0 (0) 94-+2 ( 2 ) 83 c 17 (20) 75 f 2 (3)
a Air sampling of off-gases from municipal treatment was conducted; air was with 14C-radiolabeledpollutant and the radioactivity recovery from front and back tandem pair of cartridges was determined. Percent accuracy t standard deviation (C.V.) for triplicate analysis. _._-____
-
_ _ _ I
-
-_lll_l__ll_
- ~ _ _ _ _ -
Table VII. Estimated Levels of Vapor-Phase Halogenated Hydrocarbons in Ambient Air in Bound Brook, NJ (9/19-20/78)" cornp ound 1,l-dichloroethane chloroform 1,2-dichloroethane l,l,l-trichloroethane carbon tetrachloride trichloroethylene tetrachloroethylene chlorobenzene m -dichlorobenzene o-dichlorobenzene
L1
L2
L5
L4
L8
L6
N D ~
ND
ND
TC
ND
ND
5.1 ?. 0.56 0.61 i 0.10 6.4 i 0.51 2.3 i 0.37 7.5 i 0.63 10.3 t 1.1 2,32t 0.29 0.80 t 0.14 0,66 f 0.09
3.7 f 0.47 0.58 t 0.06 5.8 i 0.05 1.78 f 0 3.1 t 0.55 5.1 c 0.63 0.75 i 0.06 0.66 c 0.05 0.39 f 0.03
2.3 0.35 t 0 4.8 f 0.44 1.3 -t 0 3.9 t 0.57 8.4 2.1 t 0.54 0.82 ?- 0 0.89 t 0.04
3.7 ?I 0.67 0.45 i 0.03 8.6 t 0.29 2.3 c 0.15 6.1 t 0.63 7.4 i 0.80 0.16 t 0.06 0.33 i 0.01 0.10 t 0.01
3.6 0.58 f 0.03 8.6 + 0.03 2.3 i 0.67 3.9 c 0.15 8.1 ?: 0.59 0.37 f 0.09 0.61 ?: 0.02 0.14 i: 0
6.2 i 0.28 0.32 c 0.09 2.5 + 0.73 1.0 t 0.26 1.7 c 0.20 1.3 f 0.17 0,26e 0.10 0.15 t 0.02 0.09 t 0.02
Mean of triplicate determinations with i standard deviation, expressed in pg/m 3 , Sampling volume was approximately 30 L. L1,L2,etc, are locations of sampling in Bound Brook. N D = not detected. T = trace. 1___11----
-
~
capillary trap via the thermal desorption chamber and cryogenically trapped into the trap followed by heating the trap and injecting the vapor onto the chromatographic column. The corresponding olefin (which might be formed by dehydration or by dehydrahalogenation during the cooling and beating cycle of the capillary trap) was monitored on the capillary column. No dehydration or dehydrohalogenation was obLerved as evidenced by the loss of parent compound or the appearance of the corresponding olefii (22). In another experiment, decoinposition of bis(chloromethy1) ether (BCME) was studied. BCME was introduced into the capillary trap followed by water since it was known by hydrolyze (23). No hydrolysis was evident (22,23). Overall Limits o f Detection. The overall limits of detection attainable are shown in Table 111and are dependent to a large degree on the collection efficiency of a particular compound. Generally, the sorbent Tenax GC is not regarded to be an adequate material for the collection of highly volatile substances with m y degree of reliability or sensitivity. The low molecular amines (dimethylamine) and alcohols (methanol) also have low breakthrough volumes. Accuracy and Precision. Sampling accuracy and precision is generally f30%, however both are dependent to some extent on the chemical and physical nature of the compounds. Table VI evidences the above findings, in which samples were spiked with 14C-radio-labeledcompounds and recoveries determined. The field sampling and analysis precision of this method have been determined to range from f10 to f40% relative standard deviation for different substances when replicate field sampling cartridges were examined (Table VU). The inherent analytical errors are a function of several. factors: (a) the ability to accurately determine the breakthrough volume for each of the identified organic compounds, (b) the accurate measurement of the ambient air volume sampled, (c) the percent recovery of the organic from the sampling cartridge after a period of storage, (d) the reproducibility of thermal desorption for a compound from the cartridge and its introduction into the analytical system, (e) the accuracy of de-
-
-
termining the relative molar response ratios between the identified substance and the external standard used for calibrating the analytical system, (f) the reproducibility of transmitting the sample through the high-resolution gas chromatographic column, and (g) the day-to-day reliability of the MS/COMP system. This research program on the development of an analytical technique for measuring hazardous ambient atmosphere vapors has attempted t~ furnish a comprehensive and systematic approach to this problem. It has attempted to develop and evaluate the sampling device, field collection methodology, and the entire procedure of sample analysis of hazardous vapors in the atmosphere. Until this research program was initiated, the ability to collect samples from the atmosphere and analyze a wide variety of chemical classes which contained hazardous organic compounds did not exist. For this reason, research programs to determine and evaluate the health impact of hazardous compounds in the environment have been limited in scope. Comprehensive studies on the levels of hazardous agents in all media in addition to air and the correlation of this exposure to body burden and health effeckq in man could also not be performed. Thus, a well-defined health-effects study, which requires this type of data to establish whether and associational relationship exists, has in the past suffered from the lack of adequate methods.
ACKNOWLEDGMENT The authors express appreciation to A. Ellison, B. Dimitriades, and E. Sawicki for their adroit and keen suggestions and criticisms throughout the course of the research program.
LITERATURE CITED Matz. J. Z.Gesamte Hyg. Ihre Grenzgeb. 1972, 18, 903-8. Norpoth, K.; Manegold, G.; Brucker, R.; Arnann, H. P. Zentralbl. Baktefld. Hyg. 1072, 156(8),341-352. Jones, P. W. "Analysls of Nonpartlculate Organic Compounds In Arnbient Atmospheres"; 67th Alr Pollution Control Association, Annual Meetlng, Mtg.; Denver, CO, June 1972: No. 74-265. Dunham, C. L., Ed. "Blologlcal Effects of Atmospheric Poiiutants-Partlculate Polycylic Organic Matter"; National Academy of Science: Washington, DC, 1972; pp 248-251. Van Duuren, B. L. J . Natl. Cancer Inst. (U.S.) 1072, 48, 1431-1439.
Anal. Chem. 1982, 5 4 , 817-820
(6) Van Duuren, B. L. J. Nsfl. Cancer Insf. (US.)1972, 48, 1539-1540. (7) Van Duuren, B. L. Inf. J. Envlron. Anal. Chern. 1972, 7 , 233-241. (8) Van Duuren, B. L. “Interaction of Some Mutagens and Carcinogenic Agents with Nucleic Aclids”; Proceedings of the International Symposium; Publisher: Location, 1988; p 149. (9) Pellizzarl, E. D. ”Development of Analytical Techniques for Measuring Ambient Atmospheric Carclnogenic Vapors”; EPA-600/2-75-076 U.S. Environmental Protection Agency; Nov 1975. ( I O ) Peiiizzari, E. D. “Analysis of Organic Air Pollutants by Gas Chromatography and Mass Spectrciscopy”; EPA-600/2-77-100; US. Envlronmental Protection Agency: June 1977. (11) Pellizzari, E. D.; Bunch, J.; Carpenter, B.; Sawlcki, E. Environ. Scl. Technol. 1975, 9 , 556. (12) Peliizzari, E. D.; Carpenter, B.; Bunch, J.; Sawicki E. Environ. Sci. Technol. 1975, 9 , 552. (13) Pelllzzari, E. D. “The measurement of Carcinogenic Vapors In Ambient Atmospheres”; EPA-600/7-77-055; US. Environmental Protection Agency; June 1977. (14) ”Eight peak Index of Mass Spectra”; Mass Spectrometry Data Centre; AWRE, Aldermaston: Reading, RF74FR, UK, 1970 I (Tables 1 and 2), I1 (Table 3). (15) Stenhagen, E., Ed “Registry of Mass Spectra Data”; Wiiey: New York, 1974: Vol. 4. (16) Smith, D. J.; Pelllzzari, E. D.; Bursey, J. T. “Quantltatlon of Volatile
(17) (18) (19) (20) (21) (22) (23)
817
Organics from Environmental Matrices Using Relative Molar Response Factors”, ASMS: St. Louis, MO, May 1978. Pelllzzarl, E. D. “Development of Method for Carcinogenic Vapor Analysis In Ambient Atmospheres”; EPA-650/2-74-121; U.S. Envlronmental Protection Agency; July 1974. Pelllzzari, E. D.; Bunch, J. E.; Bursey, J. T.; Berkley, R. E.; Sawlcki, E,.; Krost. K. And. Left. 1978, 9 , 579. Daniels, F.; Aiberty, R. A. “Physical Chemistry”; Wliey: New York, 1972; pp 607-611. Pelllzzari, E. D.; Bunch, J. E.; Berkiey, R. E.: McRae, J. Anal. Lett. 1976. - - - - ,9 . 45. -Bunch, J. E.; Castllio, N. P.; Smith, D.; Bursey, J, T.; Pellizzarl, E. D. “Evaluation of the Basic GC/MS Computer Analysis Technque for Pollutant Analysis”; EPA Contract No. 88-02-2998; 1980. Pelllzzari, E. D.; Bunch, J. E. “Ambient Air Carcinogenic Vapors: Irnproved Sampling and Analyticai Techniques and Field Studies”; EPA60012-79-081; U.S. Environmental Protection Agency; May 1979. Tore, J. C.; Kalins, G. J. Anal. Chem. 1974, 46, 1866.
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RECEIVED for review March 19,1981. Accepted Janauary 13, 1982. This work was supported by EPA Contract No. 6802-2262, 68-02-2998, and 68-02-1228.
Organic Anailysis with a Combined Capillary Gas Chromatograph/Mass Spectrometer/Fourier Transform Infrared Spectrometer Rlchard W. Crawford,” Tomas Hlrschfeld, Russell H. Sanborn, and Carla M. Wong Lawrence Livermore National Laboratory, Livermore, California 94550
We have demonstrated, for the first tlme, a linked capillary gas chromatograph/mass spectrometer/Fourier transform infrared spectrometer (GC/MS/FT-IR). Although the ilnklng of a packed column GC/MS/FT-IR has been reported, we feel the use of a high-resolution column (SCOT) significantly Increases the analytical usefulness of this technlque. The linking of the three provldes complementary information and eliminates the possiblllty of comparing spectra from different components due to shifts In retention time. Examples are glven by uslng a known mlx of alkyl benzenes and a completely unknown siloxane.
Advances in instrumentation and the incorporation of powerful computers have created some remarkable analytical tools. One of the most powerful and popular instruments in the realm of organic qualitative and quantitative analysis is the computerized gas chromatograph/mass spectrometer (GC/MS). This instrument combines the separatory properties of the chromatographic column with the fast fingerprinting capability of the mass spectrometer. The advent of the fast scanning Fourier transform infrared spectrometer coupled with light pipes and cryogenic detectors made possible the analogous technique of GCIFT-IR, offering some of the same advantages. Hirschfeld (1)has discussed the field of “hyphenated” instruments, that is, linking multiple instruments to give complementary data about the same sample. The linking of a GC/MS to a GC/FT-IR is a natural choice as they work with the sample in the gas phalse and have similar sensitivities and speeds and the information they provide is complementary. The development of tlhis instrumentation syst,em has depended upon technological advances in the field of high-
resolution gas chromatography and interferometric infrared spectrometry (FT-IR). Mass spectrometry has had, for many years, the speed and sensitivity needed to match these other components. Erickson (2)in his excellent review of GC/FT-IR shows an almost linear plot of sensitivity vs. year, starting with the work of Low (3) in 1968 who achieved a 10 pg sensitivity and ending in 1977 with 10 ng sensitivity reported by Wall and Mantz ( 4 ) , using packed columns. Wilkins has built on this technology (5-7) for his GC/MS/FT-IR using a packed column. Golay (8) introduced the capillary or wall-coated open tubular (WCOT) column in 1957. Halasz et al. (9) developed the support-coated open tubular (SCOT) column in 1961. Scientists were excited over the vastly superior resolution of these columns. In addition, a single column type was found to be applicable to a wide variety of sample types. Unfortunately, technical and patent problems limited their use until recent years. The first use of GC/FT-IR using a SCOT column was by Azarraga et al. (10)in 1974. This is considerably more difficult than packed column work as noted by Griffiths (11) due to the low flow rates and narrow peak widths. We have designed our instrument system (12-15) to successfully overcome these problems and make use of this technology. EXPERIMENTAL SECTION Instrumentation. Initial development work on the GC/ MS/FT-IR used a packed column and simple test mixes. We found the quality of separation to be so poor that it did not justify tying together two such expensive instruments. Therefore, we decided to try a capillary column for impraving the resolution. In switching then to a SCOT column, we found serious problems not encountered in the packed column GC/MS/FT-IR linkup. These major problems were (1) splitting effluent reliably, (2) eliminating cold spots in all lines carrying sample, and (3) es-
0003-2700/82/0354-0817$01.25/00 1982 American Chemical Society
