Anal. Chem.
1982,5 4 , 1137-1 I41
helped with radioactive animal studies. Thanks are also due to Vicki Bunnelle and Gary W. Kirsch for excellent technical help.
LITERATURE CITED (1) Taws, D. R. Nature (London) 1968, 217, 1050-1051. (2) . . Venkateswarlu. P.: Slnaer. L.: Armstrona, - W. D. Anal. Biochem. 1971, 42,350-359. (3) Venkateswarlu, P. "Methods of Biochernlcal Analysls"; Gllck, D., Ed.; Wlley/Intersclence: New York, 1977;Vol. 24, pp 93-201. (4) Venkateswarlu, P. Biochern. Med. 1975, 1 4 , 368-377. (5) Venkateswarlu, P. Anta/. Blochem. 1975, 68,512-521. (6) Belisle, J.; Hagen, D. F. Anal. Biochem. 1978, 87,545-555. (7) Grlfflth, F. D.; Long, J. E. Am. Ind. Hyg. Assoc. J . 1980, 4 1 , 576-583. (8) Ubel, F. A,; borenson, S . D.; Roach, D. E. Am. Ind. Hyg. Assoc>.J . 1980, 4 1 , 5814-589. (9) Benton, F. L.; Hamill, W. H. Anal. Chem. 1948, 20,269-270.
-
1137
(10) Pecherer, B.; Gambrili, C. M.; Wilcox, G. W. Anal. Chem. 1950, 22, 3 1 1-3 15. (11) Liggett, L. M. Anal. Chem. 1954, 26, 748-750. (12) Wheeler, P. P.; Fauth, M. I . Anal. Chem. 1986, 38, 1970. (13) Jones, 8. C.; Heveran, J. E.; Senkowski, B. 2. J . Pharm. Sci. 1971, 60,1036-1039. (14) Wilson, J. N.; Marczewski, C. 2 . Anal. Chem. 1973, 45, 2409-2412. (15) Clark, L. C.; Wessler, E. P.; Miller, M. L.; Kaplan, S . Mlcrovasc. Res. 1974, 6,320-340. (16) Stein, T. P.; Robbins, W. K.; Brooks, H. B.; Wallace, H. W. J . Biorned. Mater. Res. 1975, 9 , 479-485. (17) Venkateswarlu, P. Anal. Chem. 1974, 4 6 , 878-882. (18) Venkateswarlu, P.; Sita, P. Anal. Chem. 1971, 4 3 , 758-760. (19) Orion Research "Instruction Manual: Fluoride Electrodes"; 1977. (20) Strahm, R. D. Anal. Chem. 1959, 3 1 , 615-616. (21) Venkateswarlu, P. Clln. Chlm. Acta 1975, 5 9 , 277-282.
RECEIVED for review November 25, 1981. Accepted March 1, 1982.
Sampling arid Determination of 2,4-Bis(carbonylamino)toluene and 4,4'-Bis(carbonylamino)diphenylmethane in Air Samuel P. Tucker" and James E. Arnold Natlonal Instltute for Occupational Safety and Health, Clncinnati, Ohio 45226
Separate sampllng and analytical methods for 2,4-bls(carbonylam1no)toluene (2,4-TDI) and 4,4'-bls(carbonylamino)diphenylmethane (MDI) In air were developed. The sampler for 2,4-TDI conslsts of a glass tube Containing two sectlons of glass wool coated wlth the reagent N-[(rl-nltrophenyl)methyl]propanamlne. The sampler for MDI contains a glass fiber fllter Impregnated wlth the same reagent. The dllsocyanates react wlth the reagent to form urea derlvatives whlch are analyzed by hlgh-pressure llquld chromatography. 2,4-TDI vapor at concentrations ranglng from 100 to 3500 pg/m3 can be determined for 10-L air samples. MDI can exlst In both vapor and aerosol forms and can be determined at concentrations ranglng from 80 to 1000 pg/m3 for 10-L air samples.
Exposure to 2,4-bis(carbonylamino)toluene (known as toluene 2,4-diisocyanate and 2,4-TDI) and 4,4'-bis(carbony1amino)diphenylmethane [known as 4,4'-methylenebis(pheny1 isocyanate) and MDI] in air can cause eye, nose, and throat irritation. Some people may become sensitized to TDI and MDI and develop asthmatic reactions. MDI or partly polymerized MDI can cause contact eczema ( I ) . It has been estimated that approximately 1.5 million metric tons of TDI, MDI, and polymers of MDI will be produced in the world in 1982 (2). The present OSHA standards for 2,4-TDI and MDI are 140 and 200 pg/m3, respectively, as ceiling concentrations ( 3 ) . However, NIOSH has recommended standards for TDI and MDI which may permit better worker protection. The recommendations for TDI and MDI, respectively, are 35 and 50 pg/m3 as time weighted averages for up to a 10-h shift of a 40-h workweek and 140 and 200 pg/m3 as ceiling concentrations for any 10-min period of sampling (1). A few well-known methods for determining 2,4-TDI and MDI in air involve sampling with impingers and analysis by
either colorimetry or high-pressure liquid chromatography (4-6). Impingers are cumbersome for workers to wear, and spillage can occur from many impingers. Toluene for use as a solvent for the reagent N - [(4-nitropheny1)methyllpropanamine in impingers is toxic and flammable. Also, there have been restrictions applicable to sending toluene by the U.S. Postal Service (7). A method for isocyanates in air reported by Keller and Sandridge employs a sampling tube containing a solution of N-[(4-nitrophenyl)methyl]propanamineon glass powder and thin-layer chromatography (8). Two different types of samplers have been developed which can collect TDI and MDI in air. The sampling tube for TDI vapor contains two sections of glass wool coated with the reagent N-[(4-nitrophenyl)methyl]propanamine. MDI, which can exist in both vapor and aerosol forms, may be collected inefficiently by the sampling tube. The sampler for MDI contains ti glass fiber fiter impregnated with the same reagent. 2,4-TDI and MDI react with the reagent to form urea derivatives, 2,4-TDlU and MDIU, which are analyzed by highpressure liquid chromatography (HPLC). Although N - [ (4nitrophenyl)methyl]propanamine is somewhat unstable, it reacts with 2,4-'I'DI and MDI rapidly to form urea derivatives in high yield (9).
EXPERIMENTAL SECTION Reagents. N-[(4-Nitrophenyl)methyl]propanaminehydrochloride and the urea derivatives 2,4-TDIU and MDIU were synthesized (9). Two crops of 2,4-TDIU were used; mp 137-142 and 127-130 O C . MDIU was recrystallized from benzene and dried in vacuo; mp 161-162 O C . Reagent-Coated Glass Wool. A 1 N sodium hydroxide solution (15 mL) was added to a solution prepared from 300 mg (0.0013 mol) of N - [(4-nitrophenyl)methyl]propanaminehydrochloride and 25 mL of water. The mixture was shaken. N - [ ( 4 Nitrophenyl)methyl]propanaminewas extracted with 50 mL of hexane. Then 40 mL of the hexane solution was transferred to a 50-mL beaker wrapped with aluminum foil and containing 1.8 g of silanized glass wool (Alltech Associates, Arlington Heights,
Thls artlcle not subject to US. Copyrlyiit. Publlshed 1982 by the American Chemlcal Soclety
1138
ANALYTICAL CHEMISTRY, VOL. 54, NO. 7, JUNE 1982 2 4 / 4 0 STD TAPERED JOINT
t A
IOoo5 i
9.7-LITER CHAMBER
c--J Figure 1. Generation system for MDI.
IL, or Supelco, Inc., Bellefonte, PA). Under dim light, hexane was allowed to evaporate from the beaker with the aid of a stream of nitrogen. The glass wool was kneaded with a glass tube to produce a uniform coating. Evaporation was allowed to continue until the coated glass wool appeared dry. The quantity of coated glass wool was sufficient for the preparation of front and back sections for 20 sampling tubes. After the coating of 638 mg of glass wool with a proportional quantity of N - [(4-nitropheny1)methyllpropanamine, 65 mg of the reagent was found on the glass wool by titration with HC1. Sampling Tubes. Each sampling tube consisted of a glass tube approximately 4 cm long with outside and inside diameters of 8 and 6 mm, respectively, containing two sections of glass wool coated with N-[(4-nitrophenyl)methyl]propanamine.The front section of coated glass wool was 7 mm long and was located near one end (the inlet) of the tube. The back section was 5 mm long and was in contact with the front section. Portions of coated glass wool were inserted into the tubes and compressed tightly with two pairs of tweezers. The ends of the tubes were sealed with plastic caps, Impregnated Filters. A solution of N - [(4-nitropheny1)methyllpropanamine in hexane was prepared according to the procedure for reagent-coated glass wool. Six milliliters of the solution was placed into a beaker containing six glass fiber filters which were 13 mm in diameter and free of binders. The filters were obtained from Millipore Corp., Bedford, MA. Under dim light, hexane was allowed to evaporate with the aid of a stream of nitrogen. The filters were sufficientlydry when they no longer clung to the beaker. Each filter was placed into a 13-mm filter holder (Swinnex, 13 mm, Catalogue No. SXOO 013 00, Millipore Corp.). Recovery Studies. A glass U-tube, 27 cm X 15 mm internal diameter and equipped with stopcocks, was connected to a sampling tube which was connected to a pump. 2,4-TDI in ca. 5 pL of dichloromethane solution was added to the U-tube. Air (15 or 20 L) was drawn through the system at a rate of 1 L/min to carry 2,4-TDI vapor to the sampling tube. MDI in ca. 10 pL of dichloromethane solution was added to impregnated filters. The impregnated filters were stored in sealed vials at room temperature in the dark for at least 4 h. The samples were analyzed with external standards by HPLC. Quantities of 2,4-TDI and MDI used for recovery work were determined by HPLC analysis of standard solutions of ureas prepared from 2,4-TDI and MDI solutions and solutions of N- [ (4-nitropheny1)methyllpropanamine. Generation of Controlled Atmospheres. A diagram of the generation system for MDI is shown in Figure 1. MDI (5 g) was placed into a flask which subsequently was in contact with a temperature bath maintained at ca. 135 "C. A pump forced laboratory air which was neither cleaned nor dried into the system at ca. 25 L/min. Air carried MDI to a junction with the bypass where the atmosphere could be diluted with air from the bypass. Atmospheres passed through a 9.7-L glass chamber and entered a sampling manifold. The concentration of MDI in the manifold could be regulated by adjusting the air valve for the bypass.
0
2
4
6
TIME (mm)
Figure 2. Chromatogram of 0.29 pg of 2,4-TDIU in a 50-pL aliquot of solution: column, 25 cm X 4.6 mm, packed with Partisil 10, at room temperature: mobile phase, 2:98 2-propanol-dichloromethane (v/v); flow rate, 2 mL/min; detector, UV (254 nm).
Generation systems for 2,4-TDI and MDI were similar. The generation system for 2,4-TDI was equipped with a diffusion cell (IO). A flask containing 2,4-TDI was maintained in a constant temperature bath at 17-51 "C. Air Sampling. Sampling tubes and holders for impregnated filters were connected to sampling ports of the manifold with short pieces of Tygon tubing. Air was drawn through the sampling tubes and impregnated filters at 1 L/min with one or two pumps connected to calibrated, critical orifices. Air samples containing 2,4-TDI were collected simultaneously by the sampling tube method and a reference method which was basically a method of Meddle and Wood (11). The reference method involved larger volumes of sampling media, a decrease in sampling rate to 0.5 L/min, and an increase in sampling time to 1 h. HPLC Analysis. Each section of coated glass wool and each impregnated filter were placed into a separate glass vial. Dichloromethane (1 mL) was added. Each vial was sealed and shaken for ca. 1min. Fifty-microliteraliquots were analyzed with a Perkin-Elmer Model 601 liquid chromatograph equipped with a Perkin-Elmer Model LC-55 spectrophotometer set at 254 nm. The HPLC analyticalcolumn, 25 cm X 4.6 mm internal diameter, was packed with Partisil 10 (Whatman, Inc., Clifton, NJ). The mobile phases for isocratic analyses consisted of 2-propanol and dichloromethane in the following ratios (v/v): 1.4:98.6 for MDIU and 2:98 for 2,4-TDIU. The flow rate in each case was 2 mL/min. Samples were analyzed with external standards. The analytical column was washed at intervals to remove excess N-[(4-nitropheny1)methyllpropanamine by pumping either 2-propanol or 5050 2-propanol-dichloromethane (v/v) through the column for 1 min. The maximum possible intervals between required washings ranged from ca. 20 min to ca. 70 min and seemed to depend on how much the column had been used. Particle Sizing. An electrical aerosol size analyzer, Model 3030, from Thermo-Systems, Inc., St. Paul, MN, was used to size particles from the generation system for MDI.
RESULTS AND DISCUSSION 2,4-TDIU, the urea derivative of 2,4-TDI, could be measured in a range equivalent to 1-250 pg of 2,4-TDI/mL of sample solution when 50-pL aliquots were injected into the liquid chromatograph. MDIU, the urea derivative of MDI, could be measured in a range equivalent to 0.8-150 pg of MDI/mL of sample solution when 50-pL aliquots were injected. The lower quantitation limits were the lowest levels a t which measurements could be made with a relative standard deviation of 10% or less, The detection limits (the levels at which the signal to noise ratios were 3 to 1)of 2,4-TDIU and MDIU corresponded to approximately 0.2 pg of 2,4-TDI and 0.1 pg of MDI/mL of sample solution. Typical chromatograms of 2,4-TDIU and MDIU are shown in Figures 2 and 3. MDI in air would cause little or no interference with the analysis of 2,4-TDI when the mobile phase is 2:98 2-propanol-dichloromethane(v/v). 2,4-TDI in
ANALYTICAL CHEMISTRY, VOL. 54, NO. 7, JUNE 1982
1139
Table I. Some Results of Air Sampling and Analysis for 2,4-TDI by the Sampling Tube Method and a Reference Methoda
I 0,025
A.U
expt no. 1 1
2 2 3 3 0
2
4
6
TIME ( m i n )
Flgure 3. Chromatogram of 1.4 pg of MDIU in a 50-pL aliquot of solution: column, 25 cm X 4.6 mm, packed with Partisil 10, at room temperature; mobile phase, I.4:98.6 2-propanol-dichloromethane(vlv); flow rate, 2 mL/min; detector, UV (254 nm).
air would not interfere with the analysis of MDI when the mobile phase is L.4:98.6 2-propanol-dichloromethane(v/v). N - [(4-Nitrophenyl)rriethyl]propanamine when on either glass wool or glass fiber filters is unstable in the presence of light and is unstable to a smaller degree during storage in the dark a t room temperature. Exposure of sampling tubes and impregnated filters to light for an excessive period or storage of the same itenis in the dark at room temperature for an excessive period may result in potential interferences during HPLC analyses. Exposure of four sections of coated glass wool to fluorescent lighting in a fume hood for 25 h gave rise to HPLC peaks which corresponded to an average of approximately 0.7 pg of 2,4-TlDI per section of coated glass wool. Exposure of two impregnated filters inside filter holders to fluorescent lighting in a fume hood for 25 h gave rise to potential interferences which corresponded to roughly 2 pg of MDI/filter. Storage of sections of coated glass wool in the dark at room temperature for 7 days gave rise to signals which corresponded to average quantities of approximately 0.3, 0.5, and 0.5 pg of 2,4-TDI per section. Storage of three impregnated filters in the dark for 41 days (33 days a t room temperature and 8 days a t -21 "C) gave rise to potential interferences during HPLC analysis which corresponded to an average of roughly 0.4 ELg of MDI per filter. Storage of ten sections of coated glass wool at -21 "C for 28 days gave rise to no peaks which corresponded to 2,4-TDI. Storage of six impregnated filters in the dark at -21 "C for 42 days gave rise to no peaks which corresponded to MDI. Storage of the samplers at -21 "C in the dark is recommended. However, if the samplers must be stored a t room temperature, it is recommended that sampling tubes be stored at room temperature in the dark for 7 days or less and that impregnated filters be stored for no more than ca. 21 days at room temperature in the dark. The storage times pertain to periods from times of preparation of the samplers to times of analysis. Average recoveries of 2,4-TDIU from front sections of coated glass wool after applications of 1.0-, 2.1-, 9.9- and 20.0-pg quantities of 2,4-TDI vapor from a U-tube were nearly quantitative (0.97-0.99). 2,4-TDIU was not detected on any of the corresponding back sections of coated glass wool. Humidity did not appear to be a major problem for the 2,4-TDI method. In a ruggedness test, recoveries of 2,4-TDIU from coated glass wool were above 90% after applications of 2.1-pg quantities of 2,4-TDI from a U-tube which was preceded by a bubbler of water. For a storage study, 5.8-pg quantities of 2,4-TDI were collected in sampling tubes. Average recoveries of 2,4-TDIU after 1-,7-, and 14-day storage times at room temperature in
4 4 5 5
sampling devices sampling tubes bubblers sampling tubes bubblers sampling tubes bubblers sampling tubes bubblers sampling tubes bubblers
av concn of 2,4-TDI re1 std dev nb (dm3) 0.031 6 179 0.051 3 137 0.031 101 6 2 0.003 89.2 0.030 6 67.8 0.090 59.4 3 0.04 2 38.5 5 0.008 53.9 2 0.03 2 6 526 0.029 3 458
a The reference method was basically a method of In the case of the sampling Meddle and Wood ( 1 1 ). tube method, n is the number of sampling tubes on which the average concentration of 2,4-TDI is based. In the case of the reference method, n is the number of trains of fritted glass bubblers which contained N,N-dimethylformamide, hydrochloric acid, and 1,6-hexanediamine. There were two bubblers in each bubbler train.
the dark were 0.93,0.92, and 0.91, respectively. 2,4-TDIU was found to be stable on coated glass wool at room temperature in the dark for 14 days. Air samples from the generation system for 2,4-TDI were collected simultaneously during 1-h sampling periods by the sampling tube method and the reference method. The basic method of Meddle and Wood (11)was selected as a reference if necmethod to correct for 4-methyl-l,3-benzenediamine is a hydrolysis product essary. 4-Methyl-l,3-benzenediamine of 2,4-TDI. Some analytical results are presented in Table I. The front sections of coated glass wool in experiment 5 collected an average of 35.8 pg of 2,4-TDI. 2,4-TDIU in quantities equivalent to less than 1pg of 2,4-TDI was detected on three of the six back sections in experiment 5. 2,4-TDIU was not detected on any of the other back sections in experiments 1-5. Each front section of coated glass wool had a capacity of ca. 35 big of 2,4-TDI without breakthrough occurring. The pooled relative standard deviation of measurement by the sampling tube method for experiments 1-5 was 0.033. The average concentration of 2,4-TDI based on the sampling tube method was significantly different from the average concentration of 2,4-TDI based on the reference method for a = 0.05 in each experiment in Table I except experiment no. 3. Reasons for the differences in concentrations are unclear. The collection efficiencies of the bubbler trains which contained N,N-dimethylformamide, hydrochloric acid and 1,6hexanediamine for the reference method were high; more than 94% of the analyte found in each bubbler train was found in the first bubbler in each train. Concentrations of 4methyl-1,Bbenzenediamine in air were low, and concentrations of 2,4-TDI in Table I based on the reference method are uncorrected for concentrations of 4-methyl-1,3-benzenediamine. There was interest in determining whether the sampling tube method could be used to detect a decrease in concentration of 2,4-TDI vapor caused by the presence of 1,4-diazabicyclo[2.2.2]octane (triethylenediamine), which has been used as an amine catalyst in making polyurethane foam (12). An experiment was performed which involved two sampling periods of 45 min each. 1,4-Diazabicyclo[2.2.2]octanevapor a t unmeasured concentrations was introduced into the generation system during the second sampling period. The
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ANALYTICAL CHEMISTRY, VOL. 54, NO. 7, JUNE 1982
presence of 1,4-diazabicyclo[2.2.2loctane decreased the concentration of 2,4-TDI from 362 to 17 pg/m3. Breakthrough of 2,4-TDI was not detected from any front section of coated glass wool used during the second sampling period. Results in other reports based on gas chromatographic, paper tape, and Marcali methods indicated that 1,4-diazabicyclo[2.2.2]octane vapor can reduce the concentration of TDI in air (12, 13). The sampling tube method can be used to determine 2,4TDI in air a t concentrations ranging from 17 to 580 pg/m3 for 60-L samples and from 100 to 3500 pg/m3 for 10-L samples. The upper limits of the ranges are based on 35 pg of 2,4-TDI, the approximate capacity of the front section of coated glass wool before breakthrough would occur. Quantities and concentrations of MDI in this report are uncorrected for an impurity in MDIU used for external standards. The purity of the MDIU used was at least 88%. The amount of the impurity in a sample of MDIU did not become apparent until after most of the laboratory work had been performed. The melting points of the MDIU used for external standards were similar to and above the literature value of 151-153 "C (9). MDIU of high purity was isolated near the end of the laboratory work which melted at 161-162 "C. The impurity in MDIU was detected as a shoulder in a chromatogram when the mobile phase was 1.4:98.6 2propanol-dichloromethane (v/v). Better separation was accomplished when the mobile phase contained a smaller percentage of 2-propanol. The purity of MDIU with mp 161-162 "C was determined to be high by comparing the MDIU with 4,4'-methylenebis(pheny1amine) as standards in two methods for determining the concentrations of MDI in a dichloromethane solution. One method involved formation of MDIU from MDI and HPLC. The other method involved hydrolysis of MDI to 4,4'-methylenebis(phenylamine), diazotization, and colorireaction with N-l-naphthyl-l,2-ethanediamine, metric determination (5). Average concentrations of MDI based on the two methods agreed within 4%. The presence of the impurity did not affect average values of recovery of MDIU from impregnated filters (0.96-0.99), relative standard deviations of measurements for MDI, and the conclusion that the impregnated filter method is useful for determining MDI in air. Average recoveries of MDIU from impregnated filters after applications of 0.8-, 16-, and 67-pg quantities of MDI in dichloromethane solution were nearly quantitative (0.96-0.99). For a storage study, 1 2 air samples were collected with sampling tubes simultaneously from the generation system for MDI. Six samples were analyzed after 1 day of storage at room temperature in the dark, and the other six samples were analyzed after 15 days of storage at room temperature in the dark. The average concentrations of MDI (uncorrected for recovery) based on the sets of samples stored 1and 15 days were 110 and 117 pg/m3, respectively. The quantity of MDIU found on each front section of coated glass wool corresponded to ca. 7 pg of MDI. MDIU was not detected on any of the back sections of coated glass wool. MDIU was found to be stable on coated glass wool during 15 days of storage a t room temperature in the dark. It is assumed that MDIU also is stable on impregnated filters at room temperature in the dark for the same storage time. Air samples were collected from the MDI generation system during seven 3-h sampling periods at concentrations ranging from 168 to 802 pg/m3 with samplers containing impregnated filters. MDIU in quantities which corresponded to less than 0.2 pg of MDI was detected on sections of coated glass wool which followed 2 of 19 impregnated filters. MDIU was not detected on other sections of coated glass wool which followed the other 17 filters. The pooled relative standard deviation
Table 11. Capacity of Impregnated Filters no. of samperiod
12h
first 9 h first 6 h first 3 h second 3 h third 3 h fourth 3 h
av concn" of MDI, &/m3
relstd
3 3
602
0.030 0.065
2 2 2 3 3
597 61 6 536 666 513
pies
580
dev
0.008
0.024 0.029 0.064 0.101
a Average concentrations are based on quantities uncorrected for recovery.
of measurement for the concentration range was 0.060. In one experiment in which the total concentration of MDI in the sampling manifold of the MDI generation system was ca. 500 pg/m3 according to sampling tubes connected in series, the mass median diameter of MDI particles was ca. 0.6 pm and the geometric standard deviation, ug, was ca. 2.2. The first two sampling tubes in each of two series were inefficient in collecting MDI. In one experiment to help determine the capacity of impregnated filters for MDI before either breakthrough or overloading would occur, air from the MDI generation system was drawn through impregnated filters followed by sections of coated glass wool for 3-, 6-, 9-, and 12-h periods (see Table 11). (Five grams of fresh MDI was placed into the generation system for each 3-h segment of the 6-, 9-, and 12-h periods in order to help maintain a relatively high concentration of MDI in air. MDI apparently underwent chemical change at bath temperatures near 135 "C, and concentrations of MDI in air would decrease with time.) Breakthrough of MDI from only one impregnated filter was realized; MDIU corresponding to 1.2 pg of MDI (99.5
I:
-90
" The sampler was the first sampler in each sampling The sampling period was 1 h in each case. The train. impinger was followed by a second impinger and two The bubbler was folsections of coated glass wool. lowed by a second bubbler and two sections of coated glass wool. e The sampling tube was followed by a second sampling tube. There were two sections of coated glass wool in each tube (see Experimental Section). f The filter was followed by one section of coated glass wool. [maximum sampling periods are based in part on vapor pressure data (I)]. Average collection efficiencies of different types of samplers for MDI were determined (see Table 111). The different samplers were followed by other sampling devices in sampling trains, and the average collection efficiencies were based on total quantities of MDI collected in each sampling train. Impingers and fritted gliass bubblers contained hydrochloric and acetic acids for modifications of the Marcali method (5). A satisfactory reference method for MDI in air was not found for an evaluation of the impregnated filter method. The impregnated filter method can be used to determine MDI at concentrations ranging from 4.4 to 800 kg/m3 for 180-L samples and from 80 to 1000 kg/m3 for 10-L samples. The upper limits of concentration (800 and 1000 pg/m3) were the highest approximate concentrations a t which the im-
1141
pregnated filter method was tested for a single 3-h period and for any period, respectively. Advantages of the methods reported herein include the following: (a) the samplers are small, light in weight, and convenient for personal sampling; (b) the samplers are efficient collectors of 2,4-TD1[vapor and MDI (before breakthrough would occur); ( c ) the impregnated filter can collect MDI in both vapor and aerosol forms; (d) the analytical methods are specific for 2,4-'rDI and MDI; (e) the methods are useful for determining 2,4-TDI and MDI at the OSHA and NIOSH recommended standards.
ACKNOWLEDGMENT Particle sizing by J. P. Smith, synthesis of 2,4-TDIU by B. R. Belinky, and suggestions by A. W. Teass for experimental work with impregnated filters and R. Henderson for work with 1,l-diazabicyclo[2.2.2loctane are acknowledged.
LITERATURE CITED
...
(1) "Criteria for a Recommended Standard Occupational Exposure to DiIsocyanates"; Department of Health, Education and Welfare, Natlonal Institute for Occupatlonal Safety and Health: Cincinnati, OH, 1978; DHEW (NIOSH) Publ. (U.S.), NO. 78-215. (2) Chem. Eng. News 1978, 56(37), 7. (3) Fed. Reglst. 1977, 42 (No. 240), 62869-62869A. (4) "NIOSH Manual of Analytical Methods", 2nd ed.; Department of Health, Education and Welfare, National Institute for Occupational Safety and Health: Cincinnati, OH, 1977: Vol. 1, Method No. P&CAM 141; DHEW (NIOSH) Publ. (U.S.), NO. 77-157-A. (5) "NIOSH Manual of Analytical Methods", 2nd ed.; Department of Health, Educatlon and Welfare, Natlonal Instltute for Occupational Safety and Health: Cincinnati, OH, 1977; Vol. 1, Method No. P&CAM 142; DHEW (NIOSH) Publ. (U.S.), NO. 77-157-A. (6) Dunlap, K. L.; Sandridge, R. L.; Keller, J. Anal. Chem. 1976, 4 8 , 497-499. (7) "Acceptance of Hazardous or Perishable Articles"; US. Postal Service: Washington, DC, 1977; Publicatlon 52, Chapter 6. (8) Keller, J.; Sandridge, R. L. Anal. Chem. 1979, 57, 1868-1870. (9) Hastings Vogt, C. R.; KO, C. Y.; Ryan, T. R. J. Chromatogr. 1977, 134, 451-458. (10) Nellson, A.; Booth, K. S. Am. Ind. Hyg. Assoc. J . 1975, 3 6 , 169-171. (11) Meddle, D. W.; Woad, R. Ana/yst (London) 1970, 95,402-407. (12) Smlth, D. B.; Henderson, R. J. Occup. Med. 1975, 77, 413-414. (13) Holland, D. G.; Rooney, T. A. J. Occup. Med. 1977, 79, 239-240.
RECEIVED for review October 23,1981. Accepted March 18, 1982.
