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Anal. Chem. 1983, 55,2199-2201
longer time in the SB/CD chamber. Shorter times could possibly be obtained in positions other than position two. This would of course entail measurement of slope and intercept values in each of the new positions. I t should be rioted that for the separation of progesterone/pregnenolone there is a 10% difference between the f d y optimized time and the time in the SB/CD chamber even though there is an insignificant difference between 1 and I*. This is because there is only a very slight dependence of plate length on mole fraction in this region for this particular separation. The pairis listed in Table I are difficult t o separate by use of the solvents listed. It should be noted that for four of the five separations, conventional development requires a TLC plate in the range between 26 cm and 40 cni in length wherem position 2 of the !SB/CD chamber (as shown in Table I) requires an overall plate length of about 5 cm. Thus apart from considerations of shorter analysis time, the SB/CD chamber
allows difficult separations to be performed that would not normally be obtainable by conventional TLC. I t should be noted that for several of the solute pairs in Tables I and I I , l > l*. This inequality is permissible because (tl*)minand (tJmi,, occur a t different mole fractions. Registry No. Hydrocortisone, 50-23-7;corticosterone, 50-22-6; progesterone, 57-83-0;pregnenolone, 145-13-1;estrone, 53-16-7. LITERATURE CITED (1) Perry, J. A. J . Cbromatogr. 1979, 165, 117-140. (2) Nurok, D.;Becker, R. M.; Sassic, K. A. Anal. Chem. 1982, 54,
1955-1959.
RECEIVED for review March 8, 1983. Accepted July 18, 1983. This work was presented in part a t the 3rd Biennial Symposium on Advances in Thin Layer Chromatography in Parsippany, NJ, Dec 1982. The work was supported by grants from the Research Corporation and the Society for Analytical Chemists of Pittsburgh.
Trace Determination of Low IVlolecular Weight Aliphatic Amines in Air by Gas Chromatography Kazuhiro Kuwnta,* Erniko Akiyama, Yoshiaki Yamazaki, Hiroyasu Yamasaki, and Yoshio Kuge
Environmental Pollution Control Center, 62-3, 1 Chome, Nakamichi, Higashinari-ku, Osaka City 537, J a p a n Yoshiyuki Kisa
Applied Physics and Chemistry, Facu1t:y of Engineering, Hiroshima University, Shitami, Saijo, Higashihiroshimn City 724, J a p a n Low molecular weight alliphatic amines have received much attention as odorous substances in studies of air pollution. Gas chromatography (GC) is widely used to determine such traces of the amines (1-5). However, consideralble difficulty is encountered in storing and analyzing amine samples in extremely low concentration levels because of their adsorption on solid surfaces and because of the presence of interfering organic substances. Although a number of the GC columns so far reported are discussed with respect to the resolution of C1-C4 aliphatic amines and the accuracy of the determined values (5), many of the columnin are not suitable for separation of the Cz-C3 amine isomers. The recently reported columns ( 4 , 5) offer good separation for the Cz-C3 isomers. The preparation of the columns, however, is substaiitially tedious, and interferences of water injected are often observed in the analysis. Recently, the Sep-PAK C18 (SP) cartridge has been often used to enrich and cleanup trace componeinta from food (6-91, environmental samples (10-13), biological samples (14-181, and other samples with substantial savings of the number of steps and total time. To date, the cartridge has, however, not been applied t o analysis of air samples. In this study, aL new GC analytical column, alkalized SEPABEAD GHP-1 (GHP-I.), was prepared to determine the Cl-C4 aliphatic amines without interferences of water, and handy SP cartridges impregnated with phosphoric acid were used to perform trace determination of ithese amines in air samples. EXPERIMENTAL SECTION Reagents and Materials. Hydrochloridesof the C,-C, amines, isobutylamine, n-butylamine, and diethylairnine were of special grade from Tokyo Kasei Kogyo (Tokyo, Japan), and sec-butyl-
amine and tert-butylamine were of special grade from Wako (Osaka, Japan). The other reagents used were of commercially available special grade. The water used was prepared by redistilling deionized water. SEPABEAD GHP-1 (GHP-1) (60-80 mesh) was spherically shaped organic porous polymer (styrenedivinylbenzene copolymer) from Mitsubishi Chemical (Tokyo, Japan). Sep-PAK CIS (SP) cartridge was from Waters Associates (Mildord, MA). The stock solutions containing 1000 pg/mL of an amine were made by dissolving an amine hydrochloride or a free amine in redistilled water. Standards of lower concentrations were made by neutralizing a part of the stock solution with 1-2 N potassium hydroxide solution, if required, and by appropriately diluting the solution with redistilled water. Preparation of the Analytical Column. A 10-g amount of GHP-1 was washed with 100 mL of methanol for 3 h in a Soxhlet extractor. The GI*-1 was mixed with 30 mL of methanol solution containing 1.0 g of potassium hydroxide, and the mixture was dried under reduced pressure at less than 50 "C in a rotary evaporator. The analytical column was made by packing the material into a 2 m X 2 mm i.d. glass tube and by conditioning at 200 "C for 2 days. During the conditioning,10 pL of water was injected 15-20 times to ensure preparation of stable column. Prior to use of the column, 10 p L of 1 N potassium hydroxide solution was injected twice at 170 "C. Apparatus. A Hewlett-Packard (Avondale, PA) 5830A gas chromatograph with a nitrogen-phosphorus flame ionization detector (NP-FII)) was employed. The working conditions were as follows. The injection port temperature was 180 "C, and the column temperature was isothermal at 140 "C for 3 min and then programmed from 140 to 170 "C at 10 "C/min and isothermal at 170 "C for 10 min. The NP-FID temperature was 250 "C. The carrier gas was nitrogen at 45 mL/min. On-column injection was used. Preparation of the Sampling Tube. A SP cartridge was washed with 4-5 mL of methanol. Then, 3-4 mL of 0.3% phosphoric acid in methanol was forced through the cartridge,
0003-2700/83/0355-2199$01.50/0 0 1983 American Chemical Society
2200
ANALYTICAL CHEMISTRY, VOL. 55, NO. 13, NOVEMBER 1983
,
(A)
(B)
P
(C)
Figure 1. Sep-PAK C18(SP) cartridges: (A) drylng step 1, (B) drylng step 2, (C) storage and transportation; (1) SP cartridge, (2)nitrogen 20-30 mL/min, (3) water asplrator, (4)nitrogen 80-100 mL/min, (5) silicone tube, (6) PTFE-sealed cap, (7) glass plug, (8) glass tube.
Table I. Retention Times of C, -C, Aliphatic Amines and Analytical Accuracy at a 1-ng Level on the GHP-1 Column responsea peak height i retention SD,' time, min arbitrary RSD,d avb i SDC amine units % methylamine 1.08 i 0.005 26.5 * 0.55 2.1 dime thylamine 1.93 i 0.004 12.7 i 0.25 2.0 ethylamine 2.39 i 0.003 10.2 i: 0.32 3.1 trimethylamine 2.71 f 0.001 10.1 i 0.36 3.6 isopropylamine 4.46 i 0.007 5.19 f 0.13 2.5 n-propylamine 5.63 i 0.007 6.38 f 0.17 2.7 tert-butylamine 6.54 f 0.008 2.18 i 0.09 4 . 1 diethylamine 7.02 f 0.010 5.80 i 0.19 3.3 sec-butylamine 8.22 i: 0.007 3.25 * 0.08 2.5 isobutylamine 8.73 f 0.005 3.61 i 0.08 2.2 n-butylamine 9.93 i 0.011 2.44 i 0.07 2.9 Response for 1 ng of the individual amines. Average in seven runs. Standard deviation. Relative standard deviation. (1
and the empty part of the cartridge was wiped with filter paper. The cartridge was dried for 1 h under reduced pressure in a nitrogen stream (Figure 1A) and then by passing pure nitrogen at 80-100 mL/min for 30 min (Figure 1B). The cartridge was closed with glass stoppers, sealed in a vial (Figure lC), and stored in a cool place (3-5 "C)in the dark until use. Usually, 20-50 coated sampling tubes were simultaneously prepared. Sampling and Analytical Procedure. A 2-150-L volume of air sample was sampled at 0.5-1.5 L/min through the SP cartridge. The adsorbed materials on the cartridge were removed by treatment with 1.5 mL of methanol-water (1:l). The eluate was adjusted to pH 10 with 2 N potassium hydroxide solution and brought up to 2 mL with water. A 2-4-pL aliquot of the solution was analyzed by gas chromatography. The amines were identified by retention time and quantified by peak height. The used cartridge was regenerated for repeated use by washing with 5 mL of methanol.
RESULTS AND DISCUSSION The analytical column packed with GHP-1modified with 10% potassium hydroxide was easy to prepare and was stable for long-term use compared to conventional columns ( 4 , 5 ) . The column produced an outstanding resolution for 11 C 1 4 4 aliphatic amines, especially for the Cz-C3 isomers, with little interference of water. Though the separation aspects were somewhat dependent on column temperature, the column was useful for both isothermal and temperature programming analysis. The temperature programming operation was usually
Table 11. Recovery of the Amines from the SP Cartridge recovery,a % RSD,d amine avb i SDC % methylamine 91.6 i 4.71 5.1 dimethylamine 91.8 f 4.57 5.0 e thylamine 91.7 i 4.60 5.0 trimethylamine 87.1 f 4.00 4.6 isopropylamine 91.7 i 3.93 4.3 n-propylamine 89.7 i 4.19 4.7 tert-butylamine 93.4 f 3.57 3.8 diethylamine 89.2 i 4.72 5.3 sec-butylamine 88.9 i 4.51 5.1 isobutylamine 87.5 i 4.82 5.6 n-butylamine 87.0 i 4.68 5.4 a Recovery for 6 pg of amine in 6 W Lof sample placed on the cartridge. b Average in four runs. ' Standard deviation. Relative standard deviation. Table III. Determination of the Amines in Synthetic Air Samples concna f SD,b RSD,' amine ppb % methylamine 109 f 2.27 2.1 dimethy lamine 161 f 1.25 0.8 athylamine. 80.9 f 1.84 2.3 trimethylamine 149 f 4.32 2.9 isopropylamine 68.9 i 1.83 2.7 n-propylamine 41.7 i 2.38 5.7 tcrt-butylamine 38.8 i 1.36 3.5 diethylamine 32.8 It 1.30 4.0 sec-butylamine 36.9 i 0.65 1.8 isobutylamine 53.1 c 1.19 2.2 n -butylamine 45.2 i 2.54 5.6 a A 5-L volume of a sample was sampled at 1.0 L/min; average in five runs. Standard deviation. Relative standard deviation. used from 140 to 170 "C a t 10 "C/min to complete rapidly simultarleous separation of the C1-C4 amines. Figure 2 shows a typical gas chromatogram for the C1-C4 amines under the temperature programming conditions. Because the amines were chemically inactive and nonadsorptive on the column, the amines at less than 1-ng levels were accurately determined by using a NP:FID which was selectively sensitive to nitrogen-containing compounds. Table I reports the retention times of the C1-CI amines and the analytical accuracy a t a 1-ng level of the amines. The within-day relative standard deviation of the retention times was less than 0.5%. The amines were determined at a 1-ng level with 2.0-4.1% relative standard deviation. The detection limits, defined as twice the background peak for 2 pL of water injected, were 0.02 ng for the Cl-CB amines and 0.05 ng for the C4 amines. The relative standard deviation of the determined values was 3-14% near the detection limits. The column could be used for 5 months without deterioration of the performance. The collection efficiency of the C1-CI amines was investigated by using two SP cartridges in series. Amounts of 6 pg of the amines were placed onto the first cartridge and then 50-150 L of pure air was passed at 0.5-1.5 L/min through the cartridges and the amines on each cartridge were determined. All the amines placed were recovered on the first cartridge and no amines were detected on the second. On the other hand, the amine vapors were thoroughly trapped on the first cartridge at parts-per-billion (ppb) (v/v) or ambient air levels in any sampling case. Accordingly, one SP cartridge was used to sample amines in air samples. Traces of the C1-C4 amines were placed onto the SP cartridge and recovered after nitrogen passes through the cartridge a t 120 mL/min for 30 min. Table I1 reports that the
ANALYTICAL CHEMISTRY, VOL. 55, NO. 13, NOVEMBER 1983
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Table IV. Amines in Polluted Air sample
a
air in cowshed air around cow waste deposit emission gas from a fermentation system of pig wastes solubilizer fermenter air in poultry f,arm air around a fermentation system of poultry wastes emission gas from a incinerator of poultry wastes Not detectable.
0
sample volume, L 111 88.5
amine found, ppb methylamine trimethylamine NDa 0.80 ND 0.28 ND ND
48.9 26.0 102 59.9 4.1
0.84 0.75 0.93 5.85 69.7
0.52
0.97 12.4
2
6
1
5
2201
10
I
I
I
1
0
5
0
5
Retention time, min
Flgure 2. Typical gas chromatogram of the C,--C, aliphatic amines. Amounts of the amines, 6 ng: (1) methylamine,(2) dimethylamine, (3) ethylamine, (4) trimethylamine, (5) isopropylamine, (6)n -propylamine, (7) tert-butylamine, (8) diethylamine, (9) sec-butylamine, (10) isobutylamine, (1 1) n-butylaminis.
recovery of the amines was 87-94% with 3.8-5.5% standard deviation a t a 6-pg level. Trimethylamine corresponding to 2% was observed in the !second 2-mL eluate after the first 1.5-mL eluate was removed. No other amines were detected in the second eluate. For investigation on analytical precision at part-per-billion levels of the C1-C4 amines, synthetic air samples containing 32-160 ppb of the amines were prepared in polyester bags. A volume 0f 5 L of the samples was repeatedly sampled by the use of the SP cartridges. Table I11 reports that the C1-CB aliphatic arnine vapors could be determined a t the part-perbillion level with 0.8-5.79; relative standard deviation. The detection limits were 0.1 ppb for the C1-C3 amines and 0.2 ppb for the C4 amines for 150 L of air sample. The method was applied to determination of aliphatic amines in the air in and around livestock houses. Volumes of 4-120 L of air samples were sampled at 1.0-1.5 L/min. Table IV reports typical analytical data from several sources, and Figure 3 shows typical gas chromatograms of the amines from these source^^. In emission vapors from biological cycles, the C1-C3 aliphatic amines we're successfully detected and no C4 aliphatic amines were observed. Coexisting organic components did not interfere with these determinations because of the selectivity of the NP-FID to nitrogen-containing compounds. As these features indicate, the proposed method may be useful in routinely analyzing a large number of air samples in studies of air pollution. The method may have advantages over conventional methods in terms of simple and rapid analytical procedures, high resolution of the amines, and low background effects.
Retention time, min
Flgure 3. Gas chromatograms of amlnes from polluted sources: (A) air in a cowshed, (2) trimethylamine (0.22 ng) 0.80 ppb; (6)alr around a fermentation system of poultry wastes, (1) methylamine (0.073 ng) 0.97 ppb, (2) trimethylamine (0.83 ng) 5.85 ppb.
ACKNOWLEDGMENT The authors t,hank K. Negoro, Faculty of Engineering, Hiroshima University, for his instructive advice in the study. Registry No. Methylamine, 74-89-5; dimethylamine, 124-40-3; ethylamine, 75-04-7; trimethylamine, 75-50-3; isopropylamine, 75-31-0; n-propylamine, 107-10-8; tert-butylamine, 75-64-9; diethylamine, 109-89-7; sec-butylamine,13952-84-6;isobutylamine, 78-81-9; n-butylamine, 109-73-9. LITERATURE CITED DI Corcla, A.; Samperl, R. Anal. Chem. 1974, 46, 977-981. Dunn, S. R.; Slmenoff, M. L.; Wesson, L. G., Jr. Anal. Chem. 1976, 4 8 , 41-43. Kuwata, K.; Yamazakl, Y.; Ueborl, M. Bunsekl Kagaku 1980, 29, 170-175. DI Corcla, A.; Samperl, R.; Severinl, C. J. Chromatogr. 1979, 770, 325-329. Kuwata, K.; Yamazakl, Y.; Uebori, M. Anal. Chem. 1980, 52, 1980-1962. Finley, J. W.; Duang, E. J. Chromatogr. 1981, 207, 449-453. Hurst, W. J.; McKlm, J. M.; Martin, R. A. J. Food Sci. 1981, 46, 419-424. Lawrence, J. F.; Lancaster, F. E.; Conacher, H. B. S. J. Chromatogr . 1981, 270, 168-173. Libert, B. J. Chromatogr. 1981, 270, 540-543. Bushway, R. J. J. Liq. Chromatogr. 1982, 5 , 49-62. Mills, G. L.; Qulnn, J. G. Mar. Chem. 1981, 70, 93-102. Saner, W. A.; Glbert, J. J. Liq. Chromatogr. 1980, 3 , 1753-1765. Wolkoff, A. W.; Greed, C. J. Llq. Chromatogr. 1981, 4 , 1459-1472. Bennett, H. P. J.; Browne, C. A.; Soloman, S. J. Llq. Chromatogr. 1980, 3, 1353-1365. Ghoos, Y.; Rutgeerts, P.; Vantrappen, G. J. Llq. Chromatogr. 1982, 5, 175-186. Lafont, R.; Pennetler, J. L. J. Chromatogr. 1982, 236, 137-149. Renberg, L.; Lindstrom, K. J. Chromatogr. 1981, 274, 327-334. Watson, D. R., Spazlanl, E. J. Liq. Chromatogr. 1982, 5 , 525-535.
RECEIVED for review May 2, 1983. Accepted June 24, 1983.
