LITERATURE CITED National Academy of Sciences, "inputs, Fate and Effects of Petroleum in the Marine Environment", A Report of the Ocean Affairs Board, National Academy of Sciences, Washington, D.C., 1975. (2) "Baseline Studies of Pollutants in the Marine Environment and Research Recommendations",Office of the international Decade of Ocean Exploration, National Science Foundation, Washington, D.C., 1972. (3) "Marine Pollution Monitoring (Petroleum)",Nat. Bur. Stand. (U.S.), Spec. (1)
Pub/., 409, 29 (1974). (4) J. W. Farrington,and P. A.
Meyers, Chapter 5 in "Environmental Chemistry, Voi. I", Specialist Periodical Report No. 35, The Chemical Society, U.K., 1975.
(5)J-W; Farrington, J. M. Teal, J. G. Quinn, T. Wade, and K. A. Burns, Bull. Env i m . Contarn. Toxicol., 10, 129 (1973).
(6)G. C. Medeiros and J. W. Farrington, in Ref. 3, p 167. (7) ,J. W. Farrington, J. M. Teal,J. G. Quinn, P. L. Parker,J. K. Winters, T. L. Wade, and K. Burns, in Ref. 3, p 163. (8)J. W. Farrington and G. C. Medeiros, "Proceedings, 1975 Conference on
(9)
Prevention and Control of Oil Poilution", American Petroleum Institute, Washington, D.C., 1975, p 115. J. G. Quinn and T. L. Wade, Marine Memorandum Series No. 33, Graduate School of Oceanography,Universify of Rhode island, Kingston, R.i. 02881, 1974.
RECEIVEDfor review March 4, 1976. Accepted July 9,1976. This wojk was supported by $he Office for the International Decade of Ocean Expbration Grants GX-28334 (WHOI), GX-28340 (URI), by grants from the National Science Foundation (GA-19472),and by the Office of Naval Research (N00014-66, Contract C0-241), and by Grant 802724 of the US. Environmental Protection Agency (WHOI). This is contribution No. 3729 of the Woods Hole Oceanographic Institution.
Gas Chromatographic Separation sf Lower Aliphatic Amines Yasuyuki Hoshika Aichi Environmental Research Center, 7-6, Tsuji-machl, Kita-ku, Nagoya-shi, Aichi, Japan
A mixture of 13 lower aliphatic amines were separated by 8 TENAX-GC column in temperature programming gas chromatography. Primary amines were converted Into corresponding Schiff bases by reaction with benzaldehyde. Residual secondary and tertiary amines were analyzed in the forms of their free amines. The amines separated are eight primary amines: methyl-, ethyl-, n-propyl-, Isopropyl-, n-butyl-, Isobutyl-, n-amyl-, and isoamylamlnes; three secondary amines: dimethyl-, diethyl-, and di-n-propylamines; and two tertiary amines: trimethyl- and triethylamlnes.
Qualitative and quantitative analysis of ammonia and lower aliphatic amines are problems commonly encountered in odor pollution analysis, because these compounds have odor threshold values a t ppm or ppb levels in air (1-3). Direct separation of the mixtures by gas chromatography (GC) with Lubrol MO, paraffin and undecanol(4,5), THEED and T E P (6), triethanolamine (7), PEG 1500 and 20 M (8), Amine 220 (9), squalane and glycerine ( I O ) , Chromosorb 103 (11,12),Pennwalt (12) have been used. However, in general when these columns are employed, the GC separation of the mixtures of ammonia and lower aliphatic amines, such as methyl-, dimethyl-, trimethyl-, ethyl-, diethyl-, triethyl-, and isopropylamines is poor. In this study, to achieve complete chromatograms, separations of the mixtures of free amines and Schiff base derivatives of amines, the amines and derivatives were chromatographed simultaneously using TENAX-GC (13) column packing. Primary amines were converted into corresponding Schiff bases by reaction with benzaldehyde (14); residual secondary and tertiary amines were analyzed in the forms of their free amines, since they do not react with benzaldehyde. However, in this present method, ammonia was not analyzed, because ammonia only reacted with benzaldehyde but did not give the corresponding peak in the chromatograms.
EXPERIMENTAL Reagents. Ammonia (28%,wt % aq. soln) and dimethylamine (40%, wt % aq. soln) were obtained from Katayama Chemical Industries, Ltd., Osaka, Japan. Methyl- (40%,wt % aq. soln), trimethyl- (30%,w t 1716
% aq. soln), ethyl- (70%, wt % aq. soln), diethyl-, triethyl-, and isopropylamines were obtained from Tokyo Kasei Kogyo Ltd., Tokyo, Japan. n-Propyl- and n-butylamines were obtained from Wako Pure Chemical Industries, Ltd., Osaka, Japan. Isobutyl-, n-amyl-, isoamyl-, and di-n-propylamines were obtained from PolyScience Corp., Niles, Ill. Benzaldehyde (9596, min.) was obtained from Wako Pure Chemical Industries Ltd., Osaka, Japan. n-Propylbenzene was obtained from Tokyo Kasei Kogyo, Ltd., Tokyo, Japan. n-Hexyl alcohol was obtained from PolyScience Corp. All reagents used were guaranteed or reagent grade chemicals. Preparation of Schiff Base. The procedure for the preparation of all the Schiff bases listed in Table I was as follows. The amines (1-6 X mol) and benzaldehyde ( 5 X mol) were mixed in 2 ml of n-hexyl alcohol, at room temperature. The Schiff base formation reaction was rapid and exothermic; therefore the reaction time also was sufficient to form the derivatives of Schiff bases in a few minutes. Apparatus. The gas chromatograph used was a Shimadzu Model GC5APbT (dual columns system) instrument equipped with on-column injection, a thermal conductivity detector (TCD),and a digital integrator (Shimadzu Model ITG-SA) for the determination of the
Table I. Relative Retention Times (RtR) of Ammonia and 13 Lower Aliphatic Amines in the Free Form, and the Schiff Base Derivatives (n-Propylbenzene = 1.OO) Compounds
Rt R
Ammonia
0.07
Primary amine Schiff bases
RtR
Class
Primary in free Methylamine Ethylamine n-Propylamine Isopropylamine n-Butylamine Isobutylamine n-Amylamine Isoamylamine Secondary in free Dimethylamine Diethylamine Di-n-propylamine Tertiary in free Trimethylamine Triethylamine
ANALYTiCAL CHEMISTRY, VOL. 48, NO. 12, OCTOBER 1976
0.15 0.25 0.4 1 0.33
0.58 0.53
0.72 0.68
0.24 0.48 0.74 0.29 0.62
Methylamine Ethylamine n-Propylamine Isopropylamine n-Butylamine Isobutylamine n-Amylamine Isoamylamine
1.14
1.19 1.28 1.20 1.40 1.32 1.54 1.47
relative retention times. The relative retention times of all the compounds listed in Table I were calculated using n-propylbenzene as an internal standard. Chromatographic Conditions. The GC column consisted of a 3 m X 3 mm i.d. glass column,packed with TENAX-GC (made by Enka nv Arnhem/Holland), obtained from Shimadzu Ltd., Kyoto, Japan, 60/80 mesh, Lot No. 30704. The columns were preconditioned at 280 "C for 20 h with a constant flow of Nz (50 ml/min) through the columns, before being connected with the TCD. The chromatographic conditions for the analysis were: carrier gas (Nz)flow rate, 50 ml/min; column temperature (programming),holding for 1min at 100 "C and heating the column oven at a rate of 10 OC/min from 100 to 250 "C, maintaining this temperature for 15 min and then cooling to the starting temperature; injection port and detector temperatures, 250 "C; and bridge current, 66 mA. Procedure. The sample solution was prepared by dissolving ammonia and 13 lower aliphatic amines and n-propylbenzene (4 X mol) as an internal standard, in 2 ml of n-hexyl alcohol. One p1 of sample was injected with a 1O-fi1Hamilton microsyringe (701-N)into the GC column. Benzaldehydefor Schiff base formation reactions was introduced directly to the sample solution.
Particularly, in the case of benzaldehyde, an intermediate, crystalline addition consisting of 2 mol of benzaldehyde and 1 mol of ammonia has been isolated. 2C&jCHO
+ NH3
CGH~CHOHNHCHOHC~H~
Therefore, it is sufficiently considered that, when warmed a t column temperature, the addition compounds break up into "hydroamide", aldehyde, and water. 2C&,CHOHNHCHOHC6H5 (C&&H=N)~CHC&I5 iC&I&HO
+ 3Hz0
Therefore, in this present method, ammonia is not only analyzed, but in the case of large amounts present along with the amine mixtures may give the interfering effect. Because the ammonia will disappear benzaldehyde will react with the lower aliphatic primary amines. In such case in general, the addition to the amine mixtures of benzaldehyde of large amounts is necessary.
RESULTS AND DISCUSSION The relative retention times of ammonia and 13 lower aliphatic free amines and the derivatives of Schiff bases are listed in Table I. The retention time of n-propylbenzene was defined as unity. Complete separation of ammonia and 13 lower aliphatic free amines were obtained, except for the overlap of n-amyl- and di-n-propylamines peaks, and the incomplete resolution of ethyl-, and trimethylamines. All primary amines were quantitatively converted to the corresponding Schiff bases by the reaction with benzaldehyde. Only the secondary and tertiary amines remained as free amines. The Schiff bases were resolved, except for the derivatives of ethyl- and isopropylamines. Analytical times for the GC determination of this method was about 25 min. No evidence was found for the interference of water in the analysis. Ammonia in the solution reacted with benzaldehyde in the mole ratio more than 2, quantitatively, but did not give the corresponding peak in 25 min, in the chromatogram. This was also confirmed from the chromatogram of the product by the direct reaction of ammonia with benzaldehyde, which was not used as solvent. It has been reported that aromatic aldehydes in general reacted with aqueous or alcoholic ammonia a t room temperature to give the so-called "hydroamides" (15).These are high-melting, crystalline substances formed according to the following equation: 3ArCHO
+ 2NH3 - Ar(N=CHAr)z + 3H20
ACKNOWLEDGMENT The author thanks G . Muto, University of Tokyo, and K. Yoshimoto, Aichi Environmental Research Center, for useful suggestions.
LITERATURE CITED Summer, "Methods of Air Deodorization",'ElsevierPublishing Company, Amsterdam, 1963, p 46. G. Leonardos, D. Kendall, and N. Barnard, J. AirPollut Control Assoc., 19,
(1) W. (2)
91 (1969). (3) T. M. Hellman and F. H. Small, J. Air Pollut. Control Assoc., 24, 979 (1974). (4) A. T. James, Biochem. J., 52, 242 (1952). (5)A. T. James and A. J. P. Martin, Ana/yst(London), 77, 915 (1952). (6) Y. L. Sze, M. L. Borke, and D. M. Ottenstein, Anal. Chem., 35, 240 (1963). (7) R. E. Burks, Jr., E. B. Baker, P. Clark, J. Esslinger, and J. C. Lacey,Jr., J. Agric. FoodCbem., 7, 778 (1959). (8) A. DiCorcla and R. Samperi, Anal. Chem., 46, 977 (1974). (9) S. R. Dunn, M. L. Simenhoff, and L. G. Wesson, Jr., Anal. Chem., 48,41 (1976). (10) Y. Kaburaki,Y. Mikami, Y. Okabayashi,and Y. Saida, 6unsekiKagaku(Japn Anal.), 18, 1100 (1969). (11) C. E. Andreand A. R. Mosier, Anal. Chem., 45, 1971 (1973). (12) A. R. Mosier, C. E. Andre, and F. G. Viets, Jr., Envkon. Sci. Techno/., 7, 642 (1973). (13) J. M. H. Daemen, W. Dankelman,and M. E. Hendriks, J. Chromatogr. Sci., 13,79 (1975). (14) Y. Hoshika, J. Chromatogr., 115, 596 (1975). (15) M. M. Sprung, Chem. Rev., 26, 297 (1939).
RECEIVEDfor review April 12, 1976. Accepted June 29, 1976
Coupled Gas Chromatography-Atomic Absorption Spectrometry for the Nanogram Determination of Chromium Wayne R. Wolf Nutrient Composition Laboratory, Nutrition Institute, Agricultural Research Servlce, U S . Department of Agriculture, Beltsville, Md. 20705
A slmple lnexpenslve interface to introducethe effluent from a gas chromatograph directly into the burner of a commercial atomic absorption spectrometer has been developed. Determlnation of chromium In the nanogram range by chelationextraction of volatile chelates has been demonstrated, wlth
a detection limit of 1.0 ng. Analysis of single samples is obtained in less than 1 min from injection Into the GC-AAS. The use of this selective, relatively interference-free detection system was tested in recovery studles and in the determination of chromium content of NBS SRM 1571 Orchard Leaves.
ANALYTICAL CHEMISTRY, VOL. 48,
NO. 12,
OCTOBER 1976
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