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Anal. Chem. 1988, 58, 1571-1572 (15) Axner, 0.;Bergllnd. T.: Heully, J. L.; Lindgren, I.; Rubinsztein-Dunlop, Ha J . APPl. PhyS. 1984, 55, 3215-3225. (16) Axner, 0.;Llndgren, 1.; Magnusson, I.; Rublnzszteln-Dunlop, H. Anal. Chem. M85, 57, 776-778. (17) Axner, 0.;Magnusson, I . Phys. Scr. 1985, 37, 587-591. (18) Omenetto, 0.; Berthoud, T.; Cavalll, P.; Rossl, 0. Anal. Chem. 1985, 57. 1256-1281. (19) Hurst. G. S. Anal. Chem. 1981, 53, 1448A-1456A. (20) Fassea, J. D.: Moore, L. J.; Travis, J. C.; De Voe, J. R. Science (Washington. D.C.)1985, 230, 262-267. (21) Nlemax, K. Appl. Phys. 6 1985, 38, 147-157. (22) Brlllet, W. L.; Gallagher, A. Phys. Rev. A 1980, 22, 1012-1017. (23) Llao, P. F.; Bjorkholm, J. E. Phys. Rev. Lett. 1978, 36, 1543-1545. (24) Nlemax, K. Appl. Phys. 6 1983, 32,59-62. (25) Niemax, K.; Weber, K.-H. Appl. Phys. 6 1985, 36, 177-180. (26) Lorenzen. C.J.; Nlemax, K.; Pendrlll, L. R. Opt. Commun. 1981, 39, 370-374.
' Present address:
ERNO, Bremen, FRG.
K a y Niemax* Jorg Lawrenz Andreas Obrebski Karl-Heinz Weber' Institut fur Spektrochemie und angewandte Spektroskopie Bunsen-Kirchhoff-Strasse 11 D-4600 Dortmund, Federal Republic of Germany
RECEIVEDfor review November 22,1985. Accepted February 13,1986. Financial support by the Deutsche Forschungsgemeinschaft is gratefully acknowledged.
Determination of Total Nitrogen in Oil Shale Sir: Cooper and Evans (I)report that fixed NH4+-Noccurs along with organic N in samples of Green River Formation oil shale from Colorado Core Hole No. 1. Total N was determined by a modified Kjeldahl method employing concentrated H2S04in a sealed tube at 400 "C for 3 h (2, 3). A digestion temperature of 400 "C was chosen rather than the 420 "C used in earlier work (2) so that the results would be more comparable to those for sediments from the Argentine Basin (3). In addition, the oil shales have a high organic content and there is less loss of tubes in the muffle furnace at the lower temperature (2). Fixed NH4+-Nwas determined by a KOBr-HF method (2,4). Because exchangeable NH4+-N was found to be negligible in these samples, the difference between total N and fixed NH4+-Nis reported as organic N. In a recent attempt to establish the mineralogical residence of the fixed NH4+-N in oil shale samples, ",+-containing minerals were concentrated by treating with dilute HCl to remove carbonates and with alkaline NaOCl (household bleach) to remove organic matter. When fixed NH4+-Nand total-N were determined on a sample of spent shale from Fischer assay that had been treated with HC1 and NaOCl (sample 781.5st), fixed NH4+-N was found to be 0.59% whereas total N was found to be only 0.15% (Table I). Clearly, not all of the fixed NH4+-N was extracted by the method for total N; therefore, a new method of analysis for total N content of oil shale was developed. EXPERIMENTAL S E C T I O N Total N was determined by combining techniques for determining total N by sealed-tube digestion and for extracting fixed NH4+-Nwith HF (3). A sample (ground to pass a 170-meshsieve) of a size estimated to give a titer between 3 and 5 mL in the final step was weighed into a 10 X 75 mm2 Pyrex test tube. A 0.1-mL portion of concentrated H2S04was added to the sample, which was allowed to stand for 1h at room temperature before it was placed in an oven at 50 "C for 1h. The sample then was placed in a vacuum oven at 50 "C for 16 h. After the sample was removed from the vacuum oven, 0.4 mL of concentrated HzS04and 1 drop of HzS04diluted 1:l with water were added. The tube was sealed with a propane-oxygen torch, placed in a protective casing made from pipe, and the casing was placed in a muffle furnace maintained between 400 and 425 'C for 3 h. The casing (which contained several tubes) was removed from the oven, and, after it had cooled, the tube was removed and opened with a propane-oxygen torch to release pressure. The tube was scored with a file and the top was broken off. The contents of the tube were transferred completely to a 50-mL polypropylene tube with sufficient demineralized water to make the volume about 5 mL. To this was added 5 mL of 10
Table I. Total N, Fixed NH4+-N,and Organic N in Samples of Oil Shale from Colorado Core Hole No. 1 digestion fixed sample NH4+-N Only deDth," total N,* m % %' % o f N %d %ofN 772.3 781.5 781.5s 781.5st 789.3 813.2 819.4 819.4s
0.37 0.91 0.70 0.64 0.60 0.64 0.68 0.48
0.26 0.62 0.46 0.15 0.46 0.39 0.44 0.29
70 68 66 23 77 61 65 60
0.12 0.41 0.32 0.59 0.23 0.33 0.18 0.13
32 45 46 92 38 52 26 27
organic N %ofN
%'
0.25 0.50 0.38 0.05 0.37 0.31 0.50 0.35
68 55 54 8 62 48 74 73
"Depth to top of sample: s denotes spent shale from Fischer assay; t indicates that sample was treated first with HC1 and then with NaOC1. *By sealed-tube digestion + HF treatment. Standard deviation is estimated to be 0.020 by the method of Youden (6). cBy sealed-tube digestion only. Data from ref 1. Standard deviation is estimated to be 0.067 by the method of Youden ( 6 ) . dData from ref 1. Standard deviation is estimated to be 0.019 by the method of Youden (6). eBy difference between total N and fixed NHat-N because exchangeable NHdt-N is negligible.
N HF:0.2 N HC1. The tube was stoppered and shaken on a mechanical shaker for 16 h. At the end of the shaking period no solid material remained. Three drops of thymol blue indicator (1%alcoholic solution) were added, and the pH was adjusted to the first color change of the indicator by cautious addition of 5 N NaOH. The solution became cloudy upon addition of the NaOH solution. The mixture was transferred to a 100-mL Kjeldahl distillation flask, and the pH was adjusted by adding 5 N NaOH sufficiently past the second color change of the indicator that the color remained blue throughout the distillation which followed. The distillation and determination of NH, were carried out by using a method described elsewhere (5). The flask containing the sample was attached to a steam distillation unit, and 25 mL of distillate was collected with 5 mL of boric acid-indicator solution. The NH3 content was determined by titrating with 0.005 N HZSOb R E S U L T S AND DISCUSSION When sealed-tube digestion was followed by HF treatment, the total N content of the HC1- and NaOC1-treated sample of spent shale from Fischer assay was found to be 0.64% rather than the 0.15% found by using sealed-tube digestion alone (Table I); thus, 4 times more N was extracted from this sample when H F treatment was added. Because extraction of total
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N from samples of oil shale treated with HC1 and NaOCl is incomplete by sealed-tube digestion alone, the question arises as to the ComPleteneSs of extraction from untreated samples. Therefore, total N contents of some untreated oil shale S a m ples from Colorado Core Hole No. 1 were determined by the new procedure, and the results are compared with those obtained earlier (1) by using sealed-tube digestion alone (Table I). Applying the new procedure increases the values for total N by an average of 23 % . The newly determined content of total N, value of fixed NH4+-N reported earlier (I),and organic N content based upon the new values for total N are given in Table I. All values are the mean of a t least three determinations. Estimates of standard deviation are based upon all replicates of all samples (6). Total N averages 0.64% in the samples of raw shale rather than 0.43% as reported ( I ) . Because total N is larger, fixed NH4+-Nrepresents a smaller percentage of total N (average of 39% for raw shale rather than 58%). That fixed NH4*-N not extracted by sealed-tube digestion is released by H F provides support for the idea that it is tightly held within silicate lattices.
ACKNOWLEDGMENT I am grateful to D. L. Lawlor of the Laramie Energy Technology Center (now Western Research Institute) for providing samples of the raw and retorted shale.
LITERATURE CITED (1) Cooper, J. E.; Evans, W. S. Science (Washington, D.C.)1983, 209, 492-493. (2) Stevenson, F. J. Anal. Chem. 1960, 32, 1704-1706. (3) Stevenson, F. J.; Cheng, C.-N. Geochim. Cosmochim. Acta 1972, 36, 653-67 1. (4) Silva, J. A.; Bremner, J. M. Soil Sci. Soc. Am. Proc. 1966, 30, 587-594. (5) Keeney, D. R.; Nelson, W. D. In Methods of Soil Analysis, Part.?, 2nd ed.; Page, A. L., Ed.; American Society of Agronomy: Madison, WI, 1982; pp 643-698. (6) Youden, W. J. Statistical Methods for Chemists; Wiley: New York, 1951; pp 15-17.
James E. Cooper Department of Geology The University of Texas a t Arlington Arlington, Texas 76019 RECEIVED for review January 3,1986. Accepted March 3,1986.
Macrocyclic Polyamines as Selective Eluting Reagents for Multivalent Anions in Anion Exchange Chromatography Sir: In the separation of anions by means of anion exchange chromatography, the stationary phase strongly or irreversibly retains multivalent anions, and their effective elution with conventional electrolyte solutions is difficult to achieve without affecting the retention of monovalent anions (1). Thus, selective eluting reagents for the highly charged anions are desired in order to extend the utility of anion exchange chromatography. Recently, Dietrich et al. and Kimura et al. have reported that polyprotonated macrocyclic polyamines strongly bind with trivalent and tetravalent anions through electrostatic interactions although their interactions with monovalent anions are not so strong (2-4). This recently reported phenomenon will be applicable to selective reduction of the retention for highly charged anions. This correspondence describes the use of the macrocyclic polyamines as selective eluting reagents for highly charged anions in anion exchange chromatography. Macrocyclic polyamines, 1,5,9,13-tetraazacyclohexadecane((16)aneN4)and 1,5,9,13tetraazacycloheptadecane ( (17)aneN4) (Figure l),selectively reduce retention times of benzenepolycarboxylates without influencing the retention of the benzenemonocarboxylate. EXPERIMENTAL SECTION Macrocyclic polyamines, (16)aneN4and (17)aneN4,were prepared according to the reported procedures (5). They were identified by lH NMR and CHN analysis. Benzene-1,2,4-tricarboxylic, benzene-1,3,5-tricarboxylic,and benzene-1,2,4,5tetracarboxylic acids were obtained from Tokyo Kasei Co. and were recrystallized from ethanol or a ethanol-water mixture (1:l). Stock solutions of 1.0 X M of each solute were prepared in water, and sample solutions for injection were prepared by diluting or mixing the stock solutions. Amounts of the solutes injected were 20-200 nmol. Two kinds of mobile phases having almost the same anionic composition and pH were used in order to evaluate the effect of the polyamines on the retention of the polycarboxylates. One contained (16)aneN4or (17)aneN4,but the other did not. One mobile phase containing a macrocyclic polyamine was prepared from stock solutions of lithium perchlorate and the tetrahydro-
chloride of each polyamine and from a Tris buffer. The other mobile phase, the polyamine-free one, was prepared from stock solutions of lithium perchlorate and sodium chloride and from the Tris buffer. Chloride concentrations in the stock solution of sodium chloride and in the Tris buffer were determined by argentometry. For the stock solution of the tetrahydrochloride of each polyamine, concentrations of chloride and the polyamine were determined. The chloride concentrations were determined by argentometry, and the polyamine concentrations were determined by means of titration with a standardized copper(I1) solution. The pH of the mobile phases was maintained at 7.1. The chromatographic system consisted of Gasukuro Kougyo pump, Model APS 5, a Rheodyne 7125 injector (20 wL), and a Mitsumi Scientific UV monitor, Model LDC. Solutes were detected by absorption at 254 nm. The separation of the anions was conducted by using a stainless-steel column (4 mm i.d. X 70 mm) packed with a Diaion CAOBA (strong basic anion exchange resin of porous type, capacity 3.2 mequiv/g of resin) under ambient conditions.
RESULTS AND DISCUSSION The benzenepolycarboxylates used are completely dissociated in the p H region higher than 7.0 (6, 7), and 15- to 18-membered macrocyclic polyamines interact strongly with trivalent and tetravalent anions in the neutral pH region (4). Thus, the pH of the mobile phase was maintained at 7.1. At pH 7.1, (16)aneN4 or (17)aneN4exists predominantly as triprotonated and diprotonated species (7, 8). Figure 2 shows the effect of (16)aneN4 on the retention of the benzenepolycarboxylates. For the sake of comparison, the elution of a monovalent anion, benzoate, was also examined. On the elution with the polyamine-free mobile phase, the solutes eluted within 60 min were benzoate (Bez) and benzene-1,2,4-tricarboxylate(Trt). Benzene-1,3,5-tricarboxylate (Trs) and benzene-l,2,4,5-tetracarboxylate (Pyr)were difficult to elute. The mobile phase containing (16)aneN4,on the other hand, could elute all solutes within 60 min. It is noteworthy that the retention of the monovalent carboxylate, Bez, is little affected by the polyamine; namely, both mobile phases with
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