-303
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300
S C A N NUMBER
Figure 2. Pyrogram (800 'C/lO s) of a used catalyst from an un saturated hydrocarbon reactor
apparently has taken place leading to the formation of some oxygen-containing oligomers which may have subsequentl) deposited in the catalyst. T h e results obtained thus can be useful in providing information pertaining to the reaction mechanisms that might have taken place under the catalytic conditions used. The results can also provide useful information for the regeneration of the used catalyst. Figure 2 shows the pyrogram of another used catalyst recovered from a C 4 olefin reactor. Styrene was observed as the single major pyrolyzate in this case. A small amount of other aromatic fragments was also observed.
It is well known th-it predominantly styrene monomer is recovered in the pyrolysis of polystyrene. The observation of styrene as the single major pyrolyzate in the pyrograrn of a used catalyst thu? indicates polystyrene may have been deposited in the catalyst during the reaction. Styrene monomer must have resulted from dimerization of the original feed. In our experience, a small amount of sample (- 10 mg) has been generally adequate for this type of analysis. The catalyst recovered from the reactor can Le directly used for analysis without any pretreatment or extraction. Valuable information pertaining to the chemical characteristics of the nonvolatile organic deposits can be obtained in less than an hour from the time a catalyst sample is taken from the reactor.
LITERATURE CITED (1) T. A. Gough and C. E R . Jones, Cbromatograaphia, 8, 696 (1975). (2) C.E. R . Jones and G. E. J. Reynolds, B r . Polym. J . , 1, 197 (1969). (3) R . L. Hanson, N . E. Vanderborgh. and D. G. Brookins, Anal. Chem., 49, 390 (1977). (4) R . P. Suggate, N . Z . J . Sci., 15, 601 (1972). (5) J. Romovacek and J. Kubat, Anal. Chem., 40, 1119 (1968). (6) H. L. C. Meuzelaar. P. G. Kistemaker. and M. A . Posthumus. Biomed. Mass Spectrom., 1, 312 (1974). (7) W. B. Stavinoha and S. T. Weintraub, Anal. Chem., 46, 757 (1974). 181 J. P. Anhalt and C. Fenselau. Anal. Chem.. 47. 219 119751. (9) J Shen, Anal Cbem , 49, 886 (1977)
R E ~ E IED \ for review July 25, 1977. Accepted September 6 , 1977. Permission for Publication by the Standard Oil Company (Ohio) is gratefully acknowledged by the authors.
Removal of Europium Shift Reagents from Nuclear Magnetic Resonance Samples Gary
P. Juneau'
Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803
T h e addition of tris-(1.1.1,2,2,3.3-heptafluoro-7,7-di- fractions are collected. Eu(fod)3is eluted in the first two or methyloctane-4.6-dionato)europium(III), Eu(fodI3,to organic three fractions and can be found b> its bright red-orange substrates containing complex-forming functional groups, e.g..
-OH, -NH2, etc., generally results in downfield displacements of NMR signals ( 2 , 2). These lanthanide induced shifts are sometimes useful in separating overlapping signals and obtaining information concerning intermolecular distances. Approximately 15 mg of the substrate is usually required to obtain acceptable spectra using continuous wave NMR spectrometers, and in many instances where only a small quantity of a sample is available, it is quite desirable to recover the sample after completion of the shift reagent experiment. Bisbenzylisoquinoline alkaloids and sesquiterpene lactones have been successfully separated from Eu(fod)s by this method. Reagent grade chloroform and methanol were used in the procedure. The Eu(fod)3 was supplied by Aldrich Chemical Co. and the silica gel by Brinkman Instruments, Inc. Active silica gel, 50-200 mesh, suitable for column chromatography, is swelled with chloroform and poured into a 1 cm X 10 cm column. The solution containing the mixture of the sample plus the shift reagent is carefully poured into the top. The column is then eluted with 25 mL of chloroform followed by 15 mL of 20% methanol in chloroform, and 3-mL
' Present
address, Mississippi State Chemistry Laboratory. Mississippi State, Starkville, Miss. 39759.
fluorescence under short-wave ultraviolet light. The substrate can be located in the methanol-chloroform fractions by fluorescence or by evaporation. After the procedure is completed, no evidence o l the shift reagent can be found in the NMR spectrum of the purified substrate. While this technique permits easy recovery of valuable organic samples for other experiments, it is difficult to ensure the purity and quality of the shift reagent removed. The europium complex should not be re-used because it may be partially hydrolyzed or contaminated with traces of associated nucleophiles such as alcohols, water, etc., from the solvents.
ACKNOWLEDGMENT The author acknowledges George Newkome for his helpful advice.
LITERATURE CITED (1) A Cockerill G Davies, R Harden, and D Rackham, Cbem Rev , 7 3 , 553 (1973) (2) B C Mayo, Cbem SOC Rev , 2 (1) 49 11973)
RECEIVED for review May 16, 1977. Accepted September 9, 1977. This work was supported by the Chemistry gepartment of Louisiana State University a t Baton Rouge.
ANALYTICAL CHEMISTRY, VOL.
49,NO. 14,DECEMBER 1977
2375
