ANALYTICAL CHEMISTRY, VOL. 51, NO. 4, APRIL 1979
be readily modified (by substituting a nebulizer--burner assembly for the cuvette) t o permit element specific detection.
H. N. T e n n e y and F. E . Sturgis, Ana/. Chem., 26, 946 (1954). J . C. Sternberg and W . Kennard, J . Chromatogr.. 2, 53 (1959). E. T. McGuinness and M. C . Cullen, J . Chem. Educ., 47, A9 (1970). J. G. Gonzales and R. T. Ross, Anal. Lett., 5 , 683 (1972). J. E. Longbottom, Anal. Chem., 44, 111 (1972). S. E. Manahan and D. R . Jones. Anal. Lett., 6 , 745 (1973). F. Fernandez. A t . Absorp. News/., 18(2), 33 (1977). J. C. VanLoon, J. Lichwz, and B. Radzuk, J . Chromatogr., 136, 301 (1977). P. T. Graham, R. V. Lindsey, G. W . Parshall, M. L. Peterson, and G. M. Whitman. J . Am. Chem. SOC.,7 9 , 3416 (1957). R . E. Bozak, J . Chem. Educ., 43, 73 (1966). J. E . Herz, J . Chem. Educ., 43, 599 (1966). D. T. Haworth and T . Liu, J . Chem. Educ., 53, 730 (1976). S.R. Lawson, M.S. Thesis, Marquette University, Milwauk , Wis., 1978. R. Mavrodineanu, "Fbme Spectroscopy", R. Mawodineanu dnd H. Boiteux, Ed., 1965, Part I, p 62.
ACKNOWLEDGMENT T h e authors express their thanks to John Naleway of Marquette University, for his continued support of our research efforts.
LITERATURE CITED Snyder, "Chromatography", 2nd e d . , E. Heftmann, Publishing Corp., New York, 1967, pp 93-96.
(1) L. R .
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Ed., Reinhold
(2) J. F. K. Huber, J . Chromatog. Sci., 7 , 172 (1969). (3) R. D. Conlon. Anal. Chem., 41, 107A (1969). (4) M . N. Munk, J . Chromatog. Sci., 8 , 491 (1970). (5) H. Veening, J . Chem. Educ., 47, A549, A675, A749 (1970). (6) S. H. Byrne, Jr., Modern Practices of Liquid Chromatography", J. J. Kirkland, Ed., Wiley-Interscience.New York, 1971, Chapter 3. (7) M. N. Munk, in "Basic Liquid Chromatography",N. Haden et al., Ed., Varian Aerograph, Palo Alto, Calif., 1971, Chapter 6. (8) J. G. Koen, J. F. K. Huber, H. Poppe, and G. den Boef, J . Chromatogr. Sci., 8 , 192 (1970). (9) D. L. Ford and W. Kennard. J . OilColour Chem. Assoc., 49, 299 (1966).
RECEIVED for review April 5,1978. Accepted January 25,1979. Acknowledgment is made t o the donors of the Petroleum Research Fund, administered by the American Chemical Society, and t o the Committee of Research, Marquette University, for support of this research.
AIDS FOR ANALYTICAL CHEMISTS Microprocessor-Controlled Digital Integrator for Nuclear Magnetic Resonance Measurements F. Morley, I.
K. O'Neill,' M. A. Pringuer,* and P.
B. Stockwell"
Laboratory of the Government Chemist, Cornwall House, Stamford St., London SE 9NQ, United Kingdom
aspects of the integration procedure and performs all the necessary data processing functions. The system which will be described in detail elsewhere (9) is a plug-in retrofit module which does not degrade spectrometer performance. Integration. For integration purposes, the NMR spectrum is divided into discrete zones; a maximum of six zones can be used. Each zone is positioned so that the beginning and end of each zone can be positioned anywhere within the spectrum but must not overlap another zone. The sixth zone is used t o specify a reference peak for quantitative measurements and can be positioned anywhere within the spectrum and not necessarily sequentially with the other zones. As a spectrum is scanned, the position of the zones is detected by a wiper mounted on the pen carriage and a linear transducer mounted along the top edge of the recorder chart. The NMR signal is amplified, fed to a voltage-to-frequency converter, and the output pulses are gated within the integration zone to a five-decade counter. This displays a digital value representing the area of the peak or multiplet of peaks within a zone and is reset to zero between each zone. Spectrometer Control. The spectrometer parameters are optimized manually. A spectrum of the sample is recorded and the various zone positions and the number of zones to be accumulated are entered using the thumb wheel switches, on the integrator front panel. Automatic control is initiated through a teletype command. The various data input is also entered a t this time; namely, the values of the proton equivalent weight of the analyte under test and the weight of the standard used for reference. The microprocessor sets in motion the pen carriage of the recorder (which is linked to the spectrometer field sweep) and at the end of each traverse returns it for a further scan, until the total number of scans reaches a preset level. In addition, the microprocessor causes a dot to be marked on the chart at the start and end of each integration zone. Data Processing. As each zone is integrated, the integral value is passed to the computer memory store where a running average is maintained of each zone integration value. Then the proton equivalent weights (p.e.w.) for each zone and the ave-aged in-
Continuous wave nuclear magnetic resonance (NMR) spectroscopic observation of 'H nuclei ( I ) is an inherently quantitative phenomenon that has been used for the analysis of pharmaceuticals ( Z ) , polymers ( 3 ) ,and many other materials. Commercial NMR spectrometers, however, are designed primarily for qualitative measurements. Many improvements in sensitivity and resolution have been incorporated into instruments in recent years but there have been no significant advances in integration techniques. Experience of quantitative 'H N M R analyses ( 4 , 5 ) a t the Laboratory of the Government Chemist indicated t h a t significant effort could be saved through automation of the spectrometer integration functions. Commercially available gas chromatographic integrators were unsuitable because data output from the scanning of sequential N M R peaks was too rapid. Subsequently, a digital integrator was constructed (6, 7), primarily to handle N M R data. This paper describes an evaluation of a n automatic system for quantitative measurements, using a microprocessor to effect the various control and data processing steps. A similar system has been constructed (8) for the determination of fluorine by interfacing a commercial computer t o a N M R spectrometer. This is restricted because it will accept only Gaussian peaks free of ringing.
EXPERIMENTAL A JEOL CGO-HL spectrometer was coupled t o the microprocessor controlled integration system shown in Figure 1 . A National Semiconductor IMP 16-C microprocessor controls all 'Presently on secondment to RTZ Services Ltd, York House, Bond Street, Bristol BS1 3PE, United Kingdom. 2Present address, Life Science Research, Stock, Essex CH4 9PE, United Kingdom. 0003-2700/79/0351-0579$01 .OO/O
I
1979 American Chemical Society
580
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