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BRIEFS Multivariate Analysis of Carbon-13 Nuclear Magnetic Resonance Spectra. Identification and Quantification of Average Structures in Petroleum Distillates 49 Two series of distillate fractions from North Sea petroleum samples are investigated using D E P T 13C NMR and multivariate analysis. The content of saturated isoprenoid structures is quantitated and is used to discriminate between the two oils in all fractions. Trond Brekke*, Tanja Barth, Olav M. Kvalheim, and Einar Sletten, Department of Chemistry, University of Bergen, Bergen N-5007, Norway Simultaneous Monitoring for Parent Ions of Targeted Daughter Ions: A Method for Rapid Screening Using Mass Spectrometry/ Mass Spectrometry 56 A screening method used with MS/MS instruments that employ a quadrupole mass filter as the first analyzer is described. Scott A. McLuckey*, Gary L. Glish, and Barry C. Grant, Analytical Chemistry Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6365 Laser Desorption/Fourier Transform Ion Cyclotron Resonance Mass Spectrometry of Polymer Additives 61 The formation of both N a + and K + adducts of the additives allows for the recognition of the quasimolecular ions in a mixture spectrum. In one polyethylene extract, the molecular weights of seven compounds are determined, and two of the compounds are identified. Bruce Asamoto*, Judy R. Young, and Robert J. Citerin, BP Research, Warrensville Research Center, 4440 Warrensville Center Road, Cleveland, OH 44128-2837 Precise Relative Ion Abundances from Fourier Transform Ion Cyclotron Resonance Magnitude-Mode Mass Spectra 70
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The best FT/ICR measure of relative ion abundance is based on least-squares fit to an (unphased) magnitude-mode spectrum. Zhenmin Liang and Alan G. Marshall*, Department of Chemistry, The Ohio State University, 120 West 18th Avenue, Columbus, OH 43210
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Tekmar® P.O. Box 371856 · Cincinnati, OH 45222-1856 (800) 543-4461 Sales · (800) 874-2004 Service CIRCLE 130 ON READER SERVICE CARD 8 A · ANALYTICAL CHEMISTRY, VOL. 62, NO. 1, JANUARY 1, 1990
Determination of Organic Acids in Dilute Hydrocarbon Solution Using Poly(ethylenimine)-Coated Piezoelectric Crystals 76 Piezoelectric crystals coated with a water-soluble basic polymer are used as sensing devices for organic acids dissolved in neutral hydrocarbons. Their application as selective LC detectors is demonstrated. John M. Charlesworlh, DSTO, Materials Research Laboratory, P.O. Box 50, Ascot Vale, Victoria, Australia 3032
