Cathodic reduction of thyroxine and related compounds on silver

BriefsCathodic Reduction of Thyroxine and Related Compounds on Silver 1202 The reduction of thyroxine, liothyronine, diiodothyronine, diiodotyrosine, and monoiodotyrosine is studied on a rotating silver disk electrode. Only one convective diffusion-controlled reduction wave is observed. Mizuho Iwamoto, Andrew Webber, and Robert A.Osteryoung*, Department of Chemistry, State University of New York at Buffalo, Buffalo, N.Y. 14214 Anal. Chem., 56 (1984)Determination of Gaseous Hydrogen Sulfide byCathodic Stripping Voltammetry afterPreconcentration on a Silver Metalized PorousMembrane Electrode 1206A procedure is described for determination of gaseoushydrogen sulfide by constant potential collection as silversulfide on a porous silver electrode. The silver sulfide isdetermined by cathodic stripping voltammetry.Frantisek Opekar and Stanley Bruckenstein*, ChemistryDepartment, State University of New York at Buffalo, Buffalo,N.Y. 14214 Anal. Chem.,56 (1984)Precision in Differential Pulse and Alternate DropDifferential Pulse Polarography 1209The repeatability and the reproducibility of these twotechniques are evaluated. A theory that predicts betterprecision for ordinary DPP is experimentally verified.Per Baecklund, Leif Nyholm, and Gunnar Wikmark*, Department of Analytical Chemistry, Uppsala University, P.O. Box 531, S-751 21 Uppsala, Sweden Anal. Chem.,56 (1984) Estimation of Electrochemical Charge TransferParameters with the Kalman Filter 1214 The Potter-Schmidt formulation of the Kalman filter iscoupled to a finite difference digital simulation to estimate states and parameters in linear scan voltammograms.Teri F. Brown, Department of Chemistry, University of Idaho, Moscow, Idaho 83843, and Donna M. Caster and Steven D.Brown*, Department of Chemistry, Washington State University,Pullman, Wash. 99164-4630 Anal. Chem., 56 (1984) Normal Pulse Cathodic Stripping Voltammetry ofEthynylestradiol 1222 The cathodic stripping voltammetry of ethynylestradiol is investigated using microprocessor-based instrumentation. A suitable method is described at pharmaceutical levels of 4 Χ 10~8 Μ that overcomes interference from both organic and inorganic excipients.A. M. Bond* and I. D. Heritage, Division of Chemical andPhysical Sciences, Deakin University, Victoria 3217, Australia, and M. H. Briggs, Division of Biological and Health Sciences, Deakin University, Victoria 3217, Australia Anal. Chem., 56 (1984)* Corresponding author• Supplementary material availableNonlinear Least-Squares Analysis of Double PotentialStep Electrochemical Data 1226 A nonlinear, least-squares method is presented for extracting the homogeneous rate constant from double potential step chronoamperometric data for an EC irr system.Floyd E. Woodward*, Richard D. Goodin, Patrick J. Kinlen, and John H. Wagenknecht, Monsanto Company, 800 North Lindbergh Boulevard, St. Louis, Mo. 63167Anal. Chem.,56 (1984)Gradient Liquid Chromatography/Mass Spectrometry Using Microbore Columns and a Moving Belt Interface 1229 Spray deposition onto a moving belt allows operation with microbore columns over a wide range of flow and solvent conditions. Extra-column variances as low as 0.7 μΙ;2 are obtained. M. J. Hayes, H. E. Schwartz, Paul Vouros*, and B. L. Karger*, Barnett Institute of Chemical Analysis and Department of Chemistry, Northeastern University, Boston, Mass. 02115, and A. D. Thruston, Jr., and J. M. McGuire, Athens Environmental Research Laboratory, U.S. Environmental Protection Agency, Athens, Ga. 30613 Anal. Chem.,56 (1984) Determination of Nonderivatized Peptides by Thermospray Liquid Chromatography/Mass Spectrometry 1236 Peptides are directly extracted from solution by thermospray ionization without derivatization. The mass spectra show protonated and alkali-attached ions withoutfragmentation. The applicability of the method for chromatographic detection of peptides is discussed.David Pilosof, Hee Yong Kim, Douglas F. Dyckes, and Marvin L. Vestal*, Department of Chemistry, University of Houston,Houston, Tex. 77004 Anal. Chem., 56 (1984) Adsorption Isotherms of Polycyclic AromaticHydrocarbons on Asbestos Chrysotile by High-Pressure Liquid Chromatography 1240 The method permits determination of different isothermsmore easily and rapidly than by static adsorption. Theinfluence of HPLC solvent dryness is demonstrated and an error of <5% for the reproducibility is estimated.Hugues Ménard*, Luc Noël, Frank M. Kimmerle, Lyne Tousignant, and Maryse Lambert, Department of Chemistry, Université de Sherbrooke, Sherbrooke, Québec, Canada J1K 2R1 Anal. Chem.,56 (1984)Separation and Characterization of Very LargeNeutral Polycyclic Molecules in Fossil Fuels by Microcolumn Liquid Chromatography and Mass Spectrometry 1243 More than 400 neutral polycyclic aromatic substances,within the range of 5-9 ring structures, are tentativelyidentified by MS following chromatographic fractionationand high-efficiency microcolumn LC analysis.Milos Novotny*, Akio Hirose, and Donald Wiesler, Department of Chemistry, Indiana University, Bloomington, Ind.47405 Anal. Chem., 56 (1984) Packed Microcapillary Columns with 10-μιτι Silica Gelfor Liquid Chromatography 1249Chromatographic separations with high theoretical platevalues are demonstrated. The relation of height equivalentto theoretical plate and linear velocity for these columns isthe same as that for conventional columns.Takao Tsuda*, Isao Tanaka, and Genkichi Nakagawa,Laboratory of Analytical Chemistry, Nagoya Institute ofTechnology, Gokiso-cho, Showa-ku, Nagoya 466, JapanAnal. Chem., 56 (1984) Open Tubular Liquid Chromatography with ThermalLens Detection 1252Single-beam thermal lens detection is demonstrated for usewith open tubular liquid chromatography.Michael J. Sepaniak*, John D. Vargo, Charles N. Kettler, and Michael P. Maskarinec, Department of Chemistry, University ofTennessee, Knoxville, Tenn. 37996-1600, and AnalyticalChemistry Division, Oak Ridge National Laboratory, Oak Ridge,Tenn. 37830 Anal. Chem.,56 (1984)Surface Adsorption and ion Exchange inChromatographic Retention of Ions on Low-CapacityCation Exchangers 1258Sorption of an organic cation onto surface sulfonated cation exchangers is quantitatively explained by twoprocesses: ion exchange and surface adsorption.Robert A. Hux and Frederick F. Cantwell*, Department ofChemistry, University of Alberta, Edmonton, Alberta, CanadaT6G 2G2 Anal. Chem., 56 (1984) Gradient Elution Ion Chromatographic Determination of Inorganic Anions Using a Continuous Gradient1264Gradient elution ion chromatographic methods are described for the determination of F~, Cl~, Br -, and I~within 20 min. Techniques for the preparation of thecontinuous gradients and retention times for 18 anions aregiven. James G. Tarter, Department of Chemistry, North Texas State University, Denton, Tex. 76203 Anal. Chem., 56 (1984) Comparison of Methods for Reconstructing Chromatographic Data from Liquid Chromatography/ Fourier Transform Infrared Spectrometry 1268 Time domain chromatographic reconstruction methods areused to analyze LC/FT-IR data. The results are compared to those of spectral domain chromatographic reconstructions. Simplex optimization and quantitative analysis results also are discussed. Ching Po Wang, Daniel T. Sparks, Stephen S. Williams, andThomas L. Isenhour*, Department of Chemistry, University of North Carolina, Chapel Hill, N.C. 27514 Anal. Chem., 56 (1984)Determination of Lipid Class Concentrations in Seawater by Thin-Layer Chromatography with Flame Ionization Detection 1272A three-step Chromarod development separates seawater lipids into seven classes. Between 0.2 and 20 μg, neutral lipid FID response is curvilinear; at 3 μ%, intrarod precision is 5 to 15%. Roger P. Delmas, Christopher C. Parrish, and Robert G. Ackman*, Canadian Institute of Fisheries Technology, Technical University of Nova Scotia, P.O. Box 1000, Halifax, Nova ScotiaB3J 2X4, Canada Anal. Chem., 56 (1984)Chemical Class Separation of Organics in Shale Oil by Thin-Layer Chromatography 1277The method provides significant advantages over more conventional separation schemes, particularly with respectto time required, number of fractions obtained, and ease of operation. Timothy G. Harvey, Trevor W. Matheson*, and Kerry C. Pratt, CSIRO Division of Materials Science, Catalysis and Surface Science Laboratory, University of Melbourne, Parkville, 3052,Victoria, Australia Anal. Chem., 56 (1984)Determination of Aldicarb, Aldicarb Oxime, andAldicarb Nitrile in Water by Gas Chromatography/Mass Spectrometry 1281 Determination of the thermally labile carbamate pesticide aldicarb by GC/MS is facilitated by the use of a short capillary column. The limits of detection for aldicarb, aldicarb oxime, and aldibcarb nitrile are 0.3 ng, 1.2 ng, and0.05 ng, respectively.Michael L. Trehy and Richard A. Yost*, Department ofChemistry, University of Florida, Gainesville, Fla. 32611, andJohn J. McCreary, Department of Environmental Engineering Science, University of Florida, Gainesville, Fla. 32611 Anal. Chem., 56 (1984)Determination of Elemental Iodine by Gas Chromatography with Electron Capture Detection 1285 A GC/ECD technique for determination of elemental iodine is developed with a detection limit of 39 ng, anaccuracy of 23%, and precision of 12%.S. J. Fernandez*, L. P. Murphy, and R. A. Rankin, Exxon Nuclear Idaho Co., P.O. Box 2800, Idaho Falls, Idaho 83401Anal. Chem., 56 (1984)Collection and Determination of Volatile Organic Mercury Compounds in the Atmosphere by GasChromatography with Microwave Plasma Detection1288A method is described for t h e collection a n d determination of atmospheric organic mercury compounds t h a t is >95% efficient, with a detection limit for real samples of 0.1 ng/m 3.David S. Ballantine, Jr.*, and William H. Zoller, Department of Chemistry, University of Maryland, College Park, Md. 20742Anal. Chem.,56 (1984)Multiple-Parameter Optimization of aHydrogen-Atmosphere Flame Ionization Detector1293 A two-level factorial analysis of both positive a n d negativeH A F I D operating modes is performed t o verify i m p o r t a n t parameters a n d p a r a m e t e r interactions. This information is used as a guide in constructing simplex searches for o p t i m u m p a r a m e t e r values.Dennis G. McMinn, Department of Chemistry, GonzagaUniversity, Spokane, Wash. 99258, and Randy L. Eatherton and Herbert H. Hill, Jr.*, Department of Chemistry, Washington State University, Pullman, Wash. 99164-4630Anal. Chem.,56 {1984)Temperature Dependence of Plasma Chromatography of Aromatic Hydrocarbons 1298 T h e t e m p e r a t u r e dependence of t h e reduced mobilityp a r a m e t e r of aromatic molecules in plasmachromatography is investigated using ions produced bylaser photoionization a n d t h e N i β source reactortechnique. David M. Lubman, Department of Chemistry, University of Michigan, Ann Arbor, Mich. 48109 Anal. Chem. ,56 (1984)Laboratory Data Base for Isomer-SpecificDetermination of Polychlorinated Biphenyls 1303An isomer-specific procedure for t h e determination of polychlorinated biphenyls is described using n-alkyltrichloroacetates as retention index marker compounds. Retention indexes are reproducible in t h e range of ±1.0 to ±0.05 depending on t h e specific isomer.Ted R. Schwartz*, Randolph D. Campbell, David L. Stalling, Robert L. Little, Jimmie D. Petty, James W. Hogan, and Edwin M. Kaiser, Columbia National Fisheries ResearchLaboratory, U.S. Fish and Wildlife Service, Route 1, Columbia,Mo. 65201 Anal. Chem.,56 (1984)Pattern Recognition for Classification and Determination of Polychlorinated Biphenyls in Environmental Samples 1308T h e partial least squares in latent variables m e t h o d isapplied to gas chromatography d a t a of polychlorinatedbiphenyls. An Arochlor sample from a waste d u m p is correctly classified a n d its composition determined.W. J. Dunn III*, Department of Medicinal Chemistry andPharmacognosy, College of Pharmacy, University of Illinois atChicago, 833 South Wood St., Chicago, 111. 60680, and D. L.Stalling, T. R. Schwartz, J. W. Hogan, and J. D. Petty, U.S.Fish and Wildlife Service, Columbia National Fisheries ResearchLaboratory, Route 1, Columbia, Mo. 65201, and Erik Johansson and Svante Wold, Research Group for Chemometrics, Umea University, S 901 87 Umea, Sweden Anal. Chem., 56 (1984)Determination of Topological Similarity of Carbon Atoms in the Simulation of Carbon-13 NuclearMagnetic Resonance Spectra 1314 P a r a m e t e r s are derived t h a t enable t h e similarity of carbon environments to be computed.Gary W. Small and Peter C. Jurs*, Department of Chemistry, The Pennsylvania State University, 152 Davey Laboratory,University Park, Pa. 16802 Anal. Chem. ,56(1984)Carbon-13 Nuclear Magnetic ResonanceSpectrometric Study of Wood and Wood Pulping withCross Polarization and Magic-Angle Spinning 1323A m e t h o d for determining lignin content in wood a n d wood pulps by 13C N M R is presented, a n d 13C N M R spectra ofwood pulps prepared by some of t h e more important procedures are discussed.James F. Haw and Gary E. Maciel*, Department of Chemistry, Colorado State University, Fort Collins, Colo. 80523, and Herbert A. Sehroeder, Department of Forest and Wood Sciences, Colorado State University, Fort Collins, Colo. 80523Anal. Chem.,56 (1984) Determination of Atmospheric Degradation Productsof Toluene by Tandem Mass Spectrometry 1329Toluene in several deuterated forms is subjected to simulated atmospheric oxidation. T h e products, whichhave never been adequately characterized before, areseparated a n d identified by triple-quadrupole mass spectrometry.Robert J. O'Brien* and Bruce E. Dumdei, Chemistry Department and Environmental Sciences Doctoral Program, Portland State University, Portland, Ore. 97207, and Susan V.Hummel and Richard A. Yost, Chemistry Department,University of Florida, Gainesville, Fla. 32611 Anal. Chem., 56 (1984) Identification of Partially Hydrogenated Nitrogen-Containing Polycyclic Aromatic Hydrocarbons in Coal Liquids by Tandem Mass Spectrometry 1335 M S /M S is used to identify partially hydrogenatednitrogen-containing polynuclear aromatic hydrocarbons of four different structural types in a nitrogen-base extract of a coal liquid.K. V. Wood*, Engine/Fuel Laboratory, Institute ofInterdisciplinary Engineering, Chemistry Building, PurdueUniversity, West Lafayette, Ind. 47907, and C. E. Schmidt, U.S. Department of Energy, Pittsburgh Energy Technology Center, P.O. Box 10940, Pittsburgh, Pa. 15236, and R. G. Cooks,Department of Chemistry, Purdue University, West Lafayette, lnd. 47907, and B. D. Batts, School of Chemistry, McQuarieUniversity, North Ryde, New South Wales 2113, Australia Anal. Chem.,56 (1984) Fingerprinting of Gasoline in Combustion Aerosols by Pyrolysis-Mass Spectrometry with Factor Analysis 1339 Volatile compounds from smoke aerosols are trapped on charcoal glued to a Curie-point wire. T h e r m a l desorption of t h e volatile compounds into a mass spectrometer generates a fingerprint t h a t can be used for t h e detection of gasoline in arson samples. Rushung Tsao and Kent J. Voorhees*, Department of Chemistry and Geochemistry, Colorado School of Mines, Golden,Colo. 80401 Anal. Chem.,56 (1984)Matrix Effect in Determination of 2,3,7,8-Tetrachlorodibenzodioxin by Mass Spectrometry 1344 A matrix effect h a s been uncovered during trace analysis of samples by G C /M S. Its mechanism of action is primarily connected t o source instabilities a n d is a p p a r e n t only if an i n d e p e n d e n t m e a s u r e m e n t is m a d e t o monitor its presence. Yves Tondeur, Phillip W. Albro, J. Ronald Hass*, Donald J. Harvan, and Joanna L. Schroeder, Department of Health and Human Services, National Institute of Environmental Health Sciences, Laboratory of Molecular Biophysics, P.O. Box 12233,Research Triangle Park, N.C. 27709 Anal. Chem.,56 (1984) Detection of Trace Elements with Resonance Ionization and Time-of-Flight Mass Spectrometry1348I n s t r u m e n t a t i o n involving resonance ionization a n d time-of-flight mass spectrometry is described for t h e quantitative isotopic identification of trace elements. Detection of chromium in stainless steel is presented. Mary W. Williams*, Daniel W. Beekman, John B. Swan, and Edward T. Arakawa, Health and Safety Research Division, Oak Ridge National Laboratory, Oak Ridge, Tenn. 37830Anal. Chem.,56 (198)Determination of Extent of Silylation by IsotopeCluster Analysis of a Single Mass Spectrum 1351Isotope clusters in t h e mass spectrum of a silylated organiccompound m a y be used t o calculate t h e extent of silylationand thereby determine t h e molecular weight of t h e p a r e n tcompound.Robert J. Anderegg, Anna Brajter-Toth, and J o h n P. Toth*,Department of Chemistry, University of Maine, Orono, Me. 04473Anal. Chem.,56 (1984)Diophantine Approach to Isotopic AbundanceCalculations1356 A computer program based on a Diophantine algorithm isdeveloped for calculating t h e isotopic a b u n d a n c e of a givenformula containing polyisotopic elements.Chang S. Hsu, Analytical Division, Exxon Research and Engineering Co., Clinton Township, Route 22 East, Annandale, N.J. 08801 Anal. Chem., 56 (1984) Embedded Ion Exchange Beads as Standards for Laser Microprobe Mass Analysis of Biological Specimens 1362 A new internal s t a n d a r d system, based on loadedChelex-100 ion-chelating resin beads coembedded a n d cut together with t h e specimen, is proposed for L A M M A of tissue-bound elements. Armand H. Verbueken and René Ε. Van Grieken*, Department of Chemistry, University of Antwerp (U.I.A.), B-2610Wilrijk, Belgium, and Guido J. Paulus, Department of Pathology,University of Antwerp (U.I.A.), B-2610 Wilrijk, Belgium, andWim C. de Bruijn, Centre for Analytical Electron Microscopy,Laboratory for Electron Microscopy, 2333 AA Leiden, TheNetherlands Anal. Chem.,56 (1984)Static Secondary Ion Mass Spectrometry for Study of Surface Hydrolysis of Poly( ferf-butyl methacrylate) 1371 T h e use of static S I M S t o detect a n d quantify surface modification/degradation effects on a polymer is demonstrated a n d compared with ESCA.Joseph A. Gardella, Jr., Frank P. Novak, and David M.Hercules*, Department of Chemistry, University of Pittsburgh,Pittsburgh, Pa. 15260 Anal. Chem.,56 (1984)Simultaneous Determination of 10 Elements inWastewater, Plasma, and Bovine Liver by Inductively Coupled Plasma Emission Spectrometry withElectrothermal Atomization 1376 A sample introduction system is described for t h e electrothermal atomization of liquid a n d solidmicrosamples for multiple element assays by inductively coupled argon plasma emission spectrometry.William M. Blakemore*, Patrick H. Casey, and William R. Collie, Department of Health and Human Services, Food andDrug Administration, National Center for Toxicological Research, Jefferson, Ark. 72079 Anal. Chem.,56 (1984)Inductively Coupled Plasma SpectrometricDetermination of Minor Elements in Concentrated Brines following Precipitation 1379 A separation procedure for t h e analysis of concentrated brines is presented. Detection limits as low as 4 n g /m L are obtained for many elements. T h e significance of complex formation is discussed.Alan S. Buchanan, C.R.A. Technology, 55 Collins Street, Melbourne, 3001, Victoria, Australia, and Philip Hannaker*, Department of Geology, School of Earth Sciences, University ofMelbourne, Parkville, 3052, Victoria, AustraliaAnal. Chem.,56 (1984)Estimation of Oxygen Pressure in Graphite Furnacesfor Atomic Absorption Spectrometry 1382A scale for p o 2 as a function of t e m p e r a t u r e is proposed for semienclosed M a s s m a n n -t y p e graphite furnaces. Anders Cedergren*, Wolfgang Freeh, and Erik Lundberg, Department of Analytical Chemistry, University of Umeâ,S-901 87 Umeâ, Sweden Anal. Chem.,56 (1984)Mechanism of Atomic Vapor Loss for Aluminum and Potassium in a Constant-Temperature Carbon-TubeFurnace 1388 T h e atomic absorption study compares t h e rate of vapor loss in glassy carbon vs. graphite furnace tubes. T h e effect of t h e analyte's absorption from gas into graphite, followed by its reevaporation, is described. Yansheng Zheng*, Ray Woodriff, and J o h n A. Nichols, Montana State University, Department of Chemistry, Bozeman, Mont. 59717 Anal. Chem., 56 (1984)BriefsPolypropylene as an Adsorbent for Trace Organics in Water 1436 Polypropylene is evaluated as a solid adsorbent for t h e trace enrichment of organic compounds in aqueoussolution, a n d molecular fluorescence spectrometry is used to study pyrene adsorbed on this phase.Michael R. Rice and Harvey S. Gold*, Department of Chemistry, University of Delaware, Newark, Del. 19716Anal. Chem., 56 (1984)Simplex Optimization by Advance Prediction for Single-Element Instrumental Neutron ActivationAnalysis 1440A computational m e t h o d is developed for t h edetermination of o p t i m u m conditions for single-elementinstrumental neutron activation analysis by advanceprediction a n d simplex optimization.Donald D. Burgess* and Patrick Hayumbu, Department ofChemistry, McMaster University, Hamilton, Ontario L8S 4K1, Canada Anal. Chem., 56 (1984) Reliability of Standard Rate Constants for RapidElectrochemical Reactions 1444 A m e t h o d is outlined to test t h e reliability of s t a n d a r d rate constants, k s , for rapid electrode reactions evaluated with electrochemical perturbation techniques.Thomas Gennett and Michael J. Weaver*, Department of Chemistry, Purdue University, West Lafayette, Ind. 47907Anal. Chem., 56 (1984) Cyclic Voltammetry of Organic and Inorganic JV-Chloramines in Aqueous Solution1449Cyclic voltammetry in aqueous acid (p H = 2) distinguishes R 2NC1, RHNC1, RNC12, a n d Cl 2. T h e electrode response is linear for concentrations of oxidant above 2 X 10~4 M.F r a n k E. Scully, Jr.*, Donald M. Oglesby, and Henry J. Buck, Alfriend Chemical Laboratories, Old Dominion University,Norfolk, Va. 23508. Anal. Chem., 56 (1984) Correlation of Elution Orders in Different Liquid Chromatographic Systems without AnalyteIdentification 1452 • A scheme for correlating chromatograms for a given set of unidentified analytes using different columns or different eluents is presented.Robert E. Synovec and Edward S. Yeung*, Department of Chemistry and Ames Laboratory, Iowa State University, Ames, Iowa 50011 Anal. Chem., 56 (1984)Quantitative Ion Chromatography without Standards by Conductivity Detection 1457A conductivity detector is used to determineconcentrations of ions in LC without analyte identification.An average accuracy of ±2% a n d a detectability of 11 ng are obtained.Steven A. Wilson, Edward S. Yeung*, and Donald R. Bobbitt, Department of Chemistry and Ames Laboratory, Iowa StateUniversity, Ames, Iowa 50011 Anal. Chem., 56 (1984)Nonequilibrium Effects in Sedimentation Field Flow Fractionation 1461 Mass transfer limitations are n o t predicted by t h eequilibrium sedimentation field flow fractionation (SFFF) theory. As a result, in fast S F F F separations small particles sometimes appear smaller, a n d large particles appear larger, t h a n predicted.W. W. Yau* and J. J. Kirkland, E. I. du Pont de Nemours & Company, Central Research & Development Department, Experimental Station, Wilmington, Del. 19898Anal. Chem., 56 (1984)Liquid Chromatography Detection at the Second Harmonic of the Modulated Thermal Lens 1467A t h e r m a l lens response is detected at t h e second harmonic of t h e modulation frequency of t h e generating laser, allowing sensitive chromatographic detection with one laser. Teng-Ke Joseph Pang and Michael D. Morris*, Department of Chemistry, University of Michigan, Ann Arbor, Mich. 48109Anal. Chem., 56 (1984) Nuclear Magnetic Resonance Spectrometry of Alkyl Ligands Immobilized on Reversed-Phase LiquidChromatographic Surfaces 1470 Spin-lattice relaxation times are measured for reversed-phase chromatographic surfaces. For t h e terminal position, rotation about t h e end C-C b o n d seems to b e a major factor to relaxation.R. K. Gilpin* and M. E. Gangoda, Department of Chemistry,Kent State University, Kent, Ohio 44242 Anal. Chem. ,56(1984)Minicomputer-Based Multichannel Signal Averager for Acquisition of Weak and Transient Mass Spectra1474 T h e system is used t o acquire high- a n d low-resolution spectra from field desorption, fast atom b o m b a r d m e n t , electron ionization, and chemical ionization runs with accuracies averaging 5 p p m for high-resolution measurements.Charles R. Snelling, Jr., J. Carter Cook, Richard M. Milberg, M a r k E. Hemling, and Kenneth L. Rinehart, Jr.*, School of Chemical Sciences, University of Illinois, Urbana, 111. 61801Anal. Chem., 56 (1984)Supercritical Fluids as Spectroscopic Solvents forThermooptical Absorption Measurements 1481T h e r m a l lens and photothermal deflection measurements m a d e in CO2 near its critical point are found to be 100times more sensitive t h a n comparable measurements madein CCU. R. A. Leach and J. M. Harris*, Department of Chemistry,University of Utah, Salt Lake City, Utah 84112Anal. Chem.,56 (1984)BriefsStatistical Uncertainties of End Points at IntersectingStraight Lines 1487 Procedures are described for calculating statisticaluncertainties of titration curve end points, which are defined by t h e intersections of straight line segments. Lowell M. Schwartz* and Robert I. Gelb, Department of Chemistry, University of Massachusetts, Boston, Mass. 02125Anal. Chem., 56 (,1984) Analysis of Skin Lipids for Halogenated Hydrocarbons1492 T h e analysis of skin lipids, passively collected, shows potential applicability as an indicator of body burden of halogenated hydrocarbons.Mary S. Wolff, Environmental Sciences Laboratory, Mount Sinai School of Medicine of The City University of New York, 1 Gustave L. Levy Place, New York, N.Y. 10029 Anal. Chem., 56 (1984)Measurement of Atmospheric Peroxy Radicals by Chemical Amplification 1496 A new technique for m e a s u r e m e n t of atmospheric a n dlaboratory-generated peroxy radicals is presented. Analysis yields a precision of 1.1% and a n estimated accuracy of ±50%. Christopher A. Cantrell, Donald H. Stedman*, and Gregory J.Wendel, Department of Chemistry, The University of Michigan,Ann Arbor, Mich. 48109 Anal. Chem., 56 (1984)Theoretical and Experimental On-Line Analysis ofMultistate Melting of Polymers by DifferentialScanning Microcalorimetry 1502 A differential scanning calorimeter is interfaced to a microcomputer, a n d tested on cytochrome c a n d ribonuclease A solutions. D S C scans can bebaseline-flattened, smoothed, a n d analyzed into <10 melting transitions.Lee-Hong Chang, Shi-Jiang Li, Tom L. Ricca, and Alan G. Marshall,* Department of Chemistry, The Ohio State University, Columbus, Ohio 43210 Anal. Chem., 56 (1984)Postcolumn Addition of Buffer for Thermospray LiquidChromatography/Mass Spectrometry Identification of Pesticides 1507 M e t h o d s for postcolumn addition are evaluated a n doptimized. T h e r m o s p r a y H P L C /M S using gradient elution and postcolumn buffer addition is d e m o n s t r a t e d for determination of pesticides.Robert D. Voyksner*, Joan T. Bursey, and Edo D. Pellizzari, Analytical and Chemical Sciences, Research Triangle Institute, P.O. Box 12194, Research Triangle Park, N.C. 27709Anal. Chem., 56 (1984)Correspondence Phthalocyanine-Containing Chemically Modified Electrodes for Electrochemical Detection in LiquidChromatography/Flow Injection Systems 1514 Kelvin M. Korfhage, K. Ravichandran, and Richard P. Baldwin*, Department of Chemistry, University of Louisville,Louisville, Ky. 40292 Anal. Chem., 56 (1984)Consequences of Light Beam Misalignment in Background Corrected Atomic AbsorptionSpectrometers 1517 Darryl D. Siemer, Westinghouse Idaho Nuclear Co., Inc., P.O. Box 4000, Idaho Falls, Idaho 83403 Anal. Chem., 56 (1984)Secondary Ion Mass Spectrometric Analysis of Polymer and Coal Surfaces for Trace InorganicElements 1519 N. S. Mclntyre* and W. J. Chauvin, Surface Science Western Laboratory, Faculty of Science, University of Western Ontario, London, Ontario N6A 3K7, Canada, and R. R. Martin,Department of Chemistry, University of Western Ontario, London, Ontario N6A 5B7, Canada Anal. Chem., 56 (1984) Aids for Analytical Chemists Liquid Chromatography of Cephalosporin C onSubstituted Polystyrene Resins 1521 Daniel Sacco* and Edith Dellacherie, Laboratoire de Chimie-Physique Macromoléculaire, C.N.R.S.—E.R.A. 23, ENSIC-1, rue Grandville, 54042 Nancy Cedex, France Anal. Chem., 56 (1984)Liquid Chromatography of Phenolic Compounds on aMicrobore Anion Exchange Resin Column 1525Krishnat P. Naikwadi, Souji Rokushika*, and HiroyukiHatano, Department of Chemistry, Faculty of Science, KyotoUniversity, Sakyo-ku, Kyoto 606, Japan Anal. Chem., 56 (1984) Determination of Selenium by Liquid Chromatographywith Spectrofluorimetric Detection 1527 Yasuyuki Shibata*, Masatoshi Morita, and Keiichiro Fuwa, National Institute for Environmental Studies, 16-2 Onogawa,Yatabe, Tsukuba, Ibaragi 305, Japan Anal. Chem. ,56(1984)Determination of Oxirane Ring Position in Epoxides at the Nanogram Level by Reaction GasChromatography 1530 Athula B. Attygalle and E. David Morgan*, Department of Chemistry, University of Keele, Staffordshire ST5 5BG, United Kingdom Anal. Chem., 56 (1984)。