BRlEFS
Perspective: Analytical Biotechnology Isoelectric Focusing in Immobilized pH Gradients
Analysis of Transient Currents and Interfacial Kinetics for Neutral Carrier Membranes 1624 1602
Recently a new generation of stable acrylamido buffers was described, leading to increased resolution and use over a wider pH range of the technique of isoelectric focusing in immobilized pH gradients. This "Perspective" highlights current knowledge and predicts that this separation method will become widely used, particularly in the fields of human and animal genetics. Pier Giorgio Righetti*, Elisabetta Gianazza, Cecilia Gelfi, and Marcella Chiari, Chair of Biochemistry, Faculty of Pharmacy and Department of Biomedical Sciences and Technologies, University of Milan, Via Celoria 2, Milan 20133, Italy and Pranav K. Sinha, Institute of Clinical Chemistry and Biochemistry, Universitâtsklinikum Rudolf Virchow, Spandauer Damm 130, D-1000 Berlin 19, FRG
Articles Strategies for Background Subtraction in Electron Probe Microanalysis/X-ray Compositional Mapping 1612 The dependence of the bremsstrahlung on average atomic number can be used to make an indirect calculation of the background appropriate to each location in an X-ray compositional map. Robert L. Myklebust*, Dale E. Newbury, and Ryna B. Marinenko, Room A121, Chemistry Building, National Institute of Standards and Technology, Gaithersburg, MD 20899 Alkali-Metal and Alkaline-Earth Cation and Proton Selectivities of Dibenzo-14-crown-4 and Its Derivatives in Polymeric Membranes 1618
General and simplified digital simulation schemes are used to generate current-time and component potential-time curves and carrier concentration profiles. Attempts to fit whole transients globally, with independently determined parameters, are partially successful. James R. Sandifer*, Corporate Research Laboratories, Eastman Kodak Company, Rochester, NY 14650 and Michael L. Iglehart and Richard P. Buck, Department of Chemistry, University of North Carolina, Chapel Hill, NC 27514 Preparation and Electrochemical Characterization of Conical and Hemispherical Ultramicroelectrodes 1630 A fabrication technique allows the preparation of conical Pt-Ir ultramicroelectrodes with radii of 0.5-10 μηι. The ra dius determines the geometry of the diffusional behavior. SEM, cyclic voltammetry, and chronoamperometry are used to characterize the electrodes. Reginald M. Penner, Michael J. Heben, and Nathan S. Lewis*, Division of Chemistry and Chemical Engineering, California Insti tute of Technology, Pasadena, CA 91125 Quantitative Relationship between Electron Transfer Rate and Surface Microstructure of Laser-Modified Graphite Electrodes 1637 The electron transfer rate constant and capacitance of un treated and laser-activated highly ordered pyrolytic graph ite surfaces are correlated with the fractional surface cover age of the edge plane, indicating that both are determined by the edge plane density. Ronald J. Rice and Richard L. McCreery*, Department of Chemistry, The Ohio State University, 120 West 18th Avenue, Co lumbus, OH 43210
The attachment of pendant groups (-OH, -OCH 2 CH 2 OCH 3 , -OCH2CO2H) to the central carbon of a three-carbon bridge in dibenzo-14-crown-4 markedly alters the response of this ionophore to alkali metal cations, alkaline earth cations, and protons in solvent-polymeric membranes. Uriel Olsher* and Felix Frolow, Department of Chemical Services, The Weizmann Institute of Science, Rehovot 76100, Israel, Gil Shoham*, Department of Analytical and Inorganic Chemistry, The Hebrew University of Jerusalem, Jerusalem, Israel, and GwiSuk Heo and Richard A. Bartsch*, Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061
Two detector systems are evaluated using synthetic mix tures of 32 P-labeled sample molecules. Flow programming extends the detection limit to the sub-nCi level. Stephen L. Pentoney, Jr., and Richard N. Zare*, Department of Chemistry, Stanford University, Stanford, CA 94305 and Jeff F. Quint, Beckman Instruments, Inc., Scientific Instruments Division, Fullerton, CA 92634
Electrochemical Study of the Mechanism of Cadmium Extraction with Dithizone 1621
Near-Infrared Surface-Enhanced Raman Spectroscopy Using a Diode Laser 1648
An acetate-containing anionic cadmium dithizonate species, CdDz2(OAc)~, is identified as the species that transfers from water into dichloroethane under current scanning polarographic conditions. Wei-hua Yu and H. Freiser*, Strategic Metals Recovery Research Facility, Department of Chemistry, University of Arizona, Tucson, AZ 85721
A diode laser using Ag and Cu electrodes is used to obtain SER spectra of 6-mM solutions of the highly luminescent compound tris(2,2'-bipyridyl)ruthenium(II). No lumines cent interference is encountered. Stanley M. Angel* and Michael L. Myrick, Environmental Sci ences Division, Lawrence Livermore National Laboratory, Livermore, CA 94550
On-Line Radioisotope Detection for Capillary Electrophoresis 1642
* Corresponding author 874 A · ANALYTICAL CHEMISTRY, VOL. 61, NO. 15, AUGUST 1, 1989
BRIEFS Studies of Sputtering Atomizers for Atomic Absorption Spectroscopy
1652
Factors influencing absorption sensitivity and reproducibil ity are investigated for several sputtering atomizers used in atomic absorption analysis of solid samples. David S. Gough*, Peter Hannaford, and R. Martin Lowe, CSIRO Division of Materials Science and Technology, Locked Bag 33, Clayton, Victoria 3168, Australia Identification of Immobilized Bacteria by Aminopeptidase Profiling 1656 Incorporating an immobilized cell technique into a standard bacterial identification method allows reduction in the cell concentration and incubation period without a loss in sensi tivity. The total turnaround time is reduced from 2.5 days to 3-7 h. K. D. Hughes and F. E. Lytle*, Department of Chemistry, Purdue University, West Lafayette, IN 47907 and D. M. Huber*, Depart ment of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907 Water as a Unique Medium for Thermal Lens Measurements 1660 The effect of temperature on the thermal lens signal in water is exploited to produce photothermal focusing and defocusing and to enhance the sensitivity of the measurement. Mladen Franko and Chieu D. Tran*, Department of Chemistry, Marquette University, Milwaukee, WI 53233 Spectrophotometric Method for the Analysis of Plutonium and Nitric Acid Using Partial Least-Squares Regression 1667 PLS regression is used to quantitate plutonium and nitric acid using the absorption spectra. Pu(III) (1.99-29.9 g/L) and nitric acid (0.5-3.0 M) are calibrated simultaneously with a standard error of 0.20 g/L and 0.18 M, respectively. W. Patrick Carey and Lawrence E. Wangen, Chemical and Laser Science Division, G740, Los Alamos National Laboratory, Los Ala mos, NM 87545 and James T. Dyke*, Material Science and Tech nology Division, E501, Los Alamos National Laboratory, Los Ala mos, NM 87545 Continuum Source Atomic Absorption Spectrometry in a Graphite Furnace with Photodiode Array Detection 1670 An AA spectrometer that uses an Xe arc lamp as the source and an intensified photodiode array detector is described. The multiwavelength detection power allows simultaneous determination of several elements in a mixture and provides automatic background correction. Bradley T. Jones, Ben W. Smith, and James D. Winefordner*, Department of Chemistry, University of Florida, Gainesville, FL 32611
Polymer-Coated Cylindrical Waveguide Absorption Sensor for High Acidities 1674 Molar concentrations of nitric and hydrochloric acids are detected using an in situ sensor composed of polymer-encap sulated indicators combined with cylindrical optical ele ments. Precision is 0.05 M. W. Patrick Carey* and Michael D. DeGrandpre, Chemical and Laser Science Division, G740, Los Alamos National Laboratory, Los Alamos, NM 87545 and Betty S. Jorgensen, Material Science and Technology Division, E549, Los Alamos National Laboratory, Los Alamos, NM 87545 Picogram Level Quantitation of 2,3,7,8-Tetrachlorodibenzo/r-dioxin in Fish Extracts by Capillary Gas Chromatography/ Matrix Isolation/Fourier Transform Infrared Spectrometry 1678 GC/MI/FT-IR spectrometry is used to confirm the identity and quantitate 2,3,7,8-tetrachlorodibenzo-p-dioxin in fish extracts in the 170-220-pg range (15-45 pg/g). Recovery averages 52%. Magdi M. Mossoba*, Richard A. Niemann, and Jo-Yun T. Chen, Division of Contaminants Chemistry, Food and Drug Admin istration, 200 C St., S.W., Washington, DC 20204 Application of Cross-Correlation to Quantitative Analysis of Binary Mixtures Using Extended X-ray Absorption Fine Structure 1686 Using suitable standard spectra for calibration purposes, it is possible to extract percent composition information from EXAFS data of binary mixtures using cross-correlation analysis. Without such standards, semiquantitative trends can also be obtained. Douglas P. Hoffmann, Andrew Proctor, Martin J. Fay, and David M. Hercules*, Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260 Fourier Transform Atomic Absorption Flame Spectrometry with Continuum Source Excitation 1694 The design and performance of an FT-AA spectrometer using a 300-W Xe arc continuum source and a Michelson interferometer are presented. Detection limits for several elements are generally an order of magnitude poorer than those obtained by continuum AA methods that use echellegrating spectrometers. Mark R. Glick, Bradley T. Jones, Benjamin W. Smith, and James D. Winefordner*, Department of Chemistry, University of Florida, Gainesville, FL 32611 Mixture Analysis and Quantitative Determination of NitrogenContaining Organic Molecules by Surface-Enhanced Raman Spectrometry 1697 A correction procedure for standardization of measurements is proposed and evaluated to solve the problem of quantita tion of adsorbate in SERS. The RSD is about 15%, and linearity is achieved up to 50 μg/mL aminoacridine. J. J. Laserna, A. D. Campiglia, and J. D. Winefordner*, Depart ment of Chemistry, University of Florida, Gainesville, FL 32611
876 A · ANALYTICAL CHEMISTRY, VOL. 61, NO. 15, AUGUST 1, 1989
BRIEFS Interpreting Mass Spectra of Multiply Charged Ions
1702
Two algorithms that extract molecular mass information from the spectra of multiply charged ions are applied to the spectra of small proteins (5-40 kD) obtained by electrospray MS. Accuracy and sources of error are discussed. Matthias Mann, Chin Kai Meing, and John B. Fenn*, Department of Chemical Engineering, Yale University, New Haven, CT 06520-2159 On-Line Electrochemistry/Thermospray/Tandem Mass Spectrometry as a New Approach to the Study of Redox Reactions: The Oxidation of Uric Acid
1709
The on-line combination of electrochemistry and thermospray/tandem MS provides otherwise difficult to obtain information about redox and associated chemical reactions of biological molecules, such as the structure of reaction intermediates and products. Kevin J. Volk, Richard A Yost*, and Anna Brajter-Toth*, Department of Chemistry, University of Florida, Gainesville, FL 32611 Determination of Serum Cholesterol by a Modification of the Isotope Dilution Mass Spectrometric Definitive Method 1718 Cholesterol is determined in seven pools of human serum, with a coefficient of variation of 0.22%. The modified method uses improved chromatographic separation and a new method of implementing selected ion monitoring. Polly Ellerbe*, Stanley Meiselman, Lorna T. Sniegoski, Michael J. Welch, and Edward White V, Center for Analytical Chemistry, National Institute of Standards and Technology (formerly National Bureau of Standards), Gaithersburg, MD 20899 Desorption Chemical Ionization, Thermospray, and Fast Atom Bombardment Mass Spectrometry of Dihydropyridine — Pyridinium Salt-Type Redox Systems 1723 Trigonellyl-substituted (quaternary pyridinium salt-type) compounds and their dihydropyridine analogues undergo thermal decomposition, hydrolysis, and redox reactions under desorption ionization conditions. Lâszlo Prokai, Bih-Hsiung Hsu, Hassan Farag, and Nicholas Bodor*, Center for Drug Design and Delivery, College of Pharmacy, Box J-497, J. Hillis Miller Health Center, University of Florida, Gainesville, FL 32610 Potentiometric Homogeneous Enzyme-Linked Competitive Binding Assays Using Adenosine Deaminase as the Label 1728 The assay is based on the inhibition of an adenosine deaminase-biotin conjugate by avidin. Unlike conventional homogeneous enzyme immunoassays, this method uses an ammonium-selective electrode rather than a photometric detector. Thea L. Kjellstrôm and Leonidas G. Bâchas*, Department of Chemistry, University of Kentucky, Lexington, KY 40506-0055
Quantification of Recombinant lnterleukin-2 in Human Serum by a Specific Immunobioassay 1732 The detection limit is 2 units/mL using 0.1 mL serum. Interassay precision is 4.6%, whereas intraassay precision is 12.7%. Sensitivity, reproducibility, specificity, stability, and recovery are also discussed. R. W. Nadeau*, N. F. Oldfield, W. A. Garland, and D. J. Liberato, Department of Drug Metabolism, Hoffmann-La Roche, Inc., Nutley,NJ 07110 Conductometric Transducers for Enzyme-Based Biosensors 1737 Transducers with Cu and P t electrodes are constructed and characterized, and two enzyme immobilization methods are tested. A detection limit of ΙΟ - 6 Μ and a linear range of 2 orders of magnitude are achieved. Susan R. Mikkelsen and Garry A. Rechnitz*, Department of Chemistry, University of Delaware, Newark, DE 19716 Immobilized-Metal Affinity and Hydroxyapatite Chromatography of Genetically Engineered Subtilisin 1742 Subtilisin (MW 27500) single amino acid variants are sepa rated by immobilized-metal affinity chromatography. Selec tivity is demonstrated with the separation of two variants differing by only a methylene group. Roman M. Chicz and Fred E. Régnier*, Department of Biochemistry, Purdue University, West Lafayette, IN 47907 Subambient Temperature Modification of Selectivity in Reversed-Phase Liquid Chromatography
1749
The effect of column temperature on selectivity is examined for monomeric and polymeric Cis phases. A model for temperature induced selectivity changes is presented. Lane C. Sander* and Stephen A. Wise, Center for Analytical Chemistry, National Institute of Standards and Technology (formerly National Bureau of Standards), Gaithersburg, MD 20899 Cycling Technique for the Determination of Femtomole Amounts of Sulfite 1755 A micromethod for the fluorometric determination of sulfite is based on a coupled enzyme assay and enzymatic cycling. The method is linear with a detection limit of 150 fmol for standard and wine samples, and 290 fmol for extracts of freeze-dried needle tissue. Regina Keil, Universitât Tubingen, Institut fur Botanik, Auf der Morgenstelle 1, D-7400 Tubingen, Federal Republic of Germany, Rudiger Hampp*, Universitât Tubingen, Institut fur Botanik, Auf der Morgenstelle 1, D-7400 Tubingen, Federal Republic of Germany, and Hubert Ziegler, Technische Universitât Miinchen, Lehrstuhl fur Botanik, Arcisstrasse 21, D-8000 Munchen, Federal Republic of Germany
878 A · ANALYTICAL CHEMISTRY, VOL. 61, NO. 15, AUGUST 1, 1989
MAXIMIZE YOUR SENSITIVITY... for Volatile Organic Compounds by Dynamic Headspace Concentration
BRIEFS
Determination of Lead in Antarctic Ice at the Picogram-perGram Level by Laser Atomic Fluorescence Spectrometry 1758 LEAF allows direct analysis of decontaminated samples (20 ^L) without preliminary chemical treatment or preconcentration. Results are compared with those previously obtained for the same samples by isotope dilution mass spectrometry. Michail A. Bolshov, Claude F. Boutron*, and Aleksandr V. Zybin, Institute of Spectroscopy, USSR Academy of Sciences, Troitzk, 142092 Moscow Region, USSR, and Laboratoire de Glaciologie et Géophysique de l'Environment du CNRS, Domaine Universitaire, 2, rue Molière, B.P. 96, 38402 St. Martin d'Hères Cedex, France Cyclic Voltammetry at Microhole Array Electrodes
1763
A reversible redox-electrode reaction at microhole array electrodes is discussed. The theoretical results are confirmed experimentally for the redox-electrode reaction of [Fe(CN)6] 4_/3 ~ using cyclic voltammetry at carbon fiberepoxy composite electrodes. Koichi Tokuda*, Department of Electronic Chemistry, Graduate School at Nagatsuta, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 227, Japan and Ken-ichi Morita and Yoshihiro Shimizu, Basic Research Laboratories, Toray Industry, Inc., 1111 Tebiro, Kamakura 248, Japan Fiber-Optic Time-Resolved Fluorescence Sensor for the Simultaneous Determination of A l 3 + and Ga 3 + or l n 3 +
1768
The sensor is based on a pool of chelator solution trapped behind an ion-permeable membrane. Time-resolved fluorimetric methods are used to determine the contribution of each of two complexes to the total fluorescence signal. Mary K. Carroll, Frank V. Bright, and Gary M. Hieftje*, Department of Chemistry, Indiana University, Bloomington, IN 47405 Split Zone Flow Injection Analysis: An Approach to Automated Dilutions 1773
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An overly concentrated sample can be automatically diluted up to 15,000-fold, independent of the sample's viscosity (up to 167 cP). The dilution conditions can be preset, and the extent of the dilution can be calculated. Gregory D. Clark, Jaromir Ruzicka, and Gary D. Christian*, Center for Process Analytical Chemistry, Department of Chemistry, BG-10, University of Washington, Seattle, WA 98195 Titanium Dioxide Based Substrate for Optical Monitors in Surface-Enhanced Raman Scattering Analysis 1779 The use of Ag-coated T1O2 substrates as optical monitors for SERS is investigated. The experimental parameters and analytical capabilities are reported, and its use for in situ trace organic analysis is demonstrated. Job M. Bello, David L. Stokes, and Tuan Vo-Dinh*, Advanced Monitoring Development Group, Health and Safety Research Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6101
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880 A · ANALYTICAL CHEMISTRY, VOL. 61, NO. 15, AUGUST 1, 1989
BRIEFS
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Correspondence Exchange of Comments on the Simplex Algorithm Culminating in Quadratic Convergence and Error Estimation 1783 Steven Brumby, Research School of Chemistry, Australian National University, G.P.O. Box 4, ACT 2601, Australia and G. R. Phillips and Ε. Μ. Eyring*, Department of Chemistry, University of Utah, Salt Lake City, UT 84112
Technical Notes Construction of an Optically Transparent Thin-Layer-Electrode Cell for Use with Oxygen-Sensitive Species in Aqueous and Nonaqueous Solvents 1787 Matthew B. G. Pilkington, Barry A. Coles, and Richard G. Compton*, Physical Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX1 3QZ, England
Application of a Nested-Loop System for the Simultaneous Determination of Thorium and Uranium by Flow Injection Analysis 1789 José Luis Perez Pavon, Bernardo Moreno Cordero*, Jesus Hernandez Mondez, and Rosa Maria Isidro Agudo, Department of Analytical Chemistry, Bromatology and Food Sciences, University of Salamanca, Salamanca, Spain
Columbus, Ohio 43219-1837
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Heinrich Emanuel Merck Award for Analytical Chemistry 1990 In 1988 Ε. Merck, Darmstadt, has granted the Heinrich Emanuel Merck award for the first time. The award is endowed with DM 25,000 for the promotion of new developments in Analytical Chemistry, in particular for developing new methods in classical chemistry for sample preparation in trace analysis and their application in human environment. The next award will be granted in the scope of the European Conference on Analytical Chemistry which will take place in Vienna, August 1990. All young chemists up to the age of 45 are required to sub mit an original paper to the following adress; deadline will be the end of January 1990. Herrn Prof. Dr. Günther Tölg Institut für Spektrochemie und Angewandte Spektroskopie Postfach 1013 52 Bunsen-Kirchhoff-Str. 11 D-4600 Dortmund 1 The winner of this award will be chosen by an international jury of renowned analytical chemists. If you need more information please contact Prof. Dr. G. Tôlg. E. Merck · Frankfurter Strasse 250 · D-6100 Darmstadt 1 CIRCLE 98 ON READER SERVICE CARD
On-Line Dilution Scheme for Liquid Chromatography
1791
Javier N. Oquendo* and Joseph A. Leone*, ARCO Oil and Gas Company, Research and Technical Services, Piano, TX 75075
