A C BRIEFS

Chemistry, Michigan State University, East Lansing, Mich. 48823. Anal. Chem., 44 ... Center, Bureau of Mines, U.S. Department of the Interior,. Larami...
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A C BRIEFS Highlights of Articles in This Issue

Thermodynamic Constants of the Adducts Formed with Heterocyclic Nitrogen Bases and Nickel(ll) Dithiophosphates The free energy, enthalpy, and entropy changes for the formation of the 1:1 adducts of bis(0,0'-dimethyldithiophosphato)nickel(II) and bis(0,0'-diethyldithiophosphato)nickel(ll) with several heterocyclic nitrogen bases have been determined by a spectrophotometric method. TERESA MARSHALL and QUINTUS FERNANDO. Department of Chemistry, University of Arizona, Tucson, Ariz. 87521 Anal. Chem. 44, 1346 (1972) Concentration and Separation of Trace Metal Cations by Complexation on PolyaminePolyurea Resins The amine moiety on these insoluble resins complexes only heavy metal cations, hence there is no competition from even high concentrations of alkali and alkaline earth metals. JOSEPH DINGMAN, Jr., SIDNEYSIGGIA, CARLOS BARTON, and KATHRYN B. HISCOCK, Department of Chemistry, University of Massachusetts, Amherst, Mass. 01002 Anal. Chem., 44, 1351 (1972) Determination of Atmospheric Sulfur Dioxide by Differential Pulse Polarography Sulfur dioxide is quantitatively removed from air by dimethyl sulfoxide (DMSO), and determined by differential pulse polarography. For 10% relative error, the method is sensitive to 10_7Af SO, in DMSO (about 0.4 ppm S 0 2 in air under the conditions described). The precision is typically 5 % . ROBERT W. GARBER and CLAUDE E. WILSON, Department of Chemistry, University of Pittsburgh, Pittsburgh, Pa. 15213 Anal. Chem. 44, 1357 (1972)

Activity Studies of Charged and Uncharged Molecules Using Detergent Gel M e m b r a n e Systems Selectivity characteristics of detergent membranes are discussed. Their electrochemical behavior in the presence of uncharged molecules is approached in terms of an induced perturbation in the gel structure. CLAUDIO BOTRE, MARCO MASCINI, and ADRIANA MEMOLI, Istituto Chimico Farmaceutico, Université degli Studi, Roma, Italy Anal. Chem., 44, 1371 (1972) Evaluation of Precision of Quantitative Molecular Absorption Spectrometric Measurements A signal-to-noise ratio treatment provides a means for evaluating and optimizing the precision of a quantitative molecular absorption measurement. Both dc and photon counting measurements are considered. J. D. INGLE, Jr., and S. R. CROUCH. Department of Chemistry, Michigan State University, East Lansing, Mich. 48823 Anal. Chem., 44, 1375 (1972) Nondestructive Charged Particle Activation Analysis Using Short-Lived Nuclides The following elements can be determined at trace levels; Se, Br, Y, Ar, La, Pr, Dy, and Nd. Pertinent activation data, including accurate y-ray energies, are presented and analytical applications are discussed. JEAN-LUC DEBRUN, DAVID C. RIDDLE, and EMILE A. SCHWEIKERT, Activation Analysis Research Laboratory and Department of Chemistry, Texas A&M University, College Station, Texas 77843 Anal. Chem., 44, 1386 (1972) Ion-Exchange, Coordination, and Adsorption Chromatographic Separation of Heavy-End Petroleum Distillates

Bipolar Digipotentiogrator for Electroanalytical Uses. Direct Conversion of Charge to a Digital N u m b e r

A separation scheme is described that separates heavy-end petroleum distillates into acid, base, neutral-nitrogen, saturate, and aromatic fractions.

A bipolar digital potentiostat based upon the principle of charge injection or extraction has been built, tested, and applied to polarographic and anodic stripping analyses. It is capable of a current measuring precision of 0.01%.

D. M. JEWELL, J. H. WEBER, J. W. BUNGER, HENRY PLANCHER, and D. R. LATHAM, Laramie Energy Research Center, Bureau of Mines, U.S. Department of the Interior, Laramie, Wyo. 82070 Anal. Chem., 44, 1391 (1972)

WILLIAM W. GOLDSWORTHY and RAY G. CLEM, Lawrence Berkeley Laboratory, University of California, Berkeley, Calif. 94720 Anal. Chem., 44, 1360 (1972) Rhodanese Enzyme Determination Using Ion-Selective M e m b r a n e Electrodes A method for the determination of rhodanese enzyme activity using cyanide selective membrane electrodes is described and evaluated. R. A. LLENADOandG.A. RECHNITZ. Department of Chemistry, State University of New York, Buffalo, N.Y. 14214 Anal. Chem., 44, 1366 (1972)

Nuclear Magnetic Resonance Spectrometry of Petroleum Fractions. Carbon-13 and Proton Nuclear Magnetic Resonance Characterizations in T e r m s of Average Molecular Parameters Carbon-13 N M l t analysis and a new method of Ή ΝΜ11 analysis of aromatic cuts of petroleum crudes in terms of average parameters are discussed. The new 1 H N M R method has the advantage of using only the spectral data for the analysis, saves time, and eliminates several sources of error. D. R. CLUTTER, LEONIDAS PETRAKIS, R. L. STENGER, Jr., and R. K. JENSEN, Gulf Research and Development Com­ pany, Pittsburgh, Pa. 15230 Anal. Chem., 44, 1395 (1972) ANALYTICAL CHEMISTRY, VOL. 44, NO. 8, JULY 1972

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AC BRIEFS The K-Nearest Neighbor Classification Rule (Pattern Recognition) Applied to Nuclear Magnetic Resonance Spectral Interpretation

Quantitative Determination of S-Hydroxyindole-3Acetic Acid in Cerebrospinal Fluid by Gas Chromatography-Mass Spectrometry

The K-Nearest Neighbor Classification Rule is presented as an alternative to the Computerized Learning Machine for analysis of spectrometric data. Theoretical and empirical comparisons are made.

Dideuterium-labelled 5-hydroxyindole-3-acetic acid (5-HIAA) is used as an internal standard in this determination which takes less than 2 minutes. The standard deviation is less than 7 % in the 8-20 ng/ml range and 1-2% at higher concentrations of 5-HIAA.

B. R. KOWALSKI and C. F. BENDER, Lawrence Livermore Laboratory, University of California, Livermore, California 94550 Anal. Chem., 44, 1405 (1972) On-Line Elemental Analysis of Gas-Chromatographic Effluents Identification of gas-chromatographic effluents from multicomponent, sub-microliter mixtures has been accomplished by stop-flow, functional group analysis, with carbon, hydrogen, nitrogen, oxygen, and subsequent on-line empirical formula determinations. S. A. LIEBMAN, D. H. AHLSTROM, and T. C. CREIGHTON, Armstrong Cork Company, Research and Development Center, Lancaster Pa. 17604, and G. D. PRUDER, R. AVERITT, and E. J. LEVY, Chemical Data Systems, Inc., Oxford, Pa. 19363 Anal. Chem., 44, 1411 (1972) Predicting Gas-Chromatographic Resolution for Pairs of N-Alkane Homologs Chromatographic characteristics of binary mixtures of nalkanes have been examined over a range of experimental conditions that included those that should lead to analyses in minimum times. ROBERT S. SWINGLE and L. B. ROGERS, Department of Chemistry, Purdue University, Lafayette, Ind. 47907 Anal. Chem., 44, 1415 (1972)

LEIF BERTILSSON, ARTHUR J. ATKINSON, Jr., JAMES R. ALTHAUS, ÀSE HÀRFAST, JAN-ERIK LINDGREN, and BO HOLMSTEDT, Department of Toxicology, Swedish Medical Research Council, and Department of Pharmacology, Division of Clinical Pharmacology, Karolinska Institutet, S-104 01 Stockholm 60, Sweden Anal. Chem., 44, 1434 (1972)

Hexafluoroacetone Ketals as Derivatives for Positional and Geometrical Characterization of Double Bonds Hexafluoroacetone ketals of a series of re-alkenes are synthesized via two stereospecific reactions ( > 9 7 % ) for mass spectrometric investigation of position and geometry of double bonds. BRUCE M. JOHNSON and JAMES W. TAYLOR, Department of Chemistry, University of Wisconsin, Madison, Wis. 53706 Anal. Chem. 44, 1438 (1972)

Laser-Excited Atomic Fluorescence Flame Spectrometry as an Analytical Method A pulsed, tunable dye laser is used to excite atomic fluorescence of 13 elements in three different flames. L. M. FRASER and J. D. WINEFORDNER, Department of Chemistry, University of Florida, Gainesville, Fla. 32601 Anal. Chem., 44, 1444 (1972)

Principal-Component Analysis Applied to Chromatographic Data Principal-component analysis of high-precision gas chromatographic data has been used to characterize changes in peak shape that resulted from changes in concentration in re-alkane homologs and in overlap of two peaks. DONALD MACNAUGHTAN, Jr., L. B. ROGERS, and GRANT WERNIMONT, Department of Chemistry, Purdue University, Lafayette, Ind. 47907 Anal. Chem., 44, 1421 (1972)

Atomic Absorption Determination of Chloride Utilizing the Beilstein Test A burner assembly that provided a direct atomic absorption determination of organic and inorganic chloride solutions utilizing a modification of the Beilstein test is described. The useful analytical range is 50-200 ppm chloride. DAVID F. TOMKINSandC. W. FRANK, Department of Chemistry, University of Iowa, Iowa City, Iowa 52240 Anal. Chem., 44, 1451 (1972)

Effect of Dead Volume on Efficiency of a Gas Chromatographic System

Induction Furnace Method in Atomic Spectrometry

A systematic study of dead volume effects in gas chromatography was done. The effects of diameter, volume, and length of connecting tubing were determined at both ends of two different columns.

A new source is described for the direct analysis of solids or evaporated solutions by atomic emission and absorption spectroscopy. The fundamentals and analytical potentialities are presented.

VIRGIL MAYNARD and ELI GRUSHKA, Department of Chemistry, State University of New York at Buffalo, Buffalo, N.Y. 14214 Anal. Chem., 44, 1427 (1972)

YAIR TALMI and G. H. MORRISON, Department of Chemistry, Cornell University, Ithaca, N.Y. 14850 Anal. Chem., 44, 1455 (1972) ANALYTICAL CHEMISTRY, VOL. 44, NO. 8, JULY 1972 ·

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AC BRIEFS Emission Spectrometric Determination of Arsenic

Notes Use of Induction Furnace Source for Spectrometric Determination of Iodine Iodine can be determined in inorganic and complex biological matrices using the R F induction furnace technique. Atomic emission at the 2062 A spectral line is employed. Freezedried samples of thyroid weighing less t h a n 1 mg have been analyzed directly. YAIR T A L M I a n d G. H. M O R R I S O N . istry, Cornell University, Ithaca, N.Y.

A microwave induced plasma is used for the emission spectrometric determination of arsenic at concentrations ranging down to the parts per billion level. F. E. LICHTE a n d R. K. SKOGERBOE, D e p a r t m e n t of C h e m istry, Colorado State University, Fort Collins, Colo. 80521 A n a l . C h e m . , 44, 1480 (1972)

D e p a r t m e n t of C h e m -

A n a l . C h e m . , 44, 1467 (1972)

Determination of Aluminum in Biological Material by Atomic Absorption Spectrophotometry An atomic absorption procedure for the analysis of aluminum in biological tissue is reported. The procedure has a detection limit of 0.1 Mg/ml with both accuracy and precision at ± 10% at the 1 Mg/ml level.

Determination of Metallic-Element Impurities in Uranium Hexafluoride by Spark Source Mass Spectrometry Thirty-one elements and 233U were determined with an average precision of ± 3 3 % , a detection limit of 1 ppm or les.-, and an analysis time of ô hours. O L I N H. HOWARD, Oak Ridge Gaseous Diffusion Plant, U n i o n Carbide Corp., Nuclear Division, Oak Ridge, T e n n . 37830 A n a l . C h e m . , 44, 1482 (1972)

S. S. K R I S H N A N , K. A. GILLESPIE, a n d D. R. CRAPPER, T h e D e p a r t m e n t s of M e d i c i n e a n d Physiology, University of T o r o n t o , T o r o n t o 5, Ontario, C a n a d a A n a l . C h e m . , 44, 1469 (1972)

Ultrasonic Nebulization in Atomic Absorption Spectrophotometry Ultrasonic and pneumatic nebulization have been compared as means for delivering the analyte to an atomic absorption flame. The use of ultrasonic nebulization enhances the sensitivity by factors ranging from 2 to 4 depending on the element. T. R. COPELAND, K. W. OLSON, a n d R. K. SKOGERBOE, Dep a r t m e n t of C h e m i s t r y , Colorado State University, Fort Collins, Colo. 80521 A n a l . C h e m . , 44, 1471 (1972)

Exact Mass Measurement Accuracy from CEC 21-110B Mass Spectrometer and Commercial Data System DS-30 Mass measuring accuracy in the range 4-7 ppm has been attained in routine use for over a year. Mass spectrometer modifications, simple and inexpensive to accomplish, are described. R. S. GOHLKE, G. P. H A P P , D. P. MAIER, a n d D. W. STEWA R T , Research Laboratories, E a s t m a n K o d a k C o m p a n y , Rochester, N.Y. 14650 A n a l . C h e m . , 44, 1484 (1972)

Direct Isotopic Determination by Atomic Fluorescence Spectrometry

Determination of Mass Spectrometric Sensitivity Data for Hydroaromatic Compounds

Stable isotopes of Hg, In, Zn, and Cu were investigated. Absorption hyperfine structure of Hg is incompletely separated. Using flames, Doppler broadening appears to be the main limitation.

Low-voltage mass spectral data indicate that the sensitivity of a hydroaromatic structure can be calculated from t he sensitivity of the corresponding aromatic ring compound.

C L A U D E VEILLON a n d J O H N Y. PARK, D e p a r t m e n t of C h e m istry, University of H o u s t o n , H o u s t o n , Texas 77004 A n a l . C h e m . , 44, 1473 (1972)

J . L. S H U L T Z a n d A. G. SHARKEY, Jr., P i t t s b u r g h Energy Research Center, B u r e a u of M i n e s , U.S. D e p a r t m e n t of t h e Interior, P i t t s b u r g h , Pa., a n d R. A. BROWN, Esso Research a n d E n g i n e e r i n g Co., L i n d e n , N.J. A n a l . C h e m . , 44, 1486 (1972)

Arsenic Determination at Sub-Microgram Levels by Arsine Evolution and Flameless Atomic Absorption Spectrophotometric Technique This method not only significantly lowered the background absorption compared to that of the argon /hydrogen-entrained air flame method, but also increased the sensitivity and gave excellent reproducibility. R I C H A R D C. C H U , GEORGE P. B A R R O N , a n d P A U L A. W. B A U M G A R N E R , Pesticide Research Laboratory a n d Gradu a t e S t u d y Center, T h e Pennsylvania State University, University Park, Pa. 16802 A n a l . C h e m . , 44, 1476 (1972)

Separation and Identification of Multicomponent Mixtures Using Centri-Chromatography/Mass Spectrometry The technique of Centri-Chromatography can be combined with mass spectrometry to provide a fast efficient method of identifying components in a complex mixture. FRANCIS W. KARASEK a n d P A U L W. R A S M U S S E N , University of Waterloo, Waterloo, Ontario A n a l . C h e m . , 44, 1488 (1972) A N A L Y T I C A L CHEMISTRY, VOL. 4 4 , NO. 8 , JULY 1 9 7 2

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AC BRIEFS Tetraphenylboric Acid Salts as Stationary Phases in Gas Chromatography

Neutron Activation Analysis of Copper by Substoichiometric Extraction with Neocuproine

Sodium, potassium, rubidium, cesium, and thallium(I) tetraphenylborates are proposed as stationary phases in gas chromatography. T h e behavior of various kinds of organic compounds was studied.

As little as 7.7 ng Cu was determined with an accuracy of 8 % by neutron activation and substoichiometric extraction into chloroform. Replicate samples were found to agree within ± 1 . 8 4 relative per cent at 9 5 % confidence limits.

GEORGE E. BAIULESCU, Department of Analytical Chemistry, University of Bucharest, Romania, and VASILE A. ILIE, Institute of Chemical Researches, Bucharest, Romania

R. A. NADKARNI and B. C. HALDAR, Inorganic and Nuclear Chemistry Laboratory, Institute of Science, Bombay-32, India

Anal. Chem., 44, 1490 (1972)

Gas Chromatographic Determination of Residual Methanol in Food Additives Low levels of methanol in isohumulone and 3-hydroxy-2methyl-4if-pyran-4-one were determined by indirect headspace gas chromatography. M. A. LITCHMAN and R. P. UPTON, Pfizer Inc., Groton, Conn. 06340

Anal. Chem., 44, 1504 (1972) Comparison of Neutron Activation Analysis and Other Analyses Procedures for Fish Samples A neutron activation analysis (NAA) procedure was compared to other analysis procedures. There was 1 1 % accuracy for the six fish samples. This NAA least squares procedure gave significant time savings. N. D. ECKHOFF, C. J. PAPPAS, and C. W. DEYOE, Kansas State University, Manhattan, Kansas66502 Anal. Chem., 44, 1506(1972)

Anal. Chem., 44, 1495 (1972)

Rapid Determination of Twenty Amino Acids by Gas Chromatography

Determination of Trace Quantities of Uranium in Biological Materials by Neutron Activation Analysis Using a Rapid Radiochemical Separation

Details of a method for preparation of volatile O-re-butyl ester—TMSi derivatives of 20 amino acids and for their gas chromatographic determination in less t h a n 35 minutes are given.

Uranium was determined in biological and other materials by NAA using a solvent extraction radiochemical separation. Uranium analysis for the N B S S R M Orchard Leaves was 26 ± 3 ppb, in good agreement with two other analytical techniques.

JAMES P. HARDY and STEPHEN L. KERRIN, Space Sciences Division, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, Calif. 91103

DONALD A. BECKER and PHILIP D. LaFLEUR, Activation Analysis Section, Analytical Chemistry Division, National Bureau of Standards, Washington, D.C. 20234

Anal. Chem., 44, 1497 (1972)

Anal. Chem., 44, 1508 (1972)

Analysis of Purine and Strychnos Alkaloids by High-Speed Liquid Chromatography Good separation of three purine and two strychnos alkaloids, with Poly G-300 as stationary phase and Corasil I and Corasil I I as solid supports, using high-speed liquid chromatography has been achieved. CHENG-YI WU and SIDNEY SIGGIA, Department of Chemistry, University of Massachusetts, Amherst, Mass. 01002 Anal. Chem., 44, 1499 (1972)

Spectrophotometric Determination of Sulfite with Mercuric Thiocyanate and Ferric Ion Sulfite can be determined in the range of 1-20 ppm by reaction with mercuric thiocyanate in methanol and aqueous ethanol. The thiocyanate ion released is complexed with ferric ion and the absorbance of F e S C N 2 + measured. WILLIE L. HINZE, JAMES ELLIOTT, and RAYE. HUMPHREY, Department of Chemistry, Sam Houston State University, Huntsville, Texas 77340 Anal. Chem., 44, 1511 (1972) Trimethylphenylammonium Bromide as a Selective Quantitative Precipitant for Gold or Thallium

Use of Sample Loops with Micro-Packed Columns in Gas Chromatography A method for determining t h e optimum sample loop size to use with a particular micro-packed column is described.

A selective semimicro gravimetric method has been developed for gold and or thallium using trimethylphenylammonium bromide. The reagent precipitates AuBr 4 ~ or TlBr 4 ~ from HBr solutions.

D. E. DURBIN and JACKIE FRUGE, Honeywell, Inc., 6625 McGrew, Houston, Texas 77017

W. W. WHITE, Industrial Laboratory, Kodak Park Division, Eastman Kodak Company, Rochester N.Y. 14650

Anal. Chem., 44, 1502 (1972)

Anal. Chem., 44, 1513 (1972) ANALYTICAL CHEMISTRY, VOL. 44, NO. 8, JULY 1972 ·

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AC BRIEFS Spectrophotometric Determination of Sulfur Dioxide by Reduction of Iron(lll) in the Presence of Ferrozine

Determination of Carbon Monoxide in Blood

The determination of sulfur dioxide is based on the reduction of iron(III) in the presence of ferrozine and the format of iron(II) ferrozine chelate. Amounts in the range of 3-40 Mg/25 ml are determined spectrophotometrically using 1-cm cells with relative precision of 4 to 1%.

Carbon monoxide released from chicken blood by sulfuric acid in a modified Conway microdiffusion cell is determined spectrophotometrically by a reagent containing tetrachloropalladate(II), ethylenediaminetetraaeetatoferrate(III), and 1,10-phenanthroline with molybdate as a catalyst.

of

JACK L. LAMBERT, REGINALD R. T S C H O R N , a n d P H I L I P A. H A M L I N , D e p a r t m e n t of C h e m i s t r y , K a n s a s State University, M a n h a t t a n , K a n s . 66502

A n a l . C h e m . , 44, 1515 (1972)

A n a l . C h e m . , 44, 1529 (1972)

A M I R A T T A R I a n d B R U N O JASELKIS, D e p a r t m e n t C h e m i s t r y , Loyola University, Chicago, 111.60626

Ultrasonic Velocity in Water-Deuterium Oxide Mixtures. A Basis for Deuterium Determination in Water Solutions A precise and sensitive method, based on ultrasonic velocity measurements, for direct evaluation of deuterium content in water is described. Applications to monitoring of isotope enrichment and isotopic composition of reactor cooling waters are proposed. J . G. M A T H IESOΝ a n d Β. Ε. CONWAY, D e p a r t m e n t of C h e m ­ istry, University of O t t a w a , O t t a w a , C a n a d a A n a l . C h e m . , 44, 1517 (1972)

Differential Scanning Calorimetry as a General Method for Determining Purity and Heat of Fusion of High-Purity Organic Chemicals. Application to 64 Compounds The DSC method for determining the purity of organic compounds is expanded with modifications and additional data on organophosphates, amides, ureas, carbamates, heterocyclics, chlorophenoxy acids, esters, and halogenated compounds. C A N D A C E PLATO, Division o f C h e m i c a l T e c h n o l o g y , Food a n d Drug A d m i n i s t r a t i o n , W a s h i n g t o n , D.C. 20204 A n a l . C h e m . , 44, 1531 (1972)

Apparent Ionization Constants of Water in Aqueous Organic Mixtures and Acid Dissociation Constants of Protonated Co-Solvents in Aqueous Solution A potent iometric method using glass electrodes was developed for the determination of acidity constants of conjugate acids of basic co-solvents in aqueous solution at 25 °C. Values of p K , are: urea, 0.1 ( ± 0 . 1 ) ; A r -methylformamide, —0.1 ( ± 0 . 2 ) ; and .V-methylacetamide, 0.4 ( ± 0 . 1 ) .

Permeametry in the Knudsen-Flow Regime Knudsen-flow permeametry gives specific surface area values for fine powders that in some instances are equal to low temperature gas adsorption areas but in other cases are less.

EARL M. WOOLLEY, D e p a r t m e n t of C h e m i s t r y , B r i g h a m Y o u n g U n i v e r s i t y , Provo, U t a h 84601, a n d LOREN G. HÈPLER, D e p a r t m e n t of C h e m i s t r y , University of L e t h b r i d g e , Lethbridge, Alberta, Canada A n a l . C h e m . , 44, 1520 (1972)

J O H N F. BROCK a n d CLYDE ORR, Jr., School of C h e m i c a l Engineering, Georgia I n s t i t u t e of T e c h n o l o g y , A t l a n t a , Ga. 30332 A n a l . C h e m . , 44, 1534 (1972)

Photometric Determination of Picomole Quantities of Calcium

Low Level Calibration Mixtures for Gaseous Pollutants

Precise control of wire temperature and inclusion of a delay time significantly improved calcium determination by the helium-glow photometer. T h e mean ratio, found/true calcium concentration was 0.995. T h e mean error was 0.02 meq/1.; the relative error, 1.48%.

Techniques for producing gaseous calibration mixtures have been developed using known volume, pollutant microbubbles. An on-the-spot dilution of a microbubble is accomplished in a specially passivated container.

D A N I E L C. M A R C U S a n d REX L. J A M I S O N , D e p a r t m e n t s of M e d i c i n e a n d Physiology a n d B i o p h y s i c s , W a s h i n g t o n University, School of M e d i c i n e , a n d t h e J e w i s h H o s p i t a l of St. Louis, St. Louis, M o . 63110

ROBERT C. PAULE, N a t i o n a l B u r e a u of S t a n d a r d s , Washingt o n , D.C. 20234 A n a l . C h e m . , 44, 1537(1972)

A n a l . C h e m . , 44, 1523 (1972)

Determination of Composition of Mixtures of Diastereoisomeric Forms of Weak Acids by pH Titration Two methods are described by which the composition of a two component mixture of weak acids is determined by p H titration. One analysis is mathematical and the other experimental, but both produce an accuracy of ± 2 % or better.

Correspondence Gas Chromatographic Measurement of Adsorption Characteristics of Isobutylene-Activated Alumina System with Nonlinear Isotherm

NEIL P U R D I E , MASON B. T O M S O N , a n d GWENDOLYN K. COOK, D e p a r t m e n t of C h e m i s t r y , O k l a h o m a State University, Stillwater, Okla. 74074

S H U I C H I KAGAWA, T h e Faculty of Engineering, Nagasaki University, N a g a s a k i , J a p a n , a n d K A T S U M A FUJITA, KENJI TADA, a n d ISSEI N A K A M O R I , T h e Faculty of Engineering, K y u s h u University, F u k u o k a , J a p a n

A n a l . C h e m . , 44, 1525 (1972)

A n a l . C h e m . , 44, 1540 (1972) A N A L Y T I C A L CHEMISTRY, VOL. 4 4 , NO. 8 , J U L Y 1 9 7 2

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Improved Method for the Preparation of Sulfur Dioxide from Barium Sulfate for Isotope Ratio Studies S. A. BAILEY and J. W. SMITH, CSIRO Division of Mineralogy, P.O. Box 136, North Ryde, N.S.W., Australia 2113 Anal. Chem., 44, 1542 (1972)

Barium Ion-Selective Electrode Based on a Neutral Carrier Complex ROBERT J. LEVINS, Philip Morris, U.S.A., Research Center, P.O. Box 26583, Richmond, Va. 23261 Anal. Chem., 44, 1544 (1972)

Noble Gas Adsorption Characteristics of Charcoal Beds: Van Deemter's Coefficients Evaluation G. G. CURZIO and A. F. GENTILI, Istituto di Impianti Nucleari, University of Pisa, Italy Anal. Chem., 44, 1544 (1972)

Aids for Analytical Chemists Inexpensive Absorption Cell for Use in the Determination of Mercury by the Flameless Atomic Absorption Technique D. R. WOLBER and R. E. BOSSHART, BituminousCoal Re­ search, Inc., 350 Hochberg Road, Monroeville, Pa. 15146 Anal. Chem., 44, 1546 (1972)

"Love that luνMonitor!"

An Easily Constructed Alkali Flame Ionization Detector W. H. STEWART, Sun Oil Company, Marcus Hook, Pa. 19601 Anal. Chem., 44, 1547 (1972) Novel Type of Hydrogenator P. G. SIMONDS and C. F. SMITH, Space Sciences Division, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, Calif. 91103 Anal. Chem., 44, 1548 (1972)

Rapid Screening of Pencil Paint for Lead by a Combustion-Atomic Absorption Technique BRUCE McDUFFIE, Laboratory for Trace Methods and En­ vironmental Analysis, Department of Chemistry, State Uni­ versity of New York at Binghamton, Binghamton, N.Y. 13901 Anal. Chem., 44, 1551 (1972)

So will anyone involved with open column chrom­ atography—and rising costs. Priced under $1200, LDC's new u l t r a v i o l e t a b s o r b a n c e #1250 luvMonitor™ has a minimum detectable sensitivity of 0.002 O.D. units at 254 or 280 nm. Ranges of 0 to 0.1, 0.25, 0.50, and 1.0 density units full scale. 25 /J cell volume, 3 mm path length. Linear chart presentation data are directly convertible to con­ centration. Built-in 5" servo graphic recorder. Re­ mote and manual event marker. Write or phone us now for complete information about LDC's new #1250: the under-$1200 UV monitor that costconscious chromatographers learn to luv.

New Infrared Mulling Agent DAVID H. MARR, Hooker Chemical Corporation, Research Center, Niagara Falls, N.Y. 14302 Anal. Chem., 44, 1551 (1972)

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ANALYTICAL CHEMISTRY, VOL. 44, NO. 8, JULY 1972

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