They are used much less commonly than diphenylamine. We are currently working to extend the detection ap proach to the centralites. With electrochemical detectors, one would gain additional selectivity and sensitivity over optical detectors. In using a conventional electrochemical detector, a hydrodynamic voltammogram needs to be constructed first to obtain proper operating conditions for the detector. The normal procedure is to set the voltage on the detector to a fixed value, inject the sample, and when the peak appears for the desired constituent, measure the peak height, finish the separation, and inject the next samples with the detector set at successively higher voltages. This is quite time-consuming. One simple so lution to the problem is to prepare a stock solution of diphenylamine in the same eluting solvent as is used for the chromatographic separation. Pour this solution into a buret and connect the plastic tubing that enters into the flow cell to the buret tip. Control the buret to deliver a slow, continuous flow of solvent with the stopcock. Preferably, the flow should be the same as that which might be used in the separation, for example, 1 mL per minute. Change the voltage, measure the recorder de
flection, and repeat. Because it is a polarographic procedure, it is really rather similar to obtaining a polarogram with a manual polarograph. Be cause an oxidative mode of detection is used, we selected acetone as the major component in the mobile phase rather than methanol—which was used by other investigators—due to acetone's greater stability toward oxi dation. This makes it easier to deter mine diphenylamine and increases the sensitivity of the method. A typical chromatogram for smokeless powder, showing the diphenylamine peak, is presented in Figure 4. The peak was verified as diphenylamine by the col lection of a sample and by running its mass spectrum. Furthermore, linear calibration curves can be obtained by varying the concentration of diphenyl amine, so that a quantitative determi nation of the amount of diphenyl amine can be obtained. Thus in many cases simple visual observation, chemical tests, and in strumental methods can be used to obtain irrefutable evidence as to whether or not smokeless powder was used in a black powder gun. In addi tion there is one other simple exami nation that may provide additional in formation. Look at the injured party.
Hazards in the Chemical Laboratory
L. Bretherick, Editor, BP Research Centre, Sunbury
CONTENTS
seepages (1981) Plastic ISBN 0-85186-419-8 US & Canada $35.00 (International customers should contact the RSC directly.) I Order from: American Chemical Society Distribution Office Dept. 35 1155 Sixteenth St., N.W. Washington, DC 20036 or CALL TOLL FREE 800-424-6747 and use your VISA or MasterCard
We thank John C. Cayton and Ste phen C. Warlen of the Kansas City Regional Criminalistics Laboratory, Kansas City, Mo., for their assistance in providing ruptured firearms and photographs. This work was presented at the Benedetti-Pichler Symposium of the American Microchemical Soci ety, held at the Eastern Analytical Conference, New York City, Novem ber 1984. The detailed procedure for obtaining hydrodynamic voltammetry plots is scheduled to appear in the April issue of the Microchemical Journal.
This 17-chapter volume outlines some of the more recent NMR applications. The development of methodology to obtain high resolution NMR represents one of the promising new areas of research. At the same time, the FT technique makes high resolution experiments much easier tobe performed at high pressure. The 13C NMR experiments of rhodium carbonyl clusters presented in this text are an illustrative example of the application of this tech nique to homogeneous catalytic pro cesses. The nature of solid fossil fuels is probed with high resolution FT NMR using cross-polarization and magic angle spin ning techniques. Two-dimensional FT NMR and the new information this techni que can provide also are discussed. CONTENTS
This easy-to-use plastic-covered hand book belongs in every chemical labora tory. Its convenient dictionary form lists alphabetically 480 explosive, corrosive, and/or toxic substances, giving informa tion on the toxic effects of these sub stances as well as hazardous reactions, first aid, flash points, and disposal methods. Rounding out the book are special chapters on safety planning and management, fire protection, reactive chemical hazards, chemical hazards and toxicology, health care and first aid, and precautions against radiations. No laboratory should be without this com prehensive edition. ι Introduction · Health and Safety at Work Act 1974 • Satety Planning and Management · Fire Protec tion · Reactive Chemical Hazards · Chemical Haz ards and Toxicology · Health Care and First Aid · Hazardous Chemicals · Precautions Against Radi ations
Acknowledgment
NMR Spectroscopy: New Methods and Applications
3rd Edition
Published by the Royal Society of Chemistry, London
The powder burns of black powder differ from those of smokeless powder. A black-powder discharge throws out very small particles of carbon that tat too the skin. The carbon is embedded in the skin and may take years to go away. The burns are quite visible for about 6 years and may possibly still be seen 10 or more years later. Embedded particles of smokeless powder are more gray than black and will disap pear much more quickly, possibly within a year. The information ob tained by observation of the powder burns may not be conclusive, but could certainly aid in confirmation.
ACS Symposium Series No. 191 George C. Levy, Editor Syracuse University Based on a symposium jointly sponsored by the Divisions of Analytical, Organic, and Physical Chemistry of the ACS.
Ultra High-Field NMR · NMR Spectroscopy at 600 MHz • Two-dimensional Fourier Spectroscopy · Quadrupolar Metallic Nuclei · Deuterium NMR Spectroscopy · Metabolism of 13 C Labeled Substrates · Chemical Bond Labeling and Double-Cross Polarization NMR · NMR Spectroscopy atHigh Pressure » ,3 C Cross Polarization Magic Angle Spinning NMR · NMR of Linear and Cyclic Peptides · 31Ρ NMR Studies · 13C NMR Studies of DNA Dynamics · Photo-Chemically Induced Nuclear Polari zation of Biological Molecules · " C NMR Characteriza tion of Solid Fossil Fuels · Polyester Thermoplastic Elastomers · 23Na NMR Studies 388 pages (1982) Clothbound LC 82-11458 ISBN 0-8412-0723-2 US & Canada $54.95
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1985 Beckman/Altex Column Catalog—circle #20 for a free copy -
454 A · ANALYTICAL CHEMISTRY, VOL. 57, NO. 3, MARCH 1985
