Editorial. Sensitivity of Analytical Methods - Analytical Chemistry (ACS

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CHEMISTRY August 1960, Vol.

EDI T 0RIA 1

32, No. 9

APPLIED JOURNALS, ACS Director o f Publications, C. B. Larrabee Ediforial Director, Richard 1. Kenyan Executive Editor, James M. Crowe Assisfanf fo the Director o f Publicafions, Joseph H. Kuney Assistant to fhe Ediforial Director, Robert F. Gould ANALYTICAL CHEMISTRY Edifor, Lawrence T. Hallett Managing Edifor, Robert 0. Gibbs EDITORIAL HEADQUARTERS WASHINGTON 6, D. C. 1155 Sixteenth St., N.W. Phone REpublic 7-3337 Teletype W A 23 Associate Editors: G. Gladys Gordon, Stella Anderson, Katherine 1. Bigga, Robert J. Riley, Sue M. Solliday, Ruth Reynard Assisfont Editors: Robert J. Kelleyt Malvina 8. Preiss Ediforial Assisfants: Katherine H. Ginnane, Virginia E. Stewart, S. S. Rogers, Lorraine M. Berfuzzi Layout and Production: Joseph Jacobs ( A r t Director), Melvin D. Buckner (Art); Betty V. Kieffer, John V. Sinnett BRANCH EDITORIAL OFFICES CHICAGO 3, ILL. Room 926, 36 South Wabash Ave. Phone STate 2-5148 Teletype CG 725 Associafe Edifors: Arthur Poulos, Chester Placek, James H. Krieger HOUSTON 2, TEX. 71 8 Melrose Bldg. Phone FAirfax 3-7107 Teletype HO 72 Associafe Edifor: Bruce F. Greek NEW YORK 16, N. Y. 2 Park Ave. Phone ORegon 9-1646 Teletype NY 1-4726 Associafe Edifors: William Q. Hull, Harry Stenerson, D. Gray Weaver, Walter S. Fedor, Laurence J. White, Louis A. Agnello, Earl V. Anderson SAN FRANCISCO 4, CALIF. 703 Mechanics’ Instilute Bldg., 57 Post St. Phone EXbrook 2-2895 Teletype SF 549 Associate Edifor: Richard G. Newhall Assistanf Edifor: Joseph Sturchio EASTON, PA. 20th and Northamptun Sts. Phone Blackburn 8-91 1 1 Teletype ESTN Pa 7048 Associate Edifor: Charlotte C. Sayre Ediforial Assisfant: Elizabeth R. Rufe EUROPEAN OFFICE Bush House, Aldwych, London Phone Temple Bar 3605 Cablr JIECHEM Associafe Editor: Albert S. Hester Assisfunf Edifor: Brendan F. Somerville Confribufing Editor: R. H. Muller Advisory Board: W. H. Beamer, F. E. Beamish, C. E. Bricker, W. D. Cooke, D. D. DeFord, M. T. Kelley, C. 1. Luke, W. M. MacNevin, W. J. Mader,W. B. Mason, F. W. Mitchell, Jr., N. H. Nachtrleb, E. J. Rosenbaum, 8. F. Scribner, F. H. Stross Advertising Management REINHOLD PUBLISHING CORP. (For Branch Offices see page 130 A)

Sensitivity of Analytical Methods important criterion of a n analytical method is its sensitivity. This factor is becoming increasingly more important as the need develops for methods which are effective in the parts per million or even parts per billion range. This need for more sensitive methods and ways of attaining them was noted in some of the discussions a t the recent Analytical Summer Symposium held a t Houston. I n some cases, the research scientist finds that by overcoming his fear of making any changes in the “black boxes” with which he is working, he can make adjustments which increase the sensitivity. I n his discussion of parts per billion spectroscopy, for example, George Morrison of Sylvania Electric Products, Inc., noted that sensitivity of the emission spectroscope can be improved by making refinements in each of the three components of this apparatus: light source, light disperser, and detector. Morrison and his associates have done such things as improve control of the temperature of the d.c. arc, optimize exposure time, and adjust the optics. A similar example was cited by W. D. Cooke, Cornel1 University. H e said that the application of conventional polarographic methods is limited t o analysis of solutions of concentration greater than 10-jM. This limitation is based not on electronic sensitivity of the apparatus, but on the difficulty of measuring diffusion currents in the presence of other background currents. Other factors affecting sensitivity are fluctuations in the drop and condenser current. Some of these factors can be reduced, Cooke noted. It appears t h a t a careful study of certain mechanical factors which limit the sensitivity of a given method can often lead to means of increasing sensitivity. While any one improvement may not be particularly significant, a series of such advances may have a substantial cumulative effect. From examples cited, it would appear t h a t the sensitivity of many existing methods can be improved by a t least one order of magnitude. It may be t h a t further steps toward improving sensitivity may come from a better understanding of the basic phenomena involved. The workers cited above, in order to determine the factors limiting the sensitivity, have made careful studies of some of the basic phenomena involved. Development of new methods, based on new or original concepts, is essential to progress in the field of analysis. Of equal importance, however, is the slow, patient re-examination of existing methods with a view t o overcoming sensitivity limitations due either t o mechanical restrictions of instruments or t o a lack of understanding of the basic phenomena involved. Improvements in sensitivity of an order of magnitude or more may not be as startling as new methods, but they are significantly important. ONE

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