In This Issue
Characterizing molecular dynamics at interfaces lateral diffusion of molecules on surfaces is an important phenomenon in chromatographic studies because dynamics control separation speed. Steven L. Zulli, John M. Kovaleski, and Mary J. Wirth of the University of Delaware and X. Ron Zhu and Joel M. Harris of the University of Utah report on their work measuring the lateral diffusion coefficient of acridine orange at the interface of water and a C18 chromatographic surface by using pattern photobleaching/fluorescence recovery. They also determine the diffusion coefficient of acridine orange in bulk water by the relaxation of a transient holographic grating. The combined results of their experiments indicate that the lateral diffusion coefficient at the water/C1K interface is 35 times smaller than that in bulk water, (p. 1708)
Sensing environmental quality Optical sensors are one solution to the growing need for inexpensive analytical methods to monitor environmental pollution. Successful sensors have incorporated solvent polymeric bulk optode membranes whose behavior is based on a cation-exchange system. Markus Lerchi, Elmar Reitter, Wilhelm Simon, and Ernô Pretsch of the Swiss Federal Institute of Technology and Didarul A. Chowdhury and Satsuo Kamata of Kagoshima University (Japan) report on membranes that contain lipophilic anionic sites as well as two cation-selective carriers. The ionophore demonstrates selectivity for the analyte cation, and the chromoionophore is a lipophilized H+-selective indicator that drastically changes its optical properties on protonation. A system based on a dithiocarbamate ionophore shows high selectivity for silver and mercury ions over other toxic heavy and alkaline earth metals, (p. 1713)
Optical sensing based on polymer swelling W. Rudolph Seitz, Ziad Shakhsher, and Kenneth D. Legg of the University of New Hampshire and Polysense are interested in developing fiber-optic chemical sensors based on polymer swelling because they anticipate that the sensors will combine robustness and calibration stability with low cost. The sensors consist of a small drop of animated polystyrene on the tip of a single optical fiber with a core diameter of 100 pm. They are prepared by dip coating a partially polymerized solution, completing the polymerization on the fiber, and aminating the polymer with diethanolamine. The polymer swells as the amine groups are protonated. This is accompanied by an increase in the clarity of the polymer and a decrease in the intensity of the light reflected back into the optical fiber, (p. 1731)
Improved reagent for chemiluminescence studies Peroxyoxalate chemiluminescence is one of the most efficient and versatile chemiluminescence systems available today. In recent years, considerable efforts have been made to synthesize more effective oxalates and oxyamides. Knut Irgum, Malin Stigbrand, and Einar Pontén of the University of Umeâ (Sweden) have studied the reaction between the chemiluminescent compound Ι,Ι'-oxalyldiimidazole (ODI) and hydrogen peroxide and compared it with the reaction involving the commonly used trichlorophenyl oxalate (TCPO) and hydrogen peroxide. Results indicate that the ODI reaction is ~ 10 times more sensitive and is faster than the TCPO reaction. The estimated detection limit for hydrogen peroxide in water is 10~s M. (p. 1766) 568 A
Analytical Chemistry, Vol. 66, No. 10, May 15, 1994
Vital Coverage of the Newest Biotechnology Concepts Basic science . . . and the applications Biotechnology Progress, the journal that links you with indispensible coverage in virtually any relevant scientific discipline which affects the biotechnology/bioprocess industries. Biotechnology Progress provides bimonthly coverage on concepts and trends in these areas: Bioseparations Bioconversion Applied Biochemistry Bioinstrumentation Formulation Product delivery Bioreactor technology Applied molecular biology I Biocatalytic processes Cell culture I Bioanalysis Tissue engineering
Editor Jerome S. Schultz, Center for Biotechnology & Bioengineering, University of Pittsburgh, 300 Technology Drive, Pittsburgh. PA 15219, (412) 383-9712
Associate Editor, Reviews M.C. Flickinger, University of Minnesota Co-published by the American Chemical Society & The American Institute of Chemical Engineers
• YES I want to receive bimonthly issues of Biotechnology Progress. My 1994 subscription is covered by the ACS pro-rata refund guarantee. A|| 0lher Please check one:
U.S.
ACS/AIChE Members 1 year G $ 30 Nonmembers 1 year • $340
Europe Canada (Air Service & Mexico included) Π $ 35 D $345
• $40 • $350
Countries (Air Service included) G $ 44 • $354
Address City State Zip Π ACS member D AlChE member Mail this coupon to: Biotechnology Progress, Member & Subscriber Services, American Chemical Society, Dept, L-0011, Columbus, OH 43268-0011, Or Call: 1-800-333-9511 (U.S. only) or (614) 447-3776 FAX: (614) 447-3671 Please select your method of payment: D Payment enclosed (Payable to the American Chemical Society) D Bill me Charge my: Π Visa/MasterCard or D American Express Account No. Expiration date: Signature: Print name: Foreign payment must be made in U.S. dollars by international money order, UNESCO coupons, or U.S. bank draft. Orders accepted through your subscription agency. For nonmember rates in Japan, contact Maruzen Co., Ltd., 3-10 Nihonbashi 2-chome, Chuo-ku, Tokyo, 103, Japan. 7785Y
