Figure 6. CD spectra of (a) penicillin-V, (b) cephalosporin, and (c) penicillin-V broth (8.07 mg/mL) in aqueous pH 5.4 buffer.
guishable from each other because the Cotton bands are of opposite polarity); reserpine; tetracyclines; penicillins and cephalosporins (whose CD spectra bear no mutual similarities [see Figure 6] in comparison with the absorption spec tra); and vitamins (4). Common addi tives such as aspirin, caffeine, and most simple sugars are noninterfering (4). This list is not especially long, partly
because the point clearly has been made that the task of using CD for quality control, without chromato graphic separation, is elementary and particularly reliable. The method is easily extended to each new applica tion because its role is simply that of a detector, and extraction procedures and workup for any given sample are the same as they are for any other
method of detection. A second group of pharmaceuticals, including atropine, meperidine, dilantin, the barbitals, and the diazepams (4) are achiral. These drugs are either inherently achiral (e.g., dilantin), or they exist as exact racemic mixtures (e.g., atropine), but each group can be assayed using /3-CD-induced CD if they contain a suitable chromophore. Race mic mixtures can be included despite the fact that the enantiomers may in teract differently with β-CD, and what is actually recorded is the net induced signal. This differing interaction is, of course, part of the reason that enantio mers can be partially separated on the chiral cyclodextrin stationary phases (15). The need for two detectors in the determination of EE or optical purity was discussed earlier. Some early ex amples combined UV or RI with polarimetric detection, and cocaine and co deine (19), epinephrine (34), and Dand L-penicillamine (35) were investi gated in this manner. We have successfully used UV and CD in series for prepared mixtures of (R)- and (S)-nicotine in which solu-
Graphics for Chemical Structures
T
his exciting book presents the lat est information from recognized experts in the field of chemical structure handling on microcomputers... and includes the newest devel opments in related sys tems on both mini- and mainframe computers. The book begins with an excellent overview of the evolution of computer graphics—and will introduce you to the four general types of software packages currently available · scientific word processing packages • packages that allow graphics entry of chemical structures but do not allow substructure searching or interfacing with other systems · pack ages that allow graphics structure entry and substructure searching and interfacing with other systems · packages designed to act as front ends to molecular modeling systems. This volume continues with discussions and comparisons of various software packages for the chemist. Information managers, information scientists, systems analysts, bench chemists, physical chemists, and PC enthusiasts will find this book a vital, necessary reference. Wendy A. Warr, Editor ACS Symposium Series No. 341 LC 87-3575 ISBN 0-8412-1401-8
176 pages (1987) Clothbound US & Canada $44.95 Export $53.95
- when you need to be sure..
RADIOMETER COPENHAGEN R A D I O M E T E R A N A L Y T I C A L A/S KROCSHOJVEJ 49 • DK-288Q BACSVAERD • DENMARK
Order from: American Chemical Society, Distribution Office Dept. 58 1155 Sixteenth St., N.W., Washington, DC 20036
CIRCLE 139 ON READER SERVICE CARD
or CALL TOLL FREE θ 0 0 " Ζ Ζ 7 θ 5 ί ) Ο and use your credit card!
ANALYTICAL CHEMISTRY, VOL. 61, NO. 2, JANUARY 15, 1989 · 87 A
