Plenum: Tops in Chemistry
PRINCIPLES OF ANALYTICAL ELECTRON MICROSCOPY edited by David C. Joy, Alton D. Romig, Jr., and Joseph I. Goldstein This new volume is a practical guide to the theory and application of analytical electron microscopy. The topics covered include energy disper sive X-ray spectroscopy, electron energy-loss spectroscopy, and elec tron diffraction. 0-306-42387-l/464pp./ill./1986/$35.00 11
ION-EXCHANGE SORPTION AND PREPARATIVE CHROMATOGRAPHY OF BIOLOGICALLY ACTIVE MOLECULES
4 2
1
s
0-306-10988-3/approx. 200 pp./ill. 1986/S45.00
CHEMISTRY BY COMPUTER An Overview of the Applications of Computers in Chemistry by Stephen Wilson Details the methods and techniques of computational chemistry and gives examples of their application. The methods discussed include quantum chemistry, molecular mechanics, col lision theory, chemical kinetics, organic synthesis, Monte Carlo simulation, and molecular dynamics. 0-306-42152-6/224 pp. + index/ill. 1986/537.50
MASS SPECTROMETRY IN ENVIRONMENTAL SCIENCES edited by F. W. Karasek, O. Hutzinger, and S. Safe " . . . a useful book with a large dose of solid, fundamental information." —Applied Spectroscopy An in-depth study of mass spec trometry in the analyses of en vironmentally important compounds. 0-306-41552-6/598 pp./ill./1984/S75.00 Plenum Publishing Corporation 233 Spring Street New York, N.Y. 10013-1578
6
8
7^
by G. V. Samsonov translated by R. N. Hainsworth This new volume, translated from the original Russian, provides a thorough treatment of the theoretical basis of modern large-scale separa tion, isolation, and purification of physiologically active substances using network polyelectrolytes and dynamic column regimes. A volume in the series Macromolecular Com pounds.
10
9 5
0
2.0
1.0
3.0
Time (h)
Figure 4. Chromatogram of solvolyzed plasma steroids derivatized with bromomethyl coumarin using fluorescence detection Column, 2.25-m X 220-/im i.d., 5-μπι ODS; eluent, continuous gradient 75-100% acetonitrile in H 20; flow rate, 1.5 μί/Γηίη. Approximately 50 pg of each steroid was injected. Tentatively identified compo nents: 1 = 5«-androstan-3a, 110-diol-17-one; 2 = 5/3-androstan-3a, 110-diol-17-one; 3 = 5/3-pregnane3a,110,17a,21-tetrol-2O-one; 4 = 5/3-pregnane-3a,17a,2O0,21-tetrol-11-one; 5 = 5/3-pregnane3a,11/3,17a-20/3,21-pentol; 6 = 5|3-pregnane-3a, 17α, 20α, 21-tetrol-11-one; 7 = 5/3-pregnane3a,11/3,17a,20a:,21-pentol; 8 = 5a-androstan-3a-ol-17-one; 9 = 5-androstene-3£i-ol-17-one; 10 = 5(3-pregnane-3a,20a,21-triol; 11 = 5/3-androstan-3a,17/J-diol. Reproduced with permission from Reference 13
logical applications, laser fluorometry may be the only technique suitable for LC quantitation. There have been many recent studies on derivatization schemes to take advantage of the HeCd laser, which emits at 325 nm and is relatively reliable in its opera tion. For example (13), the analysis of a complex mixture of steroids (which exhibit only moderate fluorescence) with detectabilities on the order of 1 pg is shown in Figure 4. With high light intensities, it is pos sible to observe fluorescence derived from two-photon excitation (12). This process reaches a different set of elec tronic states, is polarization depen dent, is more restrictive, and can be resonantly enhanced, so complemen tary information is obtained compared with normal fluorescence. A continu ous laser provides detectabilities in the nanogram range. Because the twophoton process is enhanced by inci dent intensity (peak power), we re cently (14) redesigned the detector based on a copper-vapor laser. The
CIRCLE 167 ON READER SERVICE CARD 1248 A · ANALYTICAL CHEMISTRY, VOL. 58, NO. 12, OCTOBER 1986
noise equivalent is estimated to be 100 fg of 2-(4-biphenyl)-5-phenyl1,3,4-oxadiazole injected. With the im proved detectabilities, two-photon ex cited fluorescence is competitive with most other LC detectors in sensitivity. Normal fluorescence will still be slightly better in ideal cases where emission is spectrally far away from solvent Raman bands. The fact that there is so little background from the solvent here implies that solvent puri ty requirements can be relaxed. In fact, most biological matrices show very little two-photon fluorescence background, so the unique selectivity is valuable. The transverse excitation geometry and small optical volume make this detector suitable even for on-column measurements in capillary LC, SFC, or capillary zone electropho resis. Best of all, the same laser can excite both normal and two-photon fluorescence in the same optical region to maximize the information content. Optical rotation. Optical activity is a particularly interesting molecular
