You get better results when you see things our way The new Luminon spectrophotometer cells feature fully fused quartz or glass seams.. . no low melting intermediate cements to cause problems. This also insures that the cells are impervious to cleaning solutions and other deteriorating media. Luminon produces a complete line of cells for U.V., far U.V., near U.V., visible light and near I.R. And, if needed, we can produce customized cells to your specifications
Summary
For information on our complete line of low priced cells, write today.
LUMINON, INC. 122 Coit Street, Irvlngton, N. J. 07111 · 201 -373-4242 Associated with International Crystal Laboratories
CIRCLE 124 O N READER SERVICE CARE-
SARGENT-WELCH
new pH Electrodes with plug-in cables Now you can have the convenience of a whole drawerful of pH electrodes . . . without the storage mess . . . and save money too! When you've got a pH job to do, pick your electrode . . . the right length cable . . . plug in and twist . . . and you're ready to go. Break an electrode and that's all you replace . . . your cable still has a useful life. 7 electrodes + 8 cables =• 20 electrode/cable assemblies and consummate convenience.
SARGENT-WELCH Sargent-Welch Scientific Company 7300 North Linder Avenue Skokie, Illinois 60076 (312)677-0600 Skokie/ Anaheim/Birmingham/Cincinnati/Cleveland/Dallas/ Denver/Detroit/Springfield, N.J./Toronto/Montreal/Vancouver
CIRCLE 182 ON READER SERVICE CARD 1138 A · ANALYTICAL CHEMISTRY, VOL. 45, NO. 13, NOVEMBER
of nitrogen can be m e a s u r e d since t h e nitrogen line is very n a r r o w and therefore creates large local curvature. Derivative spectroscopy h a s b e e n u s e d to e x t r a c t very weak emission lines from a flame b a c k g r o u n d ( 7) a n d i m p r o v e d d e t e c t a b i l i t y has been r e p o r t e d by use of derivative spectroscopy in a t o m i c a b s o r p t i o n work (8). A p p l i c a t i o n s have been m a d e successfully in fluorescence s p e c t r a l analysis (9). H e r e , t h e ability to a m p lify s m a l l features in a d i s t r i b u t i o n with derivative t e c h n i q u e s h a s b e e n used to resolve overlapping fluorescence s p e c t r a of several c o m p o u n d s .
1973
In s u m m a r y , t h e value of derivative spectroscopy can be recognized a n d a p p l i c a t i o n s chosen to benefit from t h e t e c h n i q u e if t h e following fundam e n t a l s a n d p r o p e r t i e s are understood. Derivative spectroscopy senses c h a n g e s in i n t e n s i t y w i t h wavelength, s u c h as slope a n d c u r v a t u r e . T h e o u t p u t of a derivative spect r o m e t e r is expressible m a t h e m a t i c a l ly as a derivative of i n t e n s i t y with respect to w a v e l e n g t h . Therefore, a v a r i a b l e which, in a given a p p l i c a tion, is expressible as a function of t h e derivative of i n t e n s i t y can produce a p r e d i c t a b l e signal from a derivative s p e c t r o m e t e r . T h e signal from a derivative spect r o m e t e r often relates to a p a r a m e t e r in a more u s a b l e fashion t h a n t h e relation b e t w e e n t h a t p a r a m e t e r a n d intensity. Sensitivity, linearity, a n d bipolarity are possible properties of derivative signals which m a y b e t t e r serve t h e a p p l i c a t i o n . Finally, derivative spectroscopy can e x t r a c t more information c o n t a i n e d within a r a d i a t i o n i n t e n s i t y spectral d i s t r i b u t i o n t h a n is accessible t h r o u g h direct spectroscopy t e c h niques because of t h e specific m e a s u r e m e n t of t h e derivatives of t h a t distribution.
References (1) A. Griese and C. French. Appl. Spectra*.. 9, 78(1955). (2) G. Collier and F. Singleton, J. Appl. Chem.. 6,495(1956). (3) G. Bonf'iglioli and P. Brooctlo, Appl. Opt.. 3, 1417(1964). (4) F. Staufferand H. Sakai, ibid.. 7, 61 (1968). (5) R. Hager and R. Anderson. J. Opt. Suc. Amer.. 60, 1444 (1970). (6) R. White, ibid.. 32, 285 (1942). (7) W. Snelleman. W. Rains, K. Yee, H. Cook, and O. Menis, Anal. Chem., -12, 394(1970). (8) R. Elser and J. Wmeiordner. ibid . 41, 698(1972). (9) T. O'Haver and B. Keppler. Paper No. 305, Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, Cleveland, Ohio, 1972.
