A New Detector System for Continuous-Flow TLC

Abstract

A new d e t e c t o r s y s t e m f o r c o n t i n u o u s -f l o w TLC i s d e s c r i b e d t h a t p r o v i d e s p o s s i b i l i t i e s b o t h f o r o p t i c a l a n d f o r e l e c t r o c h e m i c a l measurements w i t h l o w d e t e c t i o n l i n i t s . 1. I n t r o d u c t i o n The a d v a n t a g e s o f t h e c o n t i n u o u s -f l o w t h i n -l a y e r c h r omatography /CFTLC/ o v e r t h e c o n v e n t i o n a l TLC methods are h i g h e r s p e e d and s e p a r a t i o n power. The b e n e f i t s o f CFTLC f i r s t came t o t h e a t t e n t i o n o f a w i d e a u d i e n c e i n 1955 when M. Mottier and E?. P o t t e r a t /I, 2 / p u b l i s h e d t h e i r w e l l known work. The o n s e t of t h e modern CFTLC e q u i p m e n t g o e s b a c k t o t h e mid-1960s when E. S t a h l / 3 / i n t r o d u c e d a c o n v e n i e n t TLC chamber. T h i s w a s f o l l o w e d by i m p o r t a n t works o f V. B r e n n e r and A. N i e d e rw i e s e r /4,5/, S. Hara 161, F. G e i s s a n d F. S c h l i t t 171, E.1'. T r u t e r 1 6 1 , L.M. L i b b e y a n d E.A. Day / 9 / a n d J . H . VanDijk /lo/.Since the selection of a mobile phase of adequate strength and selectivity is a major task is designing LSC separations, anything that simplifies this task will prove helpful. The right solvent can be chosen using,directly, the L C unit, but this is often a tedious, time consuming procedure. A much easier and faster one is to use TLC in the initial scouting for an appropriate mobile phase /14/.Under similar conditions separation by LSC and TLC proceed by the same retention mechanism, and Rf values in TLC can be used to predict k' values in LSC /same adsorbent and mobile phase/ by relationship k' = /l-Rf//Rf. However, there are several reports of the poor correlation between the TLC and LSC data. This can be accounted for by solvent demixing, variations in the adsorbent and adsorbent water content and by solvent concentratioc gradient in TLC. These

Electrochemical Detection in Thin-Layer Chromatography (TLC): A Review and Application of Direct On-Plate Square-Wave Anodic Stripping Voltammetry for TLC

“…A brief report on the use of conductimetric detection in continuous-flow TLC was published in the early 1980's, although the report provides no data on this system [20].…”