Evanescent wave sensing: new features for detection in small volumes

The association by aligned direct bonding of an evanescent wave optical sen sor and small-volume flow cells for visible absorption detection is demonst rated. We show that for sample volumes ranging from 760 to 190 nr and a sen sor interaction length of I mm, very small cross-sectional dimensions of fl uid channels are no more a serious obstacle for optical detection. The lowe st limit for the channel depth Is the penetration depth of the evanescent w ave. which is usually in the order of magnitude of a few micrometers. (C) 2 000 Elsevier Science S.A. All rights reserved.