A Comparison Between a Micro and an Ultramicro Circle®Cell for on-Line Ft-Ir Detection in a Reverse Phase HPLC System

Abstract
Caffeine and theophylline peaks separated on a 300 × 7.8 mm C18 column could be distinguished qualitatively by FT-IR detection using two types of cylindrical internal reflectance (CIRCLE®) cells. Detection limits and limits of identification, on the order of 0.2%, are lower for the micro CIRCLE® cell as compared to the ultramicro CIRCLE® cell. Maximum sample capacity of the column used was 50uL of a 0.4% solution of caffeine (1.0 micromoles).