Evaluation of temperature programming for gradient elution in packed capillary liquid chromatography coupled to electrochemical detection

A miniaturized amperometric detector compatible with temperature-programmed packed capillary liquid chromatography has been constructed and evaluated. Temperature programming could successfully be used as a tool for retention control, providing gradient action that did not influence the detector performance. A 7-μm single carbon fiber was utilized as working electrode and detection was performed in a 50-μm i.d. fused silica detection capillary which also functioned as restriction capillary. Separation of tyrosine, 3-(3,4-dihydroxyphenyl)alanine, 3-chloro-tyrosine and 3-NO₂-tyrosine was achieved in 6 min using a temperature program from 30°C to 100°C with a ramp of 8°C/min on a 25 cm 0.32 mm i.d. column packed with 3 μm Hypersil ODS. The mobile phase consisted of 50 mM citric acid (pH 3.10)-methanol (95+ 5, v/v), and the mass limit of detection was in the range 1–5 pg using 1.2 V vs the Ag/AgCl reference electrode. © 2001 John Wiley & Sons, Inc. J Micro Sep 13: 179–185, 2001