Abstract A micromachined capillary electrophoresis sys- tem has been fabricated on a glass device for the separa- tion and indirect fluorescence detection of phenols. Using this device two phenols viz., 2,4-dichlorophenol and pen- tachlorophenol, were separated within 12 s compared to under 19 min on a conventional capillary electrophoresis system using direct ultraviolet detection. The precision of the glass device ranged from 12.7%–16.7% compared to 0.42%–4.9% for the conventional system. Both systems showed good linearity in the concentration range of 0.8– 6.38 mM for the glass device and 5–130 µ M for the con- ventional system. The relationship between temperature and high voltage with baseline drift was also investigated. These results provide a foundation for the development of a miniaturised chemical analysis system for the on-line analysis of phenols in water. 1 Introduction Although phenol is formed during the natural decomposi- tion of organic material most of the phenols found in the environment result from anthropogenic emissions. Phenol can enter aquatic systems as a result of wastewater dis- charges and spills connected with its industrial use. Phe- nol is used in the production of phenolic resin that is utilised as a binding material in products such as chip- board, paints and insulating material. The chlorinated sub- stitutes of phenol such as pentachlorophenol (PCP) is used on a huge scale (800 million L/year in the USA) in creosote oil for the preservation of timber against rotting fungi and wood-boring beetles [1]. Dichlorophenol (DCP) is used in the synthesis of herbicides and pesticides and widespread throughout the environment as a result of s leachate. Phenol and compounds containing the phenol group can also be readily substituted by chlorine to for chlorophenols as a result of the chlorination of water su plies [2]. This mainly results from the fact that phenol c react rapidly with hypochlorous acid (HOCl) as a result the electrophilic attack on phenoxide anions. At low part per billion (pbb) concentrations phen lead to taste and odour problems in the general water s ply. Also, as a result of their high toxicity, they ar cluded in the Environmental Protection Agency (EPA) l of priority pollutants [3]. With the introduction of strin- gent Environmental Quality Standards (EQS’s) conc ing the level of pollutants in aquatic systems water com panies have realised the need for on-site continuous mon toring [4]. A monitor in-situ would be able to main constant checks on all priority pollutants although at th present time commercially available systems are too cu bersome for on-site analysis. By incorporating the analy of pollutants into µ -TAS [5] (miniaturised – Total Analy- sis System) technology the aim is to develop an on-line monitor for pollutants found in surface or waste w Miniaturised – Total Analysis Systems has been referre to as a lab-on-a-chip where sample handling, extraction chemical reactions, separation and detection are inte grated on one small device. Ideally, the equipment used for on-s continuous or batch analysis should be compact, portab vandal proof and relatively cheap to purchase and main tain. All these requirements rule out the use of large-sc conventional instruments. Capillary electrophoresis (CE) has been one of th most successful methods used in glass devices as a res of the increased efficiency of electroosmotic pumping in channels as small as 26 µ m diameter and 5.2 µ m in depth [6]. A capillary electrophoresis separation was first demo - strated on chip by Manz and Harrison [7, 8] in 1991 wh two fluorescent dyes (calcein and fluorescein) were sep rated. The chips were fabricated using a glass sub with 30 µ m by 10 µ m etched channels. More recently rapid electrophoretic separations were performed b Martin Arundell · Peter D. Whalley · Andreas Manz Indirect fluorescence detection of phenolic compounds by capillary electrophoresis on a glass device Fresenius J Anal Chem (2000) 367:686–691 © Springer-Verlag 2000 Received: 24 January 2000 / Revised: 27 March 2000 / Accepted: 29 March 2000 ORIGINAL PAPER M. Arundell · A. Manz ( 쾷 ) Zeneca/Smithkline Beecham Centre for Analytical Sciences, Imperial College of Science, Technology & Medicine, London, SW7 2AY, United Kingdom P. D. Whalley Water Research Centre plc, Henley Road, Medmenham, Marlow, Bucks, SL7 2HD, United Kingdom