Use of a thermal lens microscope in integrated catecholamine determination on a microchip

A new method for determination for catecholamines (CA) utilizing microchip technology and a thermal lens microscope has been developed. Microchannels with a 250 microm x 10 microm cross section were used for mixing, reaction, and detection. Epinephrine (EP), nor-epinephrine (NE), dopamine (DA), and L-dopa (LD) were determined by using coloring oxidization to aminochromes by sodium metaperiodate. A thermal lens microscope (TLM) was used for detection of the product. The sensitivity of the system was comparable for the four CA and required only 15 s for mixing of sample and reagent. The calibration lines indicated excellent linearity for concentrations of 5-20 microg mL(-1). The relative standard deviations for 10 microg mL(-1) solution were 1.08, 2.18, 2.2, and 2.5% for EP, NE, DA, and LD, respectively. CA in pharmaceutical injections were also determined by use of the system and the results correlated very well with nominal values. Results obtained by use of the integrated system suggested there was a sufficient possibility to realize high-throughput medical diagnosis systems.