Novel Trace Analysis Systems Based on Single Picoliter Microparticles Combined with Microflow Devices

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In the present study, we showed that a single 1-butanol (BuOH) droplet could be produced by infrared laser irradiation under an optical microscope and the droplet produced could be simultaneously trapped optically by the infrared laser beam. The technique was then combined with a capillary electrophoresis system. Single BuOH droplets were produced by laser irradiation and trapped stably even in the presence of an osmotic flow. An aluminum dihydroxyazobenzene chelate complex (Al^<3+>-DHAB) or rhodamine B (RhB) was then separated by capillary electrophoresis and the solute was then forced to distribute to single BuOH droplets produced by infrared laser irradiation. In the case of RhB, the lower detection limit of the dye distributed to the BuOH droplet was as low as 10^<-20>mol/dm^3, which was much lower than the ordinary detection limits in capillary electrophoresis.Laser oscillation in single dye-doped cation-exchange resin microspheres was also applied to ultratrace analysis. Laser oscillation of single RhB-doped microparticles under air was confirmed by characteristic emission spikes superimposed to the spontaneous broad emission spectrum. In the presence of organic gas vapor in air, the characteristic laser oscillation spikes from the RhB-doped microparticle were modulated owing to the change in the particle/surrounding medium refractive index conditions. The present study was also extended to laser trapping-microspectroscopy of picoliter aerosol water droplets in air. We succeeded in conducting temperature-controlled laser trapping of aerosol water droplets as well as in observing formation of supercooled water droplets down to 223 K.