Laser-based refractive index, absorbance, and fluorescence measurements with the sheath-flow cuvette

A sheath-flow cuvette is used as a detector cell for three analytical applications incorporating lasers as the light source.;Second, the cuvette is used to determine absorbance of neat solutions by a thermo-optical technique. In this technique, the sample is heated by a 2 mW modulated pump beam. A second coplanar probe beam is used to detect the change of the refractive index induced by the pump beam. A lock-in amplifier is used to demodulate the periodic change of refractive index. Absorbance detection limits of 1.1 * 10;Third, the cuvette is used to determine fluorescence of neat solutions and is also combined with capillary zone electrophoresis (CZE) as a laser-induced fluorescence detector. In this technique, a one watt argon ion laser operating at 488 nm is used as the excitation source and a microscope set at a right angle to the laser beam is used to collect the fluorescent signal. Detection limits of 1.25 * 10;First, the sheath-flow cuvette is used to determine the refractive index of neat solutions by a flow-modulation technique. In this technique, diffraction of the laser beam within the cuvette produces a change in the far-field beam-center intensity which is proportional to the difference in refractive index between the sample and sheath streams. If the flow is switched rapidly between sample and sheath, synchronous demodulation of the laser beam intensity leads to improved refractive index precision. Detection limits of 7 * 10...