AN AUTOMATIC SYSTEM FOR THERMAL LENS SPECTROMETRY AND FLOWING SAMPLES

A computer-controlled pulsed-flow system for thermal lens spectrometric detection, is developed. Flow pulses are synchronized with the laser pumping and data acquisition periods, measurements being made in static conditions at the end of the stopped-flow half-cycles. A comparative study of the measurement of FIA peaks in continuous and pulsed flow conditions is made. Using the pulsed-flow system, the dependence of sensitivity and noise on the flow and on the presence of turbulences or irregular pump pulses in the flow, is reduced. With a methyl red solution injected into a 1:1 ethanol-water carrier at a flow rate of 2.7 mL min-1, limits of detection and peak area repeativities were 2.1 x 10(-8) M and 6.0%, and 6.2 x 10(-9) M and 4.3%, for the continuous and pulsed flows, respectively. Linear dynamic range extended up to 5 x 10(-7) M.