Pulsed Laser Thermal Lens Spectrometry for Flowing Liquid Detection

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Analytical Chemistry

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The pulsed laser thermal lens spectrophotometry slgnal for flowing llquld samples Is studied as a function of solution flow rate. A sllght decrease In the signal wlth lncreaslng flow rate Is attrlbuted to the competltlon between the finite rate of thermallzatlon of absorbed energy and the rate at which heat Is removed from the monltored region of the detectlon cell. The slgnal varlance Is found to be relatlvely Independent of flow rate and is llmited by source nolse and detector shot noise. The mlnlmum observable absorbance Is measured to be 4.7 X 10-3, which corresponds to 0.12 ng of aqueous 4.8 µM 2-mercaptopyrldlne In the lrradlated volume. A model Is described that qualltatlvely descrlbes the flow rate dependent data In the case where lamlnar flow occurs.

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