USE OF PHOTOTHERMAL DEFLECTION SPECTROMETRY (PDS) FOR STUDIES OF ANALYTES IN AQUEOUS-SOLUTIONS

A crossed-beam photothermal deflection spectrophotometer (PDS) instrument was built, evaluated and applied to the determination of lanthanide neodymium. A dye laser filled with rhodamine 6 G and pumped by an argon ion laser at 514 nm was operated with outputs between 4 and 500 mW at the cuvette position and chopped at 2 Hz. The deflection of a He-Ne probe laser beam, crossing the exciting dye laser, was measured by a two-dimensional position sensitive device and two lock-in amplifiers. The setup was evaluated with a solid carbon sample and the liquids toluene and Nd3+/HClO4. A calibration curve for Nd3+ in HClO4 was obtained and the limit of detection (LOD) for Nd3+ was determined to be 2·10-6 mol/l. This LOD is, on the one hand, by 2 orders of magnitudes lower than the value obtained with the Cary 2400 spectrophotometer and, on the other hand, this transverse PDS technique is highly competitive to collinear thermal lensing and laser-induced photoacoustic spectroscopy. © 1990 Springer-Verlag.