First application of pulsed photothermal deflection spectroscopy to solid samples is demonstrated. A new densitometer for thin layer chromatography based on this method is described. The technique is suitable for direct measurements in the ultraviolet region. A pulsed excimer laser is used to produce a transient thermal refractive index gradient. The laser delivers pulses of 1-2 mJ at 10-22 pulses/s, at 351 nm. With this system the detection limit for 2,4-dinitroaniline is 750 pg. The signal is linear with amount of analyte for about three orders of magnitude.
Fotios K. Fotiou and Michael D. Morris, "Photothermal Deflection Densitometer with Pulsed-UV Laser Excitation," Appl. Spectrosc. 40, 700-704 (1986)