Concentration Profiling in Layered Liquids Using a Laser Photoacoustic Probe

Abstract

An aluminum-coated Pyrex® glass rod is used both as a photoacoustic probe and as a laser light guide to examine a three-layer solution of carbon tetrachloride, hexane, and an aqueous solution of an efficient chromophore, ferroin. The boundaries of the layers show up clearly on a signal amplitude vs. penetration depth graph. A Beer's law plot of the ferroin solution alone shows that the probe is capable of analytical determinations down to 10−7 M. Reflections from the cell walls may cause interference in quantitative analysis if the size of the cell is too small. The sensitivity of the probe is compared with that of a typical photoacoustic cell, and it is found that the probe only attenuates the signal amplitude by ∼35%. Finally, it is found that the signal amplitude transmitted by the photoacoustic probe is roughly proportional to its diameter.

Improved chromatographic detection methods based on absorbance and ultrasonic measurements

“…The advantages and disadvantages of each technique depend on the application. While PAS and PTD can be used for analysis of solid surfaces such as coal surfaces and thin layer chromatography plates(83,84), thermal lens spectrometry cannot be used for this application. For optical detection only the thermal lens method can use a single laser, an arrangement which can greatly simplify the instrumental design.…”