Analytical optoacoustic spectrometry. Part II. Ultraviolet and visible optoacoustic spectra of some inorganic, biochemical and phytochemical samples

Some preliminary studies concerned with the application of optoacoustic spectrometry to chemical analysis are described and modifications made to improve the performance of the spectrometer that was discussed in Part I of this series are reported.This instrument has been used in the investigation of a variety of sample types; several inorganic species, including rutile and anatase titanium(IV) oxide, organometallic and water-sensitive compounds, have been examined and optoacoustic spectra have been obtained from a series of haemoproteins of biological origin and from botanical samples. Where comparisons are possible the spectra obtained by using optoacoustic spectrometry are similar to those obtained by use of conventional transmission or reflectance spectrometry. In general, however, optoacoustic spectrometry has the advantage of the requirement of only small (microlitre or microgram) amounts of sample. Spectra obtained from fresh leaf tissue indicate that optoacoustic spectrometry has a particular advantage over conventional techniques in that for heterogeneous samples of this type it is possible to generate separate spectra from different compounds by observing spectra in a phase-delayed mode; this effect can be used to advantage in the examination of surface layers without interference from substrate material.