Photochromism-induced photoacoustic spectrometry for the determination of trace mercury(II) as its dithizonate in the solid state

Abstract

A new technique, photochromism-induced photoacoustic spectrometry, has been developed for the determination of mercury(II) as mercury(II) dithizonate in the solid state. A special photoacoustic cell was designed for inducing a photochromic reaction in mercury(II) dithizonate and detecting the resultant photoacoustic signal from its excited state. Interferences from all other metal ions are absent because only mercury(II) dithizonate can exhibit photochromism in the solid state. A linear standard calibration graph for Hg(II) was obtained in the quantity range from 1.5 to 450 pmol. The relative standard deviations determined at 15 and 150 pmol were 6% and 3%, respectively. When the technique is applied to water analysis with dithizone extraction, a detection limit of 3 pptr (parts per trillion) Hg(II) is easily achievable.