Particulate Material Analysis by a Laser Ionization Fast Conductivity Method. Water Content Effects

Abstract

Combined laser multiphoton ionization and fast-conductivity methods have been applied to probe organic contamination on wet particulate samples. This is a first attempt of testing such a technique for this purpose. A special emphasis has been made on establishing correlation between sample water content and detection of pyrene, which has been used as a probe contaminant in this study. Environmental (soil) and artificial samples (silica gel) have been studied. The experimental setup includes a pulsed N(2) laser and a fast-conductivity detection system, operated in an opened chamber under ambient conditions. The correlation between the observed photoionization signals and water content has been investigated in a slow-drying mode, where water has been gradually evaporated. Surface contamination of wet samples has been more efficient than moist ones. This was evident, in the case of soil samples, from the earlier appearance (at lower pyrene concentrations) of saturation-type features of the detected photoionization signals. Assumptions of a contamination model has enabled certain compensation for sample and matrix effects.