PARTICULATE MATERIAL ANALYSIS BY A LASER IONIZATION FAST CONDUCTIVITYMETHOD - WATER-CONTENT EFFECTS

Combined laser multiphoton ionization and fast-conductivity methods ha ve been applied to probe organic contamination on wet particulate samp les. This is a first attempt of testing such a technique for this purp ose. A special emphasis has been made on establishing correlation betw een sample water content and detection of pyrene, which has been used as a probe contaminant in this study, Environmental (soil) and artific ial samples (silica gel) have been studied. The experimental setup inc ludes a pulsed Nz laser and a fast-conductivity detection system, oper ated in an opened chamber under ambient conditions. The correlation be tween the observed photoionization signals and water content has been investigated in a slow-drying made, where water has been gradually eva porated. Surface contamination of wet samples has been more efficient than moist ones, This was evident in the case of soil samples, from th e earlier appearance (at lower pyrene concentrations) of saturation-ty pe features of the detected photoionization signals, Assumptions of a contamination model has enabled certain compensation for sample and ma trix effects.