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.

Detection of time‐resolved photoionization currents from pesticide‐contaminated vegetation

“…Similar behavior was observed for pyrene-contaminated soil substrates. 35,36 It was argued there that the charge build-up effects should be enhanced whenever the mean surface coverage by the UV-active neutrals becomes close to (or in excess of) a monolayer one.…”

“…Such an MPI-FC-combined method was recently reported for on-line screening of aromatic depositions onto porous substrates. 35,36 In terms of porosity, therefore, the very morphology of a common plant makes such substrates suitable for successful implementation of FC detection routines.…”

“…The experimental arrangement used here is similar to that reported for the MPI-FC characterization of PAH-contaminated soil samples. 35,36 A block diagram of the experimental setup operated at ambient laboratory conditions is shown in Fig. 1.…”

A Novel Method for Direct Nondestructive Diagnosis of Caries Affected Tooth Surfaces by Laser Multiphoton Ionization

“…It has been shown that the time integrated current is directly related to the irradiated chemical compounds. [1] The so called fast-conductivity data acquisition method allows for using MPI for direct chemical analysis under ambient conditions. The main advantage of this method is that it provides absolute results and no sample preparation is needed.…”

“…The main advantage of this method is that it provides absolute results and no sample preparation is needed. [1,2] This method has been proven to be fast and sensitive. [2] In previous studies only single laser wavelengths were applied for excitation, [1] and therefore, in most cases the signals were related to nonresonant ionization of organic compounds in the laser irradiation spot.…”