Development of solventless sampling/sample preparation and introduction techniques for on-site determinations.

摘要

Developing simple and rapid sampling/sample preparation and introduction techniques for on-site analysis is becoming increasingly important in many fields. These methods should be able to selectively preconcentrate the analytes at low concentration levels from the sample matrix, allow on-site extraction and analysis, and ensure the absence of, or at least low emissions of pollutants. Membrane extraction with a sorbent interface (MESI) and solid-phase microextraction (SPME) have been proven to meet these needs; MESI and SPME offer a number of analytical advantages, including a solventless approach, simplicity, efficiency, low cost, the capability of on-line/on-site monitoring, and good selectivity and sensitivity.;A MESI system has been used to evaluate a new technique for calibration in membrane extraction processes, by adding an analytically non-interfering internal calibrant in the carrier gas. By correcting the variation of the extraction rate of the membrane via the change in the accumulation amounts of internal calibrant in the microtrap, this approach should allow for accurate estimates of target analyte concentrations for complicated sampling conditions.;The mechanism of the mass transfer of semivolatile organic compounds (SVOCs) across a membrane has been studied. A preheating carrier gas has been used to build a temperature gradient within the membrane so that facilitates the desorption of the permeate analytes from the membrane inner surface. Therefore, the performance of on-line membrane extraction of SVOCs was improved.;MESI-Portable gas chromatography (MESI-Portable GC) for continuous on-line monitoring of biogenic volatile organic compounds (BVOCs) emissions from leaves of Eucalyptus dunnii in a greenhouse has been studied. The findings suggest that the MESI-Portable GC system is a simple and useful tool for monitoring changes in plant emissions in the field. The applicability and effectiveness of the MESI-Portable GC system have also been demonstrated in field monitoring applications, including the analysis of toluene in wastewater, volatile organic compounds (VOCs) in laboratory air, and chloroform in swimming pool water. This system has been shown to be a simple, fast, and portable tool for on-site process environmental monitoring.;A calibration-free measurement of the permeability of a poly(dimethylsiloxane) (PDMS) membrane has been developed. A mathematical model has been derived to explain the permeation process and deduce the equations for calculating the permeability. Some parameters that affect the permeability measurements of different analytes have been investigated.;Finally, a new prototype of a solid-phase microextraction-ion mobility spectrometry (SPME-IMS) system has been created to effectively couple the extraction efficiency of SPME to the detection capability of IMS. (Abstract shortened by UMI.)