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Development of analysis procedures for the determination of pesticides by use of multi-methods

The pesticide analysis methods that have been used until now, can be generically described by:

1) solid phase extraction (SPE) of the (filtered) water samples for the     isolation and enrichment of the relevant analytes

2) performing of the necessary washing steps for the separation,     respectively depletion of the matrix

3) elution of the analytes in a small amount of adequate solvent

4) chromatographic analysis.

This generic process represents the best available technology at the moment. It is however, because of the large number of worksteps that have to be done manually, very expensive. Moreover, it presents a whole series of difficulties, based particularly on the very different chemical structures and features of the substances to be analysed: not all the analytes can be equally well accumulated on the common (silica-based C18-) SPE-materials, respectively eluted again from the strongly adsorbent materials with small amounts of solvents (as it would be necessary for on-line processes). The chromatographic separation of the analytes that are sufficiently volatile can be done using the gas chromatography (GC), but requires liquid chromatographic methods (HPLC) for polar and temperature sensitive substances. Also for HPLC different chromatographic conditions, and therefore separate runs, may be required. The commonly used UV-detection has so far the disadvantage that it is not sensitive to certain analytes and therefore not selective enough.

Starting from the best available technology, the following modifications and improvements of the above mentioned generic methods have been researched

a) the enrichment of the analytes and elution in the HPLC to be done on-line,
b) the detection of the analyte to be done with mass spectroscopy (MS).

The on-line enrichment and on-line elution have the advantage that, in comparison with off-line processes, either considerably lower detection limits can be achieved for the enrichment of the same amount of sample, or the volume of the sample can be significantly decreased, maintaining the same detection limits. The resulting advantage is mainly the acceleration of the sample preparation, but also the smaller volume of sample required.

Moreover, the on-line enrichment has the advantage that it can be automated. Under adequate boundary conditions, in order to ensure the stability of the analyte until the analysis is done, it is possible to analyse, in a special configuration, up to 50 samples in one sequence, so that the enrichment and analysis interlace and are therefore more time effective.

The detection of the analyte by means of mass spectrometry presents the advantage of a higher sensitivity, together with a better selectivity of the determination.

The development work is professionally supported by:
Associate Univ. Prof. E.-E. Rosenberg, MSc. PhD. - Vienna University of Technology, Institute for Chemical Technologies and Analysis, Department for Analytical Chemistry, Univ. Prof. G. Allmaier, PhD.- Vienna University of Technology, Institute for Chemical Technologies and Analysis, Assistent Prof. Hann, PhD. MSc. - University of Natural Resources and Applied Life Sciences, Vienna, Institute for Chemistry, Department for Analysis

This research project has been financially supported by the Austrian Research Promotion Agency Ltd. (FFG).