In Situ Silicone Tube Microextraction A New Metho

Authors: Brian K Mohney Tricia Matz Jessica LaMoreaux David S Wilcox Anne Louise Gimsing Philipp Mayer Jeffrey D Weidenhamer

Publish Date: 2009/11/10

Volume: 35, Issue: 11, Pages: 1279-

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Abstract

The difficulties of monitoring allelochemical concentrations in soil and their dynamics over time have been a major barrier to testing hypotheses of allelopathic effects Here we evaluate three diffusive sampling strategies that employ polydimethylsiloxane PDMS sorbents to map the spatial distribution and temporal dynamics of rootexuded thiophenes from the African marigold Tagetes erecta Solid phase root zone extraction SPRE probes constructed by inserting stainless steel wire into PDMS tubing were used to monitor thiophene concentrations at various depths beneath marigolds growing in PVC pipes PDMS sheets were used to map the distribution of thiophenes beneath marigolds grown in thin glass boxes Concentrations of the two major marigold thiophenes measured by these two methods were extremely variable in both space and time Dissection and analysis of roots indicated that distribution of thiophenes in marigold roots also was quite variable A third approach used 1 m lengths of PDMS microtubing placed in marigold soil for repeated sampling of soil without disturbance of the roots The two ends of the tubing remained out of the soil so that solvent could be washed through the tubing to collect samples for HPLC analysis Unlike the other two methods initial experiments with this approach show more uniformity of response and suggest that soil concentrations of marigold thiophenes are affected greatly even by minimal disturbance of the soil Silicone tube microextraction gave a linear response for αterthienyl when maintained in soils spiked with 0–10 ppm of this thiophene This method which is experimentally simple and uses inexpensive materials should be broadly applicable to the measurement of nonpolar root exudates and thus provides a means to test hypotheses about the role of root exudates in plantplant and other interactionsThis research was supported by a grant from the National Science Foundation DEB 0515826 and from the European Commission MODELPROBE no 213161 Philip Boes assisted with isolation and characterization of BBT Udo Blum and two anonymous reviewers provided helpful comments on the manuscript Kelly Harrison assisted with greenhouse cultivation of plants

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