Pentacene and tetracene show readily observable photoconductivity when illuminated with light in the blue part of the visible spectrum. We measured the change of photoconductivity with hydrostatic pressure in single-crystal samples of both materials. Possible mechanisms for the observed increase in photoconductivity with pressure are discussed. We conclude that a carrier-mobility increase under pressure is most likely to cause the increase in photoconductivity in the case of pentacene. For tetracene, changes in the absorption spectrum in the range of the excitation wavelengths may also be significant. We also observe a phase transition near 0.3 GPa in tetracene, in agreement with previous results.

The purpose of this study was to develop a highly sensitive fluorescence polarisation immunoassay (FPIA) for the detection of zearalenone (ZEN). The method was optimised and validated to examine the feasibility of performing FPIA using several tracers synthesised from different fluorescence labels and chemicals structurally mimicking ZEN. Optimum extraction conditions were determined, and 4-(aminomethyl) fluorescein-labelled ZEN tracer (ZEN-4AMF) was selected as the tracer. None of the tracers mimicking ZEN gave a favourable response with the monoclonal anti-ZEN antibody. When tested on a corn matrix, the FPIA showed a detection limit of 77 lg kg )1 within 3 min, excluding extraction time. Recovery of ZEN averaged 101% (intraday) and 109% (interday), and trueness averaged 111%. Ruggedness was satisfactory but crossreactivity with ZEN analogues was relatively high. These results suggest that the current FPIA for the detection of ZEN has a potential as an easy and rapid screening tool for ZEN and its analogues in corn.

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