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New Zealand Plant Protection 68 (2015): 32-37

Photostability of pyranine and suitability as a spray drift tracer

J.J. Nairn and W.A. Forster

ABSTRACT

Pyranine, a water soluble fluorescent tracer, has been used in spray drift studies, yet there is limited information regarding analytical methods, and conflicting information on the rapidity and extent to which the pyranine may degrade. This study assessed the suitability of pyranine as a tracer for drift studies. While pyranine did decompose when exposed to sunlight whilst in solution, spray droplets dry in minutes and photodecomposition appears to be significantly slower in the solid phase. Droplet residues showed minimal photodecomposition after exposure to sunlight for 2 h. Pyranine samples could be stored in cool, dark conditions, as dried deposits or in solution, for over 2 weeks without significant degradation. Pyranine is a suitable tracer for spray drift determinations as there is no significant degradation over the time required to collect, process and measure samples allowing residues to be accurately quantified, provided liquid extracts are suitably buffered.

Keywords: photodecomposition, fluorescence, pH.

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