Some Practical Limitations of Fluorescent Tracers Used to Measure Off-Target Pesticide Deposition.

Eight tracers were chosen for the study, based on availability, cost, previous work done in this laboratory, and extent of use by other researchers. Laboratory photodegradation was determined for each of the tracers over 0 – 100 minutes under ‘light’ and ‘dark’ conditions. Storage degradation was measured on a modified set of tracers over a period of 41–45 days under ‘frozen’, ‘light lab’, and ‘dark lab’ conditions. Both studies used a Turner 112 fluorimeter.

The photodegradation data suggest that Uvitex EC would be unsuitable for use in any drift trial situation since the fluorescence decreased up to 82 % under light conditions and nearly 16 % under dark conditions. The other tracers generally showed some decreases but not nearly as marked. Storage degradation data showed that the fluorescence of Tinopal CBS-X decreased by as much as 67 % under light lab conditions. The other tracers showed some reductions but not as marked as Tinopal CBS-X.

The results are considered in terms of their practical implications in relation to protocol development for off-target pesticide deposit (drift) studies.