Determination of Trifloxystrobin in Soy Grape Juice and Natural Water by Photo- Induced Fluorescence and High-Performance Liquid Chromatography

A fluorescent (340/380 nm) photochemical product, identified at m/z 206 by mass spectrometry was obtained by photo-derivatization (15 s ultraviolet exposure) in water/acetonitrile 10/90 v/v. The photoproduct was used for indirect determination of trifloxystrobin in water and soy grape juice by high-performance liquid chromatography and fluorescence detection. Separation was made under isocratic conditions (acetonitrile/water 70/30% v/v, at 1.0 mL min-1 and 35 degrees C) with trifloxystrobin photo-derivative eluting at 3.2 min. The influence of ultraviolet exposure was evaluated in short and long terms with photoproduct showing stability up to 120 min after 15 s of ultraviolet exposure. The limit of detection was 57 mu g L-1 in water (87-109% recoveries). For soy grape juice, dispersive liquid-liquid micro-extraction was used to clean up and for pre-concentration (limit of detection of 9.5 mu g kg-1 and 93-101% recoveries) attending to the maximum residue limits for citrus juices established by regulatory agencies. Potential interference by triazoles was evaluated.