Hanot, Vincent, et al. Food analytical methods, 2015, 8, 524-530.
An analytical method for the quantification of ethephon in grapes was developed without laborious clean-up or derivatization steps. The addition of ethephon D4 as a surrogate was followed by methanol extraction. The method significantly reduced the analysis time, with sample extraction time of approximately 10 min and determination time of approximately 10 min. The use of the isotope dilution technique not only compensated for the analyte losses encountered but also prevented matrix effects.
The analytical performance was evaluated using grape samples spiked at the limits of quantification of 50 μg kg-1 and 200 μg kg-1. Validation was performed against the SANCO/12571/2013 standard with recoveries of approximately 96% and RSDs well below the acceptable 20%.
Sample preparation: A 50 ml Falcon tube received 10.0 g ± 0.1 g grapes followed by a 200 μl addition of 10 μg ml-1 ethephon D4 solution. Afterward, the 10 ml solution of 0.1% formic acid in methanol mixed with the sample at high speed for one minute. A 500-microliter sample of extract was transferred into a 0.2 μm PVDF filter vial followed by 5 μl of 25% ammonium hydroxide to achieve a final extract concentration of 1 g ml-1 of the equivalent sample.
