Elemental sulfur has been shown to be an economical and effective treatment for the prevention of powdery mildew on grapes. There has been some concern in following this practice with wine grapes, due to the possibility that sulfur residues may produce elevated levels of sulfide compounds in the finished wine. The quantitative determination of elemental sulfur at levels expected from usual vineyard practices is difficult. The official AOAC method involves a lengthy digestion, precipitation, and actual gravimetric weighing of barium sulfate formed from the sulfur. An inductively coupled plasma method has been reported to be successful, however this procedure requires an instrument that is not commonly available. We have modified the AOAC procedure so that the barium concentration remaining after precipitation is measured using an atomic absorption spectrometer (AAS). The method has been successfully applied to samples from two years of vineyard trials with sulfur and other fungicide treatments. AAS analysis has also been used to monitor sulfur dioxide residues on fumigated table grapes.
