Phosphonic acid and especially potassium dihydrogen phosphonate are widely used to restrain the ubiquitous pressure of grapevine downy mildew in viticulture. Nevertheless, phosphonic acid and its derivatives have been banned in organic viticulture in October 2013, because they have been classified as plant protection products since then. This development has fueled the need for analytical methods for sensitive phosphonate determination. Current routine analysis of phosphonic acid is usually performed by ion chromatography with conductivity detection (IC-CD), which is not always sufficiently sensitive and specific. Furthermore, the quick polar pesticide evaluation method (QuPPe) of the European Reference Laboratory in combination with LC-MS/MS is well established for most polar pesticides. However, in case of phosphonic acid, issues regarding mass transitions and poor chromatographic resolution, can occur. Therefore, we sought to evaluate a new method based on IC separation coupled with ICP-MS detection as an alternative for previously described methods. By coupling an ICP-MS to an IC, non-phosphorus-containing, coeluting substances can be eliminated and thus a higher specificity can be achieved. Hence, this contribution highlights the development and validation of an IC-ICP-MS based workflow for the robust, sensitive and reliable determination of phosphonic acid at low µg/kg levels in wine and must. This method is then compared to the previous detection by CD and the advantages and disadvantages of each are briefly described. Quantification limits are 20 µg/kg or lower with % RSDs typically
Authors: Otto Sören1, May Bianca2 and Schweiggert Ralf1
1Department of Beverage Research, Chair Analysis and Technology of Plant-based Foods, Geisenheim University
2Department of Enology, Chair Wine and Beverage Chemistry, Geisenheim University
*corresponding author: SoerenLars.Otto@hs-gm.de
Keywords: polar pesticides, IC-ICP-MS, IC-CD, phosphonic acid, organic viticulture
