Determination of metalaxyl and identification of adjuvants in wettable powder pesticide technical formulas

Foliar runoff is one of the most important processes affecting off-target movement of fungicides. In this way, RidomilA (R) Gold Plus and RidomilA (R) Gold MZ are two types of wettable powder technical formulations which contain metalaxyl and they are used for such a purpose. A method for quantitative determination of metalaxyl in pesticide formulas has been developed, validated, and subsequently applied to RidomilA (R) Gold Plus and RidomilA (R) Gold MZ. The method employs liquid-liquid extraction followed by liquid chromatography coupled with UV detection (LC-UV), using gas chromatography coupled with mass spectrometry as confirmation technique and to carry out a screening of organic adjuvants of these two selected pesticide formulas. Metalaxyl of 26.5 and 41 g/kg was detected in RidomilA (R) Gold Plus and RidomilA (R) Gold MZ, close to the manufacture specified level of 25 and 40 g/kg, respectively. Activator and utility adjuvants were detected in these two wettable powder technical formulations. Only methyl-ester-based surfactants were found within the group of nonionic surfactants, but the long-term fates of most adjuvants in soils and elsewhere in the environment are largely unknown, partially because of the lack of long-term monitoring data.