Technical Note: Gas Phase Pesticide Measurement Using Iodide Ionization Time-of-Flight Mass Spectrometry

Abstract

Abstract. Volatilization and subsequent processing in the atmosphere is an important environmental pathway for the transport and chemical fate of pesticides. However, these processes remain a particularly poorly understood component of pesticide lifecycles due to analytical challenges. Most pesticide measurements require long (hours to days) sampling times coupled with off-line analysis, inhibiting observation of meteorologically driven events or investigation of rapid oxidation chemistry. Here, we present chemical ionization time-of-flight mass spectrometry with iodide reagent ions as a fast and sensitive measurement of four current-use pesticides. These semi-volatile pesticides were calibrated with injections of solutions onto a filter and subsequently volatilized to generate gas phase analytes. Trifluralin and atrazine are detected as iodide-molecule adducts, while permethrin and metolachlor are detected as adducts between iodide and fragments of the parent analyte molecule. Limits of detection (1 second) are 0.37, 0.67, 0.56, and 1.1 µg/m3 for gas phase trifluralin, metolachlor, atrazine and permethrin, respectively. The sensitivities of trifluralin and metolachlor depend on relative humidity, changing as much as 70 % and 59 %, respectively, as relative humidity of the sample air varies from 0 to 80 %. This measurement approach is thus appropriate for laboratory experiments and potentially near-source field measurements.

Atmospheric OH Oxidation of Three Chlorinated Aromatic Herbicides

“…Alternately, the C 6 H 5 ClO 4 dihydroxyperoxide could also be formed from the C 7 H 7 ClO 4 compound detected by Iodide CIMS. The production of chlorosalicylaldehyde and chlorosalicylic acid from MCPA oxidation is intriguing: 5-chlorosalicylaldehyde is a known skin and respiratory irritant in gas and liquid phase . It is also toxic to aquatic life, specifically a reported LC 50 (lethal concentration required to kill 50% of the population) for minnows, 0.71–0.83 mg/L .…”

Atmospheric Transport of Adulticides Used to Control Mosquito Populations across an Urban Metropolitan Area

“…The study of such photochemistry and oxidation of pesticides has been observed in both field-based (i.e., agricultural studies) and chamber-based studies. Most fieldbased efforts have focused on agricultural pesticides [42][43][44][45][46][47][48][49][50][51][52][53][54][55][56], while few have focused on pesticides associated with county-level mosquito control (i.e., adulticides, such as malathion and permethrin). It is important to note that malathion and permethrin have been well characterized in chamber-based studies to be oxidized by the three principal atmospheric oxidants, ozone (O 3 ), nitrate radicals (NO 3 ), and hydroxyl radicals (OH), which are commonly present in urban atmospheres [57][58][59].…”