Atmospheric Detection of Carbamates and Phenylureas in the Okanagan Valley Using LC-ESI+-MS/MS

Date
2012-08
Authors
Fergus, Nicole Debra
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Faculty of Graduate Studies and Research, University of Regina
Abstract

This thesis describes a new analytical method for the determination of twelve carbamates, seven degradation products, and four phenylureas using liquid chromatography-positive electrospray ionization-tandem mass spectrometry with selected reaction monitoring. Chromatographic separation was achieved using a SynergiTM Fusion-RP column with a gradient elution where mobile phase A was 5 mM ammonium acetate with 0.1 v% formic acid and mobile phase B was 0.1 v% in acetonitrile. Method detection limits of 1 to 30 μg/L or 3.7 to 110 pg/m3 for a weekly air sample were achieved. This research project involves the first detection of S-ethyldipropyl thiocarbamate (EPTC), carbaryl, and diuron in gas phase atmospheric samples collected in western Canada. Atmospheric samples were collected from April to November, 2011 at Osoyoos, British Columbia, located in the Okanagan Valley where there was known historical usage of selected carbamates and phenylureas. EPTC was detected in a single sample collected from May 6th, 2011 to May 11th, 2011 at an atmospheric concentration of 23 pg/m3. Carbaryl was detected in 29 out of 32 samples with a maximum concentration of 10340 pg/m3 occurring during a five-day sample collected from June 2nd to 7th, 2011. This coincides with the period of apple tree thinning during the period of natural June drop. Two other broad maximums in atmospheric concentration of carbaryl occurred on June 7th to 15th, 2011 (3076 pg/m3) and July 13th to 19th, 2011 (4044 pg/m3). These periods of detection corresponded to the use of carbaryl on a variety of different fruit crops. Diuron was detected in 17 out of 32 samples with a maximum concentration of 563 pg/m3 occurring on an eight-day sample collected from August 3rd to 11th, 2011. Diuron can be used as a pre-emergent herbicide or a post-emergent herbicide. Atmospheric concentrations of diuron were influenced by volatilization from the soil with increasing temperature. The frequency of detection of diuron indicates that more than local sources contributed to atmospheric concentrations as diuron is not recommended to be used more than once every 90 days and has low reported usage in the Okanagan Valley.

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A Thesis Submitted to the Faculty of Graduate Studies and Research In Partial Fulfillment of the Requirements for the Degree of Master of Science in Chemistry, University of Regina. xii, 170 l.
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