Degradation of Prototype Pesticides Submitted to Conventional Water Treatment Conditions: The Influence of Major Parameters

Abstract

The behavior of several pesticides in aqueous solution, namely bifenthrin, amethrin (pyrethroid insecticides), endosulfan and endosulfan sulfate (organochlorine pesticides), disulfoton, methyl pyrimiphos, and phorate (organophosphorus pesticides), submitted to the conditions typically employed in water treatment stations was investigated. Continuous pesticide depletion was monitored by solid-phase microextraction sampling followed by gas chromatography-mass spectrometry analysis. The influence of major parameters (sodium hypochloride concentration, solution pH, and exposure time to ultraviolet (UV) light) was, thus, adequately established via two complementary approaches: factorial (2 3 , three variables-two levels) and Doehlert designs. Hence, the sodium hypochloride concentration and the solution pH produced distinct effects depending on the pesticide evaluated (for instance, acidic and basic media caused increasing rates of degradation for the organophosphorus/pyrethroid and organochlorine pesticides, respectively). Conversely, higher rates of degradation were achieved for all of the pesticides investigated when increased exposure times to UV radiation were employed. Finally, the exposure time to UV radiation that lead to complete degradation of disulfoton and endosulfan sulfate (organophosphorus and organochlorine pesticides, respectively) in aqueous media under ordinary conditions employed in water treatment stations was established; disulfoton and endosulfan sulfate were completely degraded after 10 and 40 h, respectively.

Vortex‐assisted liquid–liquid microextraction combined with gas chromatography‐mass spectrometry for the determination of organophosphate pesticides in environmental water samples and wines

“…In LPME, the pH of the aqueous phase plays an important role on the extraction capabilities of compounds having ionizable groups. Most of the OPPs are degraded in strong acidic (pH < 3) and alkaline medium . The effect of pH on the extraction performance was therefore investigated in the range of 3.0–8.0.…”

Doehlert uniform shell designs and chromatography

“…An increased implementation of Doehlert uniform shell designs in GC-MS has been observed in the last decade for developing efficient sample treatment methods by monitoring different analytical functions such as recovery [49][50][51][52][53][54][55], analytical signal [56][57][58][59][60][61] and reaction yield [51,62]. Table 4 also shows that regardless of the potential benefits of uniform shell designs, they have not gained widespread popularity among researchers for optimizing systematically and simultaneously GC-MS instrumental variables.…”

Pesticides and Herbicides

“…The effect of several water treatment oxidation processes on the pesticides bifenthrin, amethrin, endosulfan, endosulfan sulfate, disulfoton, methyl pyrimiphos, and phorate was studied by Souza et al (2010). It was found that increased exposure times to UV irradiation led to increased degradation of the pesticides, with the organophosphate pesticide disulfoton needing less time than the organochlorine pesticide endosulfan sulfate to achieve complete degradation.…”