Premium
Comparative photodegradation rates of alachlor and bentazone in natural water and determination of breakdown products
Author(s) -
Chiron Serge,
Barceló Damià,
Abian Joaquin,
Ferrer Marta,
SanchezBaeza Francisco,
Messeguer Angel
Publication year - 1995
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.5620140805
Subject(s) - alachlor , chemistry , photodegradation , chromatography , mass spectrometry , solid phase extraction , liquid chromatography–mass spectrometry , thermospray , tandem mass spectrometry , environmental chemistry , selected reaction monitoring , organic chemistry , pesticide , atrazine , photocatalysis , agronomy , biology , catalysis
The photochemical degradation of the herbicides alachlor (2‐chloro‐2′,6′‐diethyl‐ N ‐methoxymethylacetanilide) and bentazone (3‐isopropyl‐(1 H )‐2,1,3‐benzothiadiazin‐4(3 H )‐one‐2,2‐dioxide) in distilled water and in river water, under xenon arc lamp irradiation, was investigated. Analytical determinations were carried out by using a xenon arc photoreactor and online solid‐phase extraction coupled to liquid‐chromatography diode‐array and liquid‐chromatography mass‐spectrometry detection systems. Photolysis experiments were performed at low concentration (20 μg/L), and the advantages of this methodology over conventional techniques are discussed. The photodegradation of alachlor and bentazone is a process depending on the water type, humic substances, and pH. When using a solution of 4 mg/L of humic matter, the estimated alachlor and bentazone half‐lives were 84 and 150 min, respectively, using a total irradiance of 550 W/m 2 in the range of 300 to 800 nm. The degradation of alachlor and bentazone followed pseudo second‐ and first‐order kinetics, respectively. The major photodegradation products of both herbicides were identified either by on‐line solid‐phase extraction (SPE)‐liquid chromatography‐thermospray mass spectrometry (LC/TSP‐MS) or on‐line‐SPE‐LC/TSP‐tandem mass spectrometry (LC/TSP‐MS/MS). In addition to that, a total of six transformation products of alachlor were synthesized in our laboratory and their MS spectra were compared with those of the breakdown products obtained. After photodegradation, a total of 14 photoproducts resulted from alachlor dechlorination with subsequent hydroxylation and cyclization processes. The two major photoproducts were identified as hydroxy‐alachlor and 8‐ethyl‐1‐methoxymethyl‐4‐methyl‐2‐oxo‐1,2,3,4‐tetrahydroquinone. No significant breakdown products of bentazone could be identified.