An integrated on-line method for the preconcentration and simultaneous determination of metsulfuron methyl and chlorsulfuron using oxidized carbon nanotubes and second order fluorescent data

• Published in: Microchemical journal 2016-11, Vol.129, p.90-97
• Main Authors: Acebal, Carolina C., Grünhut, Marcos, Llamas, Natalia E., Insausti, Matías, Zelená, Lucie, Sklenářová, Hana, Solich, Petr, Band, Beatriz S. Fernández
• Format: Article
• Language: English
• Subjects: Automated flow system; Oxidized multiwall carbon nanotubes; Photodegradation; Second order data algorithms; Sulfonylureas
• ISSN: 0026-265X; 1095-9149
• DOI: 10.1016/j.microc.2016.06.011

Trace amounts of two sulfonylurea herbicides widely used for crops protection, metsulfuron methyl (MSM) and chlorsulfuron (CSF) were simultaneously determined taking into account the different kinetic photodegradation behavior of their photoproducts in alkaline medium. As the analytes are present at trace concentration levels, a preconcentration by sorption on a mini-column packed with oxidized multiwall carbon nanotubes (ox-MWCNTs) at pH3.0 was performed. The retained analytes were removed from the ox-MWCNTs mini-column with a mixture of ACN contained 10% (v/v) of NaOH pH12.5. A total enrichment factor of 26-fold for a 14.50mL sample volume was obtained. The eluate was photodegraded by UV radiation during 126s and the fluorescent spectra corresponding to the analytes photoproducts were registered overtime between 300 and 500nm. The kinetic second order data were analyzed by unfolded-partial least squares-residual bilinearization (U-PLS/RBL) and multidimensional-partial least squares-residual bilinearization (N-PLS/RBL) algorithms. The relative error of prediction (REP %) for N-PLS/RBL was 7.73% for MSM and 6.37% for CSF. In the case of U-PLS/RBL, this statistical parameter was 7.75% for MSM and 7.23% for CSF, respectively. The limits of detection (LOD) were 0.19μgL−1 for MSM and 1.14μgL−1 for CSF using N-PLS/RBL and 0.21μgL−1 for MSM and 1.03μgL−1 for CSF when U-PLS/RBL was applied. The entire procedure was performed in an on-line integrated fully automated flow system coupled to a low mercury UV lamp (15W, 254nm) and a spectrofluorometer. In this manner, the preconcentration, photodegradation and detection steps were performed in a reproducible way. After optimization, the method was successfully applied to the analysis of real water samples obtained in the south part of Buenos Aires province and used for irrigation and consumption. •Integrated fully automated method for determining metsulfuron methyl and chlorsulfuron in trace levels•Oxidation and characterization of ox-MWCNTs•Use of ox-MWCNTs to achieve the preconcentration of the target analytes•Application of second order algorithms to photodegradation fluorescent data•Analysis of real environmental water samples