Copper Microelectrode as Liquid Chromatography Detector for Herbicide Glyphosate

Abstract

Electrochemical behavior of herbicide glyphosate at copper microelectrode was investigated in alkaline and buffer solutions, and two mechanisms seemed to take place for glyphosate: i) complexation reaction at lower potential in alkaline and buffer solutions and ii) catalysis process at higher potential in alkaline solution. It was demonstrated that the copper microelectrode can be used as coulometric detector for glyphosate in HPLC, using the complexation reaction in buffer solution. Under optimized conditions, the detection limit for glyphosate was 5.9 Â 10 À7 mol L À1. The present method was successfully applied to the determination of glyphosate in tomato juice with a recovery of 88%. The herbicide activity of glyphosate, [N-(phosphonomethyl)glycine], is well known and its applications in agriculture are wide. Its popularity as a broad spectrum, nonselective, postemergent and systemic herbicide has remained for about 30 years [1]. This indiscriminate application generates many problems with regard to contamination of the environment, thus, the development of a robust analytical procedures for the monitoring of glyphosate in crops, fruits and vegetables has gained increasing importance [2,3].Although numerous chromatographic procedures exist in the literature for the determination of glyphosate using liquid chromatography (UV or fluorescence) and gas chromatography (mass spectrometry), they are quite complicated, require special equipment, are time consuming, and frequently generates unstable products, when derivatization procedures are required [3,4].A small number of electroanalytical methods for determination of glyphosate are reported in the literature. Bronstad and Friestad [6] analyzed this herbicide through of the secondary amino group derivatization converting to N-nitroso group, which is easily reduced and can be determined by differential pulse polarography. Sato et al.[3] determined glyphosate in urine, without derivatization, using anion-exchange chromatography with integrated pulsed amperometric detection (IPAD) at gold electrode. In this detection mode, the secondary amino group of glyphosate is oxidized in alkaline solutions, analogous to the reported for amino acids [7]. It is also reported the utilization of a Ni-Ti alloy electrode for detection of this herbicide [8].In the mid-1980s, both Kok et al. [9,10] and Stulík et al.[11] presented a novel mode of amino acids detection using copper electrode. In this detection mode, the presence of complexing agents, as amino acids, generate an enhancement in the anodic current of electrode which could be associated to the complexation between the analyte and the Cu(II) generated in the electrode surface. Other complexing agents, as coline [11] and di-and tricarboxylic acids [12], were analyzed using this detection principle. Glyphosate is a well-known complexing agent, which can coordinate transitions metal ions, as Cu(II), through the phosphonate, amine and carboxylate groups [13]. Then, this property can be utilized for glyphosate analysis us...

One-step preparation of porous copper nanowires electrode for highly sensitive and stable amperometric detection of glyphosate

“…In a comparison of the porous copper nanowires electrode with other electrochemical glyphosate detectors (Table 1), this electrode provided a lower LOD than was obtained by a Ni (1−x) Al x (OH) 2 NO 3x · nH 2 Olayered double-hydroxide-modified Pt electrode (1.0 mol L −1 ) (Khenifi et al, 2009), an electroaggregation of silver carbonate on a platinum electrode (40 mol L −1 ) (Méndez et al, 2007). It also provided a much lower LOD than reported in other works using copper with in similar principle a similar way (Moraes et al, 2010;Kodama et al, 2008;Coutinho et al, 2007c). In addition, with its large surface area the porous copper nanowires electrode provided a good operational stability which is the greatest challenge to detection based on this principle.…”

“…Applied to detect glyphosate in tomato juice with a recovery of 88 %. Coutinho et al (2007c) Amperometric biosensor using horseradish peroxidase modified poly(2,5-dimethoxyaniline)-poly(4-styrenesulphonic acid) nanoparticles on a rotating gold disk electrode.…”

Recent Development on the Electrochemical Detection of Selected Pesticides: A Focused Review

“…Glyphosate has been reported to be detected using bare and modified electrodes made of gold [28,[37][38][39][40][41][42][43][44], copper [45][46][47], carbon [48][49][50][51][52][53][54], mercury [55][56][57], and platinum [58,59]. Electrochemical methods, type of electrodes, analytical performance, measurement condition, and sample matrix for glyphosate determination are summarized in Table 1.…”

Development of instrumentation for amperometric and coulometric detection using ultramicroelectrodes

“…30,31 The principle of detection is based on the enhancement of the anodic current of copper microelectrode in the presence of complexing agents, such as glyphosate, with the formation of a soluble Cu(II) complex. Under optimized conditions, the limit of detection (S/R=3) for glyphosate was 0.59 µmol L -1 .…”

“…The present method was successfully applied to the determination of glyphosate in tomato juice without any kind of derivatization, extraction, clean-up, or preconcentration step, with recovery of 88%. 30 …”