Voltammetric Determination of the Herbicide Linuron Using a Tricresyl Phosphate-Based Carbon Paste Electrode

This paper summarises the results of voltammetric studies on the herbicide 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (Linuron), using a carbon paste electrode containing tricresyl phosphate (TCP-CPE) as liquid binder. The principal experimental conditions, such as the pH effect, investigated in Britton-Robinson buffer solutions (pH 2.0–7.0), the peak characteristics for the analyte of interest, or instrumental parameters for the differential pulse voltammetric mode were optimized for the method. As found out, the best electroanalytical performance of the TCP-CPE was achieved at pH 2.0, whereby the oxidation peak of Linuron appeared at ca. +1.3 V vs. SCE. The analytical procedure developed offers good linearity in the concentration range of 1.25–44.20 μg mL−1 (1.77 × 10−4–5.05 × 10−6 mol L−1), showing—for the first time—the applicability of the TCP-CPE for anodic oxidations in direct voltammetry (without accumulation). The method was then verified by determining Linuron in a spiked river water sample and a commercial formulation and the results obtained agreed well with those obtained by the reference HPLC/UV determination

Glassy carbon and boron doped glassy carbon electrodes for voltammetric determination of linuron herbicide in the selected samples

In this study the application of home-made unmodified (GC) and bulk modified boron doped glassy carbon (GCB) electrodes for the voltammetric determination of the linuron was investigated. The electrodes were synthesized with a moderate temperature treatment (1000A degrees C). Obtained results were compared with the electrochemical determination of the linuron using a commercial glassy carbon electrode (GC-Metrohm). The peak potential (E (p) ) of linuron oxidation in 0.1 mol dm(-3) H2SO4 as electrolyte was similar for all applied electrodes: 1.31, 1.34 and 1.28 V for GCB, GC and GC-Metrohm electrodes, respectively. Potential of linuron oxidation and current density depend on the pH of supporting electrolyte. Applying GCB and GC-Metrohm electrodes the most intensive electrochemical response for linuron was obtained in strongly acidic solution (0.1 mol dm(-3) H2SO4). Applying the boron doped glassy carbon electrode the broadest linear range (0.005-0.1 A mu mol cm(-3)) for the linuron determination was obtained. The results of voltammetric determination of the linuron in spiked water samples showed good correlation between added and found amounts of linuron and also are in good agreement with the results obtained by HPLC-UV method. This appears to be the first application of a boron doped glassy carbon electrode for voltammetric determination of the environmental important compounds

Renesansa elektroda s ugljikovom pastom; njihove modifikacije i primjene u potenciometrijskim određivanjima farmaceutika

Razvoj elektroda s ugljikovom pastom (CPE, engl. carbon paste electrode) sedamdesetih godina prošlog stoljeća privukao je velik interes znanstvene zajednice budući da je otkriveno da one nude nekoliko prednosti u odnosu na konvencionalne membranske elektrode. Početkom novog tisućljeća dodatni impuls njihovom razvoju dala je primjena ugljikovih nanomaterijala kao novog trenda u njihovu razvoju. Nakon što su uspješno razvijene CPE za potenciometrijsko određivanje više od 70 kemijskih elemenata, te su elektrode privukle dodatno zanimanje za primjenu u farmaciji i medicini. Ovim radom dat je pregled znanstvene literature u posljednjih desetak godina vezan za razvoj CPE za kvantitativno određivanje djelatnih tvari farmaceutika i njihovu primjenu u realnim uzorcima

Electrochemical behaviour of pesticides at bare and nylon 6,6-modified solid electrodes in differential pulse cathodic stripping voltammetry

The study of the voltammetric behaviour of five types of pesticides, namely paraquat dichloride, metsulfuron-methyl, lindane, chlorothalonil and glyphosate were carried out. The electrodes used were hanging mercury drop electrode (HMDE), glassy carbon electrode (GCE), HB pencil electrode (HBPE), boron doped diamond electrode (BDDE) and screen printed electrode (SPE). Due to the toxicity of mercury and to improve the detectivity for the determination of these pesticides, nylon-6,6 was used as modifier to modify the electrodes to produce nylon-6,6-modified glassy carbon electrode (Nyl-MGCE), nylon-6,6-modified HB pencil electrode (Nyl- MHBPE), nylon-6,6-modified boron doped diamond electrode (Nyl-MBDDE), and nylon-6,6-modified screen printed electrode (Nyl-MSPE). All measurements were performed using differential pulse cathodic stripping voltammetry technique (DPCSV) vs. Ag/AgCl (3.0 M KCl). Experimental parameters such as pH of Britton- Robinson buffer (BRB), accumulation time, accumulation potential and initial potential were optimized for the pesticides determination. Linear calibration plots for the paraquat dichloride and metsulfuron-methyl were obtained with the limit of detection (LOD) value of 3.66 × 10-8 M and 8.86 × 10?8 M, respectively on HMDE. The detectivity of DPCSV with nylon-6,6-modified solid electrodes were more effective compared to bare solid electrodes, where the LOD values for paraquat dichloride were 2.75 × 10-8 M (GCE), 6.42 × 10-9 M (Nyl-MGCE), 2.37 × 10-8 M (HBPE), 1.33 × 10-8 M (Nyl-MHBPE), 2.52 × 10-8 M (SPE), 1.05 × 10-8 M (Nyl- MSPE), 2.86 × 10-8 M (BDDE), and 1.54 × 10-8 M (Nyl-MBDDE). The novel sensors, Nyl-MSPE and Nyl-MHBPE were utilized for lindane and chlorothalonil analysis, and the LODs obtained were 4.26 × 10-8 M and 2.13 × 10-8 M, respectively. Efforts to study the electroactivity behaviour of metsulfuron-methyl and glyphosate were unsuccessful at all types of working electrodes that have been assessed in this study except HMDE for metsulfuron-methyl. There was no significant interfering metal ions effect found for voltammetric determination on the selected pesticides. Approximately 90% recovery was achieved for pesticides analyses. It can be concluded that the proposed DPCSV methods with nylon-6,6- modified solid electrodes were efficiently applied in this study and verified in real water samples analysis. The proposed DPCSV methods were also comparatively selective and have good coefficient of determination (R2 = 0.995)

Fenilüre herbisitlerin tayinine yönelik voltametrik sensör geliştirilmesi ve karakterizasyonu

Bu tez çalışmasında, literatürde ilk kez elektrokimyasal polimerizasyon ile tek kullanımlık kalem grafit elektrot üzerine fenilüre herbisitlerin baskılanması gerçekleştirilmiştir. Bu amaçla ilk olarak fenilüre herbisitlerinden monuron ve metoxuron‟un çevrimli voltametri tekniği kullanılarak elektrokimyasal davranıĢları incelenmiĢ ve bu herbisitlerin elektropolimerizasyonu için en uygun monomerin p-fenilendiamin olduğuna karar verilmiştir. Optimum polimerizasyon koşulları belirlenerek (film büyütme hızı, ortam pH‟sı, monomer/kalıp molekül mol oranı, polimer film kalınlığı), kalem grafit elektrotlar üzerinde molekül baskılı polimerler elektrokimyasal olarak sentezlenmiĢtir. Daha sonra kronoamperometri tekniği ile kalıp molekülü polimer matriksinden sökme çalışmaları gerçekleştirilmiştir. Sökme basamağından sonra, sensörün performansını belirlemek amacıyla yaş (wet) adsorpsiyon ile geri bağlama çalışmaları yapılmıştır. En yüksek bağlanmanın her iki kalıp molekül için analitin 10-3 M derişiminde 60 sn‟de gerçekleştiği görülmüştür. Kalıp molekülün optimum koşullarda söküldüğü sensörler ile analog moleküller (propanil, 3,4-dikloroanilin, üre, diuron) yanında seçimlilik çalışmaları yapılmış ve geliştirilen sensörlerin bu analoglar yanında seçiciliğinin oldukça yüksek olduğu gösterilmiştir. Ayrıca, monuron ve metoxuron eklenmiş zirai herbisit numunesi kullanılarak sensörün yanıtı test edilmiştir

Última generación de sistemas luminiscentes multiconmutados en flujo con aplicación en los campos agroalimentario y farmacológico

En esta Memoria se proponen una serie de mejoras científico-técnicas relativas al desarrollo y aplicación de sistemas automatizados en flujo para el análisis de moléculas de diferente índole en los campos farmacológico y agroalimentario, plasmadas en las nueve publicaciones científicas que se presentan, mostrando su versatilidad y aplicabilidad analítica. Se ha puesto especial hincapié en incrementar el nivel de automatización de los sensores en flujo descritos hasta la fecha, perfeccionando el uso de los sistemas multiconmutados en flujo en este tipo de sistemas analíticos. Se han empleado técnicas de detección luminiscentes, incidiendo especialmente en aquellas que han permitido un incremento en la selectividad y cuyo desarrollo hasta la fecha ha sido reducido, como es el caso de la Fluorescencia Inducida Fotoquímicamente. Igualmente, se han utilizado nanopartículas fluorescentes para poder llevar a cabo la determinación luminiscente de analitos que no presentan fluorescencia nativa.In this Report, several scientific/technical improvements concerning the development and the application of automated flow systems are proposed. The systems developed were applied to the analysis of molecules of different nature in the pharmacological and agri-food fields, showing its versatility and its analytical applicability. The research here described gave origin to nine scientific publications in scientific international journals. Special emphasis was placed on increasing the level of automation of the flow sensors described to date, particularly improving the potential of multicommutated flow injection analysis methods. The selection of luminescent detection techniques was performed by paying special attention to two aspects: a) increasing the selectivity of the analytical methods; b) the use of detection techniques that have been underused in flow systems, such as Photochemically Induced Fluorescence. Likewise, fluorescent nanoparticles have been used to carry out the luminescent determination of analytes that do not exhibit native fluorescence.Tesis Univ. Jaén. Departamento Química Física y Analítica. Leída el 26 de noviembre de 2018

Voltammetric Determination of the Herbicide Linuron Using a Tricresyl Phosphate-Based Carbon Paste Electrode

This paper summarises the results of voltammetric studies on the herbicide 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (Linuron), using a carbon paste electrode containing tricresyl phosphate (TCP-CPE) as liquid binder. The principal experimental conditions, such as the pH effect, investigated in Britton-Robinson buffer solutions (pH 2.0–7.0), the peak characteristics for the analyte of interest, or instrumental parameters for the differential pulse voltammetric mode were optimized for the method. As found out, the best electroanalytical performance of the TCP-CPE was achieved at pH 2.0, whereby the oxidation peak of Linuron appeared at ca. +1.3 V vs. SCE. The analytical procedure developed offers good linearity in the concentration range of 1.25–44.20 μg mL−1 (1.77 × 10−4–5.05 × 10−6 mol L−1), showing - for the first time - the applicability of the TCP-CPE for anodic oxidations in direct voltammetry (without accumulation). The method was then verified by determining Linuron in a spiked river water sample and a commercial formulation and the results obtained agreed well with those obtained by the reference HPLC/UV determination