Normal or parallel configuration in spectroelectrochemistry? Bidimensional spectroelectroanalysis in presence of an antioxidant compound

This work demonstrates how the way a chemical system is sampled plays a key role in spectroelectroanalysis, illustrated by the quantification of an analyte in presence of an antioxidant compound. For this purpose, bidimensional spectroelectrochemistry experiments were performed using epinephrine as the model analyte and ascorbic acid as antioxidant and interfering compound, as a proof of concept. This is the first time that three calibration curves are obtained simultaneously on a single spectroelectrochemistry data set, one for the electrochemical signal and two for the optical responses in normal and parallel configurations. The differences between the two optical arrangements, that are related to the diffusion process which is an essential feature for the spectroelectrochemical detection of compounds, have been experimentally demonstrated. As can be observed, the spectral signal in parallel configuration allows us to obtain the best analytical results, since in this configuration only the first micrometers of the solution adjacent to the electrode surface are sampled, thus removing the interfering effect of the antioxidant compound. This fact does not occur with either the electrochemical signal or the spectral response in normal configuration. Furthermore, it has been shown that the parallel configuration provides better results than the normal configuration in terms of sensitivity. In summary, epinephrine is successfully detected in a simple and effective way, even in the presence of a direct antioxidant compound such as ascorbic acid at different concentrations levels, which makes spectroelectrochemistry a good choice for quantitative analysis.Authors acknowledge the financial support given by Ministerio de Ciencia e Innovación and Agencia Estatal de Investigación (MCIN/AEI/ 10.13039/501100011033, PID2020-113154RB-C21) and Ministerio de Ciencia, Innovación y Universidades (Grant RED2018-102412-T). Fabiola Olmo is grateful for the contract funded by Junta de Castilla y León, the European Social Fund, and the Youth Employment Initiative

Multiamperometric-SERS detection of melamine on gold screen-printed electrodes

A new, simple and fast protocol to generate gold-based SERS substrates is presented in this work. Melamine is a compound widely used in the industry that can be toxic for humans if consumed even in low concentrations. EC-SERS is an excellent alternative to classical methods to detect and quantify this compound because Raman spectroscopy provides a fingerprint of the molecules, providing very good sensitivity. In this work, timeresolved Raman spectroelectrochemistry is employed to generate a SERS substrate and to detect melamine, all in a single experiment. The dynamic character of this technique provides valuable information about the interaction of the molecule with the generated substrate. An optimization of the spectroelectrochemical method based on a multi-pulse amperometric detection has been performed. The new protocol presented in this work shows significant figures of merit in a very short experiment time, just 25 s.Authors acknowledge the financial support from Agencia Estatal de Investigación/Ministerio de Ciencia e Innovacion /10.13039/ 501100011033 (Grant PID2020-113154RB-C21) and Ministerio de Ciencia, Innovación y Universidades (Grant RED2018-102412-T). W. Ch. thanks JCyL for his postdoctoral fellowship (Grant BU297P18). S.H. and M.P-E. thank JCyL and European Social Fund for their predoctoral fellowships

Dataset of the work “Normal or parallel configuration in spectroelectrochemistry? Bidimensional spectroelectroanalysis in presence of an antioxidant compound”

This work demonstrates how the way a chemical system is sampled plays a key role in spectroelectroanalysis, illustrated by the quantification of an analyte in presence of an antioxidant compound. For this purpose, bidimensional spectroelectrochemistry experiments were performed using epinephrine as the model analyte and ascorbic acid as antioxidant and interfering compound, as a proof of concept. This is the first time that three calibration curves are obtained simultaneously on a single spectroelectrochemistry data set, one for the electrochemical signal and two for the optical responses in normal and parallel configurations. The differences between the two optical arrangements, that are related to the diffusion process which is an essential feature for the spectroelectrochemical detection of compounds, have been experimentally demonstrated. As can be observed, the spectral signal in parallel configuration allows us to obtain the best analytical results, since in this configuration only the first micrometers of the solution adjacent to the electrode surface are sampled, thus removing the interfering effect of the antioxidant compound. This fact does not occur with either the electrochemical signal or the spectral response in normal configuration. Furthermore, it has been shown that the parallel configuration provides better results than the normal configuration in terms of sensitivity. In summary, epinephrine is successfully detected in a simple and effective way, even in the presence of a direct antioxidant compound such as ascorbic acid at different concentrations levels, which makes spectroelectrochemistry a good choice for quantitative analysis.Authors acknowledge the financial support given by Ministerio de Ciencia e Innovación and Agencia Estatal de Investigacion (MCIN/AEI/ 10.13039/501100011033, PID2020-113154RB-C21) and Ministerio de Ciencia, Innovacion y Universidades (Grant RED2018-102412-T). Fabiola Olmo is grateful for the contract funded by Junta de Castilla y Leon, the European Social Fund, and the Youth Employment Initiative

Dataset of the work “Simultaneous Raman and reflection UV/Vis absorption spectroelectrochemistry”

In the present work, a new combination of Raman and ultraviolet and visible (UV/Vis) absorption spectroelectrochemistry in reflection mode is proposed. The new experimental setup allows obtaining the two kinds of spectroscopic data without interferences concomitantly with the electrochemical information. To the best of our knowledge, it is the first time to report the simultaneous obtention of electrochemical, electronic, and vibrational information in the same experiment. This new combination provides time-resolved information about the processes that are taking place on the electrode/solution interface which has significant implications in different fields of chemistry, such as modification of electrodes, studies of electrocatalytic reaction mechanisms, development of sensors, among others. Two different systems were used to demonstrate the advantages and capabilities of the brand-new technique, namely, the oxidation of potassium ferrocyanide, an out-sphere system that is usually employed in the validation of SEC techniques, and the electrochemical-surface enhanced Raman spectroscopy (EC-SERS) detection of crystal violet by in-situ formation of the silver SERS substrate, where the UV/Vis spectra were used to follow the formation of the SERS substrate, whereas the Raman response of a probe molecule was used to confirm either the formation of a nanostructured surface and to obtain the fingerprint of the molecule with a high time resolution. The brand-new experimental setup has shown to be useful, versatile, robust, compact, and easy to use for future applications.Authors acknowledge the financial support from Ministerio de Ciencia e Innovacion (No. PID2020-113154RB-C21), Ministerio de Economía, Industria y Competitividad (No. CTQ2017-83935-RAEI/FEDERUE), Junta de Castilla y Leon (No. BU297P18), and Ministerio de Ciencia, Innovacion y Universidades (No. RED2018-102412-T). J.V.P-R acknowledges Spanish Ministry of Economy, Industry, and Competitiveness for the Juan de la Cierva postdoctoral (No. FJCI-2017-32458) and the University of Alcala (No. CCG19/CC-071). S.H. thanks JCyL and European Social Fund for her predoctoral fellowship

Dataset of the work “Multiamperometric-SERS detection of melamine on gold screen-printed electrodes”

A new, simple and fast protocol to generate gold-based SERS substrates is presented in this work. Melamine is a compound widely used in the industry that can be toxic for humans if consumed even in low concentrations. EC-SERS is an excellent alternative to classical methods to detect and quantify this compound because Raman spectroscopy provides a fingerprint of the molecules, providing very good sensitivity. In this work, time-resolved Raman spectroelectrochemistry is employed to generate a SERS substrate and to detect melamine, all in a single experiment. The dynamic character of this technique provides valuable information about the interaction of the molecule with the generated substrate. An optimization of the spectroelectrochemical method based on a multi-pulse amperometric detection has been performed. The new protocol presented in this work shows significant figures of merit in a very short experiment time, just 25 s.Authors acknowledge the financial support from Agencia Estatal de Investigación/Ministerio de Ciencia e Innovacion /10.13039/501100011033 (Grant PID2020-113154RB-C21) and Ministerio de Ciencia, Innovación y Universidades (Grant RED2018-102412-T). W. Ch. thanks JCyL for his postdoctoral fellowship (Grant BU297P18). S.H. and M.P-E. thank JCyL and European Social Fund for their predoctoral fellowships

Raman spectroelectrochemical determination of clopyralid in tap water

Clopyralid is a common herbicide used all around the world that can be dissolved in the rain stream and accumulate in underground water with the potential threat of reaching drinking water. Many methodologies have been proposed to perform quantitative analysis of this compound but, to this day, no Raman detection of clopyralid has been carried out. Here, a novel methodology to quantify clopyralid, based on Electrochemical Surface Oxidation-Enhanced Raman Scattering (EC-SOERS), is developed, using disposable silver screen-printed electrodes as substrate. The optimization of the electrolytic media is carried out, searching for the conditions where a maximum Raman enhancement is obtained. Moreover, a study about the effect of various interfering compounds, which could be present in water, on the clopyralid Raman response is performed. The results demonstrate that the presented methodology allows the determination of clopyralid in the micromolar range in tap water without any purification or preconcentration step, requiring few minutes to perform the measurement of each sample.Authors acknowledge Ministerio de Ciencia e Innovación and Agencia Estatal de Investigación (MCIN/AEI/10.13039/501100011033, PID2020-113154RB-C21), Junta de Castilla y León (Grant BU297P18) and Ministerio de Ciencia, Innovación y Universidades (RED2018–102412-T) for the support of this work. Martín Perez and Sheila Hernández acknowledge Junta de Castilla y Leon for their predoctoral contracts

Dataset of the work “Raman spectroelectrochemical determination of clopyralid in tap water”

Clopyralid is a common herbicide used all around the world that can be dissolved in the rain stream and accumulate in underground water with the potential threat of reaching drinking water. Many methodologies have been proposed to perform quantitative analysis of this compound but, to this day, no Raman detection of clopyralid has been carried out. Here, a novel methodology to quantify clopyralid, based on Electrochemical Surface Oxidation-Enhanced Raman Scattering (EC-SOERS), is developed, using disposable silver screen-printed electrodes as substrate. The optimization of the electrolytic media is carried out, searching for the conditions where a maximum Raman enhancement is obtained. Moreover, a study about the effect of various interfering compounds, which could be present in water, on the clopyralid Raman response is performed. The results demonstrate that the presented methodology allows the determination of clopyralid in the micromolar range in tap water without any purification or preconcentration step, requiring few minutes to perform the measurement of each sample.Authors acknowledge Ministerio de Ciencia e Innovacion and Agencia Estatal de Investigacion (MCIN/AEI/10.13039/501100011033, PID2020-113154RB-C21), Junta de Castilla y Leon (Grant BU297P18) and Ministerio de Ciencia, Innovacion y Universidades (RED2018–102412-T) for the support of this work. Martín Perez and Sheila Hernandez acknowledge Junta de Castilla y Leon for their predoctoral contracts