Pencil leads have been increasingly used as electrode material in electrochemical applications. Commonly denominated as pencil graphite electrodes (PGE), they represent a viable alternative to other ...standard electrodes due to their comparable electrical properties but mainly for their low cost and availability, enabling disposable applications. In order to achieve the best analytical performance literature evidences the type of lead (hardness level) and electrode surface pre-treatment are critical to the envisaged application. The present review describes the use of PGE in biosensing analysis, more specifically those sensors comprising immobilized enzymes but also briefly referring nucleic acids and other biological entities. It lays an emphasis in the immobilization process of the biological entities while focusing in the analytical performance of each biosensor, mainly sensitivity, linear range and limit of detection as comparative criteria. This review also addresses the main characteristics and properties of PGEs as transducer material in the electrochemical field.
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•Cheap pencil mines are suitable platforms for biosensor construction and provide a reliable option in disposable applications.•Careful selection of pencil hardness and pre-treatment dictate a performance akin microelectrode arrays but easier to attain.•PGEs afford all main innovations regarding usage of nanomaterials in biosensors through simple implementation procedures.•The performance of biosensors based on enzymes, living cells, antibodies, nucleic acids and aptamers is critically reviewed.
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•HPLC-potentiometric method for quantification of ten underivatized biogenic amines.•Improved selectivity and sensitivity in a greener chemistry context.•Detection limits ranged from ...9.3 to 60.5 µg L−1.•The proposed methodology was successfully applied in alcoholic beverages.•Simple, user-friendly and reliable method for food quality control.
Determination of ten biogenic amines in alcoholic beverages by HPLC coupled to a potentiometric detector for food quality control is herein presented. Biogenic amines were separated by ion-pair chromatography on a C18 column using a gradient mobile phase of acetic acid, acetonitrile, and butane-sulfonic acid. Detection was accomplished by a miniaturized amine-selective electrode. The method was validated following ICH and Eurachem guidelines. Linear regression models provided R2 values from 0.9870 ± 0.0019 to 0.9991 ± 0.0014 for tyramine and cadaverine, respectively. Detection and quantification limits depend on the molecular weight of BAs, ranging from 9.3 to 60.5 and from 31.1 to 202.3 µg L−1 for methylamine and spermine, respectively. Repeatability and intermediate precision showed RSD values lower than 5.8 and 8.3%, respectively. Accuracy of assays yielded recovery values from 86.4 to 109.9%. The biogenic amines content in red wine, white wine, and beer samples were 7.54, 5.24, and 4.58 mg L-1, respectively.
Glyphosate (GLY) is the main ingredient in the weed killer Roundup and the most widely used pesticide in the world. Studies of the harmful effects of GLY on human health began to become more ...wide-ranging after 2015. GLY is listed by the International Agency for Research on Cancer (IARC) as a carcinogenic hazard to humans. Moreover, GLY has the property to complex with transition metals and are stable for long periods, being considered a high-risk element for different matrices, such as environmental (soil and water) and food (usually genetically modified crops). Since that, it was noticed an increment in the development of new analytical methods for its determination in different matrices like food, environmental and biological fluids. Noteworthy, the application of electrochemical techniques for downstream detection sparked interest due to the ability to minimize or eliminate the use of polluting chemicals, using simple and affordable equipment.
This work aims to review the contribution of the electroanalytical methods for the determination of GLY in different food and environmental matrices. Parameters such as the electrochemical transduction techniques based on the electrical measurement signals, receptor materials for electrodes preparation, and the detection mechanisms are described in this review. The literature review shows that the electrochemical sensors are powerful detection system that can be improved by their design and by their portability to fulfil the needs of the GLY determination in laboratory benches, or even in situ analysis.
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•The sensitivity of electrochemical methods allows detection of glyphosate at ultra-low concentrations in different matrices.•Trend of electrode support modification with new materials for selective detection of glyphosate.•Different strategies to immobilized biomolecules onto modified supports.•Electrochemical biosensors can be used to monitor genotoxic effects of glyphosate.
Helicobacter pylori (H. pylori) infection is highly prevalent worldwide, affecting more than 43% of world population. The infection can be transmitted through different routes, like oral-oral, ...fecal-oral, and gastric-oral. Electrochemical sensors play a crucial role in the early detection of various substances, including biomolecules. In this study, the development of nanobody (Nb)-based immunosensor for the detection of H. pylori antigens in saliva samples was investigated. The D2_Nb was isolated and characterized using Western blot and ELISA and employed in the fabrication of the immunosensor. The sensor was prepared using gold screen-printed electrodes, with the immobilization of Nb achieved through chemical linkage using cysteamine-glutaraldehyde. The surface of the electrode was characterized using EIS, FTIR and SEM. Initially, the Nb-based immunosensor's performance was evaluated through cyclic voltammetry (CV), differential pulse voltammetry (DPV), and square wave voltammetry (SWV). The sensor exhibited excellent linearity with an R2 value of 0.96. However, further assessment with the DPV technique revealed both a low limit of detection (5.9 ng/mL, <1 cfu/mL) and high selectivity when exposed to a mixture of similar antigens. Moreover, the immunosensor demonstrated robust recovery rates (96.2%–103.4%) when spiked into artificial saliva and maintained its functionality when stored at room temperature for 24 days.
The evaluation of the biogenic amines (BAs) profile of different types of craft beers is herein presented. A previously developed and validated analytical method based on ion-pair chromatography ...coupled with potentiometric detection was used to determine the presence of 10 BAs. Good analytical features were obtained for all amines regarding linearity (R
values from 0.9873 ± 0.0015 to 0.9973 ± 0.0015), intra- and inter-day precision (RSD lower than 6.9% and 9.7% for beer samples, respectively), and accuracy (recovery between 83.2-108.9%). Detection and quantification limits range from 9.3 to 60.5 and from 31.1 to 202.3 µg L
, respectively. The validated method was applied to the analysis of four ale beers and one lager craft beer. Ethylamine, spermidine, spermine, and tyramine were detected in all analyzed samples while methylamine and phenylethylamine were not detected. Overall, pale ale beers had a significantly higher total content of BAs than those found in wheat pale and dark samples. A general least square regression model showed a good correlation between the total content of BAs and the brewing process, especially for Plato degree, mashing, and fermentation temperatures. Knowledge about the type of ingredients and manufacturing processes that contribute to higher concentrations of these compounds is crucial to ensuring consumer safety.
•HPLC-IPC method for potentiometric detection of ten biogenic amines.•Separation achieved with SBS as an ion-pair agent in less than 20 min.•No chemical derivatization procedures are ...required.•Detection limits ranged from 0.03 to 0.20 mg L−1.•The proposed methodology was applied in tomato samples.
It is described the determination of underivatized biogenic amines by ion-pair chromatography coupled to potentiometric detection, for food quality control. A wall-jet flow-cell was used to hold an amine-selective electrode, based on cucurbit6uril as an ionophore, and a commercial reference electrode. The biogenic amines were separated in less than 20 min using a C18 column as the stationary phase. This method comprises a gradient elution with a mobile phase containing lithium formate buffer, acetonitrile, and butane-sulfonic acid sodium salt as an ion-pair agent. The proposed method was validated following the International Council for harmonization guidelines. Calibration data fitted a linear regression model with R2 varying from 0.9804 to 0.9972. Repeatability intra and inter-day showed relative standard deviation values lower than 9.1% and 13.3%, respectively. Detection and quantification limits ranged from 0.03 to 0.20 mg L−1 and 0.09 to 0.61 mg L−1, respectively. Spiked tomato samples were analysed to assess the accuracy, yielding recovery values from 85.8 to 108.5%. The biogenic amines content in fresh tomatoes, canned chopped tomato, and pulp tomato was 7.11, 5.12, and 7.69 mg L−1, respectively.
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Drinking water sources are increasingly subject to various types of contamination due to anthropogenic factors and require proper treatment to remove disease-causing agents. Public drinking water ...systems use different treatment methods to provide safe and quality drinking water to populations. However, they are ineffective in removing contaminants that are considered a danger to the environment and therefore to humans. Several alternative treatment processes have been proposed, such as membrane filtration, as final purification methods. This paper aims to summarize the type of pollutant compounds, filtration processes, and membranes that have been most studied in this area with particular emphasis on how the modification of membranes, either the manufacturing process or the incorporation of nanomaterials, influences their performance.
An analytical methodology
for detecting ammonium ion (NH
4
+
) in environmental
water through potentiometry–ion
chromatography (IC) in tandem is presented here. A multielectrode
flow cell is ...implemented as a potentiometric detector after chromatographic
separation of cations in the sample. The electrodes are fabricated
via miniaturized all-solid-state configuration, using a nonactin-based
plasticized polymeric membrane as the sensing element. The overall
analytical setup is based on an injection valve, column, traditional
conductometric detector, and new potentiometric detector (in that
order), permitting the characterization of the analytical performance
of the potentiometric detector while validating the results. The limit
of detection was found to be
ca
. 3 × 10
–7
M NH
4
+
concentration after
linearization of the potentiometric response, and intra- and interelectrode
variations of <10% were observed. Importantly, interference from
other cations was suppressed in the tandem potentiometry–IC,
and thus, the NH
4
+
content in fresh- and seawater
samples from different locations was successfully analyzed. This analytical
technology demonstrated a great potential for the reliable monitoring
of NH
4
+
at micromolar levels, in contrast to
the conductivity detector and previously reported NH
4
+
potentiometric sensors functioning in batch mode or even
coupled with IC. Additionally, the suitability of the potentiometric
cell for selective multi-ion analysis in the same sample,
i.e.
, Na
+
, NH
4
+
, and K
+
in water, has been proven.
The determination of metal ions is important for nutritional and toxicological assessment. Atomic spectrometric techniques are highly efficient for the determination of these species, but the high ...costs of acquisition and maintenance hinder the application of these techniques. Inexpensive alternatives for metallic element determination are based on dedicated biosensors. These devices mimic biological systems and convert biochemical processes into physical outputs and can be used for the sensitive and selective determination of chemical species such as cations. In this work, an overview of the proposed biosensors for metal ions determination was carried out considering the last 15 years of publications. Statistical data on the applications, response mechanisms, instrumentation designs, applications of nanomaterials, and multielement analysis are herein discussed.
Glyphosate (GLY) is the most widely used non-selective broad-spectrum herbicide worldwide under well-reported side effects on the environment and human health. That's why it's necessary to control ...its presence in the environment. This work describes the development of an affordable, simple, and accurate electrochemical biosensor using a pencil graphite electrode as support, a horseradish peroxidase enzyme immobilized on a polysulfone membrane doped with multi-walled carbon nanotubes. The developed electrochemical sensor was used in the determination of GLY in river and drinking water samples. Cyclic voltammetry and amperometry were used as electrochemical detection techniques for the characterization and analytical application of the developed biosensor. The working mechanism of the biosensor is based on the inhibition of the peroxidase enzyme by GLY. Under optimal experimental conditions, the biosensor showed a linear response in the concentration range of 0.1 to 10 mg L−1. The limits of detection and quantification are 0.025 ± 0.002 and 0.084 ± 0.007 mg L−1, respectively, which covers the maximum residual limit established by the EPA for drinking water (0.7 mg L−1). The proposed biosensor demonstrated high reproducibility, excellent analytical performance, repeatability, and accuracy. The sensor proved to be selective against other pesticides, organic acids, and inorganic salts. Application on real samples showed recovery rates ranging between 98.18 ± 0.11 % and 97.32 ± 0.23 %. The analytical features of the proposed biosensor make it an effective and useful tool for the detection of GLY for environmental analysis.
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•A new biosensor for monitoring glyphosate in water samples was presented.•A novel support based on HRP/PSF/MWCNT/PGE was developed.•Optimized surface conditions for HRP immobilization and electrochemical performance.•Wide linear relationship ranging from 0.1 to 10 ppm and a low LOD of 25 ppb.•Recovery in water samples between 95.21 and 103.45 %.
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