Detection of bisphenol S via screen-printed electrodes

Screen-printed electrodes are economical, easy-to-use electrochemical sensors that can be used for in-situ real-time monitoring of toxic substances. This work represents a comparison of two SPEs electrodes for the detection of bisphenol S (BPS). BPS is an endocrine interrupts the hormonal system in humans and shows a genotoxic, cytotoxic and cancerpromoting effect. Fast and reliable detection of bisphenols is very important. Chromatographic and spectroscopic techniques are the most used methods for the detection of bisphenols, however they are expensive, complicated and consume a lot of time. On the other hand, electrochemical sensors are promising since they are fast, reliable and simple methods for in-situ measuring. In the present work the detection of BPS was performed via screen-printed electrodes with carbon nanoparticles and carbon single-wall nanotube working electrodes. Determination of BPS was carried out by cyclic voltammetry (CV) anddifferential puls voltammetry (DPV). The influence of different concentrations of BPS, scan rate and influencing BPA on detection were studied. Screen-printed electrodes showed very good electrochemical activity, sensitivity and repeatability. Screen-printed electrodes enable the miniaturization of sensors elements, using smaller volumes of samples, rapid and low cost detection without generating dangerous waste

Electrochemical sensors for detection of bisphenols

The endocrine-disrupting chemicals (EDCs) are chemicals of very high concern that have hazards with serious consequences on human health. It influences on development of metabolic disorders, reproduction and respiratory problems. They can be found in our everyday life, from food, and personal care products to medical devices, dental products, special lenses and baby drink cans. Among several EDCs, banned Bisphenol A (BPA) and his substitute Bisphenol S (BPS) have attracted attention due to high usage during the manufacturing process for water and food packaging, in the production of epoxy resins, lacquer coating and can even be found in receipt. Due to that, there is a need for the fast, reliable and commercial detection of Bisphenols in everyday life. The gold standard for the detection of Bisphenols is chromatography and enzyme-linked immunosorbent assay, expensive and robust methods. Electrochemical sensors are a new approach to the detection of EDCs in very small quantities in complex environments. The aim of this research was to study commercial screen-printed electrodes (SPEs) as receptor elements in electrochemical sensors for the detection of BPA and BPS. Scanning electron microscopic (SEM) and Fourier transform infrared spectroscopy (FT-IR) were employed for examining the surface of the SPEs working electrodes. SPE electrodes showed very good voltammetric responses toward BPA and BPS oxidation with linear ranges between 0.5 and 50.0 μM and lower limits of detection of 0.15 μM and 0.37 μM, respectively

Electrochemical sensor for detection bisphenols in thermal paper

The substances of very high concern (SVHCs) can be found in a wide range of consumer products. These substances can negatively influence human health depending on the route of exposure, exposure time and duration, amount of intake the substance by body and other factors. Increased number of carcinoma, sterility, diabetes can be due to the contact with SVHCs in our everyday life. Bisphenol A (BPA) is one of the most commercialized SVHC chemicals and is used in many different products such as plastic packaging for water and food, storage media, and even in thermal paper. Thermal paper is used for receipts in stores and tickets for parking, bus, and trains. BPA is applied on thermal paper as a dye developer. As a dye developer, it is not chemically bound to the paper so it can easily migrate and be absorbed by the skin (fingers, palm). Studies showed that typical occupational exposures of work cashiers can increase concentrations of BPA and its metabolites in urine several times. Toxicokinetic studies showed that the route of exposure has a big effect on the concentration of BPA that circulates in the body. If BPA enters the body through dermal exposure, it metabolizes as unconjugated BPA, while oral exposure leads to a conjugated form of BPA. Studies showed that only the unconjugated form can bind to estrogen receptors, leading to the conclusion that the unconjugated form is hazardous. Due to that European Commission restricted usage of BPA to 0.02 mas%. The paper manufacturers replaced BPA with bisphenol S (BPS). It is expected that 61 % of all thermal paper in the EU will be BPS-based till now. However, the wide use of BPS in thermal paper raises concern because it was shown that BPS is also toxic. New studies of urine samples collected around the world showed the presance of BPS. Due to increasing production of BPS there is a need for the development of analytical methods for the detection of SVCHs. The most used are HPLCs with mass spectrometric detection, which are expensive and time-consuming. On a another hand, electrochemical sensors are low-cost and simple method for detection of SVCHs. The present study represents fast, reliable and commercial detection of bisphenols via screen-printed electrodes (SPEs) as receptor elements. Scanning electron microscopy (SEM) was used to study the surface of the SPEs working electrodes. SPE electrodes showed very good electrochemical responses toward BPA and BPS oxidation with linear ranges between 0.5 and 50.0 μM and lower limits of detection of 0.15 μM and 0.37 μM, respectively

Facile Fabrication of an Ammonia-Gas Sensor Using Electrochemically Synthesised Polyaniline on Commercial Screen-Printed Three-Electrode Systems

Polyaniline (PANI) is a conducting polymer, widely used in gas-sensing applications. Due to its classification as a semiconductor, PANI is also used to detect reducing ammonia gas (NH3), which is a well-known and studied topic. However, easier, cheaper and more straightforward procedures for sensor fabrication are still the subject of much research. In the presented work, we describe a novel, more controllable, synthesis approach to creating NH3 PANI-based receptor elements. The PANI was electrochemically deposited via cyclic voltammetry (CV) on screen-printed electrodes (SPEs). The morphology, composition and surface of the deposited PANI layer on the Au electrode were characterised with electron microscopy, Fourier-transform infrared spectroscopy and profilometry. Prior to the gas-chamber measurement, the SPE was suitably modified by Au sputtering the individual connections between the three-electrode system, thus showing a feasible way of converting a conventional three-electrode electrochemical SPE system into a two-electrode NH3-gas detecting system. The feasibility of the gas measurements’ characterisation was improved using the gas analyser. The gas-sensing ability of the PANI-Au-SPE was studied in the range 32–1100 ppb of NH3, and the sensor performed well in terms of repeatability, reproducibility and sensitivity

A cartridge-based turning specimen holder with wireless tilt angle measurement for magnetic induction mapping in the transmission electron microscope

Magnetic induction mapping in the transmission electron microscope using phase contrast techniques such as off-axis electron holography and differential phase contrast imaging often requires the separation of the magnetic contribution to the recorded signal from the electrostatic contribution. When using off-axis electron holography, one of the experimental approaches that can be used to achieve this separation is to evaluate half of the difference between phase shift images that have been recorded before and after turning the sample over. Here, we introduce a cartridge-based sample mounting system, which is based on an existing on-axis tomography specimen holder and can be used to turn a sample over inside the electron microscope, thereby avoiding the need to remove the holder from the microscope to turn the sample over manually. We present three cartridge designs, which are compatible with all pole piece designs and can be used to support conventional 3-mm-diameter sample grids, Si3N4-based membrane chips and needle-shaped specimens. We make use of a wireless inclinometer that has a precision of 0.1° to monitor the sample holder tilt angle independently of the microscope goniometer readout. We also highlight the need to remove geometrical image distortions when aligning pairs of phase shift images that have been recorded before and after turning the sample over. The capabilities of the cartridge-based specimen holder and the turning approach are demonstrated by using off-axis electron holography to record magnetic induction maps of lithographically-patterned soft magnetic Co elements, a focused ion beam milled hard magnetic Nd-Fe-B lamella and an array of four Fe3O4 nanocrystals

Microstructural insights into the coercivity enhancement of grain-boundary-diffusion-processed Tb-treated Nd-Fe-B sintered magnets beyond the core-shell formation mechanism

We propose a dominant core-shell formation mechanism for grain-boundary-diffusion-processed (GBDP), Tb-treated, Nd2Fe14B sintered magnets. A depth-sensitive analysis of Tb-treated samples, relative to a non-GBDP Nd2Fe14B magnet, showed a 30% increase of the coercivity in the central part of the magnet. A structure-chemistry-magnetic-property analysis revealed the dominant GBDP mechanism. On the surface of the Tb-treated magnet, the Tb is released from the starting precursor following a cascade of chemical reactions between the Tb oxide and the Nd and/or the Nd-Fe-B. The released Tb diffuses along the grain boundaries, forming a core-shell structure. The calculated optimum concentration for a 30% increase in the coercivity was 50 ppm of Tb. Off-axis electron-holography measurements were used to quantitatively map the characteristic magnetic states of the samples, confirming a different magnetic domain structure in the shell than in the core. The magnetic induction in the core was found to be 26% higher than that of the shell, which has a lower magnetic saturation due to the presence of Tb. The results show that the measured increase in the coercivity is due to a structural effect, and not the magnetic contribution of the Tb. Our results pave the way towards grain-boundary-engineering studies that can be used to increase the coercivity of Nd-Fe-B magnets for e-mobility and eco-power applications