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Application of a Webcam Camera as a Cost-effective Sensor with Image Processing for Dual Electrochemical - Colorimetric Detection System
Abstract
A webcam camera as an alternative cost-effective colorimetric sensor for the simple dual electrochemical – colorimetric detection system is proposed. Performance test of the system was investigated through electrochemical and colorimetric behaviors of redox reactions of potassium ferrocyanide complex. Image processing with two color systems, RGB and HSV, was applied together with various electrochemical techniques. Color responses obtained from the webcam correlated with electrochemical signals in various electrochemical techniques. The results from the proposed dual detection system agreed well with those obtained using conventional UV–vis spectroelectrochemical system reported previously. The application of proposed system was demonstrated for studying the redox reaction of catechin and electrochemical - colorimetric behaviors of Fe(II) and Fe(III) mixture.
... Colorimetric method is convenient to rapidly achieve the target information by the visual color change. Generally, the triggered color change can be directly observed by the naked eye, and it is easy to obtain the measurable color signal by spectrometer or camera (Thajee, Paengnakorn, Wongwilai, & Grudpan, 2018). Electrochemical is another reliable analysis method. ...
... Most of the before mentioned works, have been used expensive and bulky instruments for the determination of SAs in water samples, including UV-VIS spectrophotometer [19], GC-MS [20], HPLC-DAD [21], and fluorometer [6]. To achieve on-site detection, the miniaturization of analytical systems that includes the sample preparation integrated with portable detectors based on digital images has been satisfactorily applied [22][23][24][25]. ...
... The hue parameter specifies the color as an angular value between 0°and 360°. For example, red, green, and blue are located at 0°, 120°, and 240°, respectively (Thajee et al. 2018). The saturation or chroma (S), which is also known as purity, indicates the amount of color ranging from 0 to1% or 0 to 100%. ...
The potential use of colorimetric sensors has received significant attention due to its feasibility for use in various applications. After reacting with a sample, the image of the colorimetric sensor can be captured and converted into digital data using several different color models. The analytical data can then be processed with various chemometric methods. This research study investigated the predictive performance of calibration models established using color models commonly used in analytical chemistry including RGB, CMYK, HSV and CIELAB. A total of eight commercially available colorimetric sensors were used to determine the presence of manganese (Mn ²⁺ ), copper (Cu ²⁺ ), iron (Fe ²⁺ /Fe ³⁺ ), nitrate (NO 3 – ), phosphate (PO 4 3– ), sulfate (SO 4 2– ), as well as total hardness and pH values. As external validation tests, real water samples collected in Chiang Mai, Thailand were used. Based on the resulting data obtained using the synthetic test samples, the color that was most similar to the appearing color of the chemical sensor could offer satisfactory results. However, it was not always the case especially when the strips composed of multiple colorimetric sensors or sensor array were used. When tested with external validation, the predictive performance could be improved using appropriate data preprocessing and, in this research study, a normalization method was recommended to guarantee the accuracy of the calibration models.
... Perfectly complementary to spectroelectrochemistry techniques, digital images acquisition is a non-contact, non-invasive, and cost-ef- fective technology [14][15][16][17], which allows the spatiotemporal analysis of the entire electrode surface [18,19]. The aim of this work is to show the fundamentals and effective application of pixel intensity analysis of sequential RGB digital images to quantify valuable kinetics of color transitions in electrochromic materials. ...
A new, rapid, and practical procedure to obtain quantitative kinetic information of electrochromic materials is proposed. When the transition between two colors on a colored electrode surface is monitorized by digital video, the analysis of pixel color intensity (I) in sequential RGB digital images allows us to precise the half-life time (t1/2) of the color change since a maximum value of the standard deviation of the pixel intensity (σ(I)) is reached. We simulated and analyzed the evolution of standard deviation during an electrochromic transition in different circumstances (kinetic and diffusion control). As an example of application, electrochromic transitions of a thin film model, the Prussian blue (PB), were digitally recorded during potential step chronoamperometry. From obtained t1/2, we calculated kinetic constants of the first order blue-to-transparent transition at different potential steps. The results suggest the great potential of this novel methodology to quantify the kinetics of electrochromic changes, even, in proof-of-concepts devices.
Coupling cyclic voltammetry with digital video electrochemistry allows identifying different electrochemical processes overlapped. Mathematical description of the time evolution of mean color intensities and their standard deviation at the studied electrode surface during voltametric experiments were developed. Parallel electrochemical reactions and the presence of colored intermediate species was also evaluated. Single expressions for the shape of these curves, including the maximum of peaks or the half-peak widths are analyzed on the basis of a single layer covered electrode. The good similitude among current, mean color intensities derivative and variance curves allows a statistical interpretation for these processes.
A paper-based device (PBD) for the detection of chlorpyrifos pesticide at field application was fabricated based on the principles of enzyme inhibition and image processing. Rhizopus niveus lipase, p-nitrophenol palmitate and Whatman No.1 paper were used as an enzyme, substrate and support matrix, respectively. The performance of functionalized PBD was tested for lateral flow assay reaction in pure water (negative control), artificial pesticide water (positive control) and selected fruits and vegetables wash water (test). The digital image of the PBD after the test was captured using an android smartphone and analyzed in MATLAB software. Different colour space models such as, grey, RGB, HSV and YCbCr were studied and the Cb coordinate was chosen for its higher linearity (R2 = 0.988) with pesticide concentration. Experimental variations such as paper length, relative concentration ratio of the substrate and enzyme were investigated to minimize the product cost and analysis time. The developed PBD showed a significant response over wide range of sample solution's pH and operational temperature. Further, a long-term storage stability was measured for developed PBD. The LOD and LOQ were found to be 0.065 mgL−1 and 0.198 mgL−1. The results obtained from newly developed image processing method showed 92.8% accuracy with microtiter plate assay. Higher MRL was determined in the wash water of cauliflower, grapes, coriander leaves, brinjal and bitter guard. Overall, the developed paper biosensor was precise, cost effective and most suitable for field applications.
During the last few years, color analysis of the studied surface has revealed as a non-expensive way to obtain spectrochemical data but also, spatiotemporal information of the entire surface. Mean color intensities and standard deviation calculated from the red, green and blue color histograms of digital images of surfaces have revealed particularly useful for the chemical understanding of surface kinetics. The shape of curves, the maximum of peaks or the half-peak widths depend on the kinetic constants and on the kinetic order of the surface chemical process. Some strategies allowing to obtain kinetics from RGB color intensities, and their standard deviation are proposed.
Spectroelectrochemistry (SEC) has been used for more than 50 years, but this set of techniques has not been widely used for quantitative analysis. For many years, no commercial instruments were available, which made very difficult to spread the use of SEC. Nowadays, only the creativity of the researchers is required to exploit the capabilities of SEC. This review is written with the aim of showing the potential of SEC, mainly for analytical chemistry. Here, we explain what SEC is, how analytical responses can be obtained, why these techniques are useful for sensors, with a brief description of its advantages in use, and, finally, we try to show the challenges that must be addressed in the next years. SEC can resolve interesting analytical problems using the high amount of data provided by this intrinsic trilinear technique. Given the quantitative analysis point of view of this review, the discussion of the SEC techniques is focused on UV/Vis absorption, photoluminescence and Raman SEC.
Galvanostatic copper electrodeposition and electrodissolution on graphite:copper:polypropylene composite electrodes in acidic media have been investigated to extend the technological applicability of ternary composites. Both electrochemical processes were monitored by RGB video electrochemistry. The analysis of digital images allowed the color changes on the electrode surface to be investigated. We estimate the growth rate of the copper layer in two different electrode geometries. The relatively high resistance of this composite causes a gradient of the electric resistance along the electrode involving a non-homogeneous electrodeposit growth in CuSO 4 /H 2 SO 4 aqueous solutions. Copper electrodissolution was studied in HCl and H 2 SO 4 aqueous solutions. Whereas chloride anions stabilized cuprous cation, the electrodissolution process in HCl takes place apparently by a more complicated mechanism. Dispersion of color estimated from the standard deviation of the RGB color images was also analyzed and it has been postulated as a tool for identifying possible intermediate species on the electrode surface.
White blood cells (WBCs) are one of the critical components whose number has to be reduced before blood transfusion, failing which adverse transfusion effects may occur in patients. However, due to the extremely low concentration of residual WBCs (r-WBCs) in WBC-depleted blood, it is difficult to quantify r-WBCs accurately without using expensive and voluminous instruments. Therefore, the development of a continuous cell concentration technique is required to produce a countable number of cells from rare cells, which cannot normally be detected. In this paper, we present a viscoelastic microfluidic device for sheathless, continuous concentration of WBCs. The device performance was evaluated using polystyrene particles with different sizes at various flow rate conditions in a non-Newtonian fluid compared to a Newtonian fluid. Large particles with a blockage ratio higher than 0.1 were tightly focused at the center and collected at the center outlet with a 98% collection ratio. Meanwhile, the viscosity effect of lysed blood samples with various hematocrits was considered. Finally, diluted WBCs with various dilution ratios were concentrated by ~ 18-fold and continuous concentration of WBCs in lysed blood samples was performed using a non-electrical powered hand pump sprayer. Without using an external power source, center-focused WBCs were collected at the center outlet at approximately 350 μl/min and the final number of WBCs was increased to 1.8 × 10^4 cells/ml from undetectable levels.
We have designed and fabricated a miniature microscope from off-the-shelf components and a webcam, with built-in fluorescence capability for biomedical applications. The mini-microscope was able to detect both biochemical parameters, such as cell/tissue viability (e.g. live/dead assay), and biophysical properties of the microenvironment such as oxygen levels in microfabricated tissues based on an oxygen-sensitive fluorescent dye. This mini-microscope has adjustable magnifications from 8-60×, achieves a resolution as high as <2 μm, and possesses a long working distance of 4.5 mm (at a magnification of 8×). The mini-microscope was able to chronologically monitor cell migration and analyze beating of microfluidic liver and cardiac bioreactors in real time, respectively. The mini-microscope system is cheap, and its modularity allows convenient integration with a wide variety of pre-existing platforms including, but not limited to, cell culture plates, microfluidic devices, and organs-on-a-chip systems. Therefore, we envision its widespread application in cell biology, tissue engineering, biosensing, microfluidics, and organs-on-chips, which can potentially replace conventional bench-top microscopy where long-term in situ and large-scale imaging/analysis is required.
Bipolar electrochemistry is receiving growing attention in the last years, not only because it is an important tool for studying electron transfer processes, but also because it is really fruitful in the development of new analytical sensors. Bipolar electrodes show promising applications as a direct analytical tool since oxidation and reduction reactions take place simultaneously on different parts of a single conductor. There are several electrochemical devices that provide information about electron transfer between two immiscible electrolyte solutions, but to the best of our knowledge, this is the first time that a bipolar device is able to record two spectroelectrochemical responses concomitantly at two different compartments. It allows deconvolving the electrochemical signal into two different optical signals related to the electron transfer processes occurring at two compartments that are electrically in contact. The combination of an electrochemical and two spectroscopic responses is indeed very useful, providing essential advantages in the study of a huge variety of systems. The study of three different electrochemical systems, such as reversible redox couples, carbon nanotubes and conducting polymers has allowed us to validate the new cell and to demonstrate the capabilities of this technique to obtain valuable time-resolved information related to the electron transfer processes.
Herein, we present a novel spectroelectrochemical fiber optic sensor that combines electrochemistry, spectroscopy, and electrostatic adsorption in three modes of selectivity. The proposed sensor is simple and consists of a gold mesh cover on a multimode fiber optic that uses attenuated total reflection (ATR) as the optical detection mode. The sensing is based on changes in the attenuation of the light that passes through the fiber optic core accompanying the electrochemical oxidation-reduction of an analyte at the electrode. Methylene blue and ferrocyanide were used as model analytes to evaluate the performance of the proposed sensor. The optical transmission changes generated by electrochemical manipulation showed a good linear relationship with the concentration and the limits of detection (3σ) for methylene blue and ferrocyanide at 2.0×10-7 M and 1.6×10-3 M, respectively. The sensor responses were successfully enhanced with an additional level of selectivity via an electrostatically adsorpted, self-assembled monolayer (SAM), which consisted of a silane coupling layer, a poly anion, and a poly cation. The improvement observed in the sensitivity of a SAM-modified fiber optic sensor was rather encouraging. The optimized sensor had detection limits (3σ) for 8.3×10-9 M of methylene blue and 7.1×10-4 M of ferrocyanide. The developed sensor was successfully applied to the detection of ferrocyanide in stimulated nuclear waste.