Smartphone-based colorimetric determination of sulfadiazine and sulfasalazine in pharmaceutical and veterinary formulations

A novel, simple, accurate, and low-cost colorimetric device based on an Android smartphone was developed for sulfonamide determination. A software program was developed to be used for analyzing the samples. Various parameters for digital colorimetric detection were investigated and optimized, such as the volume of the sample drop, the type of sample holder, the distance from the mobile phone camera to the sample holder, and the effect of ambient light. From the optimized conditions, a calibration curve was created by the intensity of blue channel for sulfonamides for the concentration range of 0.5–2.5?µg?mL^?1 with good linearity and a regression coefficient (R²) of 0.996. The results obtained by the smartphone method were compared with a spectrophotometric procedure at the 95% confidence level (n?=?3). Both methods correlated well with a regression coefficient (R²) of 0.997. The limit of detection of both methods was equal to 0.11?µg?mL^?1. The developed smartphone system was successfully used for the determination of sulfonamides in pharmaceutical and veterinary formulations with recoveries of 102 and 98.7%, respectively. The developed method provides good accuracy (relative error <5%) and precision (relative standard deviation <7%) and offers simple, convenient, rapid, and inexpensive determination of sulfonamides.     

Determination of iron in zeolite catalysts by a smartphone camera-based colorimetric analyzer

A colorimetric analyzer was improved to determine iron in zeolites prepared by incipient wetness impregnation. Software was installed in an Android smartphone for measuring red, green, and blue light intensities. The blue color was suitable for creating a calibration relationship for iron. The optimum distance from the smartphone camera to the sample holder was 5 cm. The brightness was controlled by a table lamp with a 7 W light emitting diode located at 25 cm above the sample holder. Under these conditions, there was no influence from ambient light. A calibration equation was created from 0–1.2% (w/w) iron and stored in the program for analysis. The results agreed well with flame atomic absorption spectrophotometric measurements with a sample throughput exceeding 40 h^?1. The relative standard deviation and the relative error were less than 1%. This method was convenient, rapid, simple, inexpensive, and easy with little chemical waste produced.     

Polymethacrylate optodes: A potential for chemical digital color analysis

The paper describes results of implementing a new kind of optical analytical method, digital color analysis (DCA), in which colorimetric polymethacrylate sensors (optodes) are used. The optodes are made of optically transparent polymethacrylate matrix with physically immobilized analytical reagent which is responsible for the extraction of the analyte into the sensing material and changing its color. The developed optodes can be used in determination of various analytes using both solid-phase spectrophotometer and naked eye. In order to improve accuracy and sensitivity of the naked-eye determination, it is possible to measure visible color changes using digital imaging of the polymethacrylate optode. The digital images then can be represented as basic color (e.g. RGB) data. The DCA determinations of Cu (II), Ag (I) and Co (II) have indicated that the developed optodes are linear in concentration ranges 0.02–0.30; 0.02–0.20 and 0.05–0.25 mg L⁻¹ appropriately with corresponding practical detection limits of 0.01; 0.02 and 0.07 mg L⁻¹.     

A GREEN METHOD FOR THE DETERMINATION OF CHROMIUM(VI) AND IRON(III) IN WATER BY SEQUENTIAL INJECTION ANALYSIS AND SPECTROPHOTOMETRIC DETECTION

In this article, an organic-reagent-free method was described for the determination of Cr(VI) and Fe(III) by double-system double-wavelength sequential injection technique with a single sample injection. In this approach, the determination of Cr(VI) was based on the detection of a blue unstable intermediate compound resulting from the reaction of Cr(VI) with hydrogen peroxide, and the determination of Fe(III) was based on the color reaction of Fe(III) with thiocyanate in acidic medium. Sequential injection analysis (SIA) parameters, including spacer solution volume, aspiration order, aspiration volumes, flow rate, acid medium, solution acidity, and reagent concentrations, were optimized. The linear range for the determination was 3.0–60.0 μg mL^?1 for Cr(VI) and 1.0–40.0 μg mL^?1 for Fe(III), respectively. The limit of detection (LOD) was 0.6 μg mL^?1 for Cr(VI) and 0.2 μg mL^?1 for Fe(III), and the limit of quantitation (LOQ) was 2.0 μg mL^?1 for Cr(VI) and 0.67 μg mL^?1 for Fe(III). The total volume of the reagent consumed in each determination was only 0.11 mL. The proposed method was applied to the simultaneous determination of Cr(VI) and Fe(III) in electroplating wastewater and environmental waters. The results were in good agreement with those obtained by atomic absorption spectrometry. The recoveries were in the range of 97.5–101.1%.     

1‐Pyrenemethanol,a Useful Fluorometric Reagent for the Detection and Determination of Carboxylic Acids in Atmospheric Samples

Abstract

A rapid fluorometric procedure for the selective and sensitive determination of carboxylic acids, based on pre‐column derivatization using 1‐pyrenemethanol, was optimized and applied to atmospheric sampling. The optimum conditions for derivatization were determined to be: reaction solvent–dichloromethane, temperature ?44°C, reaction time ?30 min, and reagent/total acid ratio ?15. Separation of the derivatives of acids up to twenty carbons by reversed‐phase (C₈) chromatography was achieved in 25 min using a water/acetonitrile gradient with a limit of detection for the derivatives of 20 pg for a 20 µL injection. A scanning detector with good spectral resolution allows qualitative identification of the components in complex samples. When used in atmospheric analysis, the recoveries of carboxylic acids from spiked samples were >80% with repeatabilities below 10% RSD. Low molecular weight acids were encountered predominantly in the vapor phase (0.20 to 92 ng/m³), whereas higher molecular weight acids were found mostly in particulate form (0.15–129 ng/m³).     

Colorimetric detection of hazardous gases using a remotely operated capturing and processing system

This paper presents an electronic system for the automatic detection of hazardous gases. The proposed system implements colorimetric sensing algorithms, thus providing a low-cost solution to the problem of gas sensing. It is remotely operated and it performs the tasks of image capturing and processing, hence obtaining colour measurements in RGB (Red–Green–Blue) space that are subsequently sent to a remote operator via the internet. A prototype of the system has been built to test its performance. Specifically, experiments have been carried out aimed at the detection of CO, CO₂, NO, NO₂, SO₂ and formaldehyde at diverse concentrations by using a chromogenic array composed by 13 active and 2 inert compounds. Statistical analyses of the results reveal a good performance of the electronic system and the feasibility of remote hazardous gas detection using colorimetric sensor arrays.     

A multi‐emitter fitting algorithm for potential live cell super‐resolution imaging over a wide range of molecular densities

Multi‐emitter fitting algorithms have been developed to improve the temporal resolution of single‐molecule switching nanoscopy, but the molecular density range they can analyse is narrow and the computation required is intensive, significantly limiting their practical application. Here, we propose a computationally fast method, wedged template matching (WTM), an algorithm that uses a template matching technique to localise molecules at any overlapping molecular density from sparse to ultrahigh density with subdiffraction resolution. WTM achieves the localization of overlapping molecules at densities up to 600 molecules μm^–2 with a high detection sensitivity and fast computational speed. WTM also shows localization precision comparable with that of DAOSTORM (an algorithm for high‐density super‐resolution microscopy), at densities up to 20 molecules μm^–2, and better than DAOSTORM at higher molecular densities. The application of WTM to a high‐density biological sample image demonstrated that it resolved protein dynamics from live cell images with subdiffraction resolution and a temporal resolution of several hundred milliseconds or less through a significant reduction in the number of camera images required for a high‐density reconstruction. WTM algorithm is a computationally fast, multi‐emitter fitting algorithm that can analyse over a wide range of molecular densities. The algorithm is available through the website. https://doi.org/10.17632/bf3z6xpn5j.1     

Detection of ultraviolet B radiation with internal smartphone sensors

Smartphones have the potential to monitor ultraviolet radiation within the terrestrial solar spectrum. Additionally, the ability to accurately estimate personal ultraviolet exposure using a smartphone may one day allow an individual control of their ultraviolet exposure. Previous studies have demonstrated the detection of ultraviolet A from 320 to 400?nm with a smartphone. However, the measurement of ultraviolet B from 280 to 320?nm is desirable to monitor biological effects such as erythema. No previous reports have been reported for the detection of ultraviolet B detection with a smartphone camera. This study characterized the ultraviolet B response of smartphone cameras and shows that these devices detect this radiation without additional hardware. Three smartphones were tested in the ultraviolet B waveband for dark response, temperature response, irradiance response, and spectral response. The used protocols adhered to international standards where applicable. All characterized smartphones were sensitive to ultraviolet B radiation; however, each type provides a unique response.     

Accuracy evaluation of a smartphone-based technology for coastal monitoring

This paper introduces a smartphone-based technique for coastal monitoring and evaluates the accuracy of data such as images, three-dimensional coordinates, and attitude that can be acquired by such a technique. First, to determine intrinsic orientation (IO) parameters of a smartphone camera, a camera calibration was performed. The results were similar or slightly better than previous studies using a non-metric camera. 3-D coordinates provided by the assisted GPS (A-GPS) embedded in the smartphone showed lower accuracy. Attitudes calculated using an accelerometer and magnetometer showed 0.33–2.04° standard deviation, compared with ω, φ, and κ of extrinsic orientation (EO) parameters. Additionally, accuracy (RMSE 0.681 pixels) of smartphone image triangulation using ground control points (GCPs) was about equal to the RMSE of 0.404 pixels of a metric camera. Finally, ortho-rectified images of a test field were generated using DEM from terrestrial laser scanning and acquired images. Additionally, mapping of a shoreline was performed using the ortho-rectified images, and a profile of a representative cross-shore was composed. The results described the actual intertidal zone well. Given the results of the cross-shore profile and the horizontal and vertical accuracy evaluation of the extracted shoreline, this smartphone-based technique is considered appropriate for applications in coastal monitoring.     

Highly sensitive curvature sensor based on an asymmetrical Mach–Zehnder interferometer

Mach–Zehnder interferometers have attracted attention due to their flexible structures and extensive applications. In this study, a simple and highly sensitive curvature sensor based on an asymmetrical Mach–Zehnder interferometer comprising an up-taper and a peanut-like section was theoretically and experimentally characterized. A simulation was conducted to investigate the influence of structural parameters on the interference spectrum. Experimental measurements show that a high curvature sensitivity of ?35.3?nm/m^?1 from 1.35 to 2.20?m^?1 was obtained and high mechanical strength was demonstrated. The temperature–curvature cross-sensitivity of 4.44?×?10^?4?m^?1/°C was lower than the curvature resolution. The high curvature sensitivity and low temperature cross-sensitivity make this sensor a candidate for practical applications.     

Electrolyte Jet Machining (EJM) of antibacterial surfaces

Electrolyte Jet Machining (EJM) has been performed on stainless steel surfaces with the aim of reducing bacterial retention through the generation of nanoscale surface morphology. Following initial EJM experiments aimed at investigating the influence of machining depth, machining speed and current density on the resulting surface roughness, three characteristic surfaces were produced with a current density of 10–18 A/cm² and a machining speed of 0.8–8 mm/s to obtain an arithmetic mean height (S_a) of 0.5–0.74 μm and a density of peaks (S_pd) of 0.25–1.26 μm⁻¹. Relatively large differences between the three surfaces in terms of S_pd allowed thorough investigation into the effects of surface feature size on bacterial retention to be performed. Reductions in the order of 90% compared to control samples were achieved for gram-positive Bacillus cereus and Staphylococcus aureus across the entire tested parameter range (S_pd = 0.25–1.26 μm⁻¹), while reductions in the order of 99% were achieved for gram-negative Escherichia coli and Pseudomonas aeruginosa for surfaces characterized by S_pd > 1 μm⁻¹. Not only do the results call attention to EJM as an innovative technology for producing antibacterial surfaces, they also highlight important differences in the behavior of gram-positive and gram-negative bacteria in relation to EJM-textured surfaces with nanoscale surface morphology.     

An electron microprobe study of the influence of beam current density on the stability of detectable elements in mixed-salts (isoatomic) microdroplets

This paper shows that a means of accurately measuring beam current during microprobe analysis of inorganic fluid microdroplets is essential, since certain elements were sublimated from such specimens under easily achieved beam current densities, i.e. S at 1·8 nA/μm², K at 2·5 nA/μm², Na at 3·5 nA/μm², P at 5·3 nA/μm². In comparison, Cl was volatilized even under the mildest conditions used (0·35 nA/μm²), and Ca, Mg and Co were stable under the severest operating conditions (7·1 nA/μm²). Elements were less stable in large (3 μm diameter) droplets than in small (1 μm) droplets under identical irradiation conditions. The onset of volatilization is a direct function of the current delivered per unit area and not of the total integrated dose. The addition of 50 g/l of urea to the mixed-salts (isoatomic) solution, or (a) the mounting of the droplets so that the carbon-celloidin support film was interposed between them and the electron source, and (b) top-coating the droplets with carbon, did not, in general, raise the threshold of volatilization of a given element, but did effectively retard the rate of loss at current densities above the volatilization threshold. A literature survey confirmed that similar losses can occur from biological tissue specimens, albeit at higher beam current densities. Finally, the possibility that local specimen heating during electron/specimen interaction is a cause of element loss during microprobe analysis is discussed.     

Investigation into fabrication of microslot arrays by electrochemical micromachining

Maskless electrochemical micromachining (EMM) is a prominent and unique surface texturing method to fabricate the arrays of microslots. This article investigates the generation of microslot arrays using maskless EMM method. The developed prototype maskless EMM setup consists of EMM cell, power supply connections, electrode holding devices and constricted vertical cross flow electrolyte system for the fabrication of microslot arrays economically. One textured cathode tool with SU-8 2150 mask is used to produce 22 microslot arrays. Influences of EMM process parameters including voltage, electrolyte concentration, inter electrode gap, flow rate and machining time on the machining performance that is, width overcut, depth and surface roughness (R_a) of microslot arrays are investigated. For lower width overcut, controlled depth, and lower surface roughness, machining with lower voltage, lower electrolyte concentration, lower inter electrode gap, higher flow rate and lower machining time are recommended. From the analysis, it is observed that the best machining conditions including inter electrode gap of 50?μm, applied voltage of 6 V, electrolyte concentration of 20?g L^?1, flow rate of 5.35 m³ hr^?1 and machining time of 1?min fabricate regular microslot array with mean width overcut of 24.321?μm, mean machining depth of 10.7?μm and mean surface roughness of 0.0101?μm.     

Thermal detectors of uncooled multi-element infrared imaging Arrays. II. New thermally uninsulated elements

A new approach to constructing the thermal element of a multi-element array on the basis of thin pyroelectric films is developed: the element is neither thermally insulated from the substrate nor separated by a gap from the substrate surface; instead, it operates owing to accumulation of the charge generated by infrared radiation during the frame. A new principle of high-speed modulation of radiation is described. Experimental results for the behavior of the pyroelectric coefficient in barium–strontium niobate films (Ba_xSr_1?xNb₂O₆), whose values reach up to (1–2)·10^?3 C/m², are presented. It is demonstrated that the specific detectivity of sensitive elements 12 × 12 μm in size in the charge accumulation mode is greater than 10⁹ cm · Hz^0.5 ·W^?1.     

Construction of an Optical Sensor for Cobalt Determination Based on Methyltrioctylammonium Chloride Immobilized on a Polymer Membrane

Abstract

An optical sensor has been designed for the determination of cobalt by spectrophotometry. The sensing membrane is made by immobilizing methyltrioctylammonium chloride on a triacetylcellulose membrane. In the presence of Co(II) and thiocyanate ions, the colorless membrane changes to blue. The response time of the optode was about 7 min. The sensor can readily be regenerated with 0.02 mol L^?1 sodium oxalate solution. This optode is stable and can be stored under water for more than a month without reagent leaching. The calibration curve was linear in the range of 8.5×10^?6–1.3×10^?4 mol L^?1 of Co(II) ion with a limit of detection 5.9×10^?6 mol L^?1. The relative standard deviations for seven replicate measurements of 3.4×10^?5 and 1×10^?4 mol L^?1 of Co(II) were 1.58 and 1.10%, respectively. The sensor was successfully applied to the determination of cobalt in food samples and vitamin B₁₂ ampoule.     

Fabrication and characterization of a new MEMS fluxgate sensor with nanocrystalline magnetic core

This paper presents a new MEMS fluxgate sensor with a Fe-based nanocrystalline ribbon magnetic core and 3D micro-solenoid coils. The excitation coils were placed vertically to the sensing coil on the chip plane. Second harmonic operation principle was adopted in this fluxgate sensor. The total size of the fluxgate sensor was 6.25 mm × 4.85 mm × 120 μm. A simple testing system was established to characterize the fabricated devices. A band pass filter was used to pick up the second harmonic signals in the sensing coils. When excitation rms current of 120 mA and the operational frequency of 200 kHz were selected for the testing of the fabricated devices, the sensitivity of the developed fluxgate sensor was 1005 V/T in the linear range of −500 μT to +500 μT. Due to the combination of the 3D structure coils with the nanocrystalline core, relatively low sensor noise was achieved. The noise power density was 544 pT/Hz^0.5@1 Hz and the noise rms level was 9.68 nT in the frequency range of 25 mHz-10 Hz.     

Peculiarities of admittance in MOS structures based on MBE-grown MCT layers

Admittance of MOS structures based on Hg_1?x Cd _x Te layers grown by molecular beam epitaxy on semi-insulating GaAs substrates is studied. Effect of anomalous generation on the Hg_1?x Cd _x Te surface in a strong electric field (≈10⁵ V/cm) is found. It is shown that the density of surface states of the MCT — SiO₂ interface depends weakly on the presence of the graded energy-gap layer and the type of semiconductor admittance.     

Electrochemical determination of hydrogen peroxide using a novel prussian blue–polythiophene–graphene oxide membrane-modified glassy carbon electrode

A polythiophene–graphene oxide compound membrane and Prussian blue were deposited sequentially on the surface of a glassy carbon electrode by cyclic voltammetry. Due to its excellent electrocatalysis and its analogy with peroxidase enzymes, Prussian blue has been widely used in amperometric biosensors. The polythiophene–graphene oxide compound membrane exhibited good electroconductibility and a large specific surface area. The fabricated Prussian blue/polythiophene/graphene oxide/glassy carbon electrode was characterized by transmission electron microscopy, scanning electron microscopy, and cyclic voltammetry. Under the optimal experimental conditions, the detection of hydrogen peroxide was studied by its amperometric current–time curve. Due to the presence of polythiophene–graphene oxide compound membrane and Prussian blue, the hydrogen peroxide sensor shows a linear calibration range of 1.0?×?10^?6–1.0?×?10^?4?mol?L^?1, detection limits of 3.2?×?10^?7?mol?L^?1 at a signal-to-noise ratio of 3, and recoveries from 95.0 to 105.0%. The results show that the modified glassy carbon electrode has potential practical application for the determination of hydrogen peroxide based on its sensitivity and long-term stability.     

DETERMINATION AND SEPARATION MECHANISM OF ACRYLAMIDE BY HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY

High-performance liquid chromatography using the negative peak method was developed for the determination and separation of acrylamide in food with methanol-water containing a background reagent of 0.01 mmol L^?1 5-sulfosalicylic acid (15/85, v/v) as the mobile phase with an ultraviolet-visible detector (λ_sig = 320 nm, λ_ref = 210 nm). The method was simple, the correlation coefficients exceeded 0.9990, and the limit of detection for acrylamide was 0.07 μg kg^?1. The concentrations of acrylamide in food were between 81 and 910 μg kg^?1. The recoveries were greater than 81.0% and the relative standard deviation was between 0.24 and 3.6%. The results showed that this method was suitable for the determination of acrylamide in food.