Analytical Signal Research Articles

Quantitative analysis of CL-20 explosive by smartphone-based chemiluminescence method.

A new smartphone-based chemiluminescence method has been introduced for the quantitative analysis of CL-20 (Hexanitroazaisowuertzitan) explosive. The solvent mixture, oxidizer agent, and concentration of the reactants were optimized using statistical procedures. CL-20 explosive showed a quenching effect on the chemiluminescence intensity of the luminol-NaClO reaction in the solvent mixture of DMSO/H2O. A smartphone was used as a detector to record the light intensity of chemiluminescence reaction as a video file. The recorded video file was converted to an analytical signal as intensity luminescence-time curve by a written code in MATLAB software. Dynamic range and limit of detection of the proposed method were obtained 2.0-240.0 and 1.1mg⋅L-1, respectively, in optimized concentrations 1.5 × 10-3mol⋅L-1 luminol and 1.0 × 10-2mol⋅L-1 NaClO. Precursors TADB, HBIW, and TADNIW in CL-20 explosive synthesis did not show interference in measurement the CL-20 purity. The analysis of CL-20 spiked samples of soil and water indicated the satisfactory ability of the method in the analysis of real samples. The interaction of CL-20 molecules and OCl- ions is due to quench of chemiluminescence reaction of the luminol-NaClO.

Assessing the Efficiency of Rapid Methods for Evaluating Selectivity and Analytical Signal Strength in Various Fluorescent Phases

Assessing the Efficiency of Rapid Methods for Evaluating Selectivity and Analytical Signal Strength in Various Fluorescent Phases

Comparison of ELSD and RID combined with HPLC for simultaneous determination of six rare sugars in food components

Evaporative light scattering detection (ELSD) and refractive index detection (RID) are two methods commonly used in high-performance liquid chromatography (HPLC) to quantitatively analyze sugars. The performance of two detectors for the detection and quantification of six rare sugars in food samples is systematically compared in this paper. Erythritol, allulose, tagatose, mannitol, isomaltulose and trehalose were separated by HPLC on an NH2 chromatographic column using a flow gradient or isocratic composition acetonitrile–water (80:20, v/v) as mobile phase. The analytical signals for six rare sugars were obtained using ELSD and RID. The intra-day and inter-day variations were lower 3.9 % and 3.5 % for ELSD and 2.4 % and 3.6 % for RID, respectively. The limits of detection (LODs) were between 0.02 mg·mL−1 and 0.06 mg·mL−1 for ELSD in the range of 0.06–0.6 mg·mL−1. The LODs of RID were between 0.1 mg·mL−1 and 1.0 mg·mL−1 within a wider dynamic range (0.4–80 mg·mL−1). The optimized method was used to analyze seven samples. Although both methods can be used for the detection of six rare sugars, the selectivity of isomaltulose and the detection results of six rare sugars under the HPLC-RID method are not as good as the HPLC-ELSD method. Therefore, the HPLC-ELSD method is more suitable for the detection of six rare sugars in food.

Direct detections of the axionlike particle revisited

Axionlike particles (ALPs) are promising dark matter candidates. Their signals in direct detection experiments arise from the well-known inverse Primakoff effect or the inverse Compton scattering of ALPs with the electron. In this paper, we revisit the direct detection of ALP by carefully considering the interference between the inverse Primakoff amplitude and the inverse Compton amplitude in the scattering process a+e→e+γ for the first time. It shows that the contribution of the interference term turns to be dominated in the scattering for a large ALP energy. Given the new analytical formula, signals or constraints of ALP couplings in various projected experiments are investigated. Our results show that these experiments may put strong constraints on ALP couplings for relatively heavy ALP. We further study projected constraints on ALP from the JUNO experiment, which shows competitive constraints on ALP couplings using a ten-year exposure. Published by the American Physical Society 2024

Hierarchically porous coralloid ZnO@Ag microspheres as SERS substrate for highly sensitive malachite green detection

The improper management and unreasonable use of malachite green (MG) in aquatic transportation and large-scale aquaculture pose a significant threat to human health. It is crucial to develop a rapid and reliable approach for detecting MG. In this study, hierarchically porous coralloid ZnO@Ag (C–ZnO@Ag) microspheres were developed as a surface-enhanced Raman scattering (SERS) substrate to detect MG content in water. The hierarchical and porous structure supporting plenty of Ag nanoparticles provides numerous “hot spots” to excite the strong enhanced local electromagnetic field for enlarging the Raman signals of analytes. Moreover, C–ZnO@Ag generates an additional pathway to improve the charge transfer between the substrate and analytes. The manifold mechanisms resulted in the Raman enhancement factor as high as 1.61 × 107 when R6G was selected as the probe. The MG solution at an ultralow concentration of 10−9 M can be successfully identified using the C–ZnO@Ag substrate, which is much lower than the maximum MG residual concentration in water set by the European Union. Therefore, the C–ZnO@Ag substrate has promising opportunities to be applied in rapid SERS-based detection of toxic organic residues.

A miniaturized additive-manufactured carbon black/PLA electrochemical sensor for pharmaceuticals detection

Additive manufacturing is a technique that allows the construction of prototypes and has evolved a lot in the last 20 years, innovating industrial fabrication processes in several areas. In chemistry, additive manufacturing has been used in several functionalities, such as microfluidic analytical devices, energy storage devices, and electrochemical sensors. Theophylline and paracetamol are important pharmaceutical drugs where overdosing can cause adverse effects, such as tachycardia, seizures, and even renal failure. Therefore, this paper aims at the development of miniaturized electrochemical sensors using 3D printing and polylactic acid-based conductive carbon black commercial filament for theophylline and paracetamol detection. Electrochemical characterizations of the proposed sensor were performed to prove the functionality of the device. Morphological characterizations were carried out, in which chemical treatment could change the surface structure, causing the improvement of the analytical signal. Thus, the detection of theophylline at a linear range of 5.00–150 μmol L−1 with a limit of detection of 1.2 μmol L−1 was attained, and the detection of paracetamol at a linear range of 1.00–200 μmol L−1 with a limit of detection of 0.370 μmol L−1 was obtained, demonstrating the proposed sensor effectively detected pharmaceutical drugs.

Analytical signal enhancement of moxidectin and abamectin derivatives for their analysis by spectrofluorometry

Analytical signal enhancement of moxidectin and abamectin derivatives for their analysis by spectrofluorometry

Real-time monitoring of the pH of white wine and beer with colorimetric sensor arrays (CSAs)

The real-time monitoring of the pH values of alcoholic beverages was performed with a compact wireless device based on a colorimetric detection method with the Hue (H) as the analytical signal working in a pH range of 2.50–6.50. This device represents the first colorimetric pH meter reported in the literature monitoring in real-time the pH value of colored solutions. This pH meter consists of I) a nitrocellulose membrane impregnated with a pH-sensitive gel; II) a CCD camera for color acquisition; III) an electronic board with the calibration profiles of H vs. pH, and IV) a display to read the measured pH. It was applied to the pH determination of a white wine, a prosecco white wine, and a double malt beer leading to the values of pHwine= 3.30, pHprosecco= 3.33, pHbeer = 4.29. The analytical performance is comparable to the glass electrode with an accuracy error ≤ 0.05 pH units.

Localised wavenumber estimation and its application to waveguide discontinuities

Wave propagation methods have been widely investigated for the potential application to the detection and localisation of discontinuities in structural waveguides. In the low-mid frequency ranges, previous preliminary works that used the analytic signal theory have considered local wavenumber estimations based on the time domain for the purpose of localisation in mechanical structures. However, these have not fully exploited the potential of this approach. This is accomplished herein for a one-dimensional infinite-like waveguide by means of two methods applied in the spatial domain; namely the Hilbert transform via the wavenumber domain estimator and the Direct Quadrature method. Modifications are proposed to make these methods more suitable to the space-wavenumber application and for the purpose of localisation. A three-dimensional plot is proposed, where local divergences of the wavenumbers indicate the positions of the discontinuities for otherwise uniform waveguides. Numerical simulations and experiments show an accurate estimation of the local wavenumbers and validate the methods with the proposed modifications for the localisation of different types of discontinuities.

Development of heat-assisted in-situ solvent formation liquid phase microextraction followed by derivatization for the simultaneous extraction of aliphatic amines from wastewater samples prior to gas chromatography-mass spectrometry

Herein, a cost-effective, rapid, and selective liquid phase microextraction procedure has been developed for the extraction of some aliphatic amines from sewage samples. The method was based on in-situ formation of chloroform as an extraction solvent into the sample solution followed by derivatization by butylchloroformate prior to gas chromatography- mass spectrometry. Chloroform is formed by the reaction of chloral hydrate and sodium hydroxide. The extraction procedure was accelerated by heating. Also heating decreases chloroform solubility in aqueous solution. To improve the analytical signals, derivatization of the analytes is done by butylchloroformate. The effect of major parameters on the extraction efficiency were studied and optimized. Under the optimized conditions, enrichment factor and extraction recovery were in the ranges of 259–296 and 78–89 %, respectively. Low limits of detection (0.08–0.12 ng mL−1) and quantification (0.28–0.41 ng mL−1), wide linear ranges, and relative standard deviations less than 6 % for intra −and inter-day precisions were acceptable. Lastly, the mentioned method was successfully performed to determine aliphatic amines in wastewater samples.

Wearable electrochemical sensors for real-time monitoring in diabetes mellitus and associated complications

This comprehensive review underscores the pivotal role wearable electrochemical sensors play in the proactive management and prevention of diabetes mellitus (DM) and its associated complications. Acknowledging the substantial impact of DM on individuals and the urgency for effective monitoring strategies, wearable sensors have emerged as a pragmatic solution. These sensors can detect analytical signals from biofluids, including sweat, tears, saliva, and interstitial fluid (ISF), employing minimally invasive techniques facilitated by technological advancements. The seamless integration of these sensors with computational platforms such as smartphones enhances their practicality for routine use. The review systematically explores diverse methodologies, encompassing both enzymatic and non-enzymatic principles, employed for the surveillance of analytes within biofluids. These foundational principles are meticulously applied to wearable devices, affording point-of-care solutions catering to the detection of individual analytes or simultaneous multiplexed analyte detection. The integration of wireless systems and the incorporation of machine learning algorithms introduce a layer of sophistication, elevating the capability of these sensors for the nuanced monitoring of DM and its complications. Through an in-depth analysis of these advancements, this review describes the significant potential of wearable electrochemical sensors as an essential tool for real-time monitoring and managing DM. The diverse approaches presented underscore the adaptability, versatility, and inherent efficacy of these sensors in addressing the multifaceted challenges intrinsic to DM and its associated complications within academic discourse.

Microfluidic paper-based analytical device for simultaneous determination of calcium and magnesium ions in human serum

BackgroundCalcium and magnesium ions are highly abundant and important cations in human body. At the same time, both dyscalcemia and dysmagnesemia are frequently encountered in the clinical practice. As deficiency or excess of Ca(II) or Mg(II) can cause severe symptoms, determining these ions in serum is of great importance. Concentration of these ions in biological samples is typically assayed in clinical laboratories with the use of expensive and specialized equipment. Since those methods cannot be easily adapted for self-diagnosis purposes, there is a great need to develop a convenient tool for reliable determination of calcium and magnesium in serum at the point-of-care. ResultsThe colorimetric methods employed for calcium and magnesium analysis were o-cresophtalein complexone assay and xylidyl blue assay, respectively. Analytical signal acquisition was accomplished using an ordinary flatbed scanner or smartphone and free software. For increased user-friendliness the device was optimized to perform simultaneous determination of calcium and magnesium ions in only 10 min. In the optimized conditions, the limit of detection for calcium ions was 0.09 mmol L−1, while for magnesium it was 0.04 mmol L−1. Determination of both ions requires only 4 μL of serum sample. The developed paper-based sensors were validated with control human serum samples and the obtained relative errors for majority of samples were below 20 %. SignificanceIn this paper, a microfluidic paper-based analytical device for simultaneous determination of calcium and magnesium ions in human serum is reported for the first time. Additionally, this is also the first report on colorimetric determination in serum of any of these ions in paper-based format. Simultaneous detection of both ions allows for fast and user-friendly screening of disturbance in calcium and magnesium homeostasis.

Application of Airborne Magnetic Data to Assess the Structures that Favour Gold Mineralization within Southern Parts of Katsina State, Nigeria

The Nigerian schist belts are endowed with gold mineralisation and to delineate the geological structures that favour gold mineralisation, the airborne magnetic data that cover the study area was employed. Also, the residual magnetic anomaly data of the research area was reduced to the Equator (RTE) followed by the application of the centre for exploration targeting (CET) plug-in and three source edge mapping techniques; analytic signal (AS), first vertical derivative (FVD) and the horizontal gradient magnitude (HGM), for structural delineation and subsequently the structural density map of the area was produced. Structural density varies from 0.186 km/km2 low to 0.93 km/km2 high. Portions within the study area with high structural densities are Bakori in the southwest, Shanono in the northeast, Gwarzo situated directly south of Shanono, north and south of Karaye, the border between Kafur and Rogo in the south, all within the schist. Since structures are conduits for the migration of mineralisation fluids, areas with high structural densities will be viable for gold mineralisation. Also, comparing the structural density map of the area to the analytic signal map of the area has revealed the high structural density portions to coincide with the high analytic signal zones. This implies that structures within these portions are responsible for the migration of mineralization fluid into these environments.

Smart Sensor-Based Monitoring Technology for Machinery Fault Detection.

Rotary machines commonly use rolling element bearings to support rotation of the shafts. Most machine performance imperfections are related to bearing defects. Thus, reliable bearing condition monitoring systems are critically needed in industries to provide early warning of bearing fault so as to prevent machine performance degradation and reduce maintenance costs. The objective of this paper is to develop a smart monitoring system for real-time bearing fault detection and diagnostics. Firstly, a smart sensor-based data acquisition (DAQ) system is developed for wireless vibration signal collection. Secondly, a modified variational mode decomposition (MVMD) technique is proposed for nonstationary signal analysis and bearing fault detection. The proposed MVMD technique has several processing steps: (1) the signal is decomposed into a series of intrinsic mode functions (IMFs); (2) a correlation kurtosis method is suggested to choose the most representative IMFs and construct the analytical signal; (3) envelope spectrum analysis is performed to identify the representative features and to predict bearing fault. The effectiveness of the developed smart sensor DAQ system and the proposed MVMD technique is examined by systematic experimental tests.

Pulsed Direct Current Arc-Induced Nanoelectrospray Ionization Mass Spectrometry.

This study explores the innovative field of pulsed direct current arc-induced nanoelectrospray ionization mass spectrometry (DCAI-nano-ESI-MS), which utilizes a low-temperature direct current (DC) arc to induce ESI during MS analyses. By employing a 15 kV output voltage, the DCAI-nano-ESI source effectively identifies various biological molecules, including angiotensin II, bradykinin, cytochrome C, and soybean lecithin, showcasing impressive analyte signals and facilitating multicharge MS in positive- and negative-ion modes. Notably, results show that the oxidation of fatty acids using a DC arc produces [M + O - H]- ions, which aid in identifying the location of C═C bonds in unsaturated fatty acids and distinguishing between isomers based on diagnostic ions observed during collision-induced dissociation tandem MS. This study presents an approach for identifying the sn-1 and sn-2 positions in phosphatidylcholine using phosphatidylcholine and nitrate adduct ions, accurately determining phosphatidylcholine molecular configurations via the Paternò-Büchi reaction. With all the advantages above, DCAI-nano-ESI holds significant promise for future analytical and bioanalytical applications.

Measurement of neuropeptide Y in aptamer-modified planar electrodes

Electrochemical impedance spectroscopy (EIS) is a powerful technique for studying the interaction at electrode/solution interfaces. The adoption of EIS for obtaining analytical signals in biosensors based on aptamers is gaining popularity because of its advantageous characteristics for molecular recognition. Neuropeptide Y (NPY), the most abundant neuropeptide in the body, plays a crucial role with its stress-relieving properties. Quantitative measurement of NPY is imperative for understanding its role in these and other biological processes. Although aptamer-modified electrodes for NPY detection using EIS present a promising alternative, the correlation between the data obtained and the adsorption process on the electrodes is not fully understood. Various studies utilize the change in charge transfer resistance when employing an active redox label. In contrast, label-free measurement relies on changes in capacitance. To address these challenges, we focused on the interaction between aptamer-modified planar electrodes and their target, NPY. We proposed utilizing −ω*Zimag as the analytical signal, which facilitated the analysis of the adsorption process using an analogous Langmuir isotherm equation. This approach differs from implantable microelectrodes, which adhere to the Freundlich adsorption isotherm. Notably, our method obviates the need for a redox label and enables the detection of NPY at concentrations as low as 20 pg/mL. This methodology demonstrated exceptional selectivity, exhibiting a signal difference of over 20-to-1 against potential interfering molecules.

Optimizing solid phase extraction and HPLC-MS/MS parameters for reliable quantification of COVID-19 pharmaceuticals in Mexico City’s wastewater: A design of experiments approach

Through the COVID-19 health crisis, a plethora of new medications, along with some discontinued pharmaceuticals, were directly tested on population to assess their efficacy in symptom management. Consequently, residues from these treatments were systematically disposed into sewage systems, presenting a novel contamination challenge in urban centers. To effectively address this issue by environmental authorities, the presence of these pollutants in wastewater must be accurately quantified. Herein, we conducted a meticulous study to validate an analytical method based on solid-phase extraction (SPE) and high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) to detect six pharmaceuticals (metformin, famotidine, indomethacin, dexamethasone, azithromycin, and ivermectin) in wastewater. Using a Plackett-Burman design (PBD), the eight parameters significantly impacting on the HPLC-MS/MS technique were established based on the analytical signal of the six analytes. Subsequently, in conjunction with a Box-Behnken design (BBD), optimal analysis conditions were determined as follows: injection volume: 10 µL, column temperature: 20 °C, capillary voltage: 4100 V, drying gas temperature and flow rate of 350 °C and 7 L min−1 respectively, nebulizer pressure: 15 psi, concentration of formic acid and ammonium acetate in the mobile phase of 0.1 % and 10 mmol/L, respectively. SPE was optimized through a univariable experimental design. OASIS HLB cartridges exhibited the highest extraction efficiency compared to highly polar and non-polar adsorbents. The optimal sample loading conditions were set as 250.0 mL of water sample at pH = 9.0. The washing conditions were 5.0 mL of a 95:5 water:methanol solution, while elution conditions were optimal using 6.0 mL of a 98:2 methanol:formic acid solution. After evaporating the eluate to dryness and reconstituting in 1.0 mL of a 98:2 methanol:formic acid solution, a concentration factor of 250 was achieved. The analytical method was validated using for matrices, namely, raw and treated wastewater, wastewater percolated through soil and groundwater. Acceptable levels of precision and accuracy were achieved for all analytes in the tested matrices. Using the validated method, the six pharmaceuticals were quantified in environmental samples, revealing high levels of metformin, dexamethasone, and azithromycin in Mexico City’s sewage. Highly polar compounds displayed mobility through environment as they were present in effluent samples, percolated wastewater, and groundwater.

Properties of processing and data acquisition methods in test methods of chemical analysis

Chemical analysis is a crucial source of information for assessing the state of the environment, evaluating the human body condition, and serving as a diagnostic tool for detecting diseases and more. The use of simple, rapid, and cost-effective analysis methods without the need for specialized laboratory conditions and personnel with specific qualifications, such as test methods, contributes to the effective implementation of well-known techniques for analyzing the chemical composition of environmental objects and for use in the field of healthcare. Scanner indication of the analytical signal in chemical analysis is an objective, fast, and automated method for assessing the color characteristics of colored samples. The use of scanner indication in obtaining the analytical signal eliminates errors associated with subjective evaluation and assists individuals with color vision impairments, speeding up data collection and processing operations. Considering and controlling the light source in scanning systems is crucial to ensuring the stability and accuracy of obtained images under different lighting conditions. To obtain the analytical signal, it is primarily necessary to process the image to obtain the region of interest, which is determined by segmentation, manual methods, and using image processing techniques. The analysis of obtained values is carried out by constructing a linear or nonlinear relationship of color values in the selected color model converted to a single value of the analytical signal to concentration. Most existing systems for scanner detection of the analytical signal in analytical test methods require human involvement in obtaining and interpreting results, limiting the application areas of these methods of analytical signal indication. Further research is focused on creating a reliable method for obtaining the analytical signal using a smartphone camera based on image processing techniques, allowing for the automation of obtaining, processing, and improving the reproducibility of results in chemical test analyses.

Evolutionary Optimized, Monocrystalline Gold Double Wire Gratings as a Novel SERS Sensing Platform.

Achieving reliable and quantifiable performance in large-area surface-enhanced Raman spectroscopy (SERS) substrates poses a formidable challenge, demanding signal enhancement while ensuring response uniformity and reproducibility. Conventional SERS substrates often made of inhomogeneous materials with random resonator geometries, resulting in multiple or broadened plasmonic resonances, undesired absorptive losses, and uneven field enhancement. These limitations hamper reproducibility, making it difficult to conduct comparative studies with high sensitivity. This study introduces an innovative approach that addresses these challenges by utilizing monocrystalline gold flakes to fabricate well-defined plasmonic double-wire resonators through focused ion-beam lithography. Inspired by biological strategy, the double-wire grating substrate (DWGS) geometry is evolutionarily optimized to maximize the SERS signal by enhancing both excitation and emission processes. The use of monocrystalline material minimizes absorption losses and ensures shape fidelity during nanofabrication. DWGS demonstrates notable reproducibility (RSD=6.6%), repeatability (RSD=5.6%), and large-area homogeneity >104µm2. It provides a SERS enhancement for sub-monolayer coverage detection of 4-Aminothiophenol analyte. Furthermore, DWGS demonstrates reusability, long-term stability on the shelf, and sustained analyte signal stability over time. Validation with diverse analytes, across different states of matter, including biological macromolecules, confirms the sensitive and reproducible nature of DWGSs, thereby establishing them as a promising platform for future sensing applications.

Wigner distribution associated with linear canonical transform of generalized 2-D analytic signals

Analytic complex signals find numerous applications in image and signal processing community. This article focuses on the discussion and definitions of three generalized two-dimensional (2-D) analytic signals (GASs). It begins by explaining the parametric Hilbert transform (PHT) and parametric Riesz transform (PRT), derived from analyzing the irrotational and solenoidal vector fields, respectively. Furthermore, the article explores the four-dimensional Wigner distributions associated with the linear canonical transform (WDLs) for these GASs. Finally, the advantages of these GASs are demonstrated through their application in envelope detection, and highlighting these WDLs potential for feature extraction. This article provides valuable insights into the field of 2-D analytic signals and their applications in various domains.