Assessment of a three-axis on-rotor sensing performance for machining process monitoring: a case study.

Online monitoring of cutting conditions is essential in intelligent manufacturing, and vibrations are one of the most effective signals in monitoring machining conditions. Generally, traditional wired accelerometers should be installed on a motionless or stable platform, such as a tool holder or lathe bed, to sense vibrations. Such installation methods would cause the signals to suffer more serious noise interferences and a low signal-to-noise ratio, resulting in less sensitivity to valuable information. Therefore, this study developed a novel three-axis wireless on-rotor sensing (ORS) system for monitoring the turning process. The Micro Electromechanical System (MEMS) accelerometer sensor node can be mounted on a rotating workpiece or spindle rotor and is more sensitive in detecting the vibrations of the entire rotor system without any modification of the lathe system and interference in the cutting procedure. The processor, data acquisition, and Bluetooth Low Energy (BLE) 5.0+ modules were developed and debugged to cooperate with a piezoelectric triaxial accelerometer, with a vibration amplitude not larger than ± 16 g. A series of turning tests were conducted and the results were compared with those from the commercial wired accelerometers, which proved that the ORS system can measure the vibration signal of the rotor system more effectively and sensitively than wired accelerometers, thus demonstrating the accurate monitoring of machining parameters.

Plasmon-mediated fluorescence with distance independence: from model to a biosensing application.

In this article, plasmon-mediated fluorescence biosensing is reported to be distance independent through a full-coupling strategy that effectively activates the entire plasmon coupling region. This concept is demonstrated through collecting the directional surface plasmon-coupled emission (SPCE) signal from fluorescent silica nanoparticles with a size that matches the entire coupling region. Based on this design, the spatial distribution of the fluorophores is confined by the dimension of the nanoparticle. Therefore, these encapsulated fluorophores occupy the maximum coupling dominant region and optimally utilize the coupling effect. Being different from the conventional plasmon-mediated fluorescence, the enhanced fluorescence response becomes nearly independent of distance changes on a wide dynamic range from 0nm to 30nm between the fluorescent nanoparticles and metal structure. Full-coupling SPCE appropriately enlarges the distribution of fluorophores, ensuring that the coupling dominant region is filled with enough fluorophores at varying distances to create a stable and detectable signal. This scale of distances is well suited for many biorecognition events. Full-coupling SPCE solves signal deviation challenges originating from the susceptible and unpredictable orientation and conformation of biomolecules on the nanoscale. Immunoassays and DNA detection are shown with high and reliable signals, demonstrating the advantages of distance-independent full coupling. Without the need of a complicated and rigorous architecture for precise distance control, full-coupling SPCE offers great promise for a general platform of chip-based biosensing and bioanalysis.

Analysis of 16 phthalic acid esters in food simulants from plastic food contact materials by LC-ESI-MS/MS.

An RP LC-ESI-MS/MS method for the determination of the migration of 16 primary phthalic acid esters from plastic samples has been developed using distilled water, 3% acetic acid, 10% alcohol, and olive oil as food simulants. Detection limits were 1.6-18.5 µg/kg in distilled water, 1.4-17.3 µg/kg in 3% acetic acid, 1.4-19.2 µg/kg in 10% alcohol, and 31.9-390.8 µg/kg in olive oil. The RSDs were in the range of 0.07-11.28%. The real plastic products inspection showed that only few analyzed samples were phthalates contaminated. Bis-2-ethylhexyl ester and dibutyl phthalate were the common items migrated from the plastic products into food and feeds, but the migration concentrations were far below the limits set by European Union (1.5 mg/kg for bis-2-ethylhexyl ester and 0.3 mg/kg for dibutyl phthalate).

An integrated electrochemical device based on immunochromatographic test strip and enzyme labels for sensitive detection of disease-related biomarkers.

A novel electrochemical biosensing device that integrates an immunochromatographic test strip and a screen-printed electrode (SPE) connected to a portable electrochemical analyzer was presented for rapid, sensitive, and quantitative detection of disease-related biomarker in human blood samples. The principle of the sensor is based on sandwich immunoreactions between a biomarker and a pair of its antibodies on the test strip, followed by highly sensitive square-wave voltammetry (SWV) detection. Horseradish peroxidase (HRP) was used as a signal reporter for electrochemical readout. Hepatitis B surface antigen (HBsAg) was employed as a model protein biomarker to demonstrate the analytical performance of the sensor in this study. Some critical parameters governing the performance of the sensor were investigated in detail. Under optimal conditions, this sensor was capable of detecting a minimum of 0.3 ng mL(-1) (S/N=3) HBsAg with a wide linear concentration range from 1 to 500 ng mL(-1). The sensor was further utilized to detect HBsAg spiked in human plasma with an average recovery of 91.3%. In comparison, a colorimetric immunochromatographic test strip assay (ITSA) was also conducted. The result shows that the SWV detection in the electrochemical sensor is much more sensitive for the quantitative determination of HBsAg than the colorimetric detection, indicating that such a sensor is a promising platform for rapid and sensitive point-of-care testing/screening of disease-related biomarkers in a large population.

A novel baseline-correction method for standard addition based derivative spectra and its application to quantitative analysis of benzo(a)pyrene in vegetable oil samples.

In the present work, a baseline-correction method based on peak-to-derivative baseline measurement was proposed for the elimination of complex matrix interference that was mainly caused by unknown components and/or background in the analysis of derivative spectra. This novel method was applicable particularly when the matrix interfering components showed a broad spectral band, which was common in practical analysis. The derivative baseline was established by connecting two crossing points of the spectral curves obtained with a standard addition method (SAM). The applicability and reliability of the proposed method was demonstrated through both theoretical simulation and practical application. Firstly, Gaussian bands were used to simulate 'interfering' and 'analyte' bands to investigate the effect of different parameters of interfering band on the derivative baseline. This simulation analysis verified that the accuracy of the proposed method was remarkably better than other conventional methods such as peak-to-zero, tangent, and peak-to-peak measurements. Then the above proposed baseline-correction method was applied to the determination of benzo(a)pyrene (BaP) in vegetable oil samples by second-derivative synchronous fluorescence spectroscopy. The satisfactory results were obtained by using this new method to analyze a certified reference material (coconut oil, BCR(®)-458) with a relative error of -3.2% from the certified BaP concentration. Potentially, the proposed method can be applied to various types of derivative spectra in different fields such as UV-visible absorption spectroscopy, fluorescence spectroscopy and infrared spectroscopy.

A novel synchronous fluorescence spectroscopic approach for the rapid determination of three polycyclic aromatic hydrocarbons in tea with simple microwave-assisted pretreatment of sample.

Many polycyclic aromatic hydrocarbons (PAHs) are carcinogenic, and some have been reported to be present in tea. People can be exposed to PAHs through tea consumption. Therefore, there is real importance for the determination of PAHs in tea. Because of the complex matrix of tea, it is hard to detect PAHs in tea without cleanup and chromatographic separation procedures. In this research, for the first time, a novel synchronous fluorescence spectroscopic approach coupling nonlinear variable-angle synchronous and matrix-isopotential synchronous scanning modes has been developed for the rapid determination of benzo(a)pyrene (BaP), benzo(k)fluoranthene (BkF), and anthracene (AN) in tea with simple microwave-assisted pretreatment of samples. This novel technique is able to resolve the spectra of the three PAHs well, even with interference from other EPA PAHs. The detection limits for BaP, BkF, and AN in tea were 0.18-0.28, 0.55-0.89, and 0.64-3.58 µg/kg, respectively, depending on various teas, with satisfactory recoveries ranging from 77.1 to 116%. The relative standard deviations achieved for BaP, BkF, and AN were 1.5, 6.6, and 8.5% for green tea; 2.9, 7.4, and 2.1% for oolong tea; and 5.6, 5.4, and 5.8% for black tea, respectively. Our results showed good correlation with those of gas chromatography-mass spectrometry. The approach developed is simple, reliable, and cost-efficient, providing an attractive alternative for the rapid selective screening of PAHs in tea.

A novel immunochromatographic electrochemical biosensor for highly sensitive and selective detection of trichloropyridinol, a biomarker of exposure to chlorpyrifos.

We present a novel portable immunochromatographic electrochemical biosensor (IEB) for simple, rapid, and sensitive biomonitoring of trichloropyridinol (TCP), a metabolite biomarker of exposure to organophosphorus insecticides. Our new approach takes the advantage of immunochromatographic test strip for a rapid competitive immunoreaction and a disposable screen-printed carbon electrode for a rapid and sensitive electrochemical analysis of captured HRP labeling. Several key experimental parameters (e.g. immunoreaction time, the amount of HRP labeled TCP, concentration of the substrate for electrochemical measurements, and the blocking agents for the nitrocellulose membrane) were optimized to achieve a high sensitivity, selectivity and stability. Under optimal conditions, the IEB has demonstrated a wide linear range (0.1-100 ng/ml) with a detection limit as low as 0.1 ng/ml TCP. Furthermore, the IEB has been successfully applied for biomonitoring of TCP in the rat plasma samples with in vivo exposure to organophosphorus insecticides like Chlorpyrifos-oxon (CPF-oxon). The IEB thus opens up new pathways for designing a simple, rapid, clinically accurate, and quantitative tool for TCP detection, as well as holds a great promise for in-field screening of metabolite biomarkers, e.g., TCP, for humans exposed to organophosphorus insecticides.

Quantum dot-based immunochromatographic fluorescent biosensor for biomonitoring trichloropyridinol, a biomarker of exposure to chlorpyrifos.

A novel and portable fluorescent sensor that integrates an immunochromatographic test strip assay (ITSA) with a quantum dot (QD) label and a test strip reader was described in this study for simple, rapid, and sensitive biomonitoring of an organophosphorus pesticide metabolite. The principle of this sensor is based on a competitive immunoreaction that was performed on an immunochromatographic test strip, where analytes compete with competitors (QD-conjugated analogs) to bind to antibodies on a test zone. Captured QDs serve as signal vehicles for fluorescent readout. In this work, 3,5,6-trichloropyridinol (TCP) is used as a model analyte to demonstrate the performance of the immunosensor. QD-TCP conjugates were synthesized and characterized with X-ray photoelectron spectroscopy (XPS) and fluorescence spectroscopy. Some parameters (e.g., the amount of QD-modified TCP and immunoreaction time) that govern sensitivity and reproducibility of ITSA were optimized. Under optimal conditions, the sensor has a wide dynamic range and is capable of detecting a minimum 1.0 ng/mL TCP standard analyte in 15 min. The sensor has been successfully applied for detection of TCP spiked in rat plasma with average recovery of 102.0%. Results demonstrate that this sensor provides a rapid, clinically accurate, and quantitative tool for TCP detection and shows great promise for in-field and point-of-care (POC) quantitative testing and screening for metabolite biomarkers, e.g., TCP, for humans exposed to pesticides.

Sensitive immunosensor for cancer biomarker based on dual signal amplification strategy of graphene sheets and multienzyme functionalized carbon nanospheres.

A novel electrochemical immunosensor for sensitive detection of cancer biomarker alpha-fetoprotein (AFP) is described that uses a graphene sheet sensor platform and functionalized carbon nanospheres (CNSs) labeled with horseradish peroxidase-secondary antibodies (HRP-Ab2). Greatly enhanced sensitivity for the cancer biomarker is based on a dual signal amplification strategy: first, the synthesized CNSs yielded a homogeneous and narrow size distribution, which allowed several binding events of HRP-Ab2 on each nanosphere. Enhanced sensitivity was achieved by introducing the multibioconjugates of HRP-Ab2-CNSs onto the electrode surface through "sandwich" immunoreactions. Second, functionalized graphene sheets used for the biosensor platform increased the surface area to capture a large amount of primary antibodies (Ab1), thus amplifying the detection response. On the basis of the dual signal amplification strategy of graphene sheets and the multienzyme labeling, the developed immunosensor showed a 7-fold increase in detection signal compared to the immunosensor without graphene modification and CNSs labeling. The proposed method could respond to 0.02 ng mL(-1) AFP with a linear calibration range from 0.05 to 6 ng mL(-1). This amplification strategy is a promising platform for clinical screening of cancer biomarkers and point-of-care diagnostics.

A novel, selective, and rapid fluorimetric method for the simultaneous analysis of coproporphyrin and uroporphyrin in urine.

A simple and rapid spectrofluorimetric method is described for the determination of the closely overlapping mixture of coproporphyrin (CP) and uroporphyrin (UP) in urine samples. Matrix Isopotential Synchronous Fluorescence Spectrometry (MISFS) was applied to improve the spectral resolution for the severely overlapped spectra of the urinary porphyrins. First-order derivative technique eliminates the background interference of each component on the other. Using these two techniques together, selectivity was improved, while maintaining a high sensitivity, and time-consuming separation processes and multiple scanning processes were avoided. The limits of detection were 0.15 nmol L(-1) and 0.1 nmol L(-1) for CP and UP, respectively. The concentrations of CP and UP were determined from the peak amplitudes of the Derivative Matrix Isopotential Synchronous Fluorescence (DMISF) spectra, at their detection points where the interference was suppressed. Porphyrins excretion in urine samples, collected from normal subjects, was studied. A comparison between the new method and the anion-exchange chromatographic method of Martinez and Mills was established using Bland-Altman method and the results indicate that these two methods are in a good agreement with each other.

A simple and rapid fluorimetric method for simultaneous determination of protoporphyrin IX and zinc protoporphyrin IX in whole blood.

Derivative variable-angle synchronous fluorescence (DVASF) spectrometry improves the spectral resolution and selectivity of the fluorescence method. The feasibility of DVASF spectrometry for the simultaneous determination of protoporphyrin IX (PP) and zinc protoporphyrin IX (ZnPP) was investigated. PP and ZnPP were distinguished from each other simultaneously and rapidly by the DVASF method. The spectra were resolved well, and the two components were determined in a single scan, avoiding the spectral compensation factor for PP and chromatographic separation. The linear range of the calibration curve for PP was from 0.190 to 152 nmol/L and for ZnPP was from 0.383 to 230 nmol/L. The detection limits of PP and ZnPP were 0.098 nmol/L and 0.088 nmol/L, respectively. The within-run imprecision (RSD, n = 5) for PP was 4.1%, and for ZnPP was 4.2%. Mean recoveries (SD) of PP and ZnPP added to a blood sample were 86.4 (7.3)% and 72.9 (6.6)%, respectively. This method should be a potential tool in the rapid routine screening of large quantities of samples.

Total internal reflection fluorescence spectroscopy for investigating the adsorption of a porphyrin at the glass/water interface in the presence of a cationic surfactant below the critical micelle concentration.

Total internal reflection fluorescence (TIRF) spectroscopy was used to investigate the adsorption behavior of meso-tetrakis(p-sulfonatophenyl)porphyrin (TPPS) at the glass/water interface in the presence of a cationic surfactant (cetyltrimethylammonium bromide, CTAB) far below the critical micelle concentration. The adsorption model of TPPS at the glass/water interface in the presence of low concentration of CTAB was proposed, which was different from the adsorption of TPPS in the presence of micelles of CTAB at the glass/water interface. TPPS and CTAB did not form stable complex at the interface in dilute system. The interfacial species of TPPS were analyzed by comparing the spectra of TPPS at the glass/water interface and in the aqueous phase. The influences of the TPPS concentration, the CTAB concentration, and the pH values on the interfacial fluorescence spectra and intensities were studied. It was demonstrated that electrostatic interaction and hydrophobicity performed an important role on the adsorption of TPPS in the presence of CTAB. The different effects of TPPS concentration on the adsorption behaviour of TPPS at different pH were observed for the first time. It was found that the adsorption isotherms of TPPS at glass/water interface could fit Freundlich equation at pH 7.1.

A novel approach for simultaneous determination of polycyclic aromatic hydrocarbons by Shpol'skii non-linear variable-angle synchronous fluorescence spectrometry.

A new method of combining low-temperature Shpol'skii effect with non-linear variable-angle synchronous fluorescence spectrometry (L-NLVASFS) has been proposed to increase spectral resolution. This coupled method was applied successfully to the simultaneous identification and quantification of some polycyclic aromatic hydrocarbons (PAHs) in mixtures, which cannot be determined by non-linear variable-angle synchronous fluorescence spectrometry at room-temperature (R-NLVASFS). The usefulness of this method is demonstrated by the analyses of synthetic mixtures and several real samples of airborne particulates.

Rapid screening method for simultaneous determination of four polycyclic aromatic hydrocarbons in water samples by derivative non-linear variable-angle synchronous fluorescence spectrometry.

Derivative non-linear variable-angle synchronous fluorescence spectroscopy (D-NLVASFS) has been developed to improve the selectivity of the fluorescence measurement without loss of sensitivity. We report a simple screening approach for the rapid and simultaneous determination of 1,2.5,6-dibenzoanthracene (DBA), 2,3-benzofluorene (BF), pyrene (Pyr) and 3,4-benzopyrene (BaP) in a mixture by using first-derivative NLVASFS. The method is efficient, fast and straightforward, and the measurement was simply based on a single spectrum via a single spectral scanning of a sample. The linear ranges 0.005-0.30, 0.02-0.30, 0.02-0.40 and 0.005-1.0 microg/mL and the detection limits 0.08, 1.14, 1.64 and 0.12 ng/mL are obtained for DBA, BF, Pyr and BaP, respectively. The method was applied to water samples spiked with the four polycyclic aromatic hydrocarbons (PAHs), with mean recoveries of 103.0% (SD 5.9%) for DBA, 96.4% (SD 4.2%) for BF, 96.2% (SD 4.0%) for Pyr and 98.2% (SD 3.0%) for BaP.