scholarly journals Photoacoustic Detection of H2 and NH3 Using Plasmonic Signal Enhancement in GaN Microcantilevers

Micromachines ◽  
2020 ◽  
Vol 11 (7) ◽  
pp. 680 ◽  
Author(s):  
Digangana Khan ◽  
Hongmei Li ◽  
Ferhat Bayram ◽  
Durga Gajula ◽  
Goutam Koley
Keyword(s):  
Limit Of Detection ◽  
Signal To Noise Ratio ◽  
Detection Sensitivity ◽  
Selective Detection ◽  
Signal To Noise ◽  
Photoacoustic Detection ◽  
Laser Illumination ◽  
Pd Nanoparticle ◽  
Sensor Devices ◽  
Reducing Gases

Photoacoustic (PA) detection of H2 and NH3 using plasmonic excitation in Pt- and Pd-decorated GaN piezotransistive microcantilevers were investigated using pulsed 520-nm laser illumination. The sensing performances of 1-nm Pt and Pd nanoparticle (NP) deposited cantilever devices were compared, of which the Pd-coated sensor devices exhibited consistently better sensing performance, with lower limit of detection and superior signal-to-noise ratio (SNR) values, compared to the Pt-coated devices. Among the two functionalization layers, Pd-coated devices were found to respond only to H2 exposure and not to NH3, while Pt-coated devices exhibited repeatable response to both H2 and NH3 exposures, highlighting the potential of the former in performing selective detection between these reducing gases. Optimization of the device-biasing conditions were found to enhance the detection sensitivity of the sensors.

Novel electrochemiluminescent materials for sensor applications

2014 ◽  
Vol 174 ◽  
pp. 357-367 ◽  
Author(s):  
Lynn Dennany ◽  
Zahera Mohsan ◽  
Alexander L. Kanibolotsky ◽  
Peter J. Skabara
Keyword(s):  
Redox Reactions ◽  
Limit Of Detection ◽  
Signal To Noise Ratio ◽  
High Sensitivity ◽  
Radical Cations ◽  
Detection Sensitivity ◽  
Sensor Development ◽  
Sensor Applications ◽  
Sensor Devices ◽  
The Impact

Electrochemiluminescence (ECL) uses redox reactions to generate light at an electrode surface, and is gaining increasing attention for biosensor development due to its high sensitivity and excellent signal-to-noise ratio. ECL studies of monodisperse oligofluorene–truxenes (T4 series) have been reported previously, showing the production of stable radical cations and radical anions, generating blue ECL. The compound in this study differs from the original structures, in that there are 2,1,3-benzothiadazole (BT) units inserted between the first and second fluorene units of the quarterfluorenyl arms. It was therefore anticipated that the incorporation of these highly luminescent and ECL-active compounds into sensor development would lead to significant decreases in detection limits. In this contribution, we report on the impact of incorporating these novel complexes into sensor devices on the ECL efficiency, as well as the ability of these to improve the detection sensitivity and decrease the limit of detection using the reagent-free detection of model analytes. The real world impact of these compounds is elucidated through the comparison with more standard ECL materials such as ruthenium-based compounds. The potential for multiple applications is to be examined within this contribution.

scholarly journals HPLC Estimation of New Impurity Methyl Ezetimibe in Ezetimibe Drug

2020 ◽  
Vol 32 (6) ◽  
pp. 1309-1313
Author(s):  
Duggirala Parvatha Venkata Vardhani Devi ◽  
Kapavarapu Maruthi Venkata Narayanarao ◽  
Pulipaka Shyamala ◽  
Rallabhandi Murali Krishna ◽  
Komali Siva Prasad
Keyword(s):  
Limit Of Detection ◽  
Signal To Noise Ratio ◽  
Gradient Elution ◽  
Hplc Method ◽  
The Novel ◽  
Signal To Noise ◽  
Drug Substances ◽  
Chromatographic Detection ◽  
Noise Ratio ◽  
Gradient Elution Mode

A new gradient elution mode HPLC method was developed and validated to detect and monitor the novel impurity namely methyl ezitimibe in ezetimibe drug substances. Chromatographic detection and analysis of methyl ezetimibe was performed on XBridge C18 column with mobile phase consisting of 0.02 M phosphate buffer (pH 5) and acetonitrile with 1 mL/min flow rate in gradient elution mode. Methyl ezetimibe was detected and monitored at 248 nm. The calibration curve was linear over range of 0.015 to 0.219% concentration. The limit of detection and quantification were computed as 0.005% (signal to noise ratio 3.60) and 0.015% (signal to noise ratio 15.96), respectively. The precision was 0.97% (%RSD) and accuracy was 93.2 to 98.2% (recovery). The developed method was proved suitable to detect and monitor methyl ezetimibe impurity in ezetimibe drug substances.

Quantitation of Sulfamethazine in Pork Tissue by Thin-Layer Chromatography

1993 ◽  
Vol 76 (2) ◽  
pp. 335-341 ◽  
Author(s):  
Joseph Unruh ◽  
Daniel P Schwartz ◽  
Robert A Barford
Keyword(s):  
Thin Layer ◽  
Limit Of Detection ◽  
Solid Phase ◽  
Signal To Noise Ratio ◽  
Internal Standard ◽  
Signal To Noise ◽  
Thin Layer Chromatographic Plate ◽  
Average Accuracy ◽  
Chromatographic Plate ◽  
Layer Chromatography

Abstract Our earlier method to detect and quantitate sulfamethazine (SMZ) in milk at the 10 ppb level was modified to quantitate SMZ in pork tissue. Sulfabromomethazine (SBZ) is added to the tissue as an internal standard. SMZ and SBZ are extracted from the tissue into water as the supernatant of a centrifuged, aqueous homogenate and are cleaned up and concentrated by a series of solid-phase extractions. The sulfonamide-containing eluate is then separated on a silica gel thin-layer chromatographic plate. SBZ and SMZ are derivatized with fluorescamine, and their fluorescence is quantitated with a scanning densitometer. The limit of detection was estimated at 0.25 ppb (signal-to-noise ratio, 3:1). The average accuracy over the analysis range (0.54-21.8 ppb [μg/kg]) was 95.6% (standard deviation = 29.4%, n = 54).

scholarly journals Eddy-covariance data with low signal-to-noise ratio: time-lag determination, uncertainties and limit of detection

2015 ◽  
Vol 8 (3) ◽  
pp. 2913-2955 ◽  
Author(s):  
B. Langford ◽  
W. Acton ◽  
C. Ammann ◽  
A. Valach ◽  
E. Nemitz
Keyword(s):  
Eddy Covariance ◽  
Random Error ◽  
Limit Of Detection ◽  
Sampling Error ◽  
Signal To Noise Ratio ◽  
Time Lag ◽  
Systematic Bias ◽  
Signal To Noise ◽  
Cross Covariance ◽  
Noise Ratio

Abstract. All eddy-covariance flux measurements are associated with random uncertainties which are a combination of sampling error due to natural variability in turbulence and sensor noise. The former is the principal error for systems where the signal-to-noise ratio of the analyser is high, as is usually the case when measuring fluxes of heat, CO2 or H2O. Where signal is limited, which is often the case for measurements of other trace gases and aerosols, instrument uncertainties dominate. We are here applying a consistent approach based on auto- and cross-covariance functions to quantifying the total random flux error and the random error due to instrument noise separately. As with previous approaches, the random error quantification assumes that the time-lag between wind and concentration measurement is known. However, if combined with commonly used automated methods that identify the individual time-lag by looking for the maximum in the cross-covariance function of the two entities, analyser noise additionally leads to a systematic bias in the fluxes. Combining datasets from several analysers and using simulations we show that the method of time-lag determination becomes increasingly important as the magnitude of the instrument error approaches that of the sampling error. The flux bias can be particularly significant for disjunct data, whereas using a prescribed time-lag eliminates these effects (provided the time-lag does not fluctuate unduly over time). We also demonstrate that when sampling at higher elevations, where low frequency turbulence dominates and covariance peaks are broader, both the probability and magnitude of bias are magnified. We show that the statistical significance of noisy flux data can be increased (limit of detection can be decreased) by appropriate averaging of individual fluxes, but only if systematic biases are avoided by using a prescribed time-lag. Finally, we make recommendations for the analysis and reporting of data with low signal-to-noise and their associated errors.

Determination of trans-phylloquinone in children's serum.

1989 ◽  
Vol 35 (5) ◽  
pp. 874-878 ◽  
Author(s):  
F Moussa ◽  
L Dufour ◽  
J R Didry ◽  
P Aymard
Keyword(s):  
Limit Of Detection ◽  
Signal To Noise Ratio ◽  
Fluorometric Detection ◽  
Vitamin K1 ◽  
Signal To Noise ◽  
Détection Signal ◽  
Coagulation Tests ◽  
Noise Ratio ◽  
Detection Signal

Abstract By optimizing the conditions for determining trans-phylloquinone and its metabolite, K-2,3-epoxide, in serum through a two-step HPLC process combined with fluorometric detection after coulometric reduction, we have been able to develop a method applicable to small volumes of serum (200 to 500 microL). The limit of detection (signal-to-noise ratio of 3) was 15 ng/L for trans-phylloquinone, 30 ng/L for K-2,3-epoxide. The trans-phylloquinone concentrations measured by this method in serum from 82 children, ages one to six years, whose results were normal for overall coagulation tests, ranged from 40 to 880 ng/L (median 175 ng/L). We discuss these findings and compare them with vitamin K1(20) values reported for adults.

scholarly journals Improving the Signal to Noise Ratio of QTF Preamplifiers Dedicated for QEPAS Applications

2020 ◽  
Vol 10 (12) ◽  
pp. 4105
Author(s):  
Piotr Z. Wieczorek ◽  
Tomasz Starecki ◽  
Frank K. Tittel
Keyword(s):  
Operational Amplifier ◽  
Narrow Band ◽  
Signal To Noise Ratio ◽  
Low Frequency ◽  
Electrical Signal ◽  
Low Noise ◽  
Detection Sensitivity ◽  
Noise Amplitude ◽  
Signal To Noise ◽  
Noise Ratio

The signal-to-noise ratio (SNR) is a major factor that limits the detection sensitivity of quartz-enhanced photoacoustic spectroscopy (QEPAS) sensors. The higher the electrical signal level compared to the noise amplitude is the lower the concentration of gases that can be detected. For this reason the preamplifier circuits used in QEPAS should be optimized for low-frequency narrow-band applications. Moreover, special care should be taken when choosing a particular operational amplifier in either a transimpedance or voltage (differential) configuration. It turns out that depending on the preamp topology different operational amplifier parameters should be carefully considered when a high SNR of the whole QEPAS system is required. In this article we analyzed the influence of the crucial parameters of low-noise operational preamplifiers used in QEPAS applications and show the resulting limitations of transimpedance and voltage configurations.

High-Voltage Spark Atomic Emission Detector for Gas Chromatography

1982 ◽  
Vol 36 (4) ◽  
pp. 369-374 ◽  
Author(s):  
Clayton L. Calkin ◽  
Sandra M. Koeplin ◽  
S. R. Crouch
Keyword(s):  
Signal To Noise Ratio ◽  
Data Acquisition System ◽  
Atomic Emission ◽  
Selective Detection ◽  
Gas Chromatograph ◽  
Signal To Noise ◽  
Emission Detector ◽  
Tungsten Electrodes ◽  
Thoriated Tungsten ◽  
Background Continuum

A dc-powered, double-gap, miniature nanosecond spark source for emission spectrochemical analysis of gas chromatographic effluents is described. The spark is formed between two thoriated tungsten electrodes by the discharge of a coaxial capacitor. The spark detector is coupled to the gas chromatograph by a heated transfer line. The gas chromatographic effluent is introduced into the heated spark chamber where atomization and excitation of the effluent occurs upon breakdown of the analytical gap. A microcomputer-controlled data acquisition system allows the implementation of time-resolution techniques to distinguish between the analyte emission and the background continuum produced by the spark discharge. Multiple sparks are computer averaged to improve the signal-to-noise ratio. The application of the spark detector for element-selective detection of metals and nonmetals is reported.

Detection of Defects in Pipes and Elbows Using Guided Waves

2014 ◽  
Author(s):  
Pugen Zhang ◽  
Shaoping Zhou ◽  
Wenchao Lv
Keyword(s):  
Numerical Simulation ◽  
Piezoelectric Transducer ◽  
High Frequency ◽  
Guided Waves ◽  
Signal To Noise Ratio ◽  
Low Frequency ◽  
The Other ◽  
Detection Sensitivity ◽  
Axial Position ◽  
Signal To Noise

This paper deals with the detection of circumferential cracks of different areas in elbow pipes using the guided waves in mode of L(0,2) which are excited by a piezoelectric transducer. The experimental results show that the circumferential cracks can be located in axial position for bend straight side by the reflected echo of defects in the pipes. The detection sensitivity depends on the location of the cracks in bend areas of the pipes. It is easier to detect cracks in the extradose of elbow while harder to detect those in the other locations of the bend. There is a relationship between the detection sensitivity and the frequency of guided waves. The signal-to-noise ratio when detecting the crack before and beyond elbows is highest for the frequency ranges from 120kHz to 130kHz; the crack on the intradose of elbow can be inspected more effectively when using frequencies near 80kHz. Therefore, the combination of high-frequency and low-frequency is used to inspect elbows. The propagation behaviors in elbows are investigated by using numerical simulation. The results of simulation intuitively explain the experimental phenomenon.

scholarly journals Miniaturized photoacoustic detection of organofluorine-based refrigerants

2020 ◽  
Vol 9 (1) ◽  
pp. 89-97
Author(s):  
Mahmoud El-Safoury ◽  
Christian Weber ◽  
Olaf Kiesewetter ◽  
Yvonne Hespos ◽  
André Eberhardt ◽  
...  
Keyword(s):  
Automotive Industry ◽  
Signal To Noise Ratio ◽  
Optimal Parameters ◽  
Signal To Noise ◽  
Photoacoustic Detection ◽  
Measuring Devices ◽  
Gas Detector ◽  
Detection Chamber ◽  
Simulation Results ◽  
Absorption Chamber

Abstract. Due to the ban on hydrofluorocarbon and haloalkane refrigerants with a high global warming potential, such as R134a, in the automotive industry, the significance of reliable and precise measuring devices for these refrigerants has risen. We present a photoacoustic gas detector for monitoring the organofluorine-based refrigerants R134a and R1234yf. The idea for this sensor is based on the three-chamber concept (a detection chamber, absorption chamber, and filter chamber). The optimal parameters and dimensions of the photoacoustic sensor components were determined via simulations. The simulation results were the cornerstone of our hardware construction. The first measurements with the newly developed sensor showed a sufficient signal-to-noise ratio for a reliable 0.5 vol. % (0.005 m3 m−3) detection resolution. The influence and importance of the filter chamber were examined and validated.

Sign in / Sign up

Export Citation Format

Share Document