Cauliflower polyaniline/multiwalled carbon nanotube electrode and its applications to hydrogen peroxide and glucose detection*

2012 ◽  
Vol 84 (10) ◽  
pp. 2055-2063 ◽  
Author(s):  
Sujittra Poorahong ◽  
Chongdee Thammakhet ◽  
Panote Thavarungkul ◽  
Proespichaya Kanatharana
Keyword(s):  
Chemical Sensor ◽  
Limit Of Detection ◽  
High Surface ◽  
Volume Ratio ◽  
Deposition Process ◽  
Glucose Biosensor ◽  
Pani Film ◽  
Scanning Electron Micrographs ◽  
Multiwalled Carbon ◽  
Relative Standard

Vertically aligned polyaniline (PANI) structures were prepared by controlling the deposition current density during a stepwise template-free electrochemical deposition process of aniline on a glassy carbon electrode (GCE). Scanning electron micrographs (SEMs) showed the formation of cauliflower PANI structures, each with a diameter of approximately 2–3 and 10 μm in length. The cauliflower-like PANI electrode was modified with multiwalled carbon nanotubes (cauliflower PANI/MWCNTs) and used as the working electrode for electrochemical detections where H2O2 and glucose were used as the models for the chemical sensor and biosensor, respectively. The sensor provided linearity in the range of 1.0 to 150 μM of H2O2 with the limit of detection (LOD) of 50 nM. This is 100-fold better than the LOD of the bare GCE. Moreover, this sensor exhibited remarkable operational stability, i.e., 50 μM H2O2 could be analyzed up to 140 times with a 2.7 % relative standard deviation (RSD). A glucose biosensor was prepared using the modified cauliflower PANI/MWCNT electrode. This had a 3.4 times higher sensitivity than an electrode modified with PANI film/MWCNTs. The regular size and high surface-to-volume ratio of the cauliflower PANI electrode will provide good opportunities for further biosensor applications.

Biosynthesised Zinc Oxide Nanoparticles for Ethanol Chemical Sensor

2019 ◽  
Vol 59 ◽  
pp. 94-104
Author(s):  
Ochieng Phyllis Emelda ◽  
Michira Immaculate Nyambura ◽  
Milua Masikini ◽  
Emmanuel Iwuoha
Keyword(s):  
Zinc Oxide ◽  
Zinc Oxide Nanoparticles ◽  
Chemical Sensor ◽  
High Surface ◽  
Volume Ratio ◽  
Modified Electrodes ◽  
Hydrogen Gas ◽  
Fine Tuning ◽  
Oxide Nanoparticles ◽  
Ethanol Sensing

Nanoparticles are considered unique sensing material as they are small and deliver sensitivity as low as parts per billion compared to their bulk counterparts used in the conventional devices. Zinc Oxide (ZnONPs) nanoparticles are considered one of the promising sensing materials due to their high surface-to-volume ratio compared to other conventional sensing materials. They have been found useful for sensing of hydrogen gas, carbon monoxide, ammonia and ethanol. Ethanol sensing forms a platform for monitoring various processes in medical and food industries. Herein, zinc oxide nanoparticles were synthesized using Spathodea campanulata plant extract as reducing and stabilizing agent. The biosynthesized nanoparticles were used to fine tuning a glassy carbon electrode (GCE) for ethanol sensing. Ethanol sensing capability of the modified GCE electrode was gauged upon its amperometric responses to different ethanol concentrations. The high surface to volume ratio of the nanoparticles greatly enhanced peak currents of the modified electrodes leading to signal towards ethanol detection.

scholarly journals Application of Packed-nanofibers Solid-phase Extraction for Determination of Rhodamine B in Sausage

2019 ◽  
Vol 8 (1) ◽  
pp. 17-21
Author(s):  
Lanlan Wei ◽  
Jianjun Deng ◽  
Tao Kang ◽  
Xuejun Kang
Keyword(s):  
Rhodamine B ◽  
High Performance ◽  
Orthophosphoric Acid ◽  
Limit Of Detection ◽  
Solid Phase ◽  
Volume Ratio ◽  
Standard Curve ◽  
Relative Standard ◽  
Limit Of Quantitation

A method for the determination of Rhodamine B in sausage was developed and validated. After extraction of Rhodamine B with acetonitrile from foodstuffs, a novel electrospun polymer nanofibers packed micro-column was used for cleaning and concentrating of the analyte in the sample. High performance liquid chromatography with fluorescence detection (HPLC-Flu) was used for the determination of Rhodamine B in the sample. The mobile phase was composed of 3.0 g L-1 phosphate buffer and methanol (3:7, volume ratio), and the pH was adjusted to 7. 0 with orthophosphoric acid. The results showed that the standard curve was linear over the validated concentrations range of 2-500 ng g-1, and the limit of detection (LOD) and the limit of quantitation (LOQ) for Rhodamine B spiked samples was 0. 2 ng g-1 and 0. 7 ng g-1, respectively. The average recoveries of Rhodamine B were 90.4% -94.3% for sausage, and the relative standard deviation of the method was from 1.7% to 3.8%. This proposed method was applied to real sample, and there was no Rhodamine B found in sausage.

scholarly journals Porous Gig-Lox TiO2 Doped with N2 at Room Temperature for P-Type Response to Ethanol

Chemosensors ◽  
2019 ◽  
Vol 7 (1) ◽  
pp. 12 ◽  
Author(s):  
Emanuele Smecca ◽  
Salvatore Sanzaro ◽  
Clelia Galati ◽  
Lucio Renna ◽  
Leonardo Gervasi ◽  
...  
Keyword(s):  
Tio2 Film ◽  
Room Temperature ◽  
Electrical Response ◽  
High Surface ◽  
Volume Ratio ◽  
Reactive Sputtering ◽  
Deposition Process ◽  
Deposition Method ◽  
Type Character ◽  
P Type

Nanostructured materials represent a breakthrough in many fields of application. Above all for sensing, the use of nanostructures with a high surface/volume ratio is strategic to raise the sensitivity towards dangerous environmental gas species. A new Dc-Reactive sputtering Deposition method has been applied to grow highly porous p-type nitrogen-doped titanium oxide layers by modifying the previously developed reactive sputtering method called gig-lox. The doping of the films was achieved at room temperature by progressive incorporation of nitrogen species during the deposition process. Two different amounts of N2 were introduced into the deposition chamber at flow rates of 2 and 5 standard cubic centimeter per minutes (sccm) for doping. It has been found that the N2 uptake reduces the deposition rate of the TiO2 film whilst the porosity and the roughness of the grown layer are not penalized. Despite the low amount of N2, using 2 sccm of gas resulted in proper doping of the TiO2 film as revealed by XPS Analyses. In this case, nitrogen atoms are mainly arranged in substitutional positions with respect to the oxygen atoms inside the lattice, and this defines the p-type character of the growing layer. Above this strategic structural modification, the multibranched spongy porosity, peculiar of the gig-lox growth, is still maintained. As proof of concept of the achievements, a sensing device was prepared by combining this modified gig-lox deposition method with state-of-the-art hot-plate technology to monitor the electrical response to ethanol gas species. The sensor exhibited a sensitivity of a factor of ≈2 to 44 ppm of ethanol at ≈200 °C as measured by a rise in the layer resistivity according to the p-type character of the material. At the higher temperature of ≈350 °C, the sensor turned to n-type as without doping. This behavior was related to a loss of nitrogen content inside the film during the annealing. It was indeed proved that p-type doping of a gig-lox sponge during growth is feasible, even at room temperature, without losing the layer porosity and the capability to host and detect environmental species. Moreover, the material integration on a device is simply done as the last production step. Easy TiO2 doping procedures, combined with porosity, are of general purpose and interest for several applications even on flexible substrates.

scholarly journals Silver Nanowires as Electron Transfer Mediators in Electrochemical Catechol Biosensors

Sensors ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 899
Author(s):  
Coral Salvo-Comino ◽  
Fernando Martin-Pedrosa ◽  
Cristina Garcia-Cabezon ◽  
Maria Luz Rodriguez-Mendez
Keyword(s):  
Electron Transfer ◽  
Limit Of Detection ◽  
Silver Nanowires ◽  
High Surface ◽  
Volume Ratio ◽  
Homogeneous Distribution ◽  
Electron Mediator ◽  
Force Microscopy ◽  
Voltammetric Detection ◽  
Order Of Magnitude

The integration of nanomaterials as electron mediators in electrochemical biosensors is taking on an essential role. Due to their high surface-to-volume ratio and high conductivity, metallic nanowires are an interesting option. In this paper, silver nanowires (AgNWs) were exploited to design a novel catechol electrochemical biosensor, and the benefits of increasing the aspect ratio of the electron mediator (nanowires vs. nanoparticles) were analyzed. Atomic force microscopy (AFM) studies have shown a homogeneous distribution of the enzyme along the silver nanowires, maximizing the contact surface. The large contact area promotes electron transfer between the enzyme and the electrode surface, resulting in a Limit of Detection (LOD) of 2.7 × 10−6 M for tyrosinase immobilized onto AgNWs (AgNWs-Tyr), which is one order of magnitude lower than the LOD of 3.2 × 10−5 M) obtained using tyrosinase immobilized onto silver nanoparticles (AgNPs-Tyr). The calculated KM constant was 122 mM. The simultaneous use of electrochemistry and AFM has demonstrated a limited electrochemical fouling that facilitates stable and reproducible detection. Finally, the biosensor showed excellent anti-interference characteristics toward the main phenols present in wines including vanillin, pyrogallol, quercetin and catechin. The biosensor was able to successfully detect the presence of catechol in real wine samples. These results make AgNWs promising elements in nanowired biosensors for the sensitive, stable and rapid voltammetric detection of phenols in real applications.

Preconcentration and determination of ranitidine hydrochloride in real samples by using modified magnetic iron oxide nanoparticles

2016 ◽  
Vol 94 (1) ◽  
pp. 9-14 ◽  
Author(s):  
Elaheh Konoz ◽  
Amir H.M. Sarrafi ◽  
Hamed Sahebi
Keyword(s):  
Human Plasma ◽  
Ph Value ◽  
Limit Of Detection ◽  
Solid Phase ◽  
High Surface ◽  
Sodium Dodecyl ◽  
Magnetic Iron Oxide Nanoparticles ◽  
Ranitidine Hydrochloride ◽  
Relative Standard

This method shows a novel, fast, and simple magnetic solid-phase extraction (SPE) and spectrophotometric procedure for preconcentration and determination of ranitidine hydrochloride in human plasma and aquatic samples by using Fe3O4 nanoparticles (NPs) modified by sodium dodecyl sulfate (SDS) as an extractor. The unique properties of Fe3O4 NPs including high surface area and strong magnetism were utilized effectively in the magnetic SPE process. The determination method is based on the SDS-coated Fe3O4 NPs with extracted ranitidine-HCl, which was subsequently monitored spectrophotometrically at λmax = 320 nm. Effects of different parameters influencing the extraction efficiency of ranitidine-HCl including the pH value, amount of SDS, and Fe3O4 NPs, extraction time, desorption solvent, desorption time, and sample volume were optimized. Under optimized conditions, the method was successfully applied to the extraction of ranitidine-HCl from human plasma and aquatic samples. The extraction recovery in human plasma and different matrixes of waters were investigated and values of 89.0%–103.4% were obtained. The calibration graph for the determination of ranitidine-HCl was linear in the range of 0.025–1.50 μg mL−1 with R2 = 0.9946. The limit of detection of the proposed method was 7.5 × 10−3 μg mL−1. The repeatability and reproducibility (relative standard deviation) of the mentioned method were 0.83% and 1.22%, respectively. The experimental results showed that the proposed method was feasible for the analysis of ranitidine-HCl in environmental and biological samples.

Detection of Glucose in Human Serum Based on Silicon Dot Probe

2020 ◽  
Vol 16 (6) ◽  
pp. 744-752
Author(s):  
Kuan Luo ◽  
Xinyu Jiang
Keyword(s):  
Quantum Dots ◽  
Blood Glucose ◽  
Human Serum ◽  
Organic Dyes ◽  
Limit Of Detection ◽  
Fasting Blood Glucose ◽  
Glucose Biosensor ◽  
Metal Nanoclusters ◽  
Glucose Levels ◽  
Highly Sensitive

Background: Diabetes Mellitus (DM) is a major public metabolic disease that influences 366 million people in the world in 2011, and this number is predicted to rise to 552 million in 2030. DM is clinically diagnosed by a fasting blood glucose that is equal or greater than 7 mM. Therefore, the development of effective glucose biosensor has attracted extensive attention worldwide. Fluorescence- based strategies have sparked tremendous interest due to their rapid response, facile operation, and excellent sensitivity. Many fluorescent compounds have been employed for precise analysis of glucose, including quantum dots, noble metal nanoclusters, up-converting nanoparticles, organic dyes, and composite fluorescent microspheres. Silicon dot as promising quantum dots materials have received extensive attention, owing to their distinct advantages such as biocompatibility, low toxicity and high photostability. Methods: MnO2 nanosheets on the Si nanoparticles (NPs) surface serve as a quencher. Si NPs fluorescence can make a recovery by the addition of H2O2, which can reduce MnO2 to Mn2+, and the glucose can thus be monitored based on the enzymatic conversion of glucose by glucose oxidase to generate H2O2. Therefore, the glucose concentration can be derived by recording the fluorescence recovery spectra of the Si NPs. Results: This probe enabled selective detection of glucose with a linear range of 1-100 μg/mL and a limit of detection of 0.98 μg/mL. Compared with the commercial glucometer, this method showed favorable results and convincing reliability. Conclusion: We have developed a novel method based on MnO2 -nanosheet-modified Si NPs for rapid monitoring of blood glucose levels. By combining the highly sensitive H2O2/MnO2 reaction with the excellent photostability of Si NPs, a highly sensitive, selective, and cost-efficient sensing approach for glucose detection has been designed and applied to monitor glucose levels in human serum with satisfactory results.

Calcium/Copper alginate framework doped with CuO nano-particles as a novel adsorbent for micro-extraction of benzodiazepines from human serum

2020 ◽  
Vol 16 ◽  
Author(s):  
Nadereh Rahbar ◽  
Fatemeh Ahmadi ◽  
Zahra Ramezani ◽  
Masoumeh Nourani
Keyword(s):  
Human Serum ◽  
High Performance ◽  
Limit Of Detection ◽  
Solid Phase ◽  
Nano Particles ◽  
Limit Of Quantification ◽  
Analytical Methodology ◽  
Fiber Fabrication ◽  
Relative Standard ◽  
Green Procedure

Background: Sample preparation is one of the most challenging phases in pharmaceutical analysis, especially in biological matrices, affecting the whole analytical methodology. Objective: In this study, a new Ca(II)/Cu(II)/alginate/CuO nanoparticles hydrogel fiber (CCACHF) was synthesized through a simple, green procedure and applied for fiber micro solid phase extraction (FMSPE) of diazepam (DIZ) and oxazepam (OXZ) as model drugs prior to high-performance liquid chromatography-UV detection (HPLC-UV). Methods: Composition and morphology of the prepared fiber were characterized and the effect of main parameters on the fiber fabrication and extraction efficiency have been studied and optimized. Results: In optimal conditions, calibration curves were linear ranging between 0.1–500 µg L−1 with regression coefficients of 0.9938 and 0.9968. Limit of detection (LOD) (S/N=3) and limit of quantification (LOQ) (S/N=10) of the technique for DIZ and OXZ were 0.03 to 0.1 µg L−1. Within-day and between-day relative standard deviations (RSDs) for DIZ and OXZ were 6.0–12.5% and 3.3–9.4%, respectively. Conclusion: The fabricated adsorbent has been substantially employed to extraction of selected benzo-diazepines (BZDs) from human serum real specimens and the obtained recoveries were also satisfactory (82.1-109.7%).

Green Dispersive Micro Solid-Phase Extraction using Multiwalled Carbon Nanotubes for Preconcentration and Determination of Cadmium and Lead in Food, Water, and Tobacco Samples

2020 ◽  
Vol 16 (4) ◽  
pp. 381-392
Author(s):  
Ayman A. Gouda ◽  
Ali H. Amin ◽  
Ibrahim S. Ali ◽  
Zakia Al Malah
Keyword(s):  
Carbon Nanotubes ◽  
Solid Phase Extraction ◽  
Multiwalled Carbon Nanotubes ◽  
Solid Phase ◽  
Certified Reference Materials ◽  
Phase Extraction ◽  
Multiwalled Carbon ◽  
Flame Atomic Absorption ◽  
Relative Standard ◽  
Separation And Preconcentration

Background: Cadmium (Cd2+) and lead (Pb2+) have acute and chronic effects on humans and other living organisms. In the present work, new, green and accurate dispersive micro solid-phase extraction (DμSPE) method for the separation and preconcentration of trace amounts of cadmium (Cd2+) and lead (Pb2+) ions in various food, water and tobacco samples collected from Saudi Arabia prior to its Flame Atomic Absorption Spectrometric (FAAS) determinations was developed. Methods: The proposed method was based on a combination of oxidized multiwalled carbon nanotubes (O-MWCNTs) with a new chelating agent 5-benzyl-4-[4-methoxybenzylideneamino)-4H- 1,2,4-triazole-3-thiol (BMBATT) to enrich and separate trace levels of Cd2+ and Pb2+. The effect of separation parameters was investigated. The validation of the proposed preconcentration procedure was performed using certified reference materials. Results: Analyte recovery values ranged from 95-102%, indicating that the method is highly accurate. Furthermore, precision was demonstrated by the relative standard deviation (RSD < 3.0%). The limits of detection were 0.08 and 0.1 μg L−1 for Cd2+ and Pb2+ ions, respectively. The preconcentration factor was 200. Conclusion: The proposed method was used for the estimation of Cd2+ and Pb2+ ion content in various real samples, and satisfactory results were obtained. The proposed method has high adsorption capacity, rapid adsorption equilibrium, extremely low LODs, high preconcentration factors and shortens the time of sample preparation in comparison to classical SPE.

scholarly journals Stability-indicating HPLC-DAD assay for simultaneous quantification of hydrocortisone 21 acetate, dexamethasone, and fluocinolone acetonide in cosmetics

2020 ◽  
Vol 18 (1) ◽  
pp. 962-973
Author(s):  
Saira Arif ◽  
Sadia Ata
Keyword(s):  
Mobile Phase ◽  
Limit Of Detection ◽  
Fluocinolone Acetonide ◽  
Internal Diameter ◽  
Forced Degradation ◽  
Specific Method ◽  
Regression Equations ◽  
Limit Of Quantification ◽  
Simultaneous Quantification ◽  
Relative Standard

AbstractA rapid and specific method was developed for simultaneous quantification of hydrocortisone 21 acetate (HCA), dexamethasone (DEX), and fluocinolone acetonide (FCA) in whitening cream formulations using reversed-phase high-performance liquid chromatography. The effect of the composition of the mobile phase, analysis temperature, and detection wavelength was investigated to optimize the separation of studied components. The analytes were finally well separated using ACE Excel 2, C18 AR column having 150 mm length, 3 mm internal diameter, and 2 µm particle size at 35°C using methanol with 1% formic acid and double-distilled deionized water in the ratio of 60:40 (v/v), respectively, as the mobile phase in isocratic mode. Ten microliters of sample were injected with a flow rate of 0.5 mL/min. The specificity, linearity, accuracy, precision, recovery, limit of detection (LOD), limit of quantification (LOQ), and robustness were determined to validate the method as per International Conference on Harmonization guidelines. All the analytes were simultaneously separated within 8 min, and observed retention times of HCA, DEX, and FCA were 4.5, 5.5, and 6.9 min, respectively. The proposed method showed good linearity with the correlation coefficient, R2 = 0.999 over the range of 1–150 µg/mL for all standards. The linear regression equations were y = 12.7x + 118.7 (r = 0.999) for HCA, y = 12.9x + 106.8 (r = 0.999) for DEX, and y = 12.9x + 96.8 (r = 0.999) for FCA. The LOD was 0.25, 0.20, and 0.08 µg/mL for HCA, FCA, and DEX and LOQ was 2.06, 1.83, and 1.55 µg/mL for HCA, FCA, and DEX, respectively. The recovery values of HCA, DEX, and FCA ranged from 100.7–101.3, 102.0–102.6, and 100.2–102.0%, respectively, and the relative standard deviation for precision (intra- and interday) was less than 2, which indicated repeatability and reproducibility. The novelty of the method was described by forced degradation experimentation of all analytes in the combined form under acidic, basic, oxidative, and thermal stress. The proposed method was found to be simple, rapid, and reliable for the simultaneous determination of HCA, DEX, and FCA in cosmetics.

scholarly journals A novel LC-MS method development and validation for the determination of phenyl vinyl sulfone in eletriptan hydrobromide

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Indhu Priya Mabbu ◽  
G. Sumathi ◽  
N. Devanna
Keyword(s):  
Method Development ◽  
Limit Of Detection ◽  
Vinyl Sulfone ◽  
Limit Of Quantification ◽  
Relative Standard ◽  
Pressure Chemical Ionization ◽  
Pressure Chemical ◽  
Development And Validation ◽  
Phenyl Vinyl

Abstract Background The aim of the present method is to develop and validate a specific, sensitive, precise, and accurate liquid chromatography-mass spectrometry (LC-MS) method for the estimation of the phenyl vinyl sulfone in the eletriptan hydrobromide. The effective separation of the phenyl vinyl sulfone was achieved by the Symmetry C18 (50 × 4.6 mm, 3.5 μm) column and a mobile phase composition of 0.1%v/v ammonia buffer to methanol (5:95 v/v), using 0.45 ml/min flow rate and 20 μl of injection volume, with methanol used as diluent. The phenyl vinyl sulfone was monitored on atomic pressure chemical ionization mode mass spectrometer with positive polarity mode. Results The retention time of phenyl vinyl sulfone was found at 2.13 min. The limit of detection (LOD) and limit of quantification (LOQ) were observed at 1.43 ppm and 4.77 ppm concentration respectively; the linear range was found in the concentration ranges from 4.77 to 27.00 ppm with regression coefficient of 0.9990 and accuracy in the range of 97.50–102.10%. The percentage relative standard deviation (% RSD) for six replicates said to be injections were less than 10%. Conclusion The proposed method was validated successfully as per ICH guidelines. Hence, this is employed for the determination of phenyl vinyl sulfone in the eletriptan hydrobromide.

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