scholarly journals Luminol Doped Silica-Polymer Sensor for Portable Organic Amino Nitrogen and Ammonium Determination in Water

Separations ◽  
2021 ◽  
Vol 8 (9) ◽  
pp. 149
Author(s):  
Sara Bocanegra-Rodríguez ◽  
Carmen Molins-Legua ◽  
Pilar Campíns-Falcó
Keyword(s):  
Limit Of Detection ◽  
Nitrogen Concentration ◽  
Amino Nitrogen ◽  
In Situ Monitoring ◽  
Luminescence Signal ◽  
The Matrix ◽  
Ammonium Determination ◽  
Portable Sensor

We propose a portable sensor, obtained by embedding luminol into the tetraethylorthosilicate/trietoxymethylsilane (TEOS/MTEOS) composite, for the quantitative determination of organic amino nitrogen and ammonium in water with the goal of achieving low levels of concentration. The method is based on the reaction between amino nitrogen compounds and hypochlorite to produce chloramino derivatives. Then, the remaining hypochlorite reacts with luminol sensor by producing a luminescence signal, which was measured by using a portable luminometer, being inversely proportional to nitrogen concentration. The liberation of the luminol from sensor is higher than 90% and the sensor is stable for at least a week at room temperature. This portable method was successfully validated and applied to the analysis of several real waters: fountain, river transition, lagoon, and seawater with recovery values between 92% and 112%, which indicated that the matrix effect was absent. The achieved limit of detection was around 10 µg·L−1, expressed as N. This sensor allows in situ monitoring owing to its simplicity, rapidity, and portability.

scholarly journals Sequential Collinear Photofragmentation and Atomic Absorption Spectroscopy for Online Laser Monitoring of Triatomic Metal Species

Sensors ◽  
2020 ◽  
Vol 20 (2) ◽  
pp. 533 ◽  
Author(s):  
Jan Viljanen ◽  
Kim Kalmankoski ◽  
Victor Contreras ◽  
Jaakko K. Sarin ◽  
Tapio Sorvajärvi ◽  
...  
Keyword(s):  
Atomic Absorption ◽  
Gas Phase ◽  
Absorption Spectroscopy ◽  
Atomic Absorption Spectroscopy ◽  
Limit Of Detection ◽  
In Situ Monitoring ◽  
Metal Species ◽  
Chemical Reaction Kinetics

Industrial chemical processes are struggling with adverse effects, such as corrosion and deposition, caused by gaseous alkali and heavy metal species. Mitigation of these problems requires novel monitoring concepts that provide information on gas-phase chemistry. However, selective optical online monitoring of the most problematic diatomic and triatomic species is challenging due to overlapping spectral features. In this work, a selective, all-optical, in situ gas-phase monitoring technique for triatomic molecules containing metallic atoms was developed and demonstrated with detection of PbCl2. Sequential collinear photofragmentation and atomic absorption spectroscopy (CPFAAS) enables determination of the triatomic PbCl2 concentration through detection of released Pb atoms after two consecutive photofragmentation processes. Absorption cross-sections of PbCl2, PbCl, and Pb were determined experimentally in a laboratory-scale reactor to enable calibration-free quantitative determination of the precursor molecule concentration in an arbitrary environment. Limit of detection for PbCl2 in the laboratory reactor was determined to be 0.25 ppm. Furthermore, the method was introduced for in situ monitoring of PbCl2 concentration in a 120 MWth power plant using demolition wood as its main fuel. In addition to industrial applications, the method can provide information on chemical reaction kinetics of the intermediate species that can be utilized in reaction simulations.

scholarly journals Determination of 77 Multiclass Pesticides and Their Metabolitesin Capsicum and Tomato Using GC-MS/MS and LC-MS/MS

Molecules ◽  
2021 ◽  
Vol 26 (7) ◽  
pp. 1837
Author(s):  
Harischandra Naik Rathod ◽  
Bheemanna Mallappa ◽  
Pallavi Malenahalli Sidramappa ◽  
Chandra Sekhara Reddy Vennapusa ◽  
Pavankumar Kamin ◽  
...  
Keyword(s):  
Limit Of Detection ◽  
Solid Phase ◽  
Graphitized Carbon Black ◽  
Limit Of Quantification ◽  
Gas And Liquid Chromatography ◽  
Relative Standard ◽  
The Matrix ◽  
Liquid Chromatography Tandem Mass ◽  
Primary Secondary Amine

A quick, sensitive, and reproducible analytical method for the determination of 77 multiclass pesticides and their metabolites in Capsicum and tomato by gas and liquid chromatography tandem mass spectrometry was standardized and validated. The limit of detection of 0.19 to 10.91 and limit of quantification of 0.63 to 36.34 µg·kg−1 for Capsicum and 0.10 to 9.55 µg·kg−1 (LOD) and 0.35 to 33.43 µg·kg−1 (LOQ) for tomato. The method involves extraction of sample with acetonitrile, purification by dispersive solid phase extraction using primary secondary amine and graphitized carbon black. The recoveries of all pesticides were in the range of 75 to 110% with a relative standard deviation of less than 20%. Similarly, the method precision was evaluated interms of repeatability (RSDr) and reproducibility (RSDwR) by spiking of mixed pesticides standards at 100 µg·kg−1 recorded anRSD of less than 20%. The matrix effect was acceptable and no significant variation was observed in both the matrices except for few pesticides. The estimated measurement uncertainty found acceptable for all the pesticides. This method found suitable for analysis of vegetable samples drawn from market and farm gates.

scholarly journals A platinum black-modified microelectrode for in situ olanzapine detection in microliter volumes of undiluted serum

2020 ◽  
Vol 127 (2) ◽  
pp. 291-299 ◽  
Author(s):  
Rajendra P. Shukla ◽  
Robert H. Belmaker ◽  
Yuly Bersudsky ◽  
Hadar Ben-Yoav
Keyword(s):  
Liquid Chromatography ◽  
Real Time ◽  
Psychotic Disorders ◽  
Limit Of Detection ◽  
Biological Fluids ◽  
In Situ Monitoring ◽  
Blood Levels ◽  
Platinum Black ◽  
Serum Samples

AbstractOlanzapine is a thienobenzodiazepine compound. It is one of the newer types of antipsychotic drugs used in the treatment of schizophrenia and other psychotic disorders. Several methods have been reported for analyzing olanzapine in its pure form or combined with other drugs and in biological fluids. These methods include high-performance liquid chromatography and liquid chromatography-tandem mass spectroscopy. Although many of the reported methods are accurate and sensitive, they require the use of sophisticated equipment, lack in situ analysis, and require expensive reagents. Moreover, several of these methods are cumbersome, require prolonged sample pretreatment, strict control of pH, and long reaction times. Here we present the development of a miniaturized electrochemical sensor that will enable minimally invasive, real-time, and in situ monitoring of olanzapine levels in microliter volumes of serum samples. For this purpose, we modified a microfabricated microelectrode with a platinum black film to increase the electrocatalytic activity of the microelectrode towards olanzapine oxidation; this improved the overall selectivity and sensitivity of the sensor. We observed in recorded voltammograms the anodic current dose response characteristics in microliter volumes of olanzapine-spiked serum samples that resulted in a limit of detection of 28.6 ± 1.3 nM and a sensitivity of 0.14 ± 0.02 µA/cm2 nM. Importantly, the platinum black-modified microelectrode exhibited a limit of detection that is below the clinical threshold (65–130 nM). Further miniaturizing and integrating such sensors into point-of-care devices provide real-time monitoring of olanzapine blood levels; this will enable treatment teams to receive feedback and administer adjustable olanzapine therapy.

A Facile In-Situ Development of L-Valine Film onto the Surface of Carbon Paste Electrode Towards the Detection of Environmentally Hazardous 4-Amino Phenol

2019 ◽  
Vol 0 (0) ◽  
Author(s):  
T. Venu Gopal ◽  
Tukiakula Madhusudana Reddy ◽  
P. Shaikshavali ◽  
G. Venkataprasad ◽  
P. Gopal
Keyword(s):  
Cyclic Voltammetry ◽  
Carbon Paste Electrode ◽  
Electrochemical Impedance ◽  
Limit Of Detection ◽  
Small Scale ◽  
Carbon Paste ◽  
Relative Standard ◽  
Paste Electrode

Abstract A small scale of environmentally hazardous 4-aminophenol can show significant impact on human health. Hence, in the present work, we have designed L-Valine film (Vf) modified carbon paste electrode (Vf/CPE) for the determination of 4-aminophenol. Herein, a facile in-situ L-Valine film was developed by electrochemical polymerization method onto the surface of bare carbon paste electrode (BCPE) with the help of cyclic voltammetry (CV) technique. A two-folds of electrochemical peak current enhancement was achieved at Vf/CPE in comparison with BCPE towards the determination of 4-aminophenol in optimum pH 7.0 of phosphate buffer solution (PBS). This was achieved due to the large surface area and conductive nature of Vf/CPE, which was concluded through the techniques of cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The effect of pH of buffer and scan rate studies were successfully studied. Morphological changes of BCPE and Vf/CPE was studied with the help of scanning electron microscopy (SEM). The formation of Vf on CPE was also analyzed by Fourier transform infrared (FTIR) spectra. Under the optimized conditions, the limit of detection (LOD) and limit of quantification (LOQ) values of 4-aminophenol were estimated with the aid of chronoamperometry (CA) technique and was found to be 9.8 μM and 32 μM, respectively. Finally the proposed method was found to have satisfactory repeatability, reproducibility and stability results with low relative standard deviation (RSD) values.

In situobservation of morphological changes of γ′ precipitates in a pre-deformed single-crystal Ni-base superalloy

2011 ◽  
Vol 44 (5) ◽  
pp. 935-944 ◽  
Author(s):  
Pavel Strunz ◽  
Gerhard Schumacher ◽  
Hellmuth Klingelhöffer ◽  
Albrecht Wiedenmann ◽  
Jan Šaroun ◽  
...  
Keyword(s):  
External Load ◽  
Morphological Changes ◽  
The Past ◽  
Subsequent Heating ◽  
Detailed Evaluation ◽  
The Matrix ◽  
Base Superalloy

Exposure of a superalloy to an external load results in anisotropic coarsening of the γ′ precipitates, so-called rafting. It was reported in the past that γ′ rafting can also occur as a result of purely thermal treatment, without the simultaneous presence of an external load, if the specimen has been pre-deformed at relatively low temperature. The evolution of γ′ morphology in pre-deformed specimens of SCA425 Ni-base superalloy was examined in the present study. Unlike in the previous experiments, the compressive stress was used for pre-straining.In situsmall-angle neutron scattering (SANS) was employed, which enabled the determination of the morphology directly at high temperature. Both for strong and for weak pre-straining, rounding of the originally cuboidal precipitates towards an ellipsoidal shape on heating was observed. Weak pre-straining (0.1, 0.5%) does not cause rafting on subsequent heating. On the other hand, the detailed evaluation of SANS data provides some indication of rafting during the subsequent heating after severe compressive pre-straining (2%). The experiment indicates the role of dislocation rearrangement at the matrix/precipitate interface during pre-straining.

Rapid Determination of Organic Matter Fractions by Ozonation Chemiluminescence

2012 ◽  
Vol 468-471 ◽  
pp. 2842-2848 ◽  
Author(s):  
Yan Liu ◽  
Ping Ping Fan ◽  
Guang Li Hou ◽  
Ji Chang Sun ◽  
Yan Cheng ◽  
...  
Keyword(s):  
Organic Matter ◽  
Rapid Determination ◽  
In Situ Monitoring ◽  
Global Ocean ◽  
Sediment Chemistry ◽  
Marine Biogeochemistry ◽  
Organic Matter Fractions ◽  
Soluble Fractions

Understanding marine biogeochemistry requires a network of global ocean in situ monitoring of various parameters on different scales in time and space. Among the various parameters involved in marine biogeochemistry, sediment chemistry is most important, and the organic matter fractions are the dominate factor in this parameter. However, classical methods of determining organic matter fractions consume a great deal of time and labor. In addition, some of these methods can produce high levels of pollution and are therefore not suitable for in situ studies. This study explored a method of rapid determination of organic matter fractions by ozonation chemiluminescence. In this method, the organic matter was separated into extractives, acid soluble fractions and acid insoluble fractions (AIF) using the classical method and then oxidized by ozone. The ozonation chemiluminescence characteristics of eight samples were subsequently used to set up a model to predict the concentrations of organic matter fractions. The model was tested using nine other organic samples and the results showed that it provided a better fit for the predicted acid soluble fractions. This study is the first to demonstrate the use of ozonation chemiluminescence for rapid determination of organic matter fractions; however, further study is required to enable its universal use.

scholarly journals Nitrate-Selective Electrodes Based on the Trinuclear Chromium(III) Pivalates

2008 ◽  
Vol 3 (1) ◽  
pp. 44-47 ◽  
Author(s):  
Mihail Revenco ◽  
Mariana Martin ◽  
Waell A.A. Dayyih
Keyword(s):  
Vinyl Chloride ◽  
Limit Of Detection ◽  
Polymeric Matrix ◽  
Nitrate Anion ◽  
Electroactive Material ◽  
Poly Vinyl Chloride ◽  
Different Types

The paper describes the analytical potentialities of the trinuclear chromium(III) complexes as potentiometric ionophores for the construction of electrodes sensitive to the presence of nitrate anion. The electroactive material containing 4,4’-bipyridil was synthesized in situ. The membrane was prepared using dioctylphthalate as a solvent mediator and poly (vinyl chloride) as a polymeric matrix. The electrodes presented a slope of 56 mV/decade, a low limit of detection (3,2.10-6 mol/l), an adequate lifetime (4 months), and suitable selectivity characteristics when compared with other nitrate electrodes. The good parameters of this electrode made possible its application to the determination of nitrate in different types of fertilizers.

scholarly journals Optimized Protocol for the In Situ Derivatization of Glutathione with N-Ethylmaleimide in Cultured Cells and the Simultaneous Determination of Glutathione/Glutathione Disulfide Ratio by HPLC-UV-QTOF-MS

Metabolites ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 292
Author(s):  
Xueni Sun ◽  
Raffaela S. Berger ◽  
Paul Heinrich ◽  
Ibtissam Marchiq ◽  
Jacques Pouyssegur ◽  
...  
Keyword(s):  
Dynamic Range ◽  
Limit Of Detection ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Internal Standard ◽  
Glutathione Disulfide ◽  
Optimized Protocol ◽  
In Situ Derivatization ◽  
In Cells

Glutathione (GSH) and glutathione disulfide (GSSG) are commonly used to assess the oxidative status of a biological system. Various protocols are available for the analysis of GSH and GSSG in biomedical specimens. In this study, we present an optimized protocol for the in situ derivatization of GSH with N-ethylmaleimide (NEM) to prevent GSH autooxidation, and thus to preserve the GSH/GSSG ratio during sample preparation. The protocol comprises the incubation of cells in NEM containing phosphate buffered saline (PBS), followed by metabolite extraction with 80% methanol. Further, to preserve the use of QTOF-MS, which may lack the linear dynamic range required for the simultaneous quantification of GSH and GSSG in non-targeted metabolomics, we combined liquid chromatographic separation with the online monitoring of UV absorbance of GS-NEM at 210 nm and the detection of GSSG and its corresponding stable isotope-labeled internal standard by QTOF-MS operated with a 10 Da Q1 window. The limit of detection (LOD) for GS-NEM was 7.81 µM and the linear range extended from 15.63 µM to 1000 µM with a squared correlation coefficient R2 of 0.9997. The LOD for GSSG was 0.001 µM, and the lower limit of quantification (LLOQ) was 0.01 µM, with the linear (R2 = 0.9994) range extending up to 10 µM. The method showed high repeatability with intra-run and inter-run coefficients of variation of 3.48% and 2.51% for GS-NEM, and 3.11% and 3.66% for GSSG, respectively. Mean recoveries of three different spike-in levels (low, medium, high) of GSSG and GS-NEM were above 92%. Finally, the method was applied to the determination of changes in the GSH/GSSG ratio either in response to oxidative stress in cells lacking one or both monocarboxylate transporters MCT1 and MCT4, or in adaptation to the NADPH (nicotinamide adenine dinucleotide phosphate) consuming production of D-2-hydroxyglutarate in cells carrying mutations in the isocitrate dehydrogenase genes IDH1 and IDH2.

scholarly journals Detection of NADH and ethanol at a graphite electrode modified with titania sol-gel/Meldola’s Blue/MWCNT/Nafion nanocomposite film

2012 ◽  
Vol 10 (1) ◽  
pp. 224-231 ◽  
Author(s):  
Jolanta Kochana ◽  
Juliusz Adamski
Keyword(s):  
Nanocomposite Film ◽  
Graphite Electrode ◽  
Limit Of Detection ◽  
Sol Gel ◽  
The Matrix ◽  
Titania Sol ◽  
Electrocatalytic Determination ◽  
Meldola's Blue ◽  
Meldola’S Blue

AbstractFor electrocatalytic determination of NADH, a graphite electrode modified with titania sol-gel/Meldola’s Blue/MWCNT/Nafion nanocomposite was proposed. The composition of the matrix film was optimised in terms of the content of carbon nanotubes and Nafion. Incorporation of a redox mediator, Meldola’s Blue, into the nanocomposite film enabled electrocatalytic determination of NADH at a low potential, −50 mV. For determination of ethanol, alcohol dehydrogenase (ADH) was immobilized into the matrix layer. Experimental conditions affecting the biosensor response were examined, including enzyme loading, temperature of measurement and pH of background electrolyte. Assessments of the analytical characteristics of the biosensor were performed with respect to sensitivity, limit of detection, operational stability, repeatability and reproducibility. The proposed biosensor showed electrocatalytic activity toward oxidation of ethanol with sensitivity of 2.24 µA L mmol−1, linear range from 0.05 to 1.1 mmol L−1, and limit of detection of 25 µmol L−1. The apparent Michaelis-Menten constant was 1.24 mmol L−1, indicating a high biological affinity of ADH/titania sol-gel/Meldola’s Blue/MWCNT/Nafion electrode for ethanol. The developed biosensor was tested in determinations of ethanol content in alcoholic beverages.

In-situ Monitoring and Determination of AlGaAs Composition During MOCVD Growth

2012 ◽  
Vol 33 (9) ◽  
pp. 985-990
Author(s):  
王鹏程 WANG Peng-cheng ◽  
徐华伟 XU Hua-wei ◽  
张金龙 ZHANG Jin-long ◽  
宁永强 NING Yong-qiang
Keyword(s):  
In Situ Monitoring ◽  
Mocvd Growth
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