The Experts below are selected from a list of 237 Experts worldwide ranked by ideXlab platform
B. Schwarz - One of the best experts on this subject based on the ideXlab platform.
-
μ-‘Diving suit’ for liquid-phase high-Q resonant detection
Lab on a Chip, 2016Co-Authors: Haitao T. Yu, Pengcheng C. Xu, Tiegang G. Xu, Yuyang Bao, Xinxin X. Li, L. Nan, Z. D. Jiang, X. Y. Wei, Ying Chen, B. SchwarzAbstract:A resonant cantilever sensor is, for the first time, dressed in a water-proof ‘diving suit’ for real-time bio/chemical detection in liquid. The μ-‘diving suit’ technology can effectively avoid not only unsustainable resonance due to heavy liquid-damping, but also inevitable nonspecific adsorption on the cantilever body. Such a novel technology ensures long-time high-Q resonance of the cantilever in solution environment for real-time Trace-Concentration bio/chemical detection and analysis. After the formation of the integrated resonant micro-cantilever, a patterned photoresist and hydrophobic parylene thin-film are sequentially formed on top of the cantilever as sacrificial layer and water-proof coat, respectively. After sacrificial-layer release, an air gap is formed between the parylene coat and the cantilever to protect the resonant cantilever from heavy liquid damping effect. Only a small sensing-pool area, located at the cantilever free-end and locally coated with specific sensing-material, is exposed to the liquid analyte for gravimetric detection. The specifically adsorbed analyte mass can be real-time detected by recording the frequency-shift signal. In order to secure vibration movement of the cantilever and, simultaneously, reject liquid leakage from the sensing-pool region, a hydrophobic parylene made narrow slit structure is designed surrounding the sensing-pool. The anti-leakage effect of the narrow slit and damping limited resonance Q-factor are modelled and optimally designed. Integrated with electro-thermal resonance excitation and piezoresistive frequency readout, the cantilever is embedded in a micro-fluidic chip to form a lab-chip micro-system for liquid-phase bio/chemical detection. Experimental results show the Q-factor of 23 in water and longer than 20 hours liquid-phase continuous working time. Loaded with two kinds of sensing-materials at the sensing-pools, two types of sensing chips successfully show real-time liquid-phase detection to ppb-level organophosphorous pesticide of acephate and E.coli DH5α in PBS, respectively. The proposed method fundamentally solves the long-standing problem of being unable to operate a resonant micro-sensor in liquid well.
Cristina M. M. Almeida - One of the best experts on this subject based on the ideXlab platform.
-
Development of a Multiresidue Method for the Determination of 24 Pharmaceuticals in Clams by QuEChERS and Liquid Chromatography-Triple Quadrupole Tandem Mass Spectrometry
Food Analytical Methods, 2019Co-Authors: João Rodrigues, Stephanie Albino, Sofia Silva, Alexandra Cravo, Vitor Vale Cardoso, Maria João Benoliel, Cristina M. M. AlmeidaAbstract:Data on different therapeutic classes of pharmaceutical compounds (PhCs) in clams or other bivalves living in natural conditions are scarce. The aim of this work was the optimization and validation of a method for the determination of PhCs in clams for further evaluation of any potential human exposure risk due to their consumption. A quick, easy, cheap, effective, rugged, and safe (QuEChERS) approach is proposed for sample clean-up and Concentration of 24 PhCs in clams, with subsequent analysis by liquid chromatography-tandem mass spectrometry. This method showed a good linear range for all PhCs with determination coefficients ( r ^2) between 0.9949 and 0.9993 and coefficients of variation (CVm) lower than 5.5%. This method allowed the quantification of target compounds at Trace Concentration levels (ng g^−1), being the most abundant PhC in clam caffeine. This PhC was detected in more than 70% of samples with Concentrations ranging from 0.10 to 12 ng g^−1 wet weight.
Md Rabiul Awual - One of the best experts on this subject based on the ideXlab platform.
-
optical mesosensors for monitoring and removal of ultra Trace Concentration of zn ii and cu ii ions from water
Analyst, 2012Co-Authors: Sherif A Elsafty, Mohamed A Shenashen, M Ismael, Mohamed Khairy, Md Rabiul AwualAbstract:Optical captor design is necessary for the controlled development of a technique for detecting and removing heavy and toxic metals from drinking water with high flexibility and low capital cost. We designed chemical mesocaptors for optical separation/extraction and monitoring/detection of Cu(II) and Zn(II) ions from water even at Trace Concentration levels without a preConcentration process. The mesoporous aluminosilica carriers with three-dimensional (3D) structures, high aluminum content, natural surfaces, and active acid sites strongly induced H-bonding and dispersive interactions with organic moieties, thereby leading to the formation of stable captors without chromophore leaching during the removal assays of Cu(II) and Zn(II) ions. Using such a tailored mesocaptor design, the direct immobilization of these hydrophobic ligands (4,5-diamino-6-hydroxy-2-mercaptopyrimidine and diphenylthiocarbazone) into ordered pore-based aluminasilica monoliths enabled the easy generation and transduction of optical colour signals as a response to metal-to-ligand binding events, even at ultra-Trace Concentrations (∼10−9 mol dm−3) of Cu(II) and Zn(II) ions in drinking water, without the need for sophisticated instruments. Theoretical models have been developed to provide insights into the effect of active site surfaces on the enhancement of the optical removal process in terms of long-term stability, reversibility, and selectivity, hence allowing us to understand the role of mesoscopic geometry and nanoscale pore orientation of mesocaptors better. Generally, this ion-capture model enables the development of a simple and effective technique for effective wastewater treatment and management.
-
a weak base fibrous anion exchanger effective for rapid phosphate removal from water
Journal of Hazardous Materials, 2011Co-Authors: Sherif A Elsafty, Md Rabiul Awual, Masao Tamada, Noriaki SekoAbstract:Abstract This work investigated that weak-base anion exchange fibers named FVA-c and FVA-f were selectively and rapidly taken up phosphate from water. The chemical structure of both FVA-c and FVA-f was the same; i.e., poly(vinylamine) chains grafted onto polyethylene coated polypropylene fibers. Batch study using FVA-c clarified that this preferred phosphate to chloride, nitrate and sulfate in neutral pH region and an equilibrium capacity of FVA-c for phosphate was from 2.45 to 6.87 mmol/g. Column study using FVA-f made it clear that breakthrough capacities of FVA-f were not strongly affected by flow rates from 150 to 2000 h−1 as well as phosphate feed Concentration from 0.072 to 1.6 mM. Under these conditions, breakthrough capacities were from 0.84 to 1.43 mmol/g indicating high kinetic performances. Trace Concentration of phosphate was also removed from feeds containing 0.021 and 0.035 mM of phosphate at high feed flow rate of 2500 h−1, breakthrough capacities were 0.676 and 0.741 mmol/g, respectively. The column study also clarified that chloride and sulfate did not strongly interfere with phosphate uptake even in their presence of equimolar and fivefold molar levels. Adsorbed phosphate on FVA-f was quantitatively eluted with 1 M HCl acid and regenerated into hydrochloride form simultaneously for next phosphate adsorption operation. Therefore, FVA-f is able to use long time even under rigorous chemical treatment of multiple regeneration/reuse cycles without any noticeable deterioration.
Fang Geng - One of the best experts on this subject based on the ideXlab platform.
-
simultaneous determination of nine Trace Concentration angiotensin peptides in human serum using ultra high performance liquid chromatography with tandem mass spectrometry with sephadex lh 20 gel solid phase extraction
IEEE Journal of Solid-state Circuits, 2019Co-Authors: Yue Shen, Mingyue Xu, Zhanling Xu, Yue Na, Ning Zhang, Fang GengAbstract:: The renin-angiotensin system is a highly complex enzymatic system consisting of multiple peptide hormones, enzymes, and receptors. Here, an assay to simultaneously quantify eight angiotensin peptides and bradykinin in human serum was developed and validated, using ultra high performance liquid chromatography coupled with tandem mass spectrometry. A pre-Concentration method of Sephadex LH-20 gel solid-phase extraction was first applied for analysis of angiotensin peptides from serum sample. The triple quadrupole mass spectrometer was operated in the positive ion mode and multiple reaction monitoring was used for drug quantification. The analytical time was within 5 min, much raising the analysis efficiency. Limits of detection ranged from 0.9 to 1.3 pg/mL, and displayed the same level of sensitivity compared with radioimmunoassay. The method was successfully applied to 22 healthy human serum samples, giving the Concentrations of angiotensin I, angiotensin II, angiotensin III, angiotensin IV, angiotensin 1-9, angiotensin 1-7, angiotensin 1-5, Asn1 ,Val5 -Angiotensin II, and bradykinin for reference. This novel metabolic profile study of vasoactive peptides based on gel solid-phase extraction Concentration provided not only an accurate quantitative assay of the serum Concentrations, but also a promising methodology for evaluating the diagnostic values of the various peptides.
Baiqing Xu - One of the best experts on this subject based on the ideXlab platform.
-
method for determination of levoglucosan in snow and ice at Trace Concentration levels using ultra performance liquid chromatography coupled with triple quadrupole mass spectrometry
Talanta, 2016Co-Authors: Lili Song, Baiqing XuAbstract:Abstract A method is developed for determination of levoglucosan at Trace Concentration levels in complex matrices of snow and ice samples. This method uses an injection mixture comprising acetonitrile and melt sample at a ratio of 50/50 (v/v). Samples are analyzed using ultra-performance liquid chromatography system combined with triple tandem quadrupole mass spectrometry (UPLC-MS/MS). Levoglucosan is analyzed on BEH Amide column (2.1 mm×100 mm, 1.7 um), and a Z-spray electrospray ionization source is used for levoglucosan ionization. The polyether sulfone filter is selected for filtrating insoluble particles due to less impact on levoglucosan. The matrix effect is evaluated by using a standard addition method. During the method validation, limit of detection (LOD), linearity, recovery, repeatability and reproducibility were evaluated using standard addition method. The LOD of this method is 0.11 ng mL−1. Recoveries vary from 91.2% at 0.82 ng mL−1 to 99.3% at 4.14 ng mL−1. Repeatability ranges from 17.9% at a Concentration of 0.82 ng mL−1 to 2.8% at 4.14 ng mL−1. Reproducibility ranges from 15.1% at a Concentration of 0.82 ng mL−1 to 1.9% at 4.14 ng mL−1. This method can be implemented using less than 0.50 mL sample volume in low and middle latitude regions like the Tibetan Plateau.
