37 results on '"Longfei Cai"'
Search Results
2. Instrument-free detection of polyphenols with a thread-based analytical device
- Author
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Jiahong Song, Zhuang Ouyang, Wei Lu, and Longfei Cai
- Subjects
length-based detection ,thread-based analytical device ,polyphenols ,instrument-free ,Science - Abstract
We described an instrument-free method for quantitative analysis of the total content of tea polyphenols by measurement of the length of a coloured band. Polyphenols react with ferrous ions to form a colourless ferrous-polyphenols complex on cotton threads, which could be adsorbed on the threads. The complex was then oxidized to form a blue-black ferric-polyphenols complex, generating a blue-black band on the cotton thread. The length of this blue-black band was then measured to detect the total content of polyphenols. The advantages of this method include low cost, rapid analysis, low consumption, easy fabrication and operation. Furthermore, the digital instrument (scanner or camera) as well as the image processing software are not required. This proposed method was used to detect polyphenols in tea leaf extracts with an analytical result agreeing well with that obtained by a standard method, which demonstrates its potential in monitoring of tea leaf quality, especially in resource-limited regions and settings.
- Published
- 2020
- Full Text
- View/download PDF
3. Distance readout of Al content with naked eyes on a cotton thread
- Author
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Chunxiu Xu, Wanjie Huang, Shunying Zhu, Ziqi Li, Longfei Cai, and Minghua Zhong
- Subjects
Physics ,QC1-999 - Abstract
We described a facile method for distance-based detection of aluminum on a thread based on the adsorption of formed complex onto thread. Chrome azurol S (CAS) containing Cetyltrimethylammonium Bromide (CTMAB) were used as chromogenic reagent, which reacts with aluminum to form AL-CAS-CTMAB complex on a thread. The complex was adsorbed onto thread to generate a colored band. Aluminum contents could be quantified by measuring the length of colored band on the thread using a ruler, thereby eliminating the need for electronic readout devices and trained personnel. This instrument-free method has features of low cost, easy to operation, fast analysis speed, disposability and low reagents/sample consumption. Moreover, considering that the thread fiber has adsorption capability to various molecules such as metal-ligand complexes and biomolecules, we believe that this technique holds the potentials to be widely adaptable to distance-based chemical and biochemical analysis.
- Published
- 2018
- Full Text
- View/download PDF
4. Visual quantification of Hg on a microfluidic paper-based analytical device using distance-based detection technique
- Author
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Longfei Cai, Yanling Fang, Yuanhui Mo, Yongshi Huang, Chunxiu Xu, Zhen Zhang, and Maoxian Wang
- Subjects
Physics ,QC1-999 - Abstract
We presented a distance-based detection method for visual quantification of mercury ions on a microfluidic paper-based analytical device (μPAD). Dithizone in NaOH solution was used as chromogenic reagent and deposited onto paper channel delimited by hydrophobic wax barrier. Reactions happened between mercury ions and dithizone to form an insoluble colored complex, producing colored precipitate on the paper channel. The length of colored precipitate could be readily measured using the printed ruler along each device. The length of precipitate increase linearly with the mercury concentrations, mercury in sample solution could be quantified by measuring the length of the colored precipitate. Being free of any electronic instruments, this method has the advantages of portability, ease of use, low cost and disposability. This presented method was used to detect mercury ions in a synthetic sample, demonstrating its potential in on-site and real time analysis.
- Published
- 2017
- Full Text
- View/download PDF
5. Iodometric Titration on Microfluidic Paper-Based Analytical Devices for Determination of Ascorbic Acid: A Laboratory Experiment for Chemical Education Undergraduates
- Author
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Xinyan Lin, Xiaoshuo Jin, Chunxiu Xu, Heyun Lai, Manbin Lin, Nailin Ren, and Longfei Cai
- Subjects
General Chemistry ,Education - Published
- 2023
6. Synthesis of GR/TiO2 Photocatalyst for Degradation of Methylene Blue─A Laboratory Experiment for Preservice Teachers
- Author
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Yifei Chen, Longfei Cai, Jiaye Gong, and Heyun Lai
- Subjects
General Chemistry ,Education - Published
- 2023
7. A Comprehensive Experiment for Training Undergraduates Majoring in Nutrition Education Using a Paper-Based Micro Acid–Base Titration
- Author
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Junsheng Huang and Longfei Cai
- Subjects
General Chemistry ,Education - Published
- 2022
8. Modification of Microfluidic Paper-Based Devices with an Oxidant Layer for Distance Readout of Reducing Substances
- Author
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Chunxiu Xu, Guoxing Zhou, Huihui Cai, Yicong Chen, Ling Huang, Longfei Cai, Jiaye Gong, and Zankai Yan
- Subjects
General Chemical Engineering ,General Chemistry - Abstract
We developed a novel strategy for modification of paper cellulose with water-insoluble oxidants for distance readout of reducing substances on microfluidic paper-based analytical devices (μPADs). Water-insoluble oxidants were formed and modified onto paper cellulose through the redox reaction that occurred between paper cellulose and potassium permanganate deposited on the paper channel, developing a yellowish-brown color on the channel. As aqueous solutions containing reducing substances flowed along the channel, reducing substances were consumed owing to the redox reaction that occurred between oxidants and reducing substances until the reducing substances were depleted, forming a discolored zone on the yellowish-brown channel. The redox reaction between insoluble oxidants and reducing substances on the paper cellulose could be used for distance-based detection of a wide variety of reducing substances, which is similar to the classical potassium permanganate titration that employs the redox reaction that occurred between potassium permanganate and reducing substances. We believe that this method will broaden the analytical applications of distance-based detection on μPADs. This method was applied to ascorbic acid assay and captopril assay in real samples with analytical results comparing well with the labeled values, demonstrating its great potential in real sample analysis.
- Published
- 2022
9. Implementing Curriculum and Program Changes at a Chinese University to Foster Excellent Chemistry Teachers for Rural Middle Schools
- Author
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Zankai Yan, Hui Pan, Minghua Zhong, Junsheng Huang, Huaiying Zhang, Heyun Lai, Nailin Ren, Longfei Cai, Dongxian Ke, and Manbin Lin
- Subjects
Educational equity ,Medical education ,Chemistry education ,010405 organic chemistry ,05 social sciences ,050301 education ,General Chemistry ,01 natural sciences ,0104 chemical sciences ,Education ,Educational research ,Undergraduate research ,Basic education ,Sociology ,Rural area ,China ,0503 education ,Curriculum - Abstract
Given the big gap between rural areas and cities and developed areas of China in basic education, it is of great significance to train a large number of excellent teachers for basic education in the vast rural areas so as to boost basic education there and achieve educational equity. Hanshan Normal University is a regional normal university located in Chaoshan, Guangdong, China. The Chemistry Education major aims to foster outstanding chemistry teachers for rural middle schools in Guangdong, especially for the Chaoshan region. The university is committed to forming a reasonable knowledge structure for Chemistry Education majors, improving their experimental skills and capabilities in experimental design and educational research while cultivating their emotion in taking root in rural areas as well. Practice has proven that this program for training outstanding chemistry teachers for rural middle schools is fruitful.
- Published
- 2021
10. Comprehensive Training of Undergraduates Majoring in Chemical Education by Designing and Implementing a Simple Thread-Based Microfluidic Experiment
- Author
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Longfei Cai, Chunxiu Xu, Zhuang Ouyang, and Xinrong Huang
- Subjects
Science instruction ,Multimedia ,Chemistry education ,010405 organic chemistry ,Technical writing ,05 social sciences ,050301 education ,General Chemistry ,Thread (computing) ,computer.software_genre ,01 natural sciences ,0104 chemical sciences ,Education ,ComputingMilieux_COMPUTERSANDEDUCATION ,0503 education ,computer - Abstract
We developed a comprehensive training module for the undergraduates majoring in chemical education with a simple microfluidic experiment. The students were required to read a scientific reference o...
- Published
- 2020
11. Visual Quantification of Fe on Cotton Thread Using a Ruler
- Author
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Liquan Luo, Xiaolin Zhang, Huibin Lin, Longfei Cai, Minghua Zhong, Xiaoning Liao, Jinhua Chen, and Chunxiu Xu
- Subjects
Science instruction ,Engineering drawing ,Scanner ,business.product_category ,010405 organic chemistry ,Cotton thread ,05 social sciences ,050301 education ,General Chemistry ,Thread (computing) ,01 natural sciences ,Electronic equipment ,0104 chemical sciences ,Education ,Ruler ,Laboratory experiment ,business ,0503 education - Abstract
We described a simple method for detection of Fe on a thread-based analytical device. Fe reacts with 1,10-phenanthroline to form a colored band on a cotton thread; the length was measured to quantify the contents of Fe using a ruler. This method has the advantages of easy operation, low cost, easy fabrication, and reduced sample/reagent consumption. Furthermore, this method is free of any electronic equipment such as camera and digital scanner. These features make this method suitable as a laboratory experiment in universities and colleges. This laboratory experiment is designed as one of selected experiments of the Comprehensive Chemistry Experiment course for the students majoring in chemistry, for the sixth and seventh semester. The students enjoyed fabricating the thread-based analytical device and used it to detect the contents in unknown samples. This laboratory experiment could be completed within 3 h.
- Published
- 2019
12. Cross Channel Thread-Based Microfluidic Device for Separation of Food Dyes
- Author
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Chunxiu Xu, Jiayi Lin, Longfei Cai, and Danli Jiang
- Subjects
Fabrication ,Materials science ,010405 organic chemistry ,business.industry ,Cross channel ,010401 analytical chemistry ,Microfluidics ,General Chemistry ,Thread (computing) ,01 natural sciences ,0104 chemical sciences ,Education ,Optoelectronics ,Sunset yellow ,Laboratory experiment ,business - Abstract
We described a method for electrophoretic separation of food dyes on a thread-based microfluidic analytical device. A cross channel thread-based microfluidic analytical device was fabricated and used to separate a mixture of food dyes. By controlling and adjusting the potentials applied onto four reservoirs, carmine and sunset yellow could be separated within 2 min. This method has the advantages of low cost, fast separation, and easy fabrication and operation, which make this very suitable for performing as a demonstration in universities. The students enjoyed this demonstration and presented some interesting and constructive questions after the demonstration, which indicated that the students were interested in the demonstration. This demonstration could also be modified to be a laboratory experiment which could be carried out within 3 h.
- Published
- 2018
13. Sample injection and electrophoretic separation on a simple laminated paper based analytical device
- Author
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Minghua Zhong, Chunxiu Xu, Xiaojun Zhang, Qingyu Zheng, and Longfei Cai
- Subjects
Materials science ,Chemical substance ,Filter paper ,010401 analytical chemistry ,Clinical Biochemistry ,Microfluidics ,Analytical chemistry ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Biochemistry ,Sample (graphics) ,Buffer (optical fiber) ,0104 chemical sciences ,Analytical Chemistry ,Dilution ,Electrophoresis ,Electrokinetic phenomena ,0210 nano-technology - Abstract
We described a strategy to perform multistep operations on a simple laminated paper-based separation device by using electrokinetic flow to manipulate the fluids. A laminated crossed-channel paper-based separation device was fabricated by cutting a filter paper sheet followed by lamination. Multiple function units including sample loading, sample injection, and electrophoretic separation were integrated on a single paper based analytical device for the first time, by applying potential at different reservoirs for sample, sample waste, buffer, and buffer waste. As a proof-of-concept demonstration, mixed sample solution containing carmine and sunset yellow were loaded in the sampling channel, and then injected into separation channel followed by electrophoretic separation, by adjusting the potentials applied at the four terminals of sampling and separation channel. The effects of buffer pH, buffer concentration, channel width, and separation time on resolution of electrophoretic separation were studied. This strategy may be used to perform multistep operations such as reagent dilution, sample injection, mixing, reaction, and separation on a single microfluidic paper based analytical device, which is very attractive for building micro total analysis systems on microfluidic paper based analytical devices.
- Published
- 2015
14. Low-cost and rapid prototyping of microfluidic paper-based analytical devices by inkjet printing of permanent marker ink
- Author
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Minghua Zhong, Longfei Cai, Shuyue Zheng, and Chunxiu Xu
- Subjects
Rapid prototyping ,Materials science ,Permanent marker ,Inkwell ,General Chemical Engineering ,Microfluidics ,Evaporation ,Nanotechnology ,General Chemistry ,Paper based ,Inkjet printing - Abstract
We described a low-cost method for rapid prototyping of a microfluidic paper-based analytical device by inkjet printing of permanent marker ink. After the evaporation of ink solvent is printed onto the paper, hydrophobic resin remains and forms hydrophobic barriers for microfluidic flow and analysis.
- Published
- 2015
15. Demonstrating Electrophoretic Separation in a Straight Paper Channel Delimited by a Hydrophobic Wax Barrier
- Author
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Longfei Cai, Wanqi Lin, and Chunxiu Xu
- Subjects
Wax ,Science instruction ,Chemistry ,business.industry ,010401 analytical chemistry ,05 social sciences ,Microfluidics ,050301 education ,General Chemistry ,01 natural sciences ,0104 chemical sciences ,Education ,Electrophoresis ,visual_art ,visual_art.visual_art_medium ,Optoelectronics ,Sunset yellow ,Laboratory experiment ,business ,0503 education ,Communication channel - Abstract
A demonstration is described of electrophoretic separation of carmine and sunset yellow with a paper-based device. The channel in the paper device was fabricated by hand with a wax pen. Electrophoretic separation of carmine and sunset yellow was achieved within a few minutes by applying potential on the channel using a simple and inexpensive power supply. This demonstration could not only motivate the students’ passion in learning analytical chemistry but also introduce two important analytical techniques (microfluidic paper-based analytical devices and electrophoresis) to the classroom. With further modification and improvement, this demonstration may be suitable for students to perform as a laboratory experiment in the teaching lab.
- Published
- 2016
16. Fabrication of a microfluidic paper-based analytical device by silanization of filter cellulose using a paper mask for glucose assay
- Author
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Yunying Wu, Longfei Cai, Junsheng Huang, Yong Wang, Heyun Lai, Chunxiu Xu, and Minghua Zhong
- Subjects
Fabrication ,Materials science ,Filter paper ,Microfluidics ,Nanotechnology ,Paper based ,Serum samples ,Biochemistry ,Analytical Chemistry ,chemistry.chemical_compound ,chemistry ,Filter (video) ,Silanization ,Electrochemistry ,Environmental Chemistry ,Cellulose ,Spectroscopy - Abstract
We developed a novel, low-cost and simple method for the fabrication of microfluidic paper-based analytical devices (μPADs) by silanization of filter cellulose using a paper mask having a specific pattern. The paper mask was penetrated with trimethoxyoctadecylsilane (TMOS) by immersing into TMOS-heptane solution. By heating the filter paper sandwiched between the paper mask and glass slides, TMOS was immobilized onto the filter cellulose via the reaction between cellulose OH and TMOS, while the hydrophilic area was not silanized because it was not in contact with the paper mask penetrated with TMOS. The effects of some factors including TMOS concentration, heating temperature and time on the fabrication of μPADs were studied. This method is free of any expensive equipment and metal masks, and could be performed by untrained personnel. These features are very attractive for the fabrication and applications of μPADs in developing countries or resource-limited settings. A flower-shaped μPAD was fabricated and used to determine glucose in human serum samples. The contents determined by this method agreed well with those determined by a standard method.
- Published
- 2014
17. Paper-Based Microfluidic Device for Determination of Nitrite in Pickled Vegetables
- Author
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Chunxiu Xu, Minghua Zhong, Yunying Wu, Longfei Cai, Jiani Hong, and Yuna Huang
- Subjects
General Chemistry - Published
- 2014
18. Distance readout of Al content with naked eyes on a cotton thread
- Author
-
Wanjie Huang, Ziqi Li, Longfei Cai, Minghua Zhong, Shunying Zhu, and Chunxiu Xu
- Subjects
chemistry.chemical_classification ,Materials science ,Chromogenic ,business.industry ,Biomolecule ,010401 analytical chemistry ,Fiber (computer science) ,General Physics and Astronomy ,02 engineering and technology ,Thread (computing) ,021001 nanoscience & nanotechnology ,01 natural sciences ,lcsh:QC1-999 ,0104 chemical sciences ,chemistry.chemical_compound ,Adsorption ,chemistry ,Colored ,Bromide ,Reagent ,Optoelectronics ,0210 nano-technology ,business ,lcsh:Physics - Abstract
We described a facile method for distance-based detection of aluminum on a thread based on the adsorption of formed complex onto thread. Chrome azurol S (CAS) containing Cetyltrimethylammonium Bromide (CTMAB) were used as chromogenic reagent, which reacts with aluminum to form AL-CAS-CTMAB complex on a thread. The complex was adsorbed onto thread to generate a colored band. Aluminum contents could be quantified by measuring the length of colored band on the thread using a ruler, thereby eliminating the need for electronic readout devices and trained personnel. This instrument-free method has features of low cost, easy to operation, fast analysis speed, disposability and low reagents/sample consumption. Moreover, considering that the thread fiber has adsorption capability to various molecules such as metal-ligand complexes and biomolecules, we believe that this technique holds the potentials to be widely adaptable to distance-based chemical and biochemical analysis.
- Published
- 2018
19. Instrument-free detection ofpolyphenols with a thread-based analytical device.
- Author
-
Jiahong Song, Zhuang Ouyang, Wei Lu, and Longfei Cai
- Published
- 2020
- Full Text
- View/download PDF
20. Selective Modification of Hydrophobic Paper Using a Surfactant for Protein Assay in Urine
- Author
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Longfei Cai, Chunxiu Xu, Yunying Wu, Minghua Zhong, and Yingcheng Chen
- Subjects
Chromatography ,Filter paper ,Pulmonary surfactant ,Chemistry ,Microfluidics ,General Chemistry ,Urine ,Bradford protein assay - Abstract
We used a surfactant to fabricate a microfluidic paper-based analytical device (µPAD) by selective modification of hydrophobic filter paper. Hydrophobic tails of the surfactant penetrate and remain...
- Published
- 2015
21. Analysis of intracellular reducing levels in human hepatocytes on three-dimensional focusing microchip
- Author
-
Chunxiu Xu and Longfei Cai
- Subjects
Chromatography ,Single-cell analysis ,Chemistry (miscellaneous) ,Chemistry ,Microfluidics ,Hydrostatic pressure ,Biophysics ,Hydrodynamic focusing ,Sample (graphics) ,Intracellular ,Fluorescence spectroscopy ,Communication channel - Abstract
A novel three-dimensional hydrodynamic focusing microfluidic device integrated with high-throughput cell sampling and detection of intracellular contents is presented. It has a pivotal role in maintaining the reducing environment in cells. Intracellular reducing species such as vitamin C and glutathione in normal and tumor cells were labeled by a newly synthesized 2,2,6,6-tetramethyl-piperidine-1-oxyl-based fluorescent probe. Hepatocytes are adherent cells, which are prone to attaching to the channel surface. To avoid the attachment of cells on the channel surface, a single channel microchip with three sheath-flow channels located on both sides of and below the sampling channel was developed. Hydrostatic pressure generated by emptying the sample waste reservoir was used as driving force of fluid on the microchip. Owing to the difference between the liquid levels of the reservoirs, the labeled cells were three-dimensional hydrodynamically focused and transported from the sample reservoir to the sample waste reservoir. Hydrostatic pressure takes advantage of its ease of generation on a microfluidic chip without any external pressure pump, which drives three sheath-flow streams to constrain a sample flow stream into a narrow stream to avoid blockage of the sampling channel by adhered cells. The intracellular reducing levels of HepG2 cells and L02 cells were detected by home-built laser-induced fluorescence detector. The analysis throughput achieved in this microfluidic system was about 59–68 cells/min. Copyright © 2013 John Wiley & Sons, Ltd.
- Published
- 2013
22. Simultaneous Determination of Trace Iron and Aluminum by Catalytic Spectrophotometry Based on a Novel Oxidation Reaction of Xylene Cyanol FF
- Author
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Longfei Cai and Chunxiu Xu
- Subjects
Time Factors ,Potassium Compounds ,Iron ,Inorganic chemistry ,Redox ,Catalysis ,Absorption ,Analytical Chemistry ,chemistry.chemical_compound ,Reaction rate constant ,Tap water ,Nitric acid ,Spectrophotometry ,medicine ,Hydrogen peroxide ,medicine.diagnostic_test ,Chemistry ,Benzenesulfonates ,Periodic Acid ,Temperature ,Water ,Hydrogen Peroxide ,Oxidants ,Trace Elements ,Plant Leaves ,Potassium periodate ,Calibration ,Oxidation-Reduction ,Aluminum - Abstract
A new, simple, sensitive and selective method for the simultaneous determination of trace iron and aluminum by catalytic spectrophotometry was presented, based on the catalytic effects of iron and aluminum on the discoloring reaction of xylene cyanol FF proceeded by hydrogen peroxide and potassium periodate in weak nitric acid medium. No catalytic effect was obtained in the presence of hydrogen peroxide or potassium periodate only. With the conditional rate constants determined in reaction systems catalyzed by Al or Fe only, the concentrations of Fe and Al in the samples can be calculated. The method was applied to the simultaneous determination of trace Fe and Al in tap water, lake water, river water and tea leaves without separation and preconcentration.
- Published
- 2008
23. Sample injection and electrophoretic separation on a simple laminated paper based analytical device
- Author
-
Chunxiu, Xu, Minghua, Zhong, Longfei, Cai, Qingyu, Zheng, and Xiaojun, Zhang
- Subjects
Electrophoresis ,Paper ,Equipment Design ,Hydrogen-Ion Concentration ,Microfluidic Analytical Techniques - Abstract
We described a strategy to perform multistep operations on a simple laminated paper-based separation device by using electrokinetic flow to manipulate the fluids. A laminated crossed-channel paper-based separation device was fabricated by cutting a filter paper sheet followed by lamination. Multiple function units including sample loading, sample injection, and electrophoretic separation were integrated on a single paper based analytical device for the first time, by applying potential at different reservoirs for sample, sample waste, buffer, and buffer waste. As a proof-of-concept demonstration, mixed sample solution containing carmine and sunset yellow were loaded in the sampling channel, and then injected into separation channel followed by electrophoretic separation, by adjusting the potentials applied at the four terminals of sampling and separation channel. The effects of buffer pH, buffer concentration, channel width, and separation time on resolution of electrophoretic separation were studied. This strategy may be used to perform multistep operations such as reagent dilution, sample injection, mixing, reaction, and separation on a single microfluidic paper based analytical device, which is very attractive for building micro total analysis systems on microfluidic paper based analytical devices.
- Published
- 2015
24. Defining microchannels and valves on a hydrophobic paper by low-cost inkjet printing of aqueous or weak organic solutions
- Author
-
Biyu Yuan, Longfei Cai, Minghua Zhong, Huolin Li, and Chunxiu Xu
- Subjects
Fluid Flow and Transfer Processes ,Aqueous solution ,Materials science ,Fabrication ,Filter paper ,Microfluidics ,Biomedical Engineering ,Diagnostic test ,Nanotechnology ,Condensed Matter Physics ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,chemistry ,General Materials Science ,Fabrication and Laboratory Methods ,Cellulose ,Inkjet printing ,Microfabrication - Abstract
We describe a simple and cost-effective strategy for rapid fabrication of microfluidic paper-based analytical devices and valves by inkjet printing. NaOH aqueous solution was printed onto a hydrophobic filter paper, which was previously obtained by soaking in a trimethoxyoctadecylsilane-heptane solution, allowing selective wet etching of hydrophobic cellulose to create hydrophilic-hydrophobic contrast with a relatively good resolution. Hexadecyltrimethylammonium bromide (CTMAB)-ethanol solution was printed onto hydrophobic paper to fabricate temperature-controlled valves. At low temperature, CTMAB deposited on the paper is insoluble in aqueous fluid, thus the paper remains hydrophobic. At high temperature, CTMAB becomes soluble so the CTMAB-deposited channel becomes hydrophilic, allowing the wicking of aqueous solution through the valve. We believe that this strategy will be very attractive for the development of simple micro analytical devices for point-of-care applications, including diagnostic testing, food safety control, and environmental monitoring.
- Published
- 2015
25. Fabrication of paper-based analytical device by silanisation of filter cellulose using alkyltrimethoxysilane coupled with UV radiation
- Author
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Wen-Yin Chen, Yunying Wu, Longfei Cai, Chunxiu Xu, and Minghua Zhong
- Subjects
Heptane ,Materials science ,Fabrication ,Chromatography ,Filter paper ,General Chemical Engineering ,Microfluidics ,Octadecyltrimethoxysilane ,Analytical chemistry ,Ethyl acetate ,General Chemistry ,Biochemistry ,Industrial and Manufacturing Engineering ,chemistry.chemical_compound ,chemistry ,Materials Chemistry ,Cellulose ,Nitrite - Abstract
A method was developed for the fabrication of microfluidic paper-based analytical devices (μPAD). This method was based on the silanisation of cellulose in filter paper using alkyltrimethoxysilane coupled with UV radiation. The filter paper sheet was hydrophobised by immersion in an octadecyltrimethoxysilane/heptane (OTMS/heptane) solution (0.25 vol. %) containing 5 vol. % of ethyl acetate (EtOAc). The hydrophobic-hydrophilic contrast was generated on the filter paper after the hydrophobised paper sheet was exposed to UV light with a metal mask creating the desired pattern on the sheet. The exposed area was oxidised to create a hydrophilic area, while the hydrophobic area was protected by the metal mask. The optimal conditions for the fabrication of μPAD were studied; these included ethyl acetate concentration (CEtOAc), immersion time, octadecyltrimethoxysilane concentration (COTMS) and exposure time. This method is cost-effective and simple. In addition, different functional groups could be further grafted for various assay purposes. To demonstrate the feasibility of the μPAD in analytical applications, a flower-shaped μPAD with eight channels and eight detection units was fabricated and used to determine the nitrite content in pickled vegetables. The nitrite content (124 µg g−1) in the sample determined by this method compared favourably with that measured using a standard method (137 µg g−1).
- Published
- 2015
26. A Simple Paper-Based Microfluidic Device for the Determination of the Total Amino Acid Content in a Tea Leaf Extract
- Author
-
Chunxiu Xu, Zefeng Chen, Longfei Cai, and Yunying Wu
- Subjects
Wax ,Chromatography ,Filter paper ,Chemistry ,Microfluidics ,General Chemistry ,Paper based ,Education ,GREEN TEA LEAF EXTRACT ,Chemical engineering ,visual_art ,visual_art.visual_art_medium ,Tea leaf extract ,Amino acid content ,Quantitative analysis (chemistry) - Abstract
An experiment was developed to demonstrate a microfluidic device in the analytical chemistry (instrumental analysis) laboratory. Students made the paper-based microfluidic device with a wax pen and a piece of filter paper and used it to determine the total quantity of amino acids in a green tea leaf extract. The device is low cost, easy-to-make, and easy-to-use. The student results compared favorably with those from standard method.
- Published
- 2012
27. Visual quantification of Hg on a microfluidic paper-based analytical device using distance-based detection technique
- Author
-
Yanling Fang, Yuanhui Mo, Yongshi Huang, Longfei Cai, Zhen Zhang, Maoxian Wang, and Chunxiu Xu
- Subjects
Wax ,Chromogenic ,010401 analytical chemistry ,Microfluidics ,Analytical chemistry ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,lcsh:QC1-999 ,0104 chemical sciences ,Mercury (element) ,chemistry.chemical_compound ,Length measurement ,chemistry ,Colored ,Reagent ,visual_art ,visual_art.visual_art_medium ,Dithizone ,0210 nano-technology ,lcsh:Physics - Abstract
We presented a distance-based detection method for visual quantification of mercury ions on a microfluidic paper-based analytical device (μPAD). Dithizone in NaOH solution was used as chromogenic reagent and deposited onto paper channel delimited by hydrophobic wax barrier. Reactions happened between mercury ions and dithizone to form an insoluble colored complex, producing colored precipitate on the paper channel. The length of colored precipitate could be readily measured using the printed ruler along each device. The length of precipitate increase linearly with the mercury concentrations, mercury in sample solution could be quantified by measuring the length of the colored precipitate. Being free of any electronic instruments, this method has the advantages of portability, ease of use, low cost and disposability. This presented method was used to detect mercury ions in a synthetic sample, demonstrating its potential in on-site and real time analysis.
- Published
- 2017
28. AN AUTOMATED METHOD FOR DETERMINATION OF ASCORBIC ACID IN URINE BY FLOW INJECTION CHEMILUMINESCENCE COUPLING WITH ON-LINE REMOVAL OF INTERFERENCE
- Author
-
Longfei Cai and Chunxiu Xu
- Subjects
Detection limit ,Chromatography ,Vitamin C ,General Chemistry ,Urine ,Ascorbic acid ,law.invention ,Luminol ,chemistry.chemical_compound ,chemistry ,law ,Hydrogen peroxide ,Ion-exchange resin ,Chemiluminescence - Abstract
A simple and automated method for determination of ascorbic acid (AA) in complex samples by flow injection chemiluminescence (FI-CL) was presented. It is based on the inhibitory effect of ascorbic acid on the chemiluminescence reaction between luminol and hydrogen peroxide in the flow system. A home-made micro column of cation exchange resin was adapted to the FI manifold to achieve on-line removal of interference. This method was used to determine the AA content in urine samples with a detection limit of 6.03 ×10 -9 mol/L AA and recovery of 93.1-111.0%. This proposed method allows high - throughput determination of AA in urine samples without chromatographic separation, demonstrating that the FI-CL method has significant potential in determination of species in complex samples by adapting a micro column filled with various functionalized materials to the FI manifold. e-mail: cailf@zju.edu.cn INTRODUCTION Ascorbic acid, usually found in citrus fruits and vegetables, is mainly used as a cure for various diseases including scurvy, drug poisoning, liver disease and allergic reactions. Consequently, determination of ascorbic acid in foods, pharmaceuticals, and biological samples is crucial. A variety of methods have been employed for the determination of ascorbic acid in simple samples including foods, Vitamin C tablets and injections, among which iodometric method
- Published
- 2011
29. Evaluating intracellular redox status in L02 cells on microchip
- Author
-
Chunxiu Xu and Longfei Cai
- Subjects
Hydrostatic pressure ,microfluidics ,General Chemistry ,medicine.disease_cause ,Fluorescence ,chemistry.chemical_compound ,Cytolysis ,chemistry ,Biochemistry ,Single-cell analysis ,medicine ,Biophysics ,single-cell analysis ,Hydrogen peroxide ,Laser-induced fluorescence ,Oxidative stress ,Intracellular ,high-throughput - Abstract
A novel microfluidic device integrated with continuous introduction of individual cells and detection of intracellular reducing species by laser induced fluorescence (LIF) detector is reported. A single channel with one sheath-flow channel located on each side of the sampling channel was designed. The intracellular reducing species were derivatized by a newly synthesized 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO)-based fluorescent probe. The labeled cells were hydrodynamically focused by sheath-flow streams and sequentially introduced into the sampling channel under hydrostatic pressure generated by adjusting liquid levels in the reservoirs. Intracellular reducing level in intact living L02 cells was detected by LIF without cytolysis. Upon stimulation with 100 µmol L-1 hydrogen peroxide for 30 min, the intracellular reducing level decreased in response to oxidative stress. A throughput of 41-44 cells min-1 was obtained. Um novo dispositivo microfluídico integrado com introdução contínua de células individuais e detecção de espécies redutoras intracelulares por detector de fluorescência induzida por laser (LIF) é relatado. Um canal central de amostragem foi desenhado sendo flanqueado por dois outros canais auxiliares. As espécies intracelulares redutoras foram derivadas por uma sonda fluorescente baseada na recém-sintetizada 2,2,6,6-tetrametil-piperidina-1-oxilo (TEMPO). As células marcadas foram hidrodinamicamente focadas pelas correntes da bainha de fluxo e sequencialmente introduzidas no canal de amostragem sob pressão hidrostática gerada por ajuste dos níveis de líquido nos reservatórios. O nível de redução intracelular em células vivas intactas L02 foi detectada por LIF sem citólise. Após estimulação com 100 mmol L-1 de peróxido de hidrogênio, durante 30 minutos, o nível de redução intracelular diminuiu em resposta ao estresse oxidativo. Foi obtida uma taxa de transferência de 41-44 células min-1.
- Published
- 2013
30. Analysis of intracellular reducing levels in human hepatocytes on three-dimensional focusing microchip
- Author
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Chunxiu, Xu and Longfei, Cai
- Subjects
Lab-On-A-Chip Devices ,Cell Adhesion ,Hepatocytes ,Humans ,Ascorbic Acid ,Hep G2 Cells ,Glutathione ,Fluorescent Dyes - Abstract
A novel three-dimensional hydrodynamic focusing microfluidic device integrated with high-throughput cell sampling and detection of intracellular contents is presented. It has a pivotal role in maintaining the reducing environment in cells. Intracellular reducing species such as vitamin C and glutathione in normal and tumor cells were labeled by a newly synthesized 2,2,6,6-tetramethyl-piperidine-1-oxyl-based fluorescent probe. Hepatocytes are adherent cells, which are prone to attaching to the channel surface. To avoid the attachment of cells on the channel surface, a single channel microchip with three sheath-flow channels located on both sides of and below the sampling channel was developed. Hydrostatic pressure generated by emptying the sample waste reservoir was used as driving force of fluid on the microchip. Owing to the difference between the liquid levels of the reservoirs, the labeled cells were three-dimensional hydrodynamically focused and transported from the sample reservoir to the sample waste reservoir. Hydrostatic pressure takes advantage of its ease of generation on a microfluidic chip without any external pressure pump, which drives three sheath-flow streams to constrain a sample flow stream into a narrow stream to avoid blockage of the sampling channel by adhered cells. The intracellular reducing levels of HepG2 cells and L02 cells were detected by home-built laser-induced fluorescence detector. The analysis throughput achieved in this microfluidic system was about 59-68 cells/min.
- Published
- 2012
31. Determination of iron and aluminum based on the catalytic effect on the reaction of xylene cyanol FF with hydrogen peroxide and potassium periodate
- Author
-
Chunxiu Xu and Longfei Cai
- Subjects
Potassium periodate ,Xylene cyanol FF ,chemistry.chemical_compound ,catalytic spectrophotometry ,iron ,Chemistry ,aluminum ,General Chemistry ,xylene cyanol FF ,Hydrogen peroxide ,Nuclear chemistry ,Catalytic effect - Abstract
A simple, sensitive and selective method for the simultaneous determination of trace iron and aluminum by catalytic spectrophotometry is presented. This method is based on the catalytic effects of iron and aluminum on the reaction of xylene cyanol FF with hydrogen peroxide and potassium periodate. Both iron and aluminum did not show catalytic effects on the oxidation reaction of xylene cyanol FF in the presence of either hydrogen peroxide or potassium periodate. However, significant catalytic effects of iron and aluminum were obtained when the two oxidants were simultaneously used. Linear calibration graphs were obtained from 3.57 × 10-8 to 3.57 × 10-7 mol L-1 for Fe and from 1.48 × 10-7 to 1.48 × 10-6 mol L-1 for Al. The detection limits, based on the 3-fold standard deviation criterion, were 1.50 × 10-8 mol L-1 for Fe and 6.10 × 10-8 mol L-1 for Al. This method was applied to the simultaneous determination of trace iron and aluminum in tap water, lake water, river water and tea leaves without separation and preconcentration. Contents of Fe and Al in tap water, lake water and river water were 3.13 × 10-7, 3.21 × 10-7, 2.74 × 10-7 mol L-1 for Fe and 1.31 × 10-6, 9.83 ×10-7, 1.43× 10-6 mol L-1 for Al, respectively. Tea leaves contained 3.10 × 10² µg g-1 Fe and 7.37 × 10² µg g-1 Al. Further research is required for understanding the catalytic mechanism of iron and aluminum on this novel oxidation reaction. Um método simples, sensível e seletivo para determinação simultânea de traços de ferro e alumínio por espectrofotometria catalítica foi desenvolvido. Esse método baseia-se nos efeitos catalíticos de ferro e alumínio sobre a reação de xileno cianol FF com peróxido de hidrogênio e periodato de potássio. Ferro e alumínio não apresentaram efeitos catalíticos sobre a reação de oxidação do xileno cianol FF em meio contendo apenas peróxido de hidrogênio ou apenas periodato de potássio. Entretanto, foram obtidos efeitos catalíticos significativos de ferro e alumínio quando ambos oxidantes foram usados simultaneamente. Gráficos de calibração linear foram obtidos no intervalo de 3,57 × 10-8 a 3,57 × 10-7 mol L-1 para Fe e de 1,48×10-7 a 1,48 ×10-6 mol L-1 para Al. Os limites de detecção, baseados no critério de 3 vezes o desvio padrão, foram 1,50 × 10-8 mol L-1 para Fe e 6,10 × 10-8 mol L-1 para Al. Este método foi aplicado para determinação simultânea de traços de ferro e alumínio em água de torneira, água de lago, de rio e folhas de chá sem etapas de separação e pré-concentração. Os teores de Fe e Al em águas de torneira, lago e rio foram 3,13 × 10-7, 3,21 × 10-7 e 2,74 × 10-7 mol L-1 para Fe e 1,31 × 10-6, 9,83 × 10-7 e 1,43 × 10-6 mol L-1 para Al, respectivamente. As quantidades de Fe e Al nas folhas de chá foram 3,10 × 10² µg g-1 Fe e 7,37 × 10² µg g-1 Al. Estudos complementares são necessários para o entendimento do mecanismo catalítico do ferro e alumínio nesta reação de oxidação inédita.
- Published
- 2011
32. A simple paper-based sensor fabricated by selective wet etching of silanized filter paper using a paper mask
- Author
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Meidie Wu, ShuoHong Lin, Fan Yang, Jiating Luo, Longfei Cai, and Chunxiu Xu
- Subjects
Fluid Flow and Transfer Processes ,Materials science ,Fabrication ,Filter paper ,Microfluidics ,technology, industry, and agriculture ,Biomedical Engineering ,Nanotechnology ,Paper based ,Condensed Matter Physics ,Colloid and Surface Chemistry ,Artificial urine ,Etching (microfabrication) ,Reagent ,Fabrication and Laboratory Methods ,General Materials Science ,Microfabrication - Abstract
We developed a novel strategy for fabrication of microfluidic paper-based analytical devices (μPADs) by selective wet etching of hydrophobic filter paper using a paper mask having a specific design. The fabrication process consists of two steps. First, the hydrophilic filter paper was patterned hydrophobic by using trimethoxyoctadecylsilane (TMOS) solution as the patterning agent. Next, a paper mask penetrated with NaOH solution (containing 30% glycerol) was aligned onto the hydrophobic filter paper, allowing the etching of the silanized filter paper by the etching reagent. The masked region turned highly hydrophilic whereas the unmasked region remains highly hydrophobic. Thus, hydrophilic channels, reservoirs, and detection zones were generated and delimited by the hydrophobic barriers. The effects of some factors including TMOS concentration, etching temperature, etching time, and NaOH concentration on fabrication of μPAD were studied. Being free of any expensive equipment, metal mask and expensive reagents, this rapid, simple, and cost-effective method could be used to fabricate μPAD by untrained personnel with minimum cost. A flower-shaped μPAD fabricated by this presented method was applied to the glucose assay in artificial urine samples with good performance, indicating its feasibility as a quantitative analysis device. We believe that this method would be very attractive to the development of simple microfluidic devices for point-of-care applications in clinical diagnostics, food safety, and environmental protection.
- Published
- 2014
33. Retraction Note: Simultaneous Determination of Trace Iron and Aluminum by Catalytic Spectrophotometry Based on a Novel Oxidation Reaction of Xylene Cyanol FF
- Author
-
Longfei Cai and Chunxiu Xu
- Subjects
Analytical Chemistry - Published
- 2009
34. Defining microchannels and valves on a hydrophobic paper by low-cost inkjet printing of aqueous or weak organic solutions.
- Author
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Longfei Cai, Minghua Zhong, Huolin Li, Chunxiu Xu, and Biyu Yuan
- Subjects
- *
MICROCHANNEL flow , *VALVES , *HYDROPHOBIC interactions , *COST analysis , *INK-jet printers , *AQUEOUS solutions - Abstract
We describe a simple and cost-effective strategy for rapid fabrication of microfluidic paper-based analytical devices and valves by inkjet printing. NaOH aqueous solution was printed onto a hydrophobic filter paper, which was previously obtained by soaking in a trimethoxyoctadecylsilane-heptane solution, allowing selective wet etching of hydrophobic cellulose to create hydrophilic-hydrophobic contrast with a relatively good resolution. Hexadecyltrimethylammonium bromide (CTMAB)- ethanol solution was printed onto hydrophobic paper to fabricate temperaturecontrolled valves. At low temperature, CTMAB deposited on the paper is insoluble in aqueous fluid, thus the paper remains hydrophobic. At high temperature, CTMAB becomes soluble so the CTMAB-deposited channel becomes hydrophilic, allowing the wicking of aqueous solution through the valve. We believe that this strategy will be very attractive for the development of simple micro analytical devices for point-of-care applications, including diagnostic testing, food safety control, and environmental monitoring. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
35. Low-cost and rapid prototyping of microfluidic paper-based analytical devices by inkjet printing of permanent marker ink.
- Author
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Chunxiu Xu, Longfei Cai, Minghua Zhong, and Shuyue Zheng
- Published
- 2015
- Full Text
- View/download PDF
36. A simple paper-based sensor fabricated by selective wet etching of silanized filter paper using a paper mask.
- Author
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Longfei Cai, Chunxiu Xu, ShuoHong Lin, Jiating Luo, Meidie Wu, and Fan Yang
- Subjects
- *
CHEMICAL milling , *SILANIZATION , *FILTER paper , *MICROFLUIDIC analytical techniques , *HYDROPHOBIC surfaces , *FABRICATION (Manufacturing) , *ENVIRONMENTAL protection - Abstract
We developed a novel strategy for fabrication of microfluidic paper-based analytical devices (μPADs) by selective wet etching of hydrophobic filter paper using a paper mask having a specific design. The fabrication process consists of two steps. First, the hydrophilic filter paper was patterned hydrophobic by using trimethoxyoctadecylsilane (TMOS) solution as the patterning agent. Next, a paper mask penetrated with NaOH solution (containing 30% glycerol) was aligned onto the hydrophobic filter paper, allowing the etching of the silanized filter paper by the etching reagent. The masked region turned highly hydrophilic whereas the unmasked region remains highly hydrophobic. Thus, hydrophilic channels, reservoirs, and detection zones were generated and delimited by the hydrophobic barriers. The effects of some factors including TMOS concentration, etching temperature, etching time, and NaOH concentration on fabrication of μPAD were studied. Being free of any expensive equipment, metal mask and expensive reagents, this rapid, simple, and cost-effective method could be used to fabricate lPAD by untrained personnel with minimum cost. A flower-shaped μPAD fabricated by this presented method was applied to the glucose assay in artificial urine samples with good performance, indicating its feasibility as a quantitative analysis device. We believe that this method would be very attractive to the development of simple microfluidic devices for point-of-care applications in clinical diagnostics, food safety, and environmental protection. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
37. Demonstrating Electrophoretic Separation in a Straight Paper Channel Delimited by a Hydrophobic Wax Barrier.
- Author
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Chunxiu Xu, Wanqi Lin, and Longfei Cai
- Published
- 2016
- Full Text
- View/download PDF
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