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Related Concept Videos

UV–Vis Spectrometers01:14

UV–Vis Spectrometers

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The absorbance of UV and visible (UV–visible) radiations is measured using a UV–visible spectrophotometer. Deuterium lamps, which emit UV radiation, and tungsten lamps, which produce radiation in the visible region, are used as light sources in UV–visible spectrophotometers. A monochromator or prism is used for diffraction grating, i.e., to split the incoming radiation into different wavelengths. A system of slits is used to focus the desired wavelength on the sample cell.
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In IR spectroscopy of carboxylic acids, the C=O bond shows a characteristic band between 1710 and 1760 cm⁻¹, and the O–H bond exhibits a broad band between 2500 and 3300 cm⁻¹.
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Spectrophotometry: Introduction01:16

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Spectrophotometry is the quantitative measurement of the absorption, reflection, diffraction, or transmission of electromagnetic radiation through a material as a function of the intensity and wavelength of the radiation. A spectrophotometer is a device used to measure the change in the radiation intensity caused by its interaction with the material.
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Coulometry is one of the rapid, most accurate, and precise analytical techniques that determine the quantity of an analyte by measuring the electrical charge needed for its complete electrolysis without using any analytical standards. The total charge passed during electrolysis correlates with the analyte amount by Faraday's laws of electrolysis. For accurate coulometric measurements, a charge equal to Faraday's constant multiplied by the number of electrons involved in the relevant...
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The Beer-Lambert law describes the relationship between absorbance and concentration, which combines the principles established by scientists Johann Heinrich Lambert and August Beer. Lambert's law states that when light passes through a medium, the loss in intensity is directly proportional to the original intensity and the path length of the light. Beer's law proposed that the transmittance of a solution remains constant if the product of concentration and path length is constant. The modern...
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Capillary electrophoresis instrumentation typically consists of several key components. A high-voltage power supply generates the electric field necessary for the separation by connecting to an anode (the positively charged electrode) and a cathode (the negatively charged electrode) located in buffer reservoirs at each end of the capillary tube. The system includes a sample vial, a fused silica capillary tube coated with polyimide for mechanical strength through which the sample components...
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Related Experiment Video

Updated: Mar 20, 2026

A Rapid and Specific Microplate Assay for the Determination of Intra- and Extracellular Ascorbate in Cultured Cells
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Performance enhanced UV/vis spectroscopic microfluidic sensor for ascorbic acid quantification in human blood.

Hongyan Bi1, Carla M Duarte2, Marina Brito1

  • 1International Iberian Nanotechnology Laboratory (INL), Av. Mestre José Veiga, 4715-330 Braga, Portugal.

Biosensors & Bioelectronics
|May 29, 2016
PubMed
Summary
This summary is machine-generated.

A new microfluidic biosensor effectively quantifies ascorbic acid using immobilized enzymes. The best method involved alumina xerogel modification, enabling rapid, low-volume blood analysis for clinical diagnosis.

Keywords:
Antioxidant analysisHuman bloodPDMS microfluidic chipSol-gelUV/vis spectroscopic sensor

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Area of Science:

  • Biomedical Engineering
  • Analytical Chemistry
  • Enzyme Immobilization

Background:

  • Quantitative analysis of antioxidants is crucial for real-time health monitoring.
  • Ascorbic acid quantification requires sensitive and specific methods.
  • Enzyme stability is a key challenge in biosensor development.

Purpose of the Study:

  • To develop a UV/vis spectroscopic microfluidic sensor for ascorbic acid quantification.
  • To compare different enzyme immobilization strategies for improved sensor performance.
  • To assess the potential of the developed microsensor for clinical diagnosis.

Main Methods:

  • Immobilization of ascorbate oxidase onto PDMS microfluidic channels using three strategies: alumina sol-gel encapsulation, physisorption with and without alumina xerogel modification.
  • Comparison of enzyme loading, retained activity, and diffusion effects on sensor performance.
  • Optimization of the immobilization protocol for enhanced enzymatic activity and stability.

Main Results:

  • Alumina xerogel modification of PDMS channels followed by enzyme adsorption yielded the best microfluidic biosensor performance.
  • Enzyme retained activity and diffusion within the microfluidic channel were more critical than enzyme loading.
  • The optimized microsensor accurately quantified ascorbic acid in human blood samples using minimal sample volumes.

Conclusions:

  • The developed alumina xerogel-modified PDMS microfluidic biosensor offers a fast, simple, and accurate method for ascorbic acid quantification.
  • This strategy enhances enzyme stability and sensor performance, suitable for low-volume clinical diagnostics.
  • The technology demonstrates significant potential for point-of-care health monitoring.