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Related Concept Videos

Indicators02:39

Indicators

Certain organic substances change color in dilute solution when the hydronium ion concentration reaches a particular value. For example, phenolphthalein is a colorless substance in any aqueous solution with a hydronium ion concentration greater than 5.0 × 10−9 M (pH < 8.3). In more basic solutions where the hydronium ion concentration is less than 5.0 × 10−9 M (pH > 8.3), it is red or pink. Substances such as phenolphthalein, which can be used to determine the pH of a solution, are called...

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Fabrication of Three-dimensional Paper-based Microfluidic Devices for Immunoassays
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Use of multiple colorimetric indicators for paper-based microfluidic devices.

Wijitar Dungchai1, Orawon Chailapakul, Charles S Henry

  • 1Electrochemical Research Group, Department of Chemistry, Faculty of Science, Chulalongkorn University, Patumwan, Bangkok 10330, Thailand.

Analytica Chimica Acta
|August 4, 2010
PubMed
Summary

This study introduces a novel multi-indicator system for paper-based microfluidic devices (microPADs) to enhance visual discrimination of analyte concentrations. This approach improves assay accuracy by using multiple indicators per analyte for better color differentiation.

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Area of Science:

  • Analytical Chemistry
  • Biomedical Engineering
  • Materials Science

Background:

  • Traditional paper-based microfluidic devices (microPADs) often use a single dye system for analyte measurement, limiting accuracy.
  • Visual discrimination of analyte concentrations in existing microPADs can be challenging.

Purpose of the Study:

  • To develop and validate a multi-indicator system for single analytes on microPADs to improve visual discrimination and assay accuracy.
  • To enable simultaneous semi-quantitative measurement of multiple analytes with enhanced precision.

Main Methods:

  • Designed microPADs utilizing multiple indicators per analyte, based on hydrogen peroxide produced by oxidase enzymes.
  • Employed a mixture of specific indicators (4-aminoantipyrine, 3,5-dichloro-2-hydroxy-benzenesulfonic acid, o-dianisidine dihydrochloride, potassium iodide, acid black, acid yellow) for glucose, lactate, and uric acid detection.
  • Validated the system using control serum and urine samples.

Main Results:

  • Successfully quantified glucose (0.5-20 mM), lactate (1-25 mM), and uric acid (0.1-7 mM) in clinically relevant ranges.
  • Demonstrated improved accuracy compared to single-indicator systems through reader studies.
  • Showcased applicability for biological sample analysis.

Conclusions:

  • The multi-indicator approach significantly enhances visual discrimination and accuracy in microPAD-based assays.
  • This method offers a more precise and reliable semi-quantitative analysis of multiple analytes.
  • The developed microPADs show promise for point-of-care diagnostics and biological sample analysis.