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Related Experiment Videos

Self-referencing intensity measurements based on square-wave gated phase-modulation fluorimetry.

H M Rowe1, Sing Po Chan, J N Demas

  • 1Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904-4319, USA.

Applied Spectroscopy
|December 9, 2003
PubMed
Summary

A new gated phase-modulation (GPM) fluorimetry method offers self-referenced intensity measurements. This technique eliminates fluctuations in excitation source intensity, enabling accurate analyte concentration determination.

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Area of Science:

  • Analytical Chemistry
  • Spectroscopy
  • Fluorescence Techniques

Background:

  • Conventional ratiometric measurements often require dual wavelengths, increasing complexity.
  • Intensity fluctuations from excitation sources can compromise measurement accuracy.
  • Self-referenced methods are desirable for robust analytical measurements.

Purpose of the Study:

  • To adapt square-wave gated phase-modulation (GPM) fluorimetry for self-referenced intensity measurements.
  • To demonstrate the effectiveness and advantages of the adapted GPM scheme.
  • To quantify analyte concentration by eliminating excitation source intensity variations.

Main Methods:

  • Utilized square-wave excitation, gated detection, a reference emitter, and a sensor molecule.

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  • Employed a ratiometric approach comparing sensor emission to reference emission.
  • Applied digital methods with Na3[Tb(dpa)3] as a long-lived reference and fluorescein as a short-lived sensor for pH measurement.

    • Main Results:

    • The adapted GPM scheme provides self-referenced intensity measurements, eliminating the need for dual wavelengths.
    • Measurements showed high accuracy, with apparent pKa values agreeing within 2% compared to conventional methods.
    • The method demonstrated excellent insensitivity to excitation source intensity fluctuations (less than 3% signal change for an 8-fold intensity change).

    Conclusions:

    • The adapted GPM fluorimetry offers a robust and accurate method for self-referenced intensity measurements.
    • This technique simplifies measurements by avoiding dual excitation or emission wavelengths.
    • The GPM method's insensitivity to source intensity fluctuations makes it highly reliable for quantitative analysis.