Dichrometer errors resulting from large signals or improper modulator phasing

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


A single-beam spectrometer equipped with a photoelastic modulator can be configured to measure a number of different parameters useful in characterizing chemical and biochemical materials including natural and magnetic circular dichroism, linear dichroism, natural and magnetic fluorescence-detected circular dichroism, and fluorescence polarization anisotropy as well as total absorption and fluorescence. The derivations of the mathematical expressions used to extract these parameters from ultraviolet, visible, and near-infrared light-induced electronic signals in a dichrometer assume that the dichroic signals are sufficiently small that certain mathematical approximations will not introduce significant errors. This article quantifies errors resulting from these assumptions as a function of the magnitude of the dichroic signals. In the case of linear dichroism, improper modulator programming can result in errors greater than those resulting from the assumption of small signal size, whereas for fluorescence polarization anisotropy, improper modulator phase alone gives incorrect results. Modulator phase can also impact the values of total absorbance recorded simultaneously with linear dichroism and total fluorescence.

Original languageEnglish (US)
Pages (from-to)706-717
Number of pages12
Issue number9
StatePublished - Sep 2012
Externally publishedYes


  • absorption
  • circular dichroism
  • ellipticity
  • fluorescence polarization anisotropy
  • linear dichroism
  • magnetic circular dichroism
  • photoelastic modulator

ASJC Scopus subject areas

  • Analytical Chemistry
  • Catalysis
  • Pharmacology
  • Drug Discovery
  • Spectroscopy
  • Organic Chemistry


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