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. Author manuscript; available in PMC: 2009 Jul 16.
Published in final edited form as: Methods Cell Biol. 2008;84:143–179. doi: 10.1016/S0091-679X(07)84006-4

Table 2.

Strengths and weaknesses of optical systems.

Characteristic Absorbance Interference Fluorescence
Radial resolutiona 20–50 10 20–50
Scan timeb 60–300 1–10 60–90
When to usec

  • Selectivity

  • Sensitivity

  • Non-dialyzable components

  • Solvent absorbs light

  • Solute does not absorb light

  • Accuracy needed

  • Short solution columns

  • Selectivity

  • Sensitivity

  • Small sample quantities

  • Non-dialyzable components
a

Approximate spacing (in microns) between data points such that each measurement can be considered an independent estimate of the concentration.

b

The minimum time (in seconds) required to complete one radial scan. The time listed for the fluorescence system is the time needed to scan all of the samples (Laue, 2006).

c

Selectivity refers to the absorbance and fluorescence systems’ ability to discriminate between components based on their spectral properties. Since the Rayleigh interference optics relies on differences in the refractive index of the sample and reference solutions, it provides no selectivity. On the other hand, the interference optics do not require that samples have an appropriate chromophore, and may be used so long as the solvent does not absorb light at ~670 nm. The interference optics require that samples are at dialysis equilibrium with the reference solution; hence, they should not be used for samples containing non-dialyzable components (e.g. detergents). The greater radial resolution of the interference optics allows them to be used with the eight-channel “short column” centerpieces (Yphantis, 1960).