Detectability interferences, LIFS

Improved LIF sensing discrimination power is required for sample matrices that contain multiple fluorophores with similar spectral emission properties or when background emission is problematic. Distinguishing among airborne bioagent hazards and common emissive interferants (albuminous, epithelium, and cellulous materials as well as aromatic hydrocarbons), is a prime example where higher selective detection is required. This can be achieved via the lifetime properties of each fluorophore, by an optode approach or both. 

The detectability limit for any given measurement is defined in terms of measurement uncertainty and for LIFS can be quite small. This limit, however, can be affected by interferences of various kinds and care must be taken in instrument design to avoid difficulties. The dynamic range for LIFS is generally controlled by radiative trapping effects. 

FIGURE 20.14 Detection of individual mitochondria sampled from a muscle tissue cross section. CE-LIF was performed on (1) cross sections that were labeled with 5 p.M NAO, (2) an unlabeled cross section, and (3) a solution of the free dye, NAO. The three traces show that mitochondria are detected when labeled with NAO and there is relatively little interference from other cellular components. The small spikes seen in (2) are likely caused by scattering of the excitation source or autofluorescence but only comprise 5% of the peaks detected in (1). Mitochondria were separated at -200 V/cm in a poly(AAP) coated capillary in 250 mM sucrose, 10 mM HEPES, pH 7.4. (Reprinted from Ahmadzadeh, H. et al.. Anal. Chem., 76, 315, 2004. Copyright 2006. With permission American Chemical Society.)... 

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