Abstract:

A novel method was presented for the determination of chitosan based on its quenching effect on the fluorescence
of Cibacron brilliant red 3B-A in B-R buffer solutions. Under the condition of λEx/λEm = 285 nm/341 nm, the degree of
fluorescence quenching of Cibacron brilliant red 3B-A was linearly proportional to the concentration of chitosan added in
the range of 0.050–2.00 μg/mL and a linear equation was fitted as follows: ΔF = 68.78c + 2.648 (c: μg/mL) (R2 = 0.999 2).
The detection limit of the fluorescence quenching method was 0.039 μg/mL. Moreover, chitosan-Cibacron brilliant red 3B-A
ion-association complex showed a significant resonance Rayleigh scattering peak at 342 nm, and the intensity of resonance
Rayleigh scattering was directly proportional to the concentration of chitosan. In the range of 0.050–6.00 μg/mL, linearity
equation of chitosan-Cibacron brilliant red 3B-A system was ΔI = 681.31c+114.95 (c: μg/mL) (R2 = 0.999 1) with detection
limit of 0.033 μg/mL. Therefore, two methods (fluorescence quenching and resonance Rayleigh scattering) by using
Cibacron brilliant red 3B-A as a probe have been established and validated for rapid determination of chitosan and chitosan
capsules. Meanwhile, the effect of the molecular weight of chitosan on its accurate determination was also investigated.
These two methods were applied in analysis of two real chitosan samples, and there was no significant difference in the
results from the two methods with acceptable recoveries.

Key words: chitosan, Cibacron brilliant red 3B-A, fluorescence quenching, resonance Rayleigh scattering