Background:
Determination of a reducing substance based on the reaction between Ce(IV) and a reducing
substance and fluorescence detection of Ce(III) generated has been reported as a selective and sensitive method. However,
this method could not be applied to the determination of alcohol due to the low reaction rate of alcohol and Ce(IV).
Objective:
We found that thiosulfate catalytically enhanced reaction of alcohols (such as, methanol, ethanol, and propanol)
and Ce(IV). Utilizing this effect, we developed a new method for the determination of alcohols.
Results:
In the presence of thiosulfate, an increase in fluorescence intensity was detected by injecting alcohol at
concentrations of several millimolar, whereas it was not observed even at the concentration of 10% v/v (2 M for ethanol) in
the absence of thiosulfate. The optimum detection conditions were determined to be 4.0 mM Ce(IV) sulfate and 0.50 mM
thiosulfate, and the detection limit (S/N = 3) of ethanol under these conditions was 1 mM. In the calibration curves, changes
in the slope were observed when the alcohol concentrations were approximately 10–25 mM. Using a thiosulfate solution
containing ethanol as the reaction solution, a calibration curve without any change in slope was obtained, although the
concentration of ethanol at the detection limit increased. The alcohols in the liquor and fuel were successfully analyzed
using the proposed detection method as a postcolumn reaction.
Conclusion:
This new alcohol detection method using a versatile fluorescence detector can be applied to the postcolumn
reaction of HPLC omitting need of time-consuming pretreatment processes.
