Zirconyl chloride upon hydrolysis in water to form Zr(OH)(+) has been found
to react to form a fluorescent derivative with not only a ketose such as f
ructose but also a hexose such as glucose and the disaccharide sucrose. Whe
n reaction conditions such as a temperature of 99 degrees C and a time of 6
0 min are used, detection limits below 1 mu g/mL are possible. All three zi
rconyl-sugar derivatives show very similar absorbance and fluorescence spec
tra, indicating a common mechanism involving formation of an enediol which
can be complexed with ZrOH+ is likely. Because the reactivity order is gluc
ose < sucrose < fructose, the reaction can be made selective for fructose a
t a lower reaction temperature and rime such as 60 degrees C at 5 min. Beca
use interference from ascorbic acid and caffeine is also avoided, the fluor
escent determination of fructose in soft drink samples after simply a dilut
ion step is possible. We have also employed this reaction for flow injectio
n analysis (FIA) using a polystyrene-divinylbenzene-packed HPLC column as a
mixing device. Using a 0.01 M HClO4 with 1% zirconyl chloride carrier, we
obtained a linear calibration curve from 2 to 30 mu g/mL with a correlation
coefficient of 0.994. A detection limit less than 2 mu g/mL was possible.
A comparison of results for the FIA of soft drinks with the enzymatic metho
d involving fructose-5-dehydrogenase confirmed the FIA method was quite spe
cific for fructose. (C) 1999 Academic Press.