P. Solich et al., SEQUENTIAL FLOW-INJECTION SPECTROFLUOROMETRIC DETERMINATION OF COUMARINS USING A DOUBLE-INJECTION SINGLE-LINE SYSTEM, Analytica chimica acta, 308(1-3), 1995, pp. 293-298
A simple and rapid flow-injection (FI) technique with spectrofluorimet
ric detection is presented for the sequential determination of two mod
el compounds: 6-methoxy-7-hydroxycoumarin (scopoletine) and 7-hydroxyc
oumarin (umbelliferone) without prior separation. A double-injection v
alve with a single-line now-injection system is used for the simultane
ous injection of a sample and a phosphate buffer solution in aqueous 5
0% (v/v) ethanol in order to measure the fluorescence signal of the an
alytes successively at pH 6.0 and 11.0. The optimum excitation and em
ission wavelengths are 350 nm and greater than or equal to 418 nm, res
pectively. Using a calculation method based on differential fluorimetr
y it is possible to determine greater than or equal to 1 mu mol l(-1)
of scopoletine in the presence of less than or equal to 9-fold molar e
xcess of umbelliferone or 1 mu mol l(-1) of umbelliferone in the prese
nce of less than or equal to 23-fold molar excess of scopoletine. This
technique can be used for sequential determination of various other f
luorescent compounds (exhibiting pH-dependent excitation spectra) in t
wo-component mixtures; it allows for a quick interchange of reagents w
ithin a single-line FIA system and the reagent consumption is decrease
d substantially.