Jw. Hofstraat et al., DETERMINATION OF FUNCTIONAL-GROUPS ON PARTICLE SURFACES BY FLUORESCENCE AND REFLECTION SPECTROSCOPY, Analytical chemistry, 66(24), 1994, pp. 4408-4415
The application of fluorescence and reflection (absorption) measuremen
ts for the determination of functional groups on surfaces has been inv
estigated. As an example, amino-functionalized silica surfaces have be
en studied that were labeled with the strongly colored fluorodinitrobe
nzene (FDNB) and the fluorescent Lucifer Yellow VS (LY). Both with ref
lection measurements and with fluorescence detection, amino groups cou
ld be quantified with concentrations as low as 10 mmol/kg, which is si
gnificantly lower than the detection limit attainable with conventiona
l titration approaches. At concentrations higher than 250 mmol/kg for
the FDNB-labeled samples and above 50 mmol/kg for the LY ones, calibra
tion curves become nonlinear. From the concentration dependence of the
LY fluorescence, information can be derived on the structure of the l
abeled surface. Finally, it is shown that the fluorescent particles ca
n also be examined individually by application of now cytometry. On th
e basis of now cytometric measurements, the concentration of functiona
l groups, homogeneity of functionalization, and particle size distribu
tions can be obtained.