horiba FluoroMax-3, Руководство по эксплуатации

Страница: 71 / 220

FluoroMax-3 v. 3.1 (3 Mar 2006) Optimizing Data
5-5
Highly opaque samples
Highly concentrated and opaque liquids often have problems with self-absorption or
complete attenuation of the beam. Intensity measurements with the excitation beam at
90° to the emission beam may not be
reproducible or detectable, and the
excitation or emission spectra may
appear distorted. Try front-face detec-
tion: the excitation light is focused to
the front surface of the sample, and
fluorescence emission is collected
from this region at an angle that
minimizes reflected and scattered
light. With front-face detection, set
the front face of the sample at 30° or
60° to the excitation beam.
An example at right shows the
difference between detection at
right-angles versus front-face.
Fluoresce
nce
int
ensity (co
unts
s
–1
)
Wavelength (nm)
Right-angle
detection
Front-face detection
Comparison of fluorescence emission signal
from sickle-cell hemoglobin using right-angle
versus front-face detection. The
β -37 trypto-
phan is primarily responsible for this fluores-
cence.