Chemistry Reference
In-Depth Information
(a)
7.0
PVP dispersion
6.0
5.0
4.0
3.0
Form I
2.0
1.0
HPMCAS dispersion
0.0
360
380
400
420
440
460
480
500
520
540
Emission wavelength (nm)
(b)
2.0
Form III
1.5
1.0
10% PVP
30% PVP
0.5
50% PVP
0.0
300
400
500
600
700
800
Emission wavelength (nm)
Figure 4.14.
(a) Fluorescence emission spectra obtained with excitation at 340 nm of crystalline
Form I of di
unisal, a 30% (w/w) amorphous dispersion of di
unisal in PVP, and a 30% (w/w)
amorphous dispersion of di
unisal in HPMCAS [79]. (b) Fluorescence emission spectra obtained
with excitation at 250nm of crystalline Form III of tenoxicam and dispersions of tenoxicam:
L
-
arginine containing 10, 30, and 50%(w/w) of PVP [25]. The vertical scale of the spectrumof Form III
has been reduced by half. Spectra were obtained using a Horiba Jobin Yvon Fluorolog 3
spectrometer. The sharp feature at 500 nmarises froma second harmonic of the Rayleigh line. The
excitation source was a 450W Xe lamp, the signal detector was a photomultiplier tube, and the
reference detector was a stabilized Si photodiode. Spectra were divided by the reference detector
signal. A1 nmslitwidthwas used for bothmonochromators for the di
unisalmaterials, and a 2 nm
slit width was used for the tenoxicam materials. Samples were packed in a solids holder covered
with a quartz plate and analyzed using a front-facing geometry at an angle of 30
°
.
Fluorescence microscopy has also been applied to amorphous and semicrystalline
solid dispersions designed for inhaled dosage forms [80]. In dosage forms where
uores-
cence differences between the drug and the polymer (or other carrier) are signi
cant,
fluorescence images can be used to assess the homogeneity of a dispersion in a very rapid
manner (requiring only the short time needed to sample the image at video rates).
Epi
fluorescence arrangements are often used for
fluorescence imaging wherein
uores-
cence emission is selected using a
filter that blocks wavelengths below 350 nm, while an
