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Microcrystalline cellulose absorption

Inspection of the data in Table II reveals a bathochromic shift of the of the triplet-triplet absorption with increasing solvent polarity, with a further bathochromic shift when the compound is adsorbed on microcrystalline cellulose. No phosphorescence emission in solution is seen from this compound at room temperature, indicating that the radiative lifetime of this triplet state is long. This is consistent with the lowest energy excited triplet state having predominantly (n, n ) character. The shape of the triplet-triplet absorption spectrum also suggests that this is the case(20). [Pg.93]

The MSC has been shown to work well in several empirical studies [9, 10], which showed an improvement in the performance of multivariate calibrations and a reduction in the number of factors in PCA. For example, NIR reflectance spectra of 20 powder samples of microcrystalline cellulose are shown in Figure 4.8a. Due to differences in particles size from sample to sample, there are significantly different baseline offsets. The same spectra are shown in Figure 4.8b after multiplicative scatter correction. The different baseline offsets observed in Figure 4.8a are so large that they mask important differences in the water content of these samples. These differences are revealed in the water absorption band at 1940 nm after the baseline offsets have been removed by MSC. [Pg.84]

Rhinocort is a commercially available mucoadhesive transnasal powder preparation of beclomethasone dipropionate with hydroxypropyl cellulose (HPC) as a gelforming drug carrier developed by Suzuki and Makino [49], The HPC has been shown to promote the absorption of low-molecular-weight drugs, but it was not that effective with a peptide drug salmon calcitonin. Microcrystalline cellulose has been shown to be effective for the promotion of absorption of calcitonin in humans, producing about 10% bioavailability with rapid absorption onset [49], In the study... [Pg.656]

Powder Leuprolide, calcitonin, FITC-dextran Hydroxypropyl cellulose, microcrystalline cellulose In rabbits Enhanced absorption 49... [Pg.673]

Powder Dry blending Octreotide Dextran, microcrystalline cellulose, semicrystalline cellulose, hydoxyethyl starch, microcrystalline chitosan, pectin, alginic acid In rats Correlation between carrier calcium binding properties and their potential as nasal absorption enhancers for peptides 40... [Pg.673]

Oechslein, Fricker, and Kissel " studied various powder formulations of mucoadhesive polymers for their efficacy to increase the nasal absorption of octreotide in rats. Although chitosan showed the highest water uptake (chitosan > microcrystalline cellulose > semicrystalline cellulose > pectin = hydroxyethyl starch = alginic acid = Sephadex G25), the highest peptide drug bioavailability was found after coadministration of alginic acid and Sephadex G25 powders (4.1 and 5.56%, respectively). The authors concluded that the calcium-binding properties of the polymers used correlated better with the increased octreotide bioavailability. [Pg.1175]

Wilkinson, F., Leicester, P.A., Ferreira, L.F.V., and Freires, V.M.M.R. (1991) Photochemistry on surfaces triplet-triplet energy transfer on microcrystalline cellulose studied by diffuse reflectance transient absorption and emission spectroscopy, Photochem. Photobiol., 54, 599-608. [Pg.330]

Ground-state absorption spectrum for powdered microcrystalline cellulose is also shown in Figure 1. It exhibits R values quite close to unity for visible (Vis) and near infrared (NIR) spectral regions and shows a significative absorption in the ultraviolet (UV). Silica and silicalite also have a reflectance close to unity in the Vis and NIR regions and differ from cellulose by the fact that UV absorption is smaller. In the case of silicas with different porosity, but with the same particle size, significant variations of the reflectance were detected [7]. [Pg.270]

Fig. 39. Remission function values of rhodamine B isothiocyanate onto microcrystalline cellulose, normalized to the maximum of the absorption of the dye. Curve (1) is a T3 pe II sample with 0.035 /i.mol/g. Curve (2) is a Type I sample 0.030 /tmol/g . Curve (3) is... Fig. 39. Remission function values of rhodamine B isothiocyanate onto microcrystalline cellulose, normalized to the maximum of the absorption of the dye. Curve (1) is a T3 pe II sample with 0.035 /i.mol/g. Curve (2) is a Type I sample 0.030 /tmol/g . Curve (3) is...
UV/Vis ground-state diffuse-reflectance absorption and luminescence studies showed in most cases a huge increase of fluorescence emission quantum yield when compared to solution studies for several dyes, when they are entrapped into microcrystalline cellulose, due to the reduction of mobility and formation of planar and emissive conformers and to the amount and type of aggregates which are formed. The emission depends on the solvent used to adsorb the probes. In some... [Pg.345]

ENISO 14852-1999 Aqueous Not exceeding six months Preferably between 20 and 25< Aniline, microcrystalline cellulose powder, ashless cellulose filters or poly-(3-hydroxybutyrate as positive reference CO2 evolution (CO2 or DIG analyser or apparatus for titrimetric determination after complete absorption in a basic solution)... [Pg.122]

Owing to the hydrophilic nature of chitosan, this compound has been used directly as compressible diluent in tablets. Chitosan has excellent properties as excipient for direct compression of tablets, where the addition of 50% chitosan results in rapid disintegration. The DD determines the extent of moisture absorption. Also, in immediate-release formulations, e.g., as a disintegrant in small amounts, where it has been found to have effects similar to or better than those of microcrystalline cellulose. Chitosan at concentrations higher than 5% is a better disintegrate than corn starch and microcrystalline cellulose, depending on chitosan crystallinity, DD, MW and particle size [61]. In addition, it has excellent tablet binder properties compared to other excipients [62]. [Pg.282]

Schmidt and coworkers have carried out determinations of the surface acidity of pharmaceutical excipients and used a variety of absorption indicators to span the ranges of observed the acid strengths. In one study, the surface acidity of microcrystalline cellulose and dicalcium phosphate anhydrate was evaluated using thymol blue, bromcresol green, bromcresol purple, and phenol red as the absorption indicators. " Using the pH dependence of dye absorbance published in the paper, it was concluded that Hq was approximately 1.0 for dicalcium phosphate anhydrate, and approximately 4.0 for microcrystalline cellulose. [Pg.16]

Diffuse reflectance laser flash photolysis and laser-induced luminescence, hoth in time-resolved mode or ground-state absorption spectroscopy in the diffuse reflectance mode, are important techniques that have been used by several research groups to study opaque and crystalline systems [1—8]. These solid-state photochemical methods have been applied by us to study several organic compounds adsorbed onto different hosts such as microcrystalline cellulose [7, 8], p-tertbutylcalix[n]arenes (n = 4, 6, and 8) and their derivatives [10—12], silicalite, cyclodextrins [7, 12, 13], and silica [l4j. [Pg.216]

Ground-state diffuse reflectance absorption spectra for BZP adsorbed onto C12-1500, C12-1700, and microcrystalline cellulose [7] were obtained with the use of... [Pg.219]

A lifetime distributions analysis provided important information and revealed an important quenching effect in the case of adsorption from water, comparable to the case of adsorption onto microcrystalline cellulose [7], due to the more efficient hydrogen abstraction reaction from the glycoside rings of cellulose when compared with hydrogen abstraction from the alkyl chains of the modified celluloses. Diffuse reflectance transient absorption spectra revealed the presence of the triplet state of BZP in all supports under study, and also of the diphenylketyl radical and BZP OH radicals. [Pg.223]


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See also in sourсe #XX -- [ Pg.38 ]




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