Title of article :
Determination of molecular parameters of hydroxyethyl and hydroxypropyl celluloses by chromatography with dual detection
Author/Authors :
Marcelo ، نويسنده , , Gema and Saiz، نويسنده , , Enrique and Tarazona، نويسنده , , M. Pilar، نويسنده ,
Issue Information :
روزنامه با شماره پیاپی سال 2007
Pages :
7
From page :
45
To page :
51
Abstract :
Hydroxyethylcellulose (HEC) and hydroxypropylcellulose (HPC) were studied by means of size exclusion chromatography with dual detection, i.e. employing simultaneously a refractive index (concentration sensitive) and a multiangle light scattering (molecular weight sensitive) detectors. The eluent was water and water solutions containing different concentrations of ionic salts. Molecular weight distributions and averages, coefficients of the scaling law of molecular dimensions and unperturbed dimensions were thus obtained from a single polydisperse sample of each polymer. Measurements were performed at 25 °C and the anomalous chromatographic behaviour, due to a combination of ion and size exclusion mechanisms, found when using pure water as eluent is transformed into a size exclusion mechanism by the addition of ionic salts. However, the two polymers behave on a different way in presence of salts. Thus, HEC, which is of low degree of substitution (DS), is close to theta conditions in the aqueous salt solutions (i.e. the q exponent of the scaling law has a value close to 0.5), whereas in the case of HPC the addition of salt improves the quality of the solvent up to a value of q around 0.6. Unperturbed dimensions are also calculated for both celluloses.
Keywords :
Size exclusion chromatography , Light Scattering , Unperturbed dimensions , Scaling laws , Solution properties , Hydroxypropylcellulose (HPC) , Hydroxyethylcellulose (HEC)
Journal title :
Journal of Chromatography A
Serial Year :
2007
Journal title :
Journal of Chromatography A
Record number :
1522483
Link To Document :
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