Unperturbed dimensions of Carrageenans in different salt solutions.
Commercial samples of kappa-, iota-, and lambda-carrageenans were studied by means of Size Exclusion Chromatography with dual detection, i.e. employing a Refractive Index (concentration sensitive) and Multiangle Light Scattering (size sensitive) detectors. The eluent was water containing 0.1 M concentration of different ionic salts, namely LiCl, NaCl, KCl and NaI, with the exception of kappa-carrageenan that aggregates in presence of KCl. 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 degrees C and all the systems were above theta conditions with values of the q exponent of the scaling law ranging from 0.51 to 0.59. Extrapolation to unperturbed conditions provides values of the characteristic ratio C(N)=56+/-1 and 40+/-5 respectively for lambda- and iota-carrageenans regardless of the ionic salt employed. However, kappa-carrageenan gives C(N)=31, 35 and 59, respectively, in presence of LiCl, NaCl and NaI, which clearly indicates that this polymer behaves on a different way in presence of NaI than with the other two salts. A tentative explanation of this difference is provided.
Marcelo
Gema
G
Departamento de Química Física, Universidad de Alcalá, 28871-Alcalá de Henares, Madrid, Spain.
Saiz
Enrique
E
Tarazona
M Pilar
MP
D002236:Carbohydrate Conformation; D002351:Carrageenan / Q000737:chemistry*; D002850:Chromatography, Gel; D008094:Lithium / Q000737:chemistry; D008970:Molecular Weight; D009994:Osmolar Concentration; D011189:Potassium Chloride / Q000737:chemistry; D012031:Refractometry; D012492:Salts / Q000737:chemistry*; D012542:Scattering, Radiation; D012965:Sodium Chloride / Q000737:chemistry; D012974:Sodium Iodide / Q000737:chemistry; D012996:Solutions / Q000737:chemistry*
D012492:Salts; D012996:Solutions; D012965:Sodium Chloride; D011189:Potassium Chloride; D002351:Carrageenan; D008094:Lithium; D012974:Sodium Iodide