Characterization of hydroxypropylmethylcellulose (HPMC) using comprehensive two-dimensional liquid chromatography

Various hydroxyl-propylmethylcellulose (HPMC) polymers were characterized according to size and compositional distributions (percentage of methoxyl and hydroxyl-propoxyl substitution) by means of comprehensive two-dimensional liquid chromatography (LC × LC) using reversed-phase (RP) liquid chromatography in the first dimension and aqueous size-exclusion chromatography (aq-SEC) in the second dimension. RP separation was carried out in gradient-elution mode applying 0.05% TFA in water and 1-propanol, while 0.05% TFA in water was used as mobile phase in aqueous SEC. A two-position ten-port switching valve equipped with two storage loops was used to realize LC × LC. Detection of HPMC was accomplished by charged-aerosol detection (CAD). Data processing to visualize chromatograms was carried out using Matlab software. The significant influence of the LC × LC temperature on (the retention of) HPMC was studied using a column oven which allowed accurate temperature control. Due to the phenomenon of thermal gelation, which is a result of methyl and hydroxypropyl substitution of anhydroglucose units from the cellulose backbone, we were able to obtain additional, specific information on compositional characteristics of various HPMC samples. As the retention behaviour of gelated and non-gelated polymer proved to be different, the fraction of the polymer that is gelated in the chromatographic column could be monitored at different temperatures. Moreover, the temperature at which half of the polymer is gelated could be correlated with the cloud-point temperature. As a result, differences in inherent cloud points of modified cellulose can be used as a further distinguishing property in "temperature-responsive" LC × LC

Birch pollen-related food allergy: clinical aspects and the role of allergen-specific IgE and IgG4 antibodies

Birch pollen-related food allergy is highly prevalent and often perennial. High food allergen-specific IgG(4)/IgE ratios seem associated with food tolerance, potentially because specific IgG(4) blocks IgE binding to food allergens. Thus, the presence of food allergen-specific IgG(4) antibodies is no diagnostic marker for birch pollen-related food allergy

Foaming behavior of water-soluble cellulose derivatives: hydroxypropyl methylcellulose and ethyl hydroxyethyl cellulose

Hydroxypropyl methylcellulose and ethyl hydroxyethyl cellulose could be interesting candidates for production of lightweight, foamed packaging material originating from non-fossil, renewable resources. The foaming ability of nine different grades of the two cellulose derivatives, using water as the blowing agent, was investigated using a hot-mold process. The foaming process was studied by evaluating the water loss during the heating, both in a real-time experiment and by thermal gravimetric analysis. Further, the development of the rheological properties of the derivative-water mixtures during a simulated foaming process was assessed using dynamical mechanical thermal analysis and viscosity measurements. Five of the studied derivatives showed promising properties for hot-mold foaming and the final foams were characterized with regard to their apparent density. It was concluded that the foamability of these systems seems to require a rather careful tailoring of the viscoelastic properties in relation to the water content in order to ensure that a network structure is built up and expanded during the water evaporation