Characterization of hydroxypropylmethylcellulose films using microwave non-destructive testing technique

The applicability of microwave non-destructive testing (NDT) technique in characterization of matrix property of pharmaceutical films was investigated. Hydroxypropylmethylcellulose and loratadine were selected as model matrix polymer and drug, respectively. Both blank and drug loaded hydroxypropylmethylcellulose films were prepared using the solvent-evaporation method and were conditioned at the relative humidity of 25, 50 and 75% prior to physicochemical characterization using microwave NDT technique as well as ultraviolet spectrophotometry, differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR) techniques. The results indicated that blank hydroxypropylmethylcellulose film exhibited a greater propensity of polymer–polymer interaction at the O–H and C–H domains of the polymer chains upon conditioned at a lower level of relative humidity. In the case of loratadine loaded films, a greater propensity of polymer–polymer and/or drug–polymer interaction via the O–H moiety was mediated in samples conditioned at the lower level of relative humidity, and via the C–H moiety when 50% relative humidity was selected as the condition for sample storage. Apparently, the absorption and transmission characteristics of both blank and drug loaded films for microwave varied with the state of polymer–polymer and/or drug–polymer interaction involving the O–H and C–H moieties. The measurement of microwave NDT test at 8 GHz was sensitive to the chemical environment involving O–H moiety while it was greatly governed by the C–H moiety in test conducted at a higher frequency band of microwave. Similar observation was obtained with respect to the profiles of microwave NDT measurements against the state of polymer–polymer and/or drug–polymer interaction of hydroxypropylmethylcellulose films containing chlorpheniramine maleate. The microwave NDT measurement is potentially suitable for use as an apparent indicator of the state of polymer–polymer and drug–polymer interaction of the matrix.