Penetration studies of clotrimazole from semisolid formulation using step-scan FT-IR photoacoustic spectroscopy

Purpose. The aim of this study was to elucidate the potential use of the st ep-scan FT-IR photoacoustic spectroscopy (PAS) for the nondestructive deter mination of drug penetration into membranes. Methods. The penetration of clotrimazole from a 10% (w/w) suspension in Vas eline(R) into a dodecanol-collodion acceptor membrane was studied by three methods: the step-scan FT-IR PAS with a phase modulation, a multilayer memb rane system, and a modified libration model. Based on Fick's second law, th e diffusion coefficient of the drug in the membrane was derived by numerica l fitting of the experimental data. Results. The three methods applied provided almost the same diffusion coeff icient D = 2.2 10(-9) cm(2)/s for clotrimazole in the membrane. Because of the non-destructive mode of operation, the accuracy of results obtained by FT-IR PAS is much better than that attainable by other two methods. Conclusions. Step-scan FT-IR photoacoustic spectroscopy in conjunction with a phase modulation is useful to determine the penetration of drug through membranes. The fact that samples can be investigated without elaborate prep aration is an advantage of this spectroscopic technique.