title: Performance characteristics of UV imaging instrumentation for diffusion, dissolution and release testing studies.
abstract: UV imaging is capable of providing spatially and temporally resolved absorbance measurements, which is highly beneficial in drug diffusion, dissolution and release testing studies. For optimal planning and design of experiments, knowledge about the capabilities and limitations of the imaging system is required. The aim of this study was to characterize the performance of two commercially available UV imaging systems, the D100 and SDI. Lidocaine crystals, lidocaine containing solutions, and gels were applied in the practical assessment of the UV imaging systems. Dissolution of lidocaine from single crystals into phosphate buffer and 0.5% (w/v) agarose hydrogel at pH 7.4 was investigated to shed light on the importance of density gradients under dissolution conditions in the absence of convective flow. In addition, the resolution of the UV imaging systems was assessed by the use of grids. Resolution was found to be better in the vertical direction than the horizontal direction, consistent with the illumination geometry. The collimating lens in the SDI imaging system was shown to provide more uniform light intensity across the UV imaging area and resulted in better resolution as compared to the D100 imaging system (a system without a lens). Under optimal conditions, the resolution was determined to be 12.5 and 16.7 line pairs per mm (lp/mm) corresponding to line widths of 40μm and 30μm in the horizontal and vertical direction, respectively. Overall, the performance of the UV imaging systems was shown mainly to depend on collimation of light, the light path, the positioning of the object relative to the line of 100μm fibres which forms the light source, and the distance of the object from the sensor surface.
authors: Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark.
authors: Sabrine S
authors: SS
authors: Jensen
authors: Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark.
authors: Henrik
authors: H
authors: Jensen
authors: Paraytec Limited, York House, Outgang Lane, Osbaldwick, York, YO19 5UP, United Kingdom.
authors: David M
authors: DM
authors: Goodall
authors: Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark. Electronic address: jesper.ostergaard@sund.ku.dk.
authors: Jesper
authors: J
authors: Østergaard
mesh_terms: D002626:Chemistry, Pharmaceutical / Q000379:methods*; D004058:Diffusion; D065546:Drug Liberation; D020100:Hydrogels / Q000032:analysis / Q000378:metabolism; D008012:Lidocaine / Q000032:analysis* / Q000378:metabolism; D012995:Solubility; D013056:Spectrophotometry, Ultraviolet / Q000379:methods
chemical_list: D020100:Hydrogels; D008012:Lidocaine
keywords: Dissolution imaging; Dissolution testing; Instrument performance; Spatial resolution; UV imaging