UV/Vis Spectrophotometry and UV Imaging

Abstract

The present chapter describes typical instrumentation and principles of UV/Visible spectrophotometry and UV imaging measurements. The absorption of light as a function of wavelength depends on the structural properties of molecules as well as the solvent in which they are dissolved, including solvent polarity, pH, temperature and the presence of complexing agents. The absorbance measured for an analyte can be linearly related to concentration through Lambert-Beer’s law. Instrument related and chemical parameters causing deviations from Lambert-Beer’s law are discussed in relation to quantitative applications of spectrophotometry. Practical issues to be considered in quantitative analysis are briefly covered, as is the use of UV/Vis spectrophotometry for compound identification and physicochemical profiling, including pKa and kinetic studies. Recent UV imaging equipment facilitating spatially (2D) resolved absorbance measurements in real-time is described and selected applications in drug dissolution and release testing reviewed.