第十一章抗生素类药物分析ppt.ppt.ppt

The Analysis of Steroid Hormone Drugs Conjugated bonding systems: 1.α,β-unsaturated ketone group 2. Steroids with aromatic ring A Infrared spectrophotometry Principles : Electromagnetic radiation ranging between 500 cm-1 and 4000 cm-1(2500 and 20000 nm)is passed through a sample and is absorbed by the bonds of the molecules in the sample causing them to stretch or bend. The wavelength of the radiation absorbed is characteristic of the bond absorbing it. The intensity with which a bond absorbs radiation depends on its dipole moment. The order of intensity of absorption is: C–O C– Cl C –N C– C–OH C–C–H The intensity depends on the relative electronegativity of the atoms involved in the bond. The intensity of the stretching of carbon-carbon double bonds is increased when they are conjugated to a polar double bond. The order of intensity is : C=C–C=O C=C–C=C C=C–C– Two types of instrument are commonly used for obtaining IR spectra: dispersive instruments which use a monochromator to select each wavenumber in turn in order to monitor its intensity after the radiation has passed through the sample and Fourier transform instruments that use an interferometer. A qualitative fingerprint check for the identity of raw material used in manufacture and for identifying drugs. Used in synthetic chemistry as a preliminary check for compound identity particularly for the presence or absence of a carbonyl group, which is difficult to check by any other method. Can be used to characterize samples in the solid and semi-solid states such as creams and tablets. Used as a fingerprint test for films, coatings and packaging plastics. Can be used to detect polymorphs of drugs (polymorphs are different crystal forms of a molecule that have different physical properties such as solubility and melting point which may be important in the manufacturing process)