山东置子大家 Analytical chemistry Chapter 8 visible spectrophotometry Learning objectives >To introduce the basic principles and the measurement methods of spectrophotometry >To understand the Beer's law,to deeply understand the relationship between absorbance,transmittance and absorptivity; >To understand the color-forming reactions,be familiar with the procedure of establishment of the working condition; >To present modern instrumentation for obtain spectra from solids,liquids and gases
Analytical chemistry Chapter 8 visible spectrophotometry Learning objectives ➢To introduce the basic principles and the measurement methods of spectrophotometry ➢To understand the Beer’s law, to deeply understand the relationship between absorbance, transmittance and absorptivity; ➢To understand the color-forming reactions, be familiar with the procedure of establishment of the working condition; ➢To present modern instrumentation for obtaining molecular spectra from solids, liquids and gases
归东理工大军 Analytical chemistry 8.1 Introduction Molecular systems can be identified by their characteristic energy term schemes consists of discrete electronic,vibrational and rotational states.At room temperature the substances are mainly in their ground states. After absorbing appropriate types of electromagnetic radiation,transitions from ground states to excited states will be induced in the molecules of the sample. These excited states usually decay to their original ground states within 108s,with by emitting the previously absorbed radiation in all directions with the same or a lower frequency,or by radiationless 2025/4/3 relaxation
Analytical chemistry 2025/4/3 2 8.1 Introduction Molecular systems can be identified by their characteristic energy term schemes consists of discrete electronic, vibrational and rotational states. At room temperature the substances are mainly in their ground states. After absorbing appropriate types of electromagnetic radiation, transitions from ground states to excited states will be induced in the molecules of the sample. These excited states usually decay to their original ground states within 10-8 s, with by emitting the previously absorbed radiation in all directions with the same or a lower frequency, or by radiationless relaxation
G归东2大子 Analytical chemistry Molecular spectra can be obtained in the absorption or emission mode from samples.They are images of the interactions mentioned above and contain analytical information about the sample. Molecular absorption spectroscopy is used primarily for quantitative analysis and is probably more extensively applied in chemical and clinical laboratories throughout the world than any other single method. 2025/4/3 3
Analytical chemistry 2025/4/3 3 Molecular spectra can be obtained in the absorption or emission mode from samples. They are images of the interactions mentioned above and contain analytical information about the sample. Molecular absorption spectroscopy is used primarily for quantitative analysis and is probably more extensively applied in chemical and clinical laboratories throughout the world than any other single method
G归东理工大图 Analytical chemistry 8.2 Absorption spectroscopy 1.Introduction for radiant energy (1).Spectral regions The spectrum of radiant energy is conveniently broken down into several regions,as shown in the figure below 210-2nm10nm102nm104nm0.1cm10cm103cm105cm 2 X ultraviolet infrared microwave Radio ray ray waves 2025/4/3 Visible
Analytical chemistry 2025/4/3 4 8.2 Absorption spectroscopy 1. Introduction for radiant energy (1). Spectral regions The spectrum of radiant energy is conveniently broken down into several regions, as shown in the figure below ray X ray ultraviolet infrared microwave Radio waves 10-2 nm 10 nm 102 nm 104 nm 0.1 cm 10cm 103 cm 105 cm Visible
G山东理王大 Analytical chemistry The limits of these regions are determined by the practical limitations of appropriate experimental methods of production and detection of radiation. The differentiation of spectral regions has additional significance for the chemist in that the interactions of the radiations with chemical systems follow different mechanisms and provide different kinds of information. (2).Nature of light An investigation into the properties of electromagnetic energy reveals an essential duality in our understanding of the nature of light. 2025/4/3 5
Analytical chemistry 2025/4/3 5 The limits of these regions are determined by the practical limitations of appropriate experimental methods of production and detection of radiation. The differentiation of spectral regions has additional significance for the chemist in that the interactions of the radiations with chemical systems follow different mechanisms and provide different kinds of information. (2). Nature of light An investigation into the properties of electromagnetic energy reveals an essential duality in our understanding of the nature of light