UV-Vis Spectrophotometer

A UV-Vis spectrophotometer is an analytical instrument based on the principle of UV-Vis spectrophotometry, which performs analysis by utilizing the absorption of radiation in the UV-Vis spectral region by substance molecules.

I. Working Principle

Molecules and atoms in a substance absorb the light energy of specific wavelengths in the incident light, which will cause molecular vibrational energy level transitions and electronic energy level transitions. Due to the differences in the molecules, atoms, and molecular spatial structures of different substances, their absorption of light energy also varies. Each substance has a unique and fixed absorption spectrum curve. According to the Lambert-Beer law, that is:

A = εbc

(where A is the absorbance, ε is the molar absorptivity, b is the thickness of the cuvette, and c is the concentration of the solution), qualitative and quantitative analysis of substances can be carried out by measuring the absorbance.

II. Basic Structure

Light source: Provides sufficient intensity and stable continuous spectrum. For example, a tungsten lamp is used in the visible light region, and a deuterium lamp is used in the ultraviolet region.

Monochromator: Decomposes the composite light emitted by the light source and separates the monochromatic light of the required wavelength from it. There are two types of dispersion elements: prisms and gratings.

Cuvette: Used to hold the test solution, generally made of quartz or glass. Quartz cuvettes are suitable for both the ultraviolet and visible light regions, while glass cuvettes are only suitable for the visible light region.

Detector: Detects the intensity of the transmitted light through photoelectric conversion elements, converting light signals into electrical signals. Common detectors include phototubes, photomultiplier tubes, etc.

Signal processor: Amplifies, processes, and displays the electrical signals output by the detector, and can present data in the form of absorbance, transmittance, etc.

III. Functional Features

Wavelength scanning: Can scan within a certain wavelength range to obtain the absorption spectrum of a substance, which is used for qualitative analysis and determining the maximum absorption wavelength.

Quantitative measurement: Conducts quantitative analysis of substances through methods such as the standard curve method, coefficient method, single-wavelength method, dual-wavelength method, and multi-wavelength method to determine the content of target substances in samples.

Kinetic testing: Tests the trend of sample concentration changing with time at a selected wavelength, which can be used to study chemical reaction kinetics, etc.

Multi-wavelength testing: Freely selects multiple wavelengths and automatically measures the absorbance and transmittance values of the sample at multiple wavelengths, which is used for the analysis of complex samples.

IV. Application Fields

Chemical analysis: Accurately determines the absorption spectra of organic compounds, inorganic compounds, and complexes at specific wavelengths, and conducts qualitative and quantitative analysis of compounds. For example, determining the active ingredients and purity of drugs in drug research and development.

Materials research: Studies the optical properties such as transmission, reflection, and absorption of materials to help understand the structure and characteristics of materials.

Biomedical analysis: Widely used in the determination of biomolecules such as proteins, nucleic acids, and enzymes. By measuring the absorption spectra of biological samples, it helps understand the structure and function of biomolecules and provides support for disease diagnosis and treatment.

Pharmaceutical industry: Used for quality control of drugs and determination of active ingredients of drugs to ensure that drugs meet safety and quality standards.

Environmental monitoring: Used for the detection of pollutants in water bodies, soil, and the atmosphere, to understand the types and concentrations of pollutants in samples, and provide data support for environmental protection.

Food industry: Used for the detection and quality control of food components, to understand the content and proportion of various components in food, and ensure food safety and quality.