The UV visible spectrophotometer achieves quantitative and qualitative analysis by measuring the absorption characteristics of substances in the UV to visible light range (190-900nm). The core measurement mode and corresponding scenarios are as follows:
1. Transmission mode (T%)
Principle: Measure the transmittance ratio of the sample to the incident light using the formula
T%=I0I × 100%, where I is the transmitted light intensity and I0 is the incident light intensity.
Applicable scenarios:
Solution concentration determination: By drawing a standard curve (such as the Beer Lambert law), the solute concentration in the solution can be quickly calculated, such as in the detection of heavy metal ions (such as lead and cadmium) in environmental monitoring.
Analysis of Film Thickness and Uniformity: Measure the transmittance of optical films (such as filters and coatings), evaluate their thickness and surface uniformity.
Research on material transparency: Analyze the transparency of materials such as glass and plastic, and optimize the design of optical devices.
2. Absorption mode (A)
Principle: The absorbance and transmittance have a negative logarithmic relationship (A=- log10T), which directly reflects the sample's ability to absorb light.
Applicable scenarios:
Quantitative analysis: Based on the Beer Lambert law (A=ε bc), quantitatively determine the concentrations of nucleic acids, proteins, drug components, etc. in a solution, such as DNA purity detection (A260/A280 ratio).
Chemical reaction kinetics research: By monitoring real-time changes in absorbance, analyzing kinetic parameters such as reaction rate constants and equilibrium constants.
Water quality testing: Determine the concentration of pollutants such as nitrate and nitrite in water bodies, in compliance with environmental standards (such as GB5749-2022).
3. Spectral Scan Mode
Principle: Continuously scan the absorption spectrum of the sample in the UV visible band to obtain the position and intensity of characteristic absorption peaks.
Applicable scenarios:
Qualitative identification of substances: Identifying unknown compound structures, such as drug intermediates and organic dye analysis, by comparing standard spectral libraries (such as NIST databases).
Purity assessment: detecting impurity absorption peaks in the sample to evaluate the purity level of chemical reagents or drugs.
Research on Complex Composition: Analyze the structure of complexes formed between metal ions and ligands, such as the characteristic absorption peak (510nm) of iron ortho phenanthrene complexes.
4. Kinetic Mode
Principle: Continuously monitor the absorbance over time at a fixed wavelength and calculate the reaction rate.
Applicable scenarios:
Enzyme activity measurement: By monitoring the absorbance changes of products or substrates in enzyme catalyzed reactions, the enzyme activity unit (such as U/mL) is calculated.
Research on photocatalytic reactions: Analyze the efficiency of photocatalysts in degrading organic pollutants under light irradiation and optimize reaction conditions.
Drug release research: simulate the internal environment and monitor the drug release rate from carriers (such as nanoparticles, hydrogels).
5. Multi wavelength mode
Principle: Simultaneously measuring absorbance at multiple specific wavelengths to improve analysis efficiency.
Applicable scenarios:
Multi component mixture analysis: By selecting the characteristic absorption wavelengths of each component (such as using dual wavelength method to determine hemoglobin concentration), simultaneous quantification can be achieved.
Complex system research: Analyze the synergistic effects of multiple components in biological samples such as blood and urine, such as combined detection of liver function indicators (total bilirubin, direct bilirubin).
summary
The measurement mode of UV visible spectrophotometer covers a wide range of needs from simple concentration determination to complex kinetic research. Transmittance and absorbance modes are suitable for routine quantitative analysis; Spectral scanning mode is used for qualitative identification; Dynamics mode focuses on the reaction process; The multi wavelength mode improves the efficiency of multi-component analysis. Selecting appropriate modes based on experimental objectives can significantly improve analysis accuracy and data reliability.