What is the principle of colorimetric determination

What is the principle of colorimetric determination?

Colorimetry is a quantitative analytical technique based on the light absorption properties of substances. Its core principles can be summarized as follows:

‌Relationship Between Light and Color‌

Light, as an electromagnetic wave, exhibits wave-particle duality, with different wavelengths corresponding to distinct colors (e.g., red, green, blue).

Substances absorb specific wavelengths of light, while reflecting or transmitting the rest, resulting in the observed color of the solution.

‌Quantitative Analysis Basis‌

‌Lambert-Beer Law‌: The absorbance (A) of a solution is directly proportional to the concentration (c) of the substance and the optical path length (l), expressed as A=k⋅c⋅lA=k⋅c⋅l, where kk is the absorptivity coefficient.

By measuring absorbance, the concentration of the analyte can be determined.

‌Color Development Reaction and Condition Control‌

‌Chromogenic Agents‌: React with the analyte to form colored compounds (e.g., complexes, associations).

‌Reaction Conditions‌: Temperature, pH, and development time must be controlled to ensure color stability.

‌Key Experimental Considerations‌

‌Wavelength Selection‌: Measurements are performed at the maximum absorption wavelength to enhance sensitivity.

‌Standard Curve Method‌: A calibration curve is established using standard solutions of known concentrations to calculate unknown sample concentrations.

‌Applications and Limitations‌

‌Applications‌: Widely used in environmental monitoring (e.g., heavy metals), food analysis (e.g., reducing sugars), and medical testing.

‌Limitations‌: Affected by the specificity of the color reaction and interfering substances, requiring stringent optimization of experimental conditions.

SH121 degassing vibration instrument

Applicable standard:GB/T17625 DL429.4 standard, used for oil dissolved gas component content determination method (gas chromatography) oscillation degassing;

Oscillating degassing of water-soluble acids in oil (colorimetric method) can also be used for constant temperature and timing oscillation in other physical and chemical experiments.