Spectral analysis, total nitrogen, total phosphorus, ammonia nitrogen, formaldehyde testing, visible spectrophotometer

Spectral analysis, total nitrogen, total phosphorus, ammonia nitrogen, formaldehyde testing, visible spectrophotometer

Based onLambert Beer Law：

$$A=\epsilon \cdot c\cdot l$$

among which

• $A$A: Absorption

• $\epsilon$εMolar absorption coefficient (material characteristic constant)

• $c$cSolution concentration

• $l$l: Optical path length (colorimetric dish thickness, usually 1 cm)
  Conclusion: absorbance$A$Compared to solution concentration$c$Directly proportional, quantitative analysis can be conducted based on this.

Spectral analysis, total nitrogen, total phosphorus, ammonia nitrogen, formaldehyde testing, visible spectrophotometer

1. light source

• Tungsten lamp or halogen lampIt emits visible light (400-800 nm) and has high stability.

2. Monochromator

• Grating or prismSeparate composite light into single wavelength light.

• Wavelength selectorManually or automatically adjust the wavelength (accuracy ± 1 nm).

3. sample room

• cuvetteGlass or quartz material (quartz can be extended to the ultraviolet region), with a typical optical path length of 1 cm.

4. detector

• Phototube or photodiodeConvert optical signals into electrical signals.

5. Signal Processor and Display

• Convert the electrical signal into absorbance/transmittance values and display the results.

Main application scenarios

1. Concentration measurement

• Quantitative analysis of dyes, metal ions (Fe ² ⁺/Cu ² ⁺), and biochemical indicators (blood glucose) in solution.

2. Study on Chemical Reaction Dynamics

• Monitor changes in absorbance during the reaction process (such as enzymatic reaction rate).

3. Water quality/environmental testing

• Measure COD (chemical oxygen demand), ammonia nitrogen, total phosphorus, etc. (with accompanying colorimetric reagents).

4. food industry

• Detection of pigment content and additive concentration (such as lemon yellow in beverages).

5. Teaching and Research

• Basic Analytical Chemistry Experiment.

5、 Operation process

1. Power-on preheating

• Stable light source (usually takes 10-15 minutes).

2. Wavelength setting

• Select the maximum absorption wavelength of the test substance (e.g. KMnO ₄ is 525 nm).

3. Blank correction

• Spectral analysis 721: Use a solvent (such as distilled water) to zero the visible spectrophotometer (absorbance A=0).

4. Sample measurement

• Inject the test solution into the colorimetric dish and place it in the sample chamber to read the absorbance value.

5. data analysis

• Calculate the concentration based on the standard curve.

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