The absorption curves of copper persulfate and praseodymium-rubidium filter are plotted to understand the correctness of the scale on the wavelength dial of the spectrophotometer. 2. Master the wavelength correction method of the 721 spectrophotometer (praseodymium-rubidium filter method) and the repeatability check. 3. This experiment is from Mudanjiang Medical College undergraduate 5-year laboratory guide for testing majors.
Operation method
Preparation of absorption curves for copper persulfate and praseodymium rubidium filters and experiments on the calibration of the spectrophotometer at 721 wavelengths
Principle
The praseodymium-rubidium filter has a maximum absorption peak of 529 nm in the visible region, and this property was utilized to calibrate the 721 spectrophotometer
Materials and Instruments
Copper Sulfate Standard Storage Solution Serum Total Protein Measurement Solution Move I. Calibration For more product details, please visit Aladdin Scientific website.
721 Spectrophotometer Praseodymium-Rubidium Filter Coordinate Paper Flasks Straws
1. Warming up the instrument
2. Set the wavelength at 580nm, adjust the T % to the maximum, use a strip of white paper to observe whether there is a spot of uniform light intensity in the absorption cell, adjust the light source bulb to meet the requirements.
3. put the sensitivity knob at the lowest end, the wavelength dial at 529nm, repeatedly adjust the transmittance and 100% until stable, the praseodymium-rubidium filter into the optical path, carefully rotate the wavelength dial to find the lowest point of the T-value, at this time the wavelength should be 529nm (λm)
4. Calculate the wavelength error: Δλ = λ - λm
5. Calibration: adjust the wavelength at 529nm, take out the praseodymium-rubidium filter, adjust the T-value to 100%, then insert the praseodymium-rubidium filter, open the cover plate, adjust the wavelength calibration screws, so that the value is the lowest. Repeat the wavelength correction steps to check the wavelength error until it meets the requirements.
Repeatability check
1. Use distilled water as a blank to fix the wavelength dial in the first 690nm, adjust the transmittance of 100%.
2. Measure the copper sulfate standard solution (31.35mol/L or 2000ug/ml) five times consecutively and record the results.
The transmittance values were recorded.
3. Calculate: Δl=lmax-lmin.
Lmax. lmin are the maximum and minimum values of transmittance, and Δl is generally required to be less than 0.5%.
Absorption curve
1. Five different concentrations of protein standard solution, record the absorbance value.
2. Take the concentration as the horizontal coordinate and absorbance as the vertical coordinate to draw the absorption curve. Plot the absorption curve with concentration as the horizontal coordinate and absorbance as the vertical coordinate.