UV visible spectrophotometer is a key equipment used for quantitative analysis in laboratories, and its accuracy directly affects the reliability of detection results. To ensure stable instrument performance, it is necessary to manage it through systematic calibration, performance verification, and daily quality control (QC) processes.
1、 Calibration: laying the foundation for accuracy
Calibration needs to be conducted regularly, with core items including wavelength accuracy and photometric accuracy.
Wavelength calibration: Use standard substances (such as the 218.9nm and 259.3nm characteristic peaks of deuterium lamps, or specific absorption peaks of holmium glass filters) to scan and verify the instrument wavelength reading. If the deviation exceeds ± 1nm, it needs to be adjusted to the standard value through instrument software or hardware.
Luminescence calibration: Using a neutral density filter or standard solution (such as the absorbance value of potassium dichromate solution at a specific wavelength) as a reference, adjust the instrument's absorbance reading to the standard range. For example, the absorbance values of potassium dichromate at 235nm, 257nm, and 313nm must comply with pharmacopoeia or ISO standards.
2、 Performance validation: Ensure continuous compliance
Performance validation should cover indicators such as wavelength repeatability, photometric linearity, and stray light.
Wavelength repeatability: Repeatedly scan the peak position of the standard substance, calculate the standard deviation of multiple measurement results, and require ≤ 0.5nm.
Luminescence linearity: Prepare a series of concentration standard solutions (such as 0.1-1.0Abs), test the linear relationship between absorbance and concentration, and the correlation coefficient R ² should be ≥ 0.999.
Scattered light: Use high concentration filters (such as 1% transmittance) or cut-off filters to detect non target wavelength light leakage, and the proportion of stray light should be ≤ 0.1%.
3、 Daily QC: Preventive Maintenance
Daily QC mainly focuses on rapid inspection to ensure that the instruments are in a controllable state.
Power on self-test: Run the instrument self-test program after daily startup to check basic parameters such as wavelength, luminosity, and noise.
Standard solution testing: Use a known concentration of standard solution (such as 0.5Abs nickel solution) for daily calibration, and the absorbance deviation should be ≤ ± 0.005Abs.
Environmental monitoring: Record laboratory temperature and humidity (usually requiring 15-30 ℃, humidity ≤ 70%) to avoid temperature and humidity fluctuations affecting instrument stability.
Recording and tracing: Establish calibration, validation, and QC logs, record abnormal data and handling measures, and meet system requirements such as ISO17025.
4、 Maintenance and Precautions
Regularly replace the light source: deuterium lamps have a lifespan of about 2000 hours, tungsten lamps have a lifespan of about 1000 hours, and need to be replaced in advance according to the duration of use.
Clean the sample pool: Wipe with a dust-free cloth or ethanol to avoid fingerprints or stains affecting the transmittance.
Software update: Install firmware updates released by instrument manufacturers in a timely manner to fix potential algorithm deviations.
Through closed-loop management of calibration, performance verification, and daily QC, instrument errors can be minimized to ensure accurate and reliable testing data, providing solid support for the laboratory quality system.