The calibration of microbial fluorescence detector is a key step to ensure its accurate and reliable detection of microbial content. The following is a detailed introduction to its calibration method:
Preparation before calibration
-Selection of standard substances: Based on the measurement range and accuracy requirements of the instrument, select appropriate microbial standard substances, such as suspensions of bacteria, yeast, etc. with known concentrations, or samples containing specific microorganisms. These standard substances should have stable biological characteristics and repeatability to ensure the accuracy of calibration.
-Instrument and equipment inspection: Conduct a comprehensive inspection of the microbial fluorescence detector, including power connection, light source stability, detector sensitivity, signal transmission lines, etc., to ensure that all components of the instrument are working properly. At the same time, clean the optical system of the instrument to avoid dust, impurities, and other factors that may affect the detection of fluorescence signals.
-Environmental condition control: Calibration should be carried out in a stable environment, with temperature controlled within a specific temperature range and relative humidity maintained within a specific humidity range. Avoid factors such as direct sunlight and electromagnetic interference that may affect the performance of the instrument to ensure the reliability of calibration results.
Calibration steps
-Zero calibration: place the probe of the instrument in the blank solution without microorganisms, adjust the zero adjustment knob of the instrument to make the fluorescence intensity displayed by the instrument zero or close to zero, so as to eliminate the influence of the background noise and dark current of the instrument on the measurement results.
-Sensitivity calibration: Use a series of standard microbial samples of different concentrations to measure in order from low to high. Record the fluorescence intensity values corresponding to each concentration sample and draw a standard curve. Determine the sensitivity coefficient of the instrument, which is the change in fluorescence intensity caused by a change in unit microbial concentration, through methods such as linear regression analysis.
-Repetitive calibration: Under the same conditions, perform multiple repeated measurements on standard microbial samples of the same concentration, generally no less than [X] times. Calculate the mean and relative standard deviation (RSD) of the measurement results to evaluate the repeatability and precision of the instrument. If the RSD exceeds the specified allowable range, it is necessary to investigate the cause and make corresponding adjustments and optimizations until the instrument's repeatability meets the requirements.
-Accuracy calibration: Using a standard microbial sample with a known accurate concentration, compare its detection results with the actual concentration, and calculate the measurement error of the instrument. If the error exceeds the allowable range, the accuracy of the instrument can be improved by adjusting the calibration coefficient of the instrument or repairing or debugging the instrument.
calibration cycle
-Regular calibration: Microbial fluorescence detectors should have a reasonable calibration cycle based on their frequency of use and importance. Generally speaking, it is recommended to perform a comprehensive calibration every [specific time interval] to ensure that the instrument is always in good working condition.
-Periodic verification: Periodic periodic verification can be conducted between two calibrations, using rapid testing methods or portable standard equipment to randomly check the key performance indicators of the instrument. If any abnormal situation is found in the instrument, it should be calibrated or repaired in a timely manner to ensure the reliability of the test results.
Calibration Records and Reports
-Detailed records: During each calibration process, detailed information such as the calibration time, location, environmental conditions, calibration materials and methods used, calibration data and results should be recorded. These records will provide important basis for the performance evaluation, maintenance management, and subsequent traceability of the instrument.
-Calibration report: After the calibration is completed, a formal calibration report should be issued, clearly stating whether the various calibration parameters of the instrument meet the requirements and whether the instrument can be used for normal testing work. The calibration report should be signed and stamped by professional metrologists, and archived for future reference.