Problem 1: No fluorescence signal or continuous reading of zero

First, check the status of the reagents: confirm that the culture medium and substrate solution are within their expiration dates, and that there are no precipitates, discoloration, or bubbles in the bottle; Check if the reagent pipeline is blocked or leaking, and ensure that the pump valve is working properly. Check if the light source (LED) and detector (photomultiplier tube) are damaged, which can be verified through the instrument self-test program. If it is a low-temperature environment, confirm whether the constant temperature cultivation unit has reached the set temperature (usually 37 ℃ or 44.5 ℃) and whether the heating system is faulty.

Problem 2: High background fluorescence or frequent false alarms

Due to sample interference or contamination. Chemical substances in certain industrial wastewater, such as strong oxidants, heavy metals, and high concentrations of organic compounds, may inhibit enzyme activity or produce spontaneous fluorescence, leading to false positives. The incoming water quality should be checked, and pre-treatment measures such as neutralization, dilution, and filtration should be added if necessary. At the same time, check whether the sample pool, pipeline, and colorimetric dish are clean, as residual biofilm or dirt can breed fluorescent background. Regularly perform deep cleaning with acid or specialized cleaning agents.

Problem 3: Bacterial detection but abnormally prolonged cultivation time

Reflect the inhibition of microbial activity. It may be due to incomplete removal of fungicides (such as residual chlorine) in the sample. Ensure that the neutralizing agent (such as sodium bisulfite) is added sufficiently and mixed evenly. Check if the cultivation temperature is accurate, as low temperatures can significantly delay bacterial growth. Confirm that the sample has not been subjected to heat or cold during the sampling and transportation process, which may affect the bacterial activity.

Question 4: Instrument alarm "blockage" or "abnormal liquid level"

Check if the sampling filter, injection tube, and waste liquid tube are blocked by algae, sediment, or fibers. Clean or replace the filter element, and use reverse flushing or compressed air to unclog the pipeline. Confirm if the waste liquid tank is full and if the float level gauge is stuck. Check whether the peristaltic pump tube is aging, deformed, or loose, which affects the accuracy of liquid delivery.

Problem 5: Poor data repeatability or calibration failure

System calibration and validation are required. Regularly test quality control samples prepared using standard strains (such as Escherichia coli ATCC25922) to verify instrument sensitivity and accuracy. Check the accuracy of automatic injection to ensure accurate sample and reagent volumes. If the calibration curve deviates, it may be necessary to reconfigure the reagents or contact the manufacturer to calibrate the optical system.