Check the expiration date label: Calibration solutions are usually labeled with an expiration date or an expiration date after opening, such as 1 year for unopened solutions and 3 months for opened solutions. If it exceeds the marked deadline, it is generally not recommended to continue using it.

Check storage conditions: Confirm whether the calibration solution is stored according to the required storage conditions. For example, whether it is protected from light and sealed, and whether the storage temperature meets regulations. For example, some calibration solutions need to be refrigerated (4-10 ℃) for storage. If they are not stored as required, they may deteriorate prematurely even before the expiration date.

Observing physical properties: Carefully observe the appearance of the calibration solution to see if there is any precipitation, suspension, or turbidity, if the color has changed, and if the odor is abnormal. If these situations occur, it may indicate that the calibration solution has deteriorated and should not be used again.

Calibration verification: After calibrating the instrument with this calibration solution, measure a standard sample with a known concentration. If the deviation between the measurement result and the standard value exceeds the allowable range, such as ± 5%, or the calibration result differs significantly from the newly opened calibration solution of the same type, it may indicate that the old calibration solution has expired.

Reference instrument error message: The Thermo Fisher iCAPQ instrument itself may monitor and provide feedback on the status of the calibration solution. If the instrument displays error prompts or warning messages related to calibration, such as calibration failure or abnormal calibration parameters, it may also indicate that there is a problem with the calibration solution and further inspection is needed to determine if it has expired or deteriorated.