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This application literature introduces the process improvement of using the Sievers M9 TOC analyzer with sample conductivity function for detecting the first stage conductivity. Many users choose M9 analyzer to detect the first stage conductivity, in order to simplify the cumbersome process of using desktop instruments to detect conductivity and improve detection efficiency. Using M9 analyzer to detect conductivity can greatly reduce the inherent instability when using desktop instruments to detect conductivity, while achieving automation of data transmission.

However, in some cases, significant sources of instability still exist, sometimes causing the test results reported by the analyzer to exceed the ± 2% accuracy limit specified in the pharmacopoeia. This application literature provides suggestions to users to help them improve their detection process capabilities and reduce the instability of out of specification (OOS) results.

Data and Discussion

The traditional M9 conductivity detection procedure involves first performing a single point calibration of 1.4 mS/cm, followed by confirmation with 25 µ S/cm HCl. According to the requirement of ± 2% accuracy specified by USP, the confirmation result must be within 24.5-25.5 µ S/cm to be considered passed. When conducting a 25 µ S/cm confirmation, small deviations in the 1.4 mS/cm calibration can cause the confirmation result to exceed the specification standard by ± 2%. In addition, when CO2 in the air enters the standard solution, it will increase the conductivity of the HCl standard.

We evaluate the causes of unstable detection through experimental data and determine the conditions that can significantly reduce instability, in order to improve the efficiency of the detection process and increase the success rate of meeting the ± 2% specification standard. We used 12 M9 analyzers for single point calibration at 1.4 mS/cm and 100 µ S/cm, respectively, and then tested the accuracy of each confirmed concentration point within a certain range.

suggestion

The calibration tasks and confirmation standards for firmware and software used in the 2.0 upgrade version can provide users with flexible and robust measurement processes, greatly improving process capabilities. Here are our operational suggestions:

1. Perform 100 µ S/cm calibration.

2. Confirm within the range of 25-100 µ S/cm. According to statistics, 100 µ S/cm KCl confirmed the highest stability.

3. Follow the recommendations for maintaining the instrument before confirmation.

4. Use linear standard tasks to confirm low concentration measurement performance.

Conclusion

Performing 100 µ S/cm calibration instead of 1.4 mS/cm calibration can improve the accuracy of conductivity measurements for various confirmation standards used in pharmacopoeia water testing. This suggestion can significantly solve the problem of unstable measurement results and improve the performance of pharmacopoeia compliance. Users can decide whether to implement this suggestion based on their existing process capabilities and frequency of exceeding specifications. If the instability of the operation is already small, users may not see significant process improvements.

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