PURELAB® flex Real time TOC System

Importance of the Topic

Resistivity alone indicates inorganic ion levels in ultrapure water but fails to detect organic contaminants that can compromise sensitive analytical techniques such as HPLC and GC-MS. Real-time monitoring of total organic carbon (TOC) provides a universal measure of organic purity, ensuring reliable water quality for critical laboratory and industrial applications.

Objectives and Overview of the Study

This technology note describes the integration of an online, real-time TOC monitoring module into the PURELAB® flex ultrapure water system. The goals are to explain the monitoring principle, validate its performance under transient contamination events, and compare its response time to that of a commonly used competing TOC monitor.

Methodology and Instrumentation

• Principle of operation:

• Measure water resistivity before UV exposure.
• Expose water to high-energy UV light (185/254 nm) to oxidize organic compounds into ionic species.
• Measure resistivity after UV photo-oxidation; TOC is inferred from the resistivity change.

• Key components in the PURELAB flex system:

• UV lamp and oxidation chamber for continuous irradiation.
• Dual resistivity sensors (pre- and post-oxidation).
• Recirculation pump and downstream purification pack to remove oxidation products.
• Automated calibration routine monitoring UV lamp efficiency and triggering lamp replacement when required.

Main Results and Discussion

Transient contamination tests were performed by injecting 3 ml of a 100 ppm methyl ethyl ketone solution at different points in the competitor’s TOC monitor cycle. Four test conditions (start of oxidation, start of fill, mid oxidation, mid fill) were assessed. Graphical data reveal:

• The PURELAB flex TOC monitor detected contamination immediately under all test conditions.
• The competing monitor exhibited significant lag or complete failure to register elevated TOC during early dispense periods.

This demonstrates the superiority of ELGA’s real-time approach in ensuring that dispensed water meets organic purity requirements at every moment.

Benefits and Practical Application of the Method

• Ensures consistent organic purity for sample and standard preparation, avoiding bias in trace-level analyses.
• Enables continuous data logging for trend analysis, system diagnostics, and preventive maintenance.
• Automated UV lamp calibration reduces downtime and manual intervention.
• Immediate contamination alerts safeguard critical processes in pharmaceuticals, semiconductor manufacturing, and QA/QC laboratories.

Future Trends and Opportunities

• Integration with IoT platforms and laboratory information management systems (LIMS) for remote monitoring and analytics.
• Advanced sensor materials and miniaturized photoreactors to lower detection limits and reduce power consumption.
• Application of machine learning algorithms to predict maintenance needs and detect subtle contamination patterns.
• Extension of real-time TOC monitoring to bioprocess water applications and inline continuous manufacturing.

Conclusion

The PURELAB flex real-time TOC monitoring system provides a robust, automated solution for detecting organic impurities in ultrapure water. Its rapid response and reliable calibration ensure that water used in high-precision analytical workflows remains free of novel organic contaminants, enhancing data quality and operational reliability.

References

Tech Note 18, PURELAB® flex Real time TOC System, ELGA LabWater/VWS (UK) Ltd., 2019.