Data processing: VITA method (dwell-time coupled integration)

The NDIR signal is detected parallel to the gas flow. To this end, a high-accuracy, digital flow sensor is arranged very close to the NDIR detector. Prior to signal integration, occurring flow variations are compensated to a constant gas flow by computer-controlled normalization of the signal. In this way, the dwell time of the analyte gas in the NDIR cell is considered in peak integration. As a consequence, the signals of CO2 molecules, which - compared to the average - are spectrometrically detected over a longer (or shorter) period due to temporarily lower (or higher) analyte gas flow rates, will be integrated with a correspondingly lower (or higher) weight because of the previously performed normalization.

The innovative problem solution:

By the use of the NDIR detector in combination with the VITA method, the analysis of TIC, TC, TOC and NPOC is made safe, precise and extremely reliable.

Advantages:

• Sample volumes in ml range are combusted in a comparatively short time, which results in a high sensitivity of the method and a high sample throughput.
• High reproducibility and accuracy of the analytical results obtained in fast analyses and at reduced matrix effects: The result of integration is independent of short-term gas flow variations as may be caused e. g. by sample evaporation, water condensation or inertia of flow control systems. That`s why, without sacrificing analytical quality, peak integration can be started already while the sample is still being injected.
• Ruggedness: As the system does without a complicated and expensive pneumatic system, the operation of the equipment is made easy and reliable.
• Calibration of long-term stability and longer service life of catalysts: Thus, flow variations occurring in the long term due to aging effects or contamination of flow controllers, baking of catalysts, etc. do not necessarily require recalibration and reduce the frequency of catalyst replacement.
• Predestined for measurements at trace level: The system even copes with large sample volumes.