TOC in ultrapure water systems

Especially in ultrapure water systems, an increased organic load may cause in leading to the drop out of processes. It is today's standard to set an alarm at 0.1-0.2 mg/l (ppm) C. Analysers with a short response time, accurate determination of TOC (total organic carbon) or TC (total carbon) and simple calibration and validation techniques are an advantage.

Many online analysers are characterized by so called memory effects. Thereby contaminations are measured, which originate from previous measurements. Additionally, response times at humidified components may be dragged out due to substances contained in the water. In principle: the lower the TOC concentration, the longer the response time. To protect the water system, contaminated water is discharged. If the analysers's response time is too long, there is a risk that expensive, unpolluted steam condensate or boiler feed water will be drained off and the reserve container is emptied. This should be avoided. Through the help of appropriate actions, like assuring a sufficient sample speed can be remedied. But even the permanent rinsing of the tubes and components, which come into contact with the sample, as well as using appropriate materials and above all a specialized measurement technique can counteract the carry over effect.

The QuickTOC_condensate provides accurate and stable TOC or TC values in low measuring ranges. Inorganic carbon (carbonate) becomes carbonic acid when exposed to heat and pressure, this can lead to the corrosion of the pipes and the boiler. In TC-mode inorganics are also considered. The sample is injected to the oven via a closed tubing system. Inert materials and a pump that is installed downstream make sure that no memory effects of previous measurements occur. With LAR's combustion method at 1,200°C all carbons are 100% oxidised to CO₂. Thus, the QuickTOC_condensate provides measurement values in the range of 1 µg/l (ppb) C in a response time of only 3 minutes. In TC-mode even in one minute. A multi stream option is available with up to 6 streams. LAR's QuickTOCcondensate uses the patented calibration and validation method QuickCalibration, wherein instead of using liquid standards a defined test gas is used. Such a test gas is stable for a long period and usable for months. Moreover, the TOC analyser can be validated and calibrated remotely at any time.

The QuickTOC_condensate is already successfully applied in numerous ultrapure water applications and supports the user in the correct management and optimization of their processes.