What is TOC? Why are TOC measurements used? How is TOC measured? Where is TOC measured? Are TOC measurements with continuous flow better than batch process TOC measurements? What is response time vs. update time? What maintenance is required for the 550? Are chemicals, gases or reagents required for operating the 550?Total Organic Carbon is a term used to describe the measurement of organic (carbon based) contaminants in a water system. Organic contamination can come from a variety of sources, since "organics" are compounds such as sugar, sucrose, alcohol, petroleum, PVC cement, plastic based derivatives, etc.
- Organics may exist in the feed water.
- Organics may result from the leaching or shedding of various components within the purification or water distribution system.
- Organics may result from the formation of biofilms (bacteria) in the water system.
Generally organic contaminants are non-ionic and as such are not detected by standard conductivity measurements. Therefore, high resistivity (low conductivity) measurements in an ultrapure water system may not detect high levels of TOC from high levels of contamination. High levels of TOC can:
- Degrade water purification systems.
- Reduce semiconductor yields.
- Contaminate pharmaceutical batches.
- Damage power and steam generation equipment.
TOC is used to monitor both the quality and equipment efficiency of many water purification processes. It is used in many of the industries and applications that we already service:
- Semiconductor Industry
- Pharmaceutical Industry
- Power and Steam Generation
TOC can be measured both on- and off-line. Off-line measurements (lab methods) are typically used for high concentrations (>1 ppm). On-line measurements are typically used for sub-ppm (<1000ppb) detection and quicker response than the lab methods. Most of the industries Thornton services use on-line measurements for the faster response, which is required for process control.
- After Reverse Osmosisto monitor membrane efficiency (especially where Thin Film Composite or TFC membranes are used).
- After Deionization(DI) beds to monitor resin life and efficiency and to monitor shedding of new resins.
- After the Final Polish to ensure low organic levels have been maintained after storage of pure water in tanks.
- On Recycle (return of wet bench discharge waters) and Reclaim (reusing discharged waters in secondary applications outside the fab) lines, to ensure proper, low organic levels before return to the water system.
- After TOC destruct UV lamps to monitor UV light efficiency.
- Before the Point of Use distribution lines to ensure final water quality.
- Monitor Boiler Feed water to prevent damage to turbines and other equipment.
- To meet UPS <643> and EP 2.2.44 requirements. TOC is a pharmaceutical measurement required when producing USP purified water, WFI (Water for Injection), and HPW (Highly Purified Water).
On November 15, 1996, the USP allowed on-line TOC measurements as an alternative test method to existing offline heavy metals test methodologies. On May 15, 1998, the USP required TOC measurements as a new component of the test methodologies established in USP 23 <643>. The use of quantitative TOC measurements by USP 23 <643> replaced the previous laboratory USP test procedure, thus providing a qualitative test method. TOC measurements are used to monitor return loops from the point of use lines back to the storage tanks as well as in other areas of the water purification system.
Yes. A TOC analyzer, which measures continuous flow, can "see" the whole representative sample of organics in the water system. Much like a movie with continuous frames, a continuous flow doesn't miss a frame or a TOC excursion.
However, a batch process is like a single frame photograph that takes a "snapshot" of the system. If "snapshots" are taken periodically, TOC excursions can be measured erroneously, as in a portion of an excursion where the magnitude of the excursion is missed, or an entire excursion may be missed entirely! If a batch process TOC unit has a response time of 5 minutes or 30 minutes, significant and important information may never be identified until it's too late.
- Response time: The time it takes for the organics in water to be oxidized and measured in a TOC analyzer. This is the time water takes traveling from the first conductivity sensor, through the spiral quartz tube to the second conductivity sensor, and then to process the TOC measurement. The response time for the 550 TOC Analyzer Model is less than a minute!
- Update time: The time it takes to update a measurement. The Update time for the 550 is 2 seconds!
- The 550 requires replacement of the UV lamp every 4000 hours.
- The 550 should be calibrated on a yearly basis.
- Field calibration of the sensor board is available with easy-to-use, pluggable Sensor Board Calibration Resistors.
- TOC/Resistivity calibration can be performed at the factory or in the field by a Thornton technician, or by using the Thornton Portable Calibration Station available in the near future.