eBook: TOC and Microbial Detection Monitoring - 8

Real-Time Compliance

USP, or those described in the "Methods of Analysis
2.2.44 TOTAL ORGANIC CARBON IN WATER FOR
PHARMACEUTICAL USE" of the European Pharmacopoeia (EP), the apparatus can be used for the
monitoring of pharmaceutical water processing system
if sufficiently pure water not contaminated with ionic
organic substances, or organic substances containing
nitrogen, sulfur, phosphorous or halogen atoms in
there chemical structures, is used as the source water
supplied to the system.

The METTLER TOLEDO TOC sensor design minimizes the
deposition of materials such as rouge by:

METTLER TOLEDO Thornton TOC systems are fully compliant
with JP governed systems intended for PW and WFI applications
with conductivity levels of sample water 2μS or less.

* Use of titanium conductivity sensors that do not rouge.
* 60µ inlet filter protects the sensor by trapping rouge particles before they enter the sensor. In heavily rouged systems,
filters should be changed more often for added protection.

Rouge and TOC Measurement Devices
Rouging of stainless steel in water purification systems is the result of the formation of iron oxide, hydroxide or carbonate either
from external sources or from destruction of the passive layer.
Color variation is a result of the oxide/hydroxide/carbonate type
and variations in the water of hydration associated with the corrosion products. These colors range from orange to red to black.

Rouge tends to form in stagnant systems; MT's continuously flowing device resists the formation of rouge.

* MT Thornton sensor sends a small amount for water sample through the analyzer at any given time through a
quartz coil with a wide surface area so that rouge particles
present are distributed over a greater surface/volume area
mitigating their interference during the oxidation
process.

Rouge is a real world problem that can be problematic for any on
line TOC measurement device. Rouge can build up over time on
quartz coils, tubing and other wetted components and surfaces.
In membrane-conductometric TOC devices, membranes can be
quite susceptible to the effects of rouge impacting its transfer efficiency, limiting the rate that CO2 can pass through and be detected. This can result in inaccurate TOC, drift and instability
requiring frequent calibration or membrane replacement.

TOC regulatory oxidation requirement
Efficiency of oxidation has little to do with the time it takes to
oxidize but more about the "dosage of light" or "photons of
light/volume". Effective oxidation depends upon available
lamp power, exposure time, and sample light absorbance.
Thornton systems utilize significantly higher lamp power and
achieve greater dosage through its unique flow-coil design
maximizing light absorbance over a shorter period of time.
The result is a continuous measurement system fully compliant with the regulatory requirements for oxidation as confirmed by global guidelines.

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eBook: TOC and Microbial Detection Monitoring

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