The need for TOC analysis is very important in the pharma industry. By quantifying carbon, TOC provides an indirect measure of organic molecules present in pharmaceutical waters. These organics come from source water , from purification & distribution system materials, bio film growing in the water utility systems etc.

Several methods are acceptable for analyzing TOC. If the instrument passes System Suitability Test (SST), it is permitted to be used. Now it's up to the user to select a particular technology that gives good accuracy, repeatability & range, low consumable, spares etc.

Since the inception of Process Analytical Technologies (PAT) as a recommended guideline, many prefer to have online TOC analyzer. The goal of FDA's recent PAT initiative is to understand and control manufacturing process.

For online analysis of TOC, the general preference is UV oxidation with conductivity detection, when compared to NDIR techniques. This is mainly because of the limitation of NDIR to measure at low levels, difficulty to produce blanks at this level, and the huge consumable cost of pure gases, power consumption of furnace, catalysts, scrubber, etc.

The second technique UV conductivity is better than NDIR as the consumables are very less. However, it is subject to false positive interferences from certain items commonly found in the water systems.

Water contains organic chlorides, nitrates, sulphates, phosphates especially etc in traces after purification. During UV oxidation, these halides get converted into acids and adds to the conductivity of water.

In general practice, before and after the UV oxidation, the conductivity is measured and the difference in conductivity is read as CO2(Carbon). This rise in conductivity is contributed by the oxidised carbon which is CO2 and the acids formed by oxidized halogens.

Thanks to the Membrane Technology, sievers use a CO2 permeable membrane. This membrane is permeable only to CO2 and not to the interfering halogens. Therefore, with seivers, you are sure it is possible to measure the real TOC and not the halogens.

Without Membrane technology, there are chances of such interfering halogenated compounds causing erroneous TOC (false positive ) readings which is due to the halogens contribution, (even a 100ppb carbon can be read as 1000ppb).This false alarms in many case leads to unwanted confusions and costly shutdowns.

GE analytical instruments "sievers" brand TOC analysers use this patented technique of UV oxidation and membrane conductivity detection and has more than 6500 customers worldwide. GE has dedicated models for CV application where a single instrument with a wide range of 0.03ppb to 50,000 ppb, can do all jobs in the pharma TOC water, whether online or offline, cleaning samples or pure water (WFI or PW).

For any info in this regard
please mail to wasank@skytechindia.com
K. Srinivasan
(Product Manager)
Skyetch Systems (India) Pvt Ltd.
Ph: 022 25861324
Fax: 022 25861660