TOC = TC-IC
通常通过测量总碳，将有机碳氧化为CO2 ，然后用电导率或NDIR检测CO2 来完成。
How does a TOC analyzer work?
TOC analyzers and sensors convert organic molecules to carbon dioxide (CO2) and the measure the CO2 that is produced to determine the TOC concentration. Different analyzers vary in the way that organics are converted to CO2, the way that CO2 is quantified, and the way that byproducts are managed.
Differences in TOC analyzers or sensors include:
- How the TOC technology converts or oxidizes organic carbon molecules to form CO2.
- How the TOC technology detects the CO2 produced. Common methods of detection are non-dispersive infrared (NDIR), direct conductometric (non-selective conductometric), and membrane conductometric (selective conductometric) detection.
- How the TOC technology deals with other ionic species that are produced after the organic molecule is oxidized.
How does Sievers membrane conductometric TOC technology work?
Sievers M9 and M5310 C TOC Analyzers use a UV-persulfate method to oxidize organic molecules to CO2, and a membrane conductometric method to quantify CO2. Sievers membrane conductometric technology separates the CO2 produced in the TOC analyzer from other byproducts of oxidation. The CO2 crosses a gas-permeable membrane while other ions (such as sulfates and chlorides, which are known to interfere with measurements and cause false high or false low TOC readings) are carried out to waste. Once the CO2 crosses the membrane, it equilibrates in the deionized water to form bicarbonate. This bicarbonate is then detected by a conductivity cell, with the increase in conductivity used to calculate the amount of carbon present.
Why do we measure TOC?
TOC is widely used to assess the purity of water in industries such as pharmaceuticals, microelectronics, municipal water treatment, and wastewater. In some industries, TOC is measured to comply with regulatory requirements. TOC can also be used for process understanding, cleaning validation and verification, leak detection, and other applications.
In municipal drinking water plants, TOC analysis is performed to ensure sufficient levels of TOC are removed from source water so that water is safe to drink. Organics monitoring is a valuable tool used in all stages of the water treatment process for treatment optimization, quality control, and regulatory compliance. Understanding and optimizing the various separation processes in drinking water treatment are important to detect changes in source water, reduce operating costs, and minimize the formation of disinfection byproducts (DBPs).
Microelectronics manufacturers monitor TOC in their process water, as TOC can cause imperfections in the way that silicon wafers and circuit boards are printed. This impacts the quality of their product.
Pharmaceutical manufacturers use TOC monitoring to measure purified water and water for injection (WFI) for compliance to USP <643>, EP 2.2.44, JP, IP, ChP and other harmonized compendia. For more robust monitoring programs, online technology is deployed to monitor water purification loops in real time for process control and immediate detection of out-of-specification (OOS) or out-of-trend (OOT) results. Immediate detection limits impact to critical equipment and in-process batches, saving time and reducing costs.
TOC is also a valuable tool for cleaning validation, verification, and monitoring. In cleaning validation, TOC is used to confirm removal of active pharmaceutical ingredient (API), detergents, cleaning agents, excipients, and degradants from equipment. This confirmation of cleanliness is used to release equipment without risk of carryover. Sievers TOC Analyzers can easily integrate directly online with a Clean-in-Place (CIP) skid to provide real-time, validated data with the highest degree of data integrity, process understanding, and process control. Sievers TOC Analyzers deliver results in compliance with 21 CFR Part 11 data management and data integrity guidelines.
The pharmaceutical industry demands lean processes and continuous improvement also known as “Quality by Design” (QbD). Having efficient processes allows for safe, high quality products to be available to patients when needed. The US FDA’s guidance document on Process Analytical Technology (PAT) not only describes how and when to deploy technology, it also strongly encourages manufacturers to embrace PAT within their systems. Total organic carbon (TOC) and conductivity monitoring are crucial aspects of purified water system quality and control. Real time data from process analytical technology ensures a controlled and well understood process while saving sampling and analysis time.