Online TOC measurement offers quality control solution for ultrapure water

The measurement of TOC (total organic carbon) in water is of vital importance to a multitude of industries that need to ensure their water is free from contaminants and harmful toxins.

What is Carbon in water?

The schematic below illustrates carbon components which make up TIC and TOC, resulting in Total Carbon content in the water.

Illustration of carbon components resulting in total carbon content in water. Ultrapure water.

TIC (total inorganic carbon) can be easily removed from the water by acidifying it to a pH < 3 and then sparging with air or nitrogen. Typically, the ultrapure water (UPW) production process removes TIC by a combination of reverse osmosis, deionization and degasification.

Total organic carbon (TOC) consists of NPOC (non-purgeable organic carbon), POC (purgeable organic carbon) and organic particulates such as algae. NPOC are organics that are dissolved in the water and cannot be removed by sparging. POC is the opposite and is removed by sparging or in some cases, these often-low molecular weight compounds dissipate from the liquid sample to the gaseous state by themselves. Also, it should be noted that sparging to remove TIC will also remove POC, so rather than a true TOC result, the instrument is measuring NPOC.

A solution is found with online TOC measurement

Total Organic Carbon is the measurement of the aggregate organic carbon impurities in a water source. Original laboratory TOC methods were developed to help correlate Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD) in drinking and waste waters.

On-line monitoring of low-level TOC is now routine in various industries. On-line TOC analysis testing has numerous advantages over conventional laboratory testing. These advantages include:

Water can be measured in its own environment
Continuous real-time data

Comparable to laboratory measurements
Low cost-of-ownership
No sample handling or contamination

The importance of measuring TOC in various industries

In semiconductor manufacturing, TOC contamination was linked to a reduction in product yields.

In the power generation industry corrosive organic acids, such as TOC contaminants, can reduce the life of turbines and other key boiler elements.
TOC is an important measure of pharmaceutical water quality using the USP<643>, EP 2.2.44 standard and Japanese Pharmacopeia(JP) method.

CA78 for Power and Energy industry applications