Principle
Total Organic Carbon (TOC) is a measure of the amount of carbon found in organic compounds in a water or soil sample. It is a key indicator used in environmental, pharmaceutical, and water quality testing. The principle behind TOC analysis involves oxidizing the organic carbon present in the sample to form CO₂, which can be quantitatively measured.
There are two primary steps in the principle:
- Oxidation: Organic compounds are chemically oxidized (often using heat or chemical agents) to convert carbon into CO₂.
- Detection: The CO₂ produced is detected and quantified, typically using techniques like non-dispersive infrared (NDIR) detection.
The TOC value is obtained by subtracting the inorganic carbon (IC) from the total carbon (TC).
Working
The TOC analysis process can be broken down into the following steps:
- Sample Preparation: The sample (liquid, solid, or gas) is collected and prepared. In liquid samples, it may involve filtration to remove particulates.
- Oxidation: The sample is oxidized to convert organic carbon into CO₂. This can be achieved through various methods:
- High-temperature combustion: Involves heating the sample at high temperatures (typically around 680-1000°C) in the presence of a catalyst and oxygen.
- Chemical oxidation: Oxidizing agents such as persulfate may be used to convert organic carbon into CO₂.
- UV oxidation: UV light is used to initiate oxidation reactions in the sample.
- Inorganic Carbon Removal: The inorganic carbon (IC), often present as carbonates and bicarbonates, is purged by adding an acid and converting it to CO₂.
- CO₂ Detection: The CO₂ produced from oxidation is detected. The most common method is non-dispersive infrared (NDIR) detection, which measures the infrared absorption of CO₂ molecules.
- Calculation: The instrument calculates the TOC based on the CO₂ concentration hdetected, after subtracting the IC.
Applications
- Water Treatment: TOC is widely used to monitor the efficiency of water treatment processes (both potable and wastewater) by quantifying the organic contaminants.
- Pharmaceutical Industry: TOC analysis is critical in ensuring water quality (such as in purified water and water for injection) and cleanliness of manufacturing equipment.
- Environmental Monitoring: It is used to assess pollution levels in rivers, lakes, and oceans. High TOC levels in these environments may indicate pollution from organic waste.
- Food & Beverage Industry: TOC analysis ensures the quality of water used in food and beverage production processes.
- Process Monitoring: TOC monitoring in water treatment plants helps operators assess the efficiency of the purification process and detect issues like filter failures or contamination events.
Read also:
Resource Person: Drx. Satish Mane