Total Organic Carbon (TOC) Analyser
Oxidises organic compounds in water to carbon dioxide and measures the CO₂ formed to give the total organic carbon content. The standard test for organic contamination in purified water and water for injections.
- Pharmaceutical
- Biotech
- Semiconductors
- Power generation
- Environmental
- Drinking water
What is TOC analyser?
A TOC analyser measures the amount of carbon in water that is bound in organic molecules. It does not identify which organics are present; it gives one number that shows how clean the water is. In pharmaceutical water systems this replaced the old 'oxidisable substances' wet-chemistry test.
The analyser first deals with inorganic carbon (dissolved CO₂, bicarbonate and carbonate), which is not part of TOC. It then oxidises the organic compounds to CO₂, for example with UV light and persulphate or by high-temperature combustion, and measures the CO₂ by conductivity or by infrared detection.
TOC analysers are used both offline in the QC laboratory, for grab samples, and online, mounted on the water distribution loop for continuous monitoring. USP <643> and Ph. Eur. 2.2.44 describe the requirements, including a system suitability test with sucrose and 1,4-benzoquinone.
Used for
- Routine release testing of purified water and water for injections
- Online continuous monitoring of pharmaceutical water loops
- Cleaning validation: rinse water and swab samples
- Monitoring of water purification system performance
- Environmental and drinking water analysis
How it works
- 01
Sample intake
Water is drawn from a vial or directly from the water loop.
- 02
Inorganic carbon
IC is removed by acidifying and sparging, or measured separately.
- 03
Oxidation
Organic carbon is oxidised to CO₂ by UV/persulphate or high-temperature combustion.
- 04
CO₂ detection
CO₂ is measured by conductivity (often through a membrane) or NDIR.
- 05
Result
The signal is converted to mg/L or µg/L of carbon using the calibration.
Advantages
- Fast and sensitive: results in minutes at µg/L (ppb) levels
- Detects a broad range of organic contamination in one measurement
- Can run online for continuous, real-time monitoring
- Non-specific, so useful for cleaning validation where residues vary
- Highly automated, with little sample preparation
Limitations
- Non-specific: does not identify the organic compound
- Very sensitive to contamination from sample containers, gloves and air
- Some compounds are hard to oxidise and may be under-recovered
- High inorganic carbon must be removed or corrected for accurately
- Requires TOC-free reagent water for standards and blanks
2 calibration procedures
Methods that use TOC analyser
Keep every TOC analyser in control: usage logs, calibration and maintenance schedules, and automatic blocking of overdue instruments.