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
Test your TOC analyser knowledge
Multiple-choice questions
Pick an answer to see whether you are right and why.
Q1. What does TOC measure?
basicQ2. Which relationship is used when total carbon and inorganic carbon are measured separately?
basicQ3. Why is 1,4-benzoquinone used in TOC system suitability?
intermediateQ4. Rw = 0.08, Rs = 0.55 and Rss = 0.53 mg/L. What is the response efficiency?
intermediateQ5. What is the TOC limit for bulk purified water and water for injections in USP <643>?
basicQ6. A TOC blank is suddenly high. Which is the most likely cause?
intermediateQ7. How many mg/L of sucrose give 0.50 mg/L of carbon? (Sucrose is about 42.1% carbon.)
advanced
Viva questions
Think of your answer first, then open it to compare.
1. Why are both conductivity and TOC tested on purified water?
Conductivity detects ionic impurities such as salts. TOC detects organic contamination, which does not raise conductivity much. Together they give a fuller picture of chemical purity.
2. Describe how a UV/persulphate TOC analyser with conductivity detection works.
The sample is acidified to turn inorganic carbon into CO₂, which is removed or measured. Persulphate and UV light oxidise the organic compounds to CO₂. The CO₂ passes (often through a membrane) into clean water, and the rise in conductivity is converted to carbon concentration.
3. What precautions do you take when sampling water for TOC?
Use certified TOC-clean vials, wear powder-free gloves, flush the sampling point, rinse the vial with sample, fill it without headspace, avoid solvents and markers nearby, and analyse within the validated hold time.
Keep every TOC analyser in control: usage logs, calibration and maintenance schedules, and automatic blocking of overdue instruments.