🧪 TOC—Total Organic Carbon
In short
Determination of total organic carbon (TOC) in water by catalytic combustion at 680°C or wet oxidation with CO₂ detection in NDIR detector. The test is performed according to PN-EN 1484:1999; Measurement range: 0.004–30,000 mg C/L (depending on analyzer). The procedure comprises 7 steps (about 1 h 11 min–1 h 56 min in total); it is used for: Drinking water quality control (Journal of Laws 2017 item 2294), Ultrapure water monitoring (pharmaceuticals, electronics, semiconductors), Wastewater treatment plant efficiency control.
At a glance
- Standard: PN-EN 1484:1999
- Category: Physicochemistry
- Procedure steps: 7
- Total time of stages: 1 h 11 min–1 h 56 min
- Measurement range: 0.004–30,000 mg C/L (depending on analyzer)
- Detection limit: 4 µg/L (catalytic combustion, Shimadzu TOC-L)
- Accuracy: ±2–5% (depending on method and range)
Overview
Total Organic Carbon (TOC) is a sum parameter describing the content of organic compounds in water, expressed as the mass of organic carbon in mg C/L. It is a universal indicator of organic pollution—it includes all dissolved and suspended organic compounds, regardless of their susceptibility to biological or chemical oxidation.
The PN-EN ISO 8245 standard provides guidelines for determining TOC and dissolved organic carbon (DOC) in various water types: drinking, groundwater, surface, marine, and wastewater. Two main methods are used: catalytic combustion at high temperature (680°C) with NDIR detection and wet oxidation (persulfate + UV) with NDIR detection.
Permissible TOC concentration in drinking water: without anomaly (Journal of Laws 2017 item 2294)—practically <5 mg C/L. Mandatory parameter in drinking water, ultrapure water (pharmaceuticals, electronics), and wastewater monitoring.
Method principle
TOC determination includes: (1) inorganic carbon (TIC) removal—sample acidification with HCl/H₃PO₄ and purging with carrier gas (O₂ or air) to expel CO₂ from dissolved carbonates/bicarbonates; (2) organic carbon oxidation—in catalytic combustion method, sample is injected into furnace with platinum catalyst at 680°C, where all organic compounds undergo complete combustion to CO₂; (3) CO₂ detection—carrier gas with CO₂ passes through NDIR (non-dispersive infrared) detector, which measures CO₂ concentration proportional to organic carbon content.
Applications
- Drinking water quality control (Journal of Laws 2017 item 2294)
- Ultrapure water monitoring (pharmaceuticals, electronics, semiconductors)
- Wastewater treatment plant efficiency control
- Surface and groundwater monitoring
- Water treatment system validation (reverse osmosis, activated carbon)
- Water for injection (WFI) purity control in pharmaceutical industry
Key parameters
| Parameter | Value |
|---|---|
| Measurement range | 0.004–30,000 mg C/L (depending on analyzer) |
| Detection limit | 4 µg/L (catalytic combustion, Shimadzu TOC-L) |
| Accuracy | ±2–5% (depending on method and range) |
| Methods | Catalytic combustion (680°C) or wet oxidation (UV/persulfate) |
| Detector | NDIR (non-dispersive infrared) |
| Analysis time | 3–10 minutes per sample |
Standard
- Standard number
- PN-EN 1484:1999
- Title (PL)
- Jakość wody — Wytyczne dotyczące oznaczania ogólnego węgla organicznego (OWO) i rozpuszczonego węgla organicznego (RWO)
- Title (EN)
- Water quality — Guidelines for the determination of total organic carbon (TOC) and dissolved organic carbon (DOC)
Step-by-step procedure
-
Analyzer startup
Turn on TOC analyzer, combustion furnace, NDIR detector, and carrier gas flow. Wait for baseline stabilization (30–60 min).
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Calibration
Prepare TOC standard series from KHP: 0.5; 1.0; 2.0; 5.0; 10.0 mg C/L (for drinking water). Run calibration sequence. Correlation coefficient r² > 0.999.
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Sample preparation
For TOC—shake sample (suspended particles). For DOC—filter through 0.45 µm. Transfer to glass vials (acid-washed and rinsed with ultrapure water).
-
Acidification and purging (TIC removal)
Analyzer automatically adds H₃PO₄ and purges sample with carrier gas (sparging), removing CO₂ from carbonates and bicarbonates.
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Combustion and detection
Sample is injected into combustion furnace (680°C, Pt catalyst). Organic compounds → CO₂. Carrier gas transports CO₂ to NDIR detector, which measures peak area.
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Result reading
Software calculates TOC concentration based on calibration curve. Result in mg C/L. Each measurement performed in replicates (typically 3×), reporting mean and deviation.
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Quality control
Blank (ultrapure water), CRM control sample, duplicates every 10 samples. Check repeatability (CV <5%). Vial cleanliness control.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| TOC analyzer | Shimadzu TOC-L, Analytik Jena multi N/C x300, Mettler Toledo 5000e, Sievers M9 | 80,000–250,000 PLN |
| Autosampler | Shimadzu ASI-L, Analytik Jena APG | 30,000–80,000 PLN |
| Sample vials (40 mL) | Glass vials with PTFE/silicone septa | 3–10 PLN/piece |
| Syringes for samples (optional) | Hamilton, for manual dosing | 200–800 PLN |
| Water purification system | Millipore Milli-Q, Hydrolab—water with TOC <0.05 mg/L | 20,000–60,000 PLN |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| Phosphoric acid (H₃PO₄) 2 mol/L | 7664-38-2 | For acidifying samples to remove inorganic carbon (TIC). p.a. purity. |
| Platinum catalyst on Al₂O₃ support | — | Combustion column packing (replacement every 3000–5000 analyses). Operating temperature 680°C. |
| Organic carbon standard solution (potassium hydrogen phthalate KHP) | 877-24-7 | C₈H₅KO₄—primary standard. 2.1254 g KHP in 1 L water = 1000 mg C/L. For analyzer calibration. |
| Inorganic carbon standard solution (Na₂CO₃ + NaHCO₃) | — | Na₂CO₃ (3.497 g) + NaHCO₃ (4.412 g) in 1 L water = 1000 mg C/L TIC. For TIC calibration. |
| Carrier gas—oxygen or synthetic air | — | Purity 99.999%. Operating pressure 100–200 kPa. |
| Ultrapure water (TOC <0.05 mg/L) | — | For preparing standards and blanks. From Milli-Q or equivalent system. |
Health and safety (OHS)
- Combustion furnace (680°C)—burn risk. Do not touch heating elements.
- Phosphoric acid (H₃PO₄)—corrosive (H314). Use gloves and glasses.
- Carrier gas (pressurized oxygen)—pressure cylinder. Secure against tipping. Do not grease.
- Work with pressure cylinders—use reducer and safety valve.
- Safety glasses and lab coat required.
Frequently asked questions
Which standard describes this test?
The test is performed according to PN-EN 1484:1999 — “Water quality — Guidelines for the determination of total organic carbon (TOC) and dissolved organic carbon (DOC)”.
How does this method work?
TOC determination includes: (1) inorganic carbon (TIC) removal—sample acidification with HCl/H₃PO₄ and purging with carrier gas (O₂ or air) to expel CO₂ from dissolved carbonates/bicarbonates; (2) organic carbon oxidation—in catalytic combustion method, sample is injected into furnace with platinum catalyst at 680°C, where all organic compounds undergo complete combustion to CO₂; (3) CO₂ detection—carrier gas with CO₂ passes through NDIR (non-dispersive infrared) detector, which measures CO₂ concentration proportional to organic carbon content.
What is the measuring range and accuracy?
Measurement range: 0.004–30,000 mg C/L (depending on analyzer); Detection limit: 4 µg/L (catalytic combustion, Shimadzu TOC-L); Accuracy: ±2–5% (depending on method and range); Methods: Catalytic combustion (680°C) or wet oxidation (UV/persulfate).
How long does the test take?
The times given for the individual stages add up to approximately 1 h 11 min–1 h 56 min. The procedure comprises 7 steps.
What equipment is required?
TOC analyzer, Autosampler, Sample vials (40 mL), Syringes for samples (optional), Water purification system. Indicative cost of the core instrument (TOC analyzer): 80,000–250,000 PLN.
Where is this test used?
Drinking water quality control (Journal of Laws 2017 item 2294); Ultrapure water monitoring (pharmaceuticals, electronics, semiconductors); Wastewater treatment plant efficiency control; Surface and groundwater monitoring; Water treatment system validation (reverse osmosis, activated carbon); Water for injection (WFI) purity control in pharmaceutical industry.
What safety precautions apply?
Combustion furnace (680°C)—burn risk. Do not touch heating elements.; Phosphoric acid (H₃PO₄)—corrosive (H314). Use gloves and glasses.; Carrier gas (pressurized oxygen)—pressure cylinder. Secure against tipping. Do not grease.; Work with pressure cylinders—use reducer and safety valve.; Safety glasses and lab coat required.
Which laboratory can perform this test?
The test is performed by laboratories accredited to ISO/IEC 17025. On LabCoda you can find them by the standard number PN-EN 1484.