Total Organic Carbon (TOC) Analyzer

Total Organic Carbon (TOC) analysis quantifies organic carbon present in water samples. It is widely used in pharmaceutical purified water systems, environmental monitoring, power plants, and wastewater treatment laboratories operating under ISO 17025.

Working Principle

TOC analyzers measure carbon by oxidizing organic compounds into CO₂ and detecting the generated carbon dioxide.

• High temperature combustion (680–1000°C)
• UV-Persulfate oxidation
• Wet chemical oxidation

The generated CO₂ is measured using Non-Dispersive Infrared (NDIR) detection.

Measurement Formula

TOC = TC − IC

Where:
TC = Total Carbon
IC = Inorganic Carbon

Inorganic carbon is removed through acidification and purging before TOC determination.

Worked Example

Measured Total Carbon (TC) = 15.5 mg/L Measured Inorganic Carbon (IC) = 4.0 mg/L

TOC = 15.5 − 4.0 = 11.5 mg/L

Result must comply with regulatory limits (e.g., ≤ 500 ppb for pharmaceutical PW).

Limit of Detection (LOD)

LOD = 3 × (σ / S)

Where:
σ = Standard deviation of blank
S = Calibration slope

Low ppb-level detection is critical for pharmaceutical compliance.

Troubleshooting Logic Flow

• High blank → Contaminated reagents
• Low recovery → UV lamp aging
• Drift → NDIR cell contamination
• Inconsistent results → Acidification error

ISO 17025 Technical Control Points

• Calibration verification standards
• Blank check documentation
• System suitability testing
• Oxidation efficiency validation
• Uncertainty estimation and traceability

Part of Laboratory Engineering Hub

TOC analysis is a key water quality monitoring technique within our complete laboratory analyzer engineering framework.

Explore the full Laboratory Engineering reference: Laboratory Analyzers – Engineering Fundamentals