Determination of water in food by automated Karl Fischer titration

Importance of the topic

Karl Fischer titration (KFT) is a selective, absolute and highly accurate technique for measuring water content in diverse food matrices. It is crucial for quality control, shelf-life assessment, and ensuring compliance with regulatory standards in the food industry. Automated KFT enhances throughput and precision, making it valuable for routine analysis of trace water levels in oils and other low-moisture samples.

Aims and overview of the study

The study aimed to develop and optimize automated volumetric and coulometric Karl Fischer titration protocols for determining water content in edible oils. A commercially available automated KFT system was employed to compare performance against traditional manual titration and evaluate method parameters across different oil types.

Methodology and instrumentation

The investigation involved:

• Volumetric KFT for higher water levels (1–100%) using an iodine titrant.
• Coulometric KFT for trace water detection (0.001–1%) via electrochemical iodine generation.
• Optimization of sample introduction: transfer volumes, air bubbles, aspiration sequences, special rinse liquids, and transfer speeds.

Instruments used

• Metrohm 841 Titrando with Dosino and Dosing Unit (807) for volumetric KFT
• Metrohm 756 KF Coulometer for coulometric KFT
• 801 Magnetic Stirrer
• 815 Robotic USB Sample Processor
• HYDRANAL® reagents and Sigma-Aldrich solvents

Main results and discussion

• Water contents in six edible oils ranged from 79 to 690 μg/g; soybean oil exhibited the lowest moisture level.
• Automated titration showed high recovery rates (volumetric: 99.4–100.2%, coulometric: 98.6–99.7%) with water standards.
• Agreement between manual and automated methods was within 97–105% for most oils; deviations in soybean oil were linked to its water content near the detection limit.
• Method optimization ensured reliable aspiration and transfer even in viscous, low-moisture samples by adjusting bubble sequences and transfer speeds.

Benefits and practical applications

Automated KFT protocols deliver:

• Increased sample throughput and reduced hands-on time.
• Improved precision and reproducibility, especially for trace water analysis.
• Adaptable sequences for diverse sample types, supporting routine QA/QC in food production.

Future trends and potential applications

• Integration with advanced robotics and sample preparation modules for end-to-end automation.
• Real-time monitoring and data analytics to support process control in food manufacturing.
• Expansion to other low-moisture matrices (powders, dehydrated ingredients, pharmaceuticals).
• Miniaturized and portable KFT systems for field analysis and on-site quality checks.

Conclusion

The study demonstrates that automated volumetric and coulometric Karl Fischer titration provides robust, accurate, and efficient determination of water in edible oils. Method optimization and reliable instrumentation ensure consistent results, making automated KFT a preferred choice for modern analytical laboratories and industrial QA/QC workflows.

Reference

• Felgner A., Schlink R., Kirschenbühler P., Faas B., Isengard H.-D. Determination of water in food by automated Karl Fischer titration. Metrohm poster 8.000.6079EN.
• Sigma-Aldrich Laborchemikalien, Seelze, Germany; HYDRANAL® reagents.
• University of Hohenheim, Institute for Food Science and Biotechnology, Stuttgart, Germany.
• Metrohm AG, Herisau, Switzerland; Deutsche Metrohm GmbH & Co. KG, Filderstadt, Germany.