First international comparative study of volatile fatty acids in aqueous samples by chromatographic techniques: Evaluating sources of error

• We describe the state of practice in measurement of volatile fatty acids (VFAs).
• Analytical improvement in measurement of VFAs by field analytical laboratories.
• Human and calibration errors were the main causes of inaccurate measurements.
• Improvement needs interlaboratory comparisons and certified reference materials.

This first international proficiency-testing scheme evaluated the analytical performance and the state of practice in measurement of volatile fatty acids in aqueous samples. Gas chromatography and high-performance liquid chromatography were used by 25 laboratories from 15 different countries. Two reference materials were selected for analysis. The performance of each laboratory was assessed by the internationally-accepted z-score. The overall performance was rather poor. Among the causes of poor analytical performance, human errors and inadequate calibration were probably the major problems encountered.