Development of quality control materials from CO/N2 gas mixture based on ISO Guide 80 for controlled environmental measurementsements

This study presents the development of quality control materials (QCMs) for monitoring carbon monoxide (CO) concentrations using a validated gas chromatography-thermal conductivity detector (GC-TCD) method. The QCMs were prepared gravimetrically according to ISO 6142, using a three-step dilution process from pure CO and nitrogen. The resulting QCMs have a target amount fraction of 1000 µmol/mol (ppm). To assess homogeneity, the QCMs were analyzed using a validated GC-TCD system calibrated with certified reference materials (CRMs). One-way analysis of variances (ANOVA) revealed excellent homogeneity among the QCMs. Stability was evaluated based on previous studies of similar CO/N2 mixtures demonstrating long-term stability. Characterization of the QCMs by GC-TCD confirmed an amount fraction of 1004.65 µmol/mol, which was found in good compatibility of the gravimetric value. A quality control chart with upper and lower control limits was implemented for five months, validating the successful preparation of the QCMs. This research offers a reliable approach for laboratories to develop in-house QCMs for CO measurements, ensuring the accuracy and traceability of their results to the (SI) units.