Magnetic Stirring May Cause Irreproducible Results in Chemical Reactions

Magnetic stirrers, the most widely used and ubiquitous devices for performing chemical reactions in laboratory settings, may cause reproducibility problems. Reproducibility in a range of chemical processes can be affected by various factors, ranging from minor to significant effects, including yield, composition, and glassware contamination. In this study, we illustrate the reproducibility issues that may arise from the use of a magnetic stirrer for three fundamental types of chemical reactions. Significant differences were found in the reaction rates and sizes of the nanoparticles obtained via parallel synthesis with the same magnetic stirrer. For catalyst preparation, differences were observed in the morphology of the metal nanoparticles and the process rate depending on the location of the reaction vessel on the magnetic stirrer. In the case of organic synthesis examples, the conversions of parallel catalytic cross-coupling reactions in vessels standing beside each other on the same magnetic stirrer can be significantly different. The results of these experiments revealed the influence of previously unaccounted-for factors, and here, we suggest a control experiment to improve reproducibility. Given the ubiquitous use of magnetic stirrers in chemistry, biology, life sciences, and material sciences, the revealed reproducibility-affecting factor is of broad concern.