Position of flask on magnetic stirrers can drastically affect reproducibility of experiments

Varying the position of a reaction vessel on a magnetic stirrer can significantly change the outcome of a chemical reaction. That’s the conclusion of scientists working with Valentine Ananikov from the Russian Academy of Sciences, who made this discovery while running the same reaction in parallel in different vials placed side-by-side on the same stirrer. ‘We found that reaction speed, product quality and even the formation of nanoparticles changed depending on the vessel’s location,’ explains Ananikov. ‘In some cases, the differences were large enough to explain why another lab might fail to reproduce the results.’ To solve this problem, the team recommends running control experiments in what they call the ’green zone’ of the stirrer, where stirring is most stable and efficient.