Scientists assume that reagents supplied commercially have been rigorously tested for purity. We have found that this assumption can be risky.

Our laboratory purchased 3 milligrams of a biomolecule from a reputable supplier to investigate its effect on nerve cells. Anomalous results forced us to test its purity. Using mass spectrometry and qualitative western blotting, we discovered unacceptable levels of contamination with several other biologically active molecules.

Several research groups have published important mechanistic conclusions based on the activity of this molecule. Contamination with other active components would call these results into question.

Reagents that are misleadingly labelled waste researchers' funds and time. Suppliers should declare the accurate composition and modes of analysis for every batch of their products.