Does your lab coat fit to your assay?

An explanation for randomly occurring spikes on microplates in fluorescence-based assays employing shorter-wavelength readouts is presented. It is demonstrated that lint originating from standard (white cotton) lab coats is most likely to be responsible for such artifacts in assays applying wavelengths at 380 nm excitation and 450 nm emission. The fluorescence properties of this lint are discussed and compared with those of optical brighteners. An alternative to the use of cotton-based lab coats is presented, which led to a reduction of spikes in a high-throughput screening campaign by 90%.