Raman on a disc: high-quality Raman spectroscopy in an open channel on a centrifugal microfluidic disc

The implausible combination of centrifugal disc microfluidics and un-covered channels provides a simple way in which Raman spectroscopy can be implemented in industrially-relevant lab-on-a disc technology. Here we demonstrate these advantages by detecting very low concentrations of melamine in liquid milk, without pre-processing, without surface enhancement of the Raman signal and with no evidence of spectral contamination from the polymeric chip itself. A limit of detection (LOD) of 203 ppm for melamine in milk was achieved from Raman spectra of milk after drying. The centrifugal disc rotation and micro-channel geometry results in rapid and reliable filling of the channels and in meniscus shape control, enabling reproducible Raman detection with quantitative precision.