A centrifugal evaporator is described having internally of a chamber a source of IR radiation which directs energy towards a sample support platform on which a microtitre plate is mounted in use, for rotation within the chamber. The wells of the microtitre plate will normally contain liquid samples which are to be evaporated whilst subjected to heat from the IR source and centrifugal force from the rotation of the platform. The swing characteristic of the latter allows the plate to be mounted and demounted with the plate generally horizontal, but as the support platform is rotated, it swings up through approximately 90 so that the wells are now substantially horizontal and the plate is now substantially vertical, so that centrifugal force pins the liquid at the bottom of the wells. A layer of thermally conductive compliant material is located between the underside of the wells of the microtitre plate and the support platform, such that during centrifuging the underside of the wells become embedded in the compliant material, to increase the area of contact between the wells and the material to increase heat transfer therebetween. Since the wells may be at least in part translucent or transparent, the compliant material is selected as being a poor conductor of electromagnetic radiation in the range 200-3000 nm.