An apparatus for heating a surface to liberate at least one analyte for detection thereof includes a source of energy to irradiate the surface and a collector to collect at least one gas from the surface, the at least one gas being capable of including the a least one liberated analyte. The apparatus further includes a detector linked to the collector to detect the presence of the at least one liberated analyte wherein the detection is used to control the power of the energy source by utilizing feedback relating to at least one condition of the surface.