Apparatus and method for downhole formation testing using a spectrometer includes a carrier conveyable into a well borehole that traverses a subterranean formation of interest, a plurality of semiconductor light sources disposed on the carrier, a fluid sample cell that receives light emitted from the plurality of semiconductor light sources, and at least one photodetector that detects light emitted from the plurality of semiconductor light sources and after the light interacts with a fluid in the fluid sample cell.