We report on a low-energy x-ray fluorescence (LEXRF) spectrometer system implemented in the European TwinMic x-ray spectromicroscope, which is operated in the 280-2200 eV energy range and allows sub-100 nm optical resolution by means of focusing with diffractive optics. The LEXRF setup is a modular system based on the use of multiple windowless large-area silicon drift detectors (SDD). The detectors are read out by a custom pulsed reset preamplifier system optimized for SDDs and specially designed and adapted to geometrical requirements for microscopies at synchrotron facilities. Moreover, a customized fast multi-channel acquisition system developed for elemental mapping applications has been adapted to the microscope requirements. Acquisition of elemental composition by LEXRF maps is accomplished by simultaneous acquisition of absorption and phase contrast images to correlate the morphological structure. The instrumental setup is described and its potential illustrated by recently performed pilot experiments.