Neurotransmitter sensing is currently a challenge in biomedical research, and optoelectronic sensing may play an important role in this field. In particular, miniature visible-light photo-spectrometers can be very useful for molecular detection. In this respect, this work evaluates a new type of spectrometer geometry based on the grism, or grating-prism, which combines an optical grating and an optical prism. The system was first designed in either transmission or reflection geometry, and then adapted to fit commercially available components so that a prototype could be fabricated in the laboratory. The comparison with a more conventional approach shows that the grism-based spectrometer offers superior resolution as well as a smaller footprint