A handheld spectrometer apparatus may comprise an accessory coupled to a spectrometer, where the accessory is configured to receive a liquid sample pipette to facilitate measurement, using the spectrometer, of a liquid sample within the pipette. A handheld spectrometer apparatus to measure a body lumen of a subject can include an illumination unit, a spectrometer unit, a housing containing the illumination unit and the spectrometer unit and an accessory comprising a plurality of optical fibers. The optical fibers can be configured to guide light from the illumination unit to the body lumen and back from the body lumen to the spectrometer unit.