Reliable volcanic gas emission monitoring is crucial when trying to create an understanding of the geophysical processes of volcanoes, and may as well prove a key ingredient in risk assessment. One of the prominent instruments used for volcanic gas flux measurements today is the mini-DOAS instrument, a ground-based optical remote sensing instrument utilizing a UV-spectrometer. Within this thesis, modifications of the mini-DOAS instrument are tested and implemented in order to increase performance at high latitude volcanoes. As the solar elevation angle is lower at high latitudes, less solar UV-light is available because of atmospheric absorption. Replacement of the Ocean Optics S2000 spectrometer with the Ocean Optics Maya2000 Pro is tested, as the Maya2000 has a higher sensitivity to UV-light. Promising results shows that a change of spectrometer at measurement stations by high latitude volcanoes will allow for measurements during a longer time of the day, as well as significantly reduced error levels in the measurements. To get experience working with the mini-DOAS instruments, a field campaign was carried out at the volcano Telica (Nicaragua). The campaign exploited a set of rapid deployment scanning mini-DOAS instruments as well as a mobile DOAS system used for traverses in order to gather data on the SO2 flux of the volcano. Calculated flux indicated an increase in the activity of the volcano. Results from this campaign was later used in a larger study of multidisciplinary observations during the 2011 explosive eruption of the volcano.