Systems and methods for processing and analyzing samples are disclosed. The system (100) may process samples, such as biological fluids, using assay cartridges which can be processed at different processing locations. The system (100) comprises a pipettor, a reagent pack (400) comprising a well (400a) containing a reagent, and a reagent storage unit (124). The reagent storage unit (124) is configured to hold the reagent pack (400) , and includes a cavity containing the reagent pack (400), a latch (144a) arranged about the cavity, the latch (144a) configured to secure and align the reagent pack (400) within the cavity, the latch including a releasing feature (144b), a cover (128) disposed over the cavity and latch 8144a), the cover (128) including a first aperture and a second aperture, wherein the first aperture aligns over the well (400a) of the reagent pack (400) thereby providing the pipettor access to the reagent contained in the well (400a). The second aperture aligns over the releasing feature (144b) thereby providing the pipettor access to actuate the releasing feature (144b) to unsecure the reagent pack (400) from the latch (144a).