The invention concerns an interfacing device (1) intended to connect a fluid injection instrument and a puncturable flask (2), comprising: a base (10) suitable for connecting the interfacing device (1) to the fluid injection instrument, an attachment means for attaching (20) the base (10) to the puncturable flask (2), arranged at a distal end (1a) of the interfacing device (1), characterised in that the attachment means for attaching (20) has a divergent proximal end (21) forming a shoulder and a convergent distal end (22) suitable for facilitating the penetration of the attachment means for attaching (20) into the puncturable flask (2).
