Device comprising: - a support tray for tubes receiving samples to be analysed and into which the tip of a pipette is intended to be inserted, this tray including a plate having an upper face and a lower face and holes arranged in a predetermined pattern, opening into these two faces and each designed to receive a tube bearing against the upper surface and with the bottom thereof projecting from the lower face of the tray, the plate of the tray being delimited by two longitudinal flanged edges parallel to each other and connected to each other by two transverse flanged edges parallel to each other; - a cover comprising a plate having an upper face and a lower face, provided with chimneys arranged in a pattern similar to the pattern of the holes in the tray and provided with stops limiting the insertion of the pipette tips, the plate of the cover being delimited by two longitudinal flanged edges parallel to each other and connected to each other by two transverse flanged edges parallel to each other; - the tray and the cover including a removable assembly system including two elastically deformable tabs formed in the flanged edges of the cover and each cooperating with a complementary seat formed in each of the flanged edges of the tray to achieve elastic interlocking, when the cover is in a stacking position above the tray and the flanged edges thereof are bearing against the tray to form a unitary assembly for holding the tubes and to position the chimneys above the tubes to guide the pipette tips penetrating the inside of the tubes and to stop them by means of the stops so that the distal end of the tip of the pipette substantially reaches the inner wall of the bottom of the tubes. - a support tray for tubes receiving samples to be analysed and into which the tip of a pipette is intended to be inserted, this tray including a plate having an upper face and a lower face and holes arranged in a predetermined pattern, opening into these two faces and each designed to receive a tube bearing against the upper surface and with the bottom thereof projecting from the lower face of the tray, the plate of the tray being delimited by two longitudinal flanged edges parallel to each other and connected to each other by two transverse flanged edges parallel to each other; - a cover comprising a plate having an upper face and a lower face, provided with chimneys arranged in a pattern similar to the pattern of the holes in the tray and provided with stops limiting the insertion of the pipette tips, the plate of the cover being delimited by two longitudinal flanged edges parallel to each other and connected to each other by two transverse flanged edges parallel to each other; - the tray and the cover including a removable assembly system including two elastically deformable tabs formed in the flanged edges of the cover and each cooperating with a complementary seat formed in each of the flanged edges of the tray to achieve elastic interlocking, when the cover is in a stacking position above the tray and the flanged edges thereof are bearing against the tray to form a unitary assembly for holding the tubes and to position the chimneys above the tubes to guide the pipette tips penetrating the inside of the tubes and to stop them by means of the stops so that the distal end of the tip of the pipette substantially reaches the inner wall of the bottom of the tubes.