An apparatus for chemical separations comprising: a microfluidic substrate having an outlet aperture for outputting an eluent of a sample; an emitter assembly having a deformable end portion, an inlet near the end portion to receive the sample eluent from the microfluidic substrate, and an electrically conductive tip to emit a spray of the sample eluent; and a force-applying unit applying a force to the emitter assembly that urges the end portion into contact with the microfluidic substrate, the deformable end portion being more elastic than the microfluidic substrate so that the contact between the microfluidic substrate and the deformable end portion produces a substantially fluid-tight seal between the outlet aperture of the microfluidic substrate and the inlet of the emitter assembly, characterised in that: the electrically conductive tip of the emitter assembly is the outlet portion of an electrical conductive emitter tube and the emitter assembly further comprises a tubing assembly disposed around and coupled to the emitter tube, and the tubing assembly comprises: a first tube section having the deformable end portion; a second tube section abutting the first tube section end-to-end; and a third tube section spatially separated from the second tube section by a gap, and the apparatus further comprises an electrically conductive block disposed around a distal end of the tubing assembly and the emitter tube, the electrically conductive block having a bore through which the tubing assembly and emitter tube extend, with the tip of the emitter tube extending beyond a distal end of the electrically conductive block. a microfluidic substrate having an outlet aperture for outputting an eluent of a sample; an emitter assembly having a deformable end portion, an inlet near the end portion to receive the sample eluent from the microfluidic substrate, and an electrically conductive tip to emit a spray of the sample eluent; and a force-applying unit applying a force to the emitter assembly that urges the end portion into contact with the microfluidic substrate, the deformable end portion being more elastic than the microfluidic substrate so that the contact between the microfluidic substrate and the deformable end portion produces a substantially fluid-tight seal between the outlet aperture of the microfluidic substrate and the inlet of the emitter assembly, characterised in that: the electrically conductive tip of the emitter assembly is the outlet portion of an electrical conductive emitter tube and the emitter assembly further comprises a tubing assembly disposed around and coupled to the emitter tube, and the tubing assembly comprises: a first tube section having the deformable end portion; a second tube section abutting the first tube section end-to-end; and a third tube section spatially separated from the second tube section by a gap, and the apparatus further comprises an electrically conductive block disposed around a distal end of the tubing assembly and the emitter tube, the electrically conductive block having a bore through which the tubing assembly and emitter tube extend, with the tip of the emitter tube extending beyond a distal end of the electrically conductive block. the electrically conductive tip of the emitter assembly is the outlet portion of an electrical conductive emitter tube and the emitter assembly further comprises a tubing assembly disposed around and coupled to the emitter tube, and the tubing assembly comprises: a first tube section having the deformable end portion; a second tube section abutting the first tube section end-to-end; and a third tube section spatially separated from the second tube section by a gap, and a first tube section having the deformable end portion; a second tube section abutting the first tube section end-to-end; and a third tube section spatially separated from the second tube section by a gap, and the apparatus further comprises an electrically conductive block disposed around a distal end of the tubing assembly and the emitter tube, the electrically conductive block having a bore through which the tubing assembly and emitter tube extend, with the tip of the emitter tube extending beyond a distal end of the electrically conductive block.