An apparatus for chemical separations, comprising: at least two substantially rigid and fluidically connected microfluidic substrates (250-1, 250-2), including a first substrate providing a separation substrate (250-2) and a second substrate providing a load substrate (250-1); the load substrate (250-1) having a fluid-conducting channel (300-1) extending from a first aperture to a second aperture wherein a first fitting (320-1) and a second fitting (320-2) are each coupled about a respective aperture, the separation substrate (250-2) having a fluid-conducting channel (300-2) extending from a first coupler (322-2) coupled about an aperture of the separation substrate (250-2), the separation substrate (250-2) and the load substrate (250-1) being coupled to each other via first (322-1) and second (322-2) couplers associated with said fittings (320-1; 320-2), said couplers (322-1, 322-2) being formed of a deformable material deformable relative to a material of the separation substrate (250-2) and a material of the load substrate (250-1) and being aligned to apertures in said substrates (250-2), (250-1) via alignment fittings (325-1, 325-2; 326-1, 326-2), wherein each of said couplers (322-1, 322-2) has an associated pair of alignment fittings (325-1, 326-1; 325-2, 326-2) with one fitting (325-1, 325-2) on the load substrate's (250-1) underside and the other fitting (326-1, 326-2) on the separation substrate's (250-2) top side, and wherein said second coupler (322-2) provides a channel for passing fluid through the fluid conducting channel (300-1) of the load substrate (250-1) to reach the fluid conducting channel (300-2) of the separation substrate (250-2). at least two substantially rigid and fluidically connected microfluidic substrates (250-1, 250-2), including a first substrate providing a separation substrate (250-2) and a second substrate providing a load substrate (250-1); the load substrate (250-1) having a fluid-conducting channel (300-1) extending from a first aperture to a second aperture wherein a first fitting (320-1) and a second fitting (320-2) are each coupled about a respective aperture, the separation substrate (250-2) having a fluid-conducting channel (300-2) extending from a first coupler (322-2) coupled about an aperture of the separation substrate (250-2), the separation substrate (250-2) and the load substrate (250-1) being coupled to each other via first (322-1) and second (322-2) couplers associated with said fittings (320-1; 320-2), said couplers (322-1, 322-2) being formed of a deformable material deformable relative to a material of the separation substrate (250-2) and a material of the load substrate (250-1) and being aligned to apertures in said substrates (250-2), (250-1) via alignment fittings (325-1, 325-2; 326-1, 326-2), wherein each of said couplers (322-1, 322-2) has an associated pair of alignment fittings (325-1, 326-1; 325-2, 326-2) with one fitting (325-1, 325-2) on the load substrate's (250-1) underside and the other fitting (326-1, 326-2) on the separation substrate's (250-2) top side, and wherein said second coupler (322-2) provides a channel for passing fluid through the fluid conducting channel (300-1) of the load substrate (250-1) to reach the fluid conducting channel (300-2) of the separation substrate (250-2). <EOS>