Method for depositing a spot product of a product of interest, and use for isolating and/or determining an analyte

Process for depositing, on a substrate (1), at least a predetermined amount of at least one product of interest (2), distributed at the surface (1a) of the substrate and delimited according to a basic area (3), which has a low value, referred to as a “spot”, according to which process:

• (a) a liquid medium (4), comprising a vehicle and the product of interest (2) homogeneously distributed in said vehicle, is prepared or is available;
• (b) a drop (5) is formed from the liquid medium, the volume of which drop is determined in relation to the predetermined amount of the product of interest to be deposited, and said drop is placed onto the surface (1a) of the substrate, in contact with the liquid medium;
• (c) the vehicle is removed at least partially from the drop (5), while it remains on the surface (1a) of the substrate (1), for example by drying, so as to allow said spot (3) to remain;
• characterized in that, in combination:
• (1) a magnetic support (6), distributed homogeneously in the form of particles in the vehicle, is prepared or is available;
• (2) the product of interest (2) is bound to the magnetic support (6), as a result of which the liquid medium, from which the drop (5) is formed, comprises transporting particles (7) distributed in the vehicle, each one comprising both the magnetic support (6) and the product of interest (2);
• (3) at least during the removal of the vehicle from the drop (5), a magnetic field (8) is generated which crosses the surface (1a) of the substrate (1) according to a section (1c) comprising, and larger than, the area of contact (1d) between the drop (5) and the substrate (1), as a result of which the spot (3) obtained comprises the transporting particles (7), and therefore the product of interest (2), according to a homogeneous surface distribution.