How was it proved that minerals pass through xylem and not phloem?

Hint: The complex tissue is formed of more than one type of cells and combinedly works as a single unit and is also involved in transportation of water and minerals. This complex tissue also provides mechanical strength to parts of plants.

Complete step-by-step answer:
Xylem functions as a conducting tissue for water and minerals via roots to different parts of the plant. Water and minerals enter the plant through the epidermis of roots from the soil, the root cortex is radially crossed, and then passes into the xylem and moves upward. It is very important for a plant to transport water and minerals from the soil to the uppermost parts of the leaves. The upward movement of water and minerals which go against the gravitational force from root to the aerial parts of the plant through xylem is known to be ‘the ascent of sap’. The tissues of Xylem carry water and dissolved minerals upwards from roots.
The elements of xylem are as follows: -
> Tracheids
> Vessel elements
> Xylem Parenchyma
 > Xylem fibres.
Additional information: As the water is absorbed by the plants, it moves deeper into the roots by the following two pathways:
Apoplast pathway which is the movement through the intercellular spaces and the walls of the cells.
Symplast pathway defined as the movement through the cytoplasm of a cell.

Note: The movement of Water and minerals are generally by a mass flow (or bulk flow) system. It is defined as the bulk movement of a substance from one point to another due to the pressure differences. Bulk flow can be obtained by either positive or negative pressure. Mass flow or bulk flow generally occurs due to the adhesive and cohesive forces of water.