support: pH-strip (w/o test field)

support of unknown material

Dye (Ponceau S) binds proteins unspecifically

Colored monoclonal antibody binds hCG specifically at epitope A

Whatman paper soaked in Ponceu S as dye reservoir

Reservoir of colored antibody reservoir:

Perhaps porous gel

PVDF Membrane w or w/o attached protein BSA

Membranes ? with attached monoclonal antibody directed against different epitope B of hCG

Flow initiated by addition of water

Flow initiated by addition of urine

Detection: Ponceau S binds BSA

Detection: Colored antibody binds hCG, hCG binds to second antibody -> stripe formation

Control field: Membrane with bound BSA

Control field: Third immobilised antibody that detects colored antibody