possibly ninhydrin - reacts with primary amino groups to give a very intense color.

Are you referring to protein in urine dip sticks??

Thanks Wayne but I heard that there is a storage for some complex that randomly labels proteins or analyte non specifically which are then captured by immobilized antibodies. It will be great help if you can shed some light on this complex or chronometer. Cheers

I need to learn lateral flow assay can someone please share the videos for different steps of this assay as are available for other tests like PCR. I am hesitant to start my assay as I feel totally blank and have just the theoretical knowldge for LFA but no hands on training. As I am out sourcing the antibodies that are quite expensive and I dont want to waste my chemicals. Therefore please share different steps of membrane assembling, blocking of membrane, making various buffers, making colloidal gold particles and dilution as well as immobilization of antibodies on membrane. I have found few videos but that are not really helpful.