The buffer efficiently minimizes cross-reactions, background and unspecific binding without inhibiting the specific binding. The Sample Tracer™ appears red, and when serum or plasma is added the Sample Tracer™ change colour to yellow. The buffer can detect serum or plasma in dilutions up to 1:100. If the advantages with minimum cross-reactions, background and unspecific binding are desired, but without serum detection, we offer a clear version of the Sample Tracer™ without colour shift by sample addition. This product we call the Sample Plus™.