A method for determining a concentration of a contaminant in a first sample, the method including producing the first sample, including adding a plurality of immuno-beads to a test substance; exposing a crystal microbalance immunosensor to the first sample; determining a change in a first motional resistance of the crystal microbalance immunosensor following exposure to the first sample (ΔR1); and determining the concentration of the contaminant in the first sample according to ΔR1.