All of the cosmetics listed in Table 1 displayed background responses of ≤0.003 in
presence of 50% PBSTM except eye make up remover C (EMR C) and shampoo D. EMR C and shampoo D displayed backgrounds of 0.01 and 0.004, respectively. It is therefore recommended that a threshold greater than 0.01 be used with the Guardian Reader™. The average responses for EMR C and shampoo D, each containing 5 ng/mL ricin in the analytical sample, were 0.030+0.005 and 0.05+0.01, respectively; both considerably above the background responses.