All of the cosmetics listed in Table 1 displayed
background responses of ≤0.003 in the 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.