2D disposable stochastic strip for ultrasensitive assay of Pb(II) and Cd(II) in sapropel

Pollution with heavy metals like Pb and Cd may have a strong influence on the quality of sapropel - which is used in cosmetics, or medical treatments. The ultrasensitive on-site assay of Pb(II) and Cd(II) when their concentration is very low is an important issue for both environment and the health of people using the sapropel. A 2D disposable strip based on graphene modified with α-cyclodextrin (as working electrode) was designed, characterised and validated for the on site simultaneous assay of Pb(II) and Cd(II) in sapropel. Silk was used as support material. Wide concentration range, from 0.01 fg mL^-1 to 1 μg mL^-1, with high sensitivities (2.96 × 10⁶ s^-1 mol^-1 L for Cd(II), and 6.80 × 10⁸ s^-1 mol^-1 L for Pb(II) when the measurements were done in standard solutions) were recorded for both ions. Validation of the proposed stochastic sensing strip and screening method for Cd and Pb ions is done versus the gold standard method - ICP-MS method using sapropel samples; recoveries of 99.15% and 99.93% were recorded for Cd(II) and Pb(II) in sapropel. The reliability of the design of sensing strip is high and the sensing strips are stable for at least ten weeks, when kept at room temperature.