Selective Solid-Phase Extraction of Lead Ions in Water Samples Using Three-Dimensional Ion-Imprinted Polymers

Ion-imprinted polymers (IIPs) have drawn much attention in the selective determination of heavy metals. In this study, 8-hydroxyquinoline-grafted gelatin with different types of functional groups was first introduced as a biomolecular monomer to enhance the selectivity of imprinted cavities. Based on its swelling and film-forming properties, a simple strategy containing formation of the hydrogel film, swelling/folding followed by cross-linking, was proposed to prepare three-dimensional IIPs with high adsorption capacity (235.7 mg g^–1), strong selectivity (imprinted factor was 2.9), and rapid kinetics. Based on the different swelling container, different morphologies of IIPs could be prepared to satisfy the requirements of practical application. Consequently, the IIPs extraction coupled with a spectrophotometric method was applied for determination of lead ions, and the limit of detection was 0.2 ng mL^–1, which could be used for monitoring of Pb­(II) in drinking water and surface water

DPV curves (A) of the MIP/ABP electrode in different concentrations of AZM (from a to i): 0.1, 0.2, 0.5, 1, 2, 5, 10, 15 and 20 μM. Calibration curve (B) of AZM under the optimized conditions.

<p>DPV curves (A) of the MIP/ABP electrode in different concentrations of AZM (from a to i): 0.1, 0.2, 0.5, 1, 2, 5, 10, 15 and 20 μM. Calibration curve (B) of AZM under the optimized conditions.</p

Current responses of 2 × 10⁻⁶ mol L⁻¹AZM and other five MACs obtained at the MIP/ABP and NIP/ABP electrodes (A). Current responses of 2 × 10⁻⁶ mol L⁻¹ AZM and 2 × 10⁻⁴ mol L⁻¹ other six compounds obtained at the MIP/ABP and NIP/ABP electrodes (B).

<p>The other conditions are the same as that in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0147002#pone.0147002.g003" target="_blank">Fig 3B</a>.</p

Interference levels of several tested substances in the determination of 2 × 10⁻⁶ mol L⁻¹ AZM by the developed sensor.

<p>Interference levels of several tested substances in the determination of 2 × 10⁻⁶ mol L⁻¹ AZM by the developed sensor.</p

Optimization of different conditions affecting the current response of AZM, including the amount of MIP (A), the ratio of AB/MIP (B), the amount of paraffin oil (C), incubation time (D), and stirring rate (E).

<p>The other conditions are the same as that in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0147002#pone.0147002.g003" target="_blank">Fig 3B</a>.</p

DPV curves (A) of the MIP/ABP electrode in different concentrations of AZM (from a to i): 0.1, 0.2, 0.5, 1, 2, 5, 10, 15 and 20 μM. Calibration curve (B) of AZM under the optimized conditions.

<p>DPV curves (A) of the MIP/ABP electrode in different concentrations of AZM (from a to i): 0.1, 0.2, 0.5, 1, 2, 5, 10, 15 and 20 μM. Calibration curve (B) of AZM under the optimized conditions.</p

Detection of AZM in real samples by the developed electrochemical method (<i>n</i> = 3) and HPLC-MS/MS method (<i>n</i> = 3).

<p>Detection of AZM in real samples by the developed electrochemical method (<i>n</i> = 3) and HPLC-MS/MS method (<i>n</i> = 3).</p

The SEM images of various electrodes, MIP and NIP.

<p>CP (A), ABP (B), MIP/ABP (C), NIP/ABP (D) electrodes, MIP (E) and NIP (F).</p

Cyclic voltammograms (A) and differential pulse voltammograms (B) of AZM on CP, ABP, MIP/CP, NIP/CP, MIP/ABP and NIP/ABP electrode in PBS (0.1 M, pH 7.0).

<p>Conditions: (A) The concentration of AZM is 1 × 10⁻⁵ mol L⁻¹, potential scan range: 0.4 V–1.0 V, scan rate: 100 mV s⁻¹; (B) The concentration of AZM is 2 × 10⁻⁶ mol L⁻¹, scan rate: 20 mV s⁻¹, pulse amplitude: 50 mV, pulse width: 40 ms.</p

Comparison of the presented MIP/ABP electrode with other reported electrodes for AZM determination.

<p>Comparison of the presented MIP/ABP electrode with other reported electrodes for AZM determination.</p