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Due to the serious risks of lead pollution to human health, it plays a great role in constructing a simple, inexpensive, portable, and user-friendly strategy for Pb2+ detection in environmental samples. Herein, a paper-based distance sensor is developed to detect Pb2+ assisted with the target-responsive DNA hydrogel. Pb2+ can activate DNAzyme to cleave its substrate strand, which results in the hydrolysis of the DNA hydrogel. The released water molecules trapped in the hydrogel can flow along the patterned pH paper due to the capillary force. The water flow distance (WFD) is significantly influenced by the amount of water released from the collapsed DNA hydrogel triggered by the addition of various Pb2+ concentrations. In this way, Pb2+ can be quantitatively detected without using specialized instruments and labeled molecules, and the limit of detection (LOD) of Pb2+ is 3.0 nM. Additionally, the Pb2+ sensor works well in lake water and tap water. Overall, this simple, inexpensive, portable, and user-friendly method is very promising for quantitative and in-field detection of Pb2+ with excellent sensitivity and selectivity. [Display omitted] • A novel paper-based distance sensor assisted with DNA hydrogel is developed. • The hydrolysis of the DNA hydrogel by Pb2+ triggers release of the water. • The water flow distance is used to assess the level of Pb2+. • The detection of Pb2+ is successfully demonstrated in lake water and tap water. [ABSTRACT FROM AUTHOR]

The possibility of using pyrolyzed paper as disposable working electrodes for trace metals determination is reported for the first time. A small piece of pyrolyzed paper (0.7×0.7 cm) was positioned at the bottom side of the electrochemical cell using a rubber O-ring, which defined the electrode area (0.48 cm; 0.18 cm 2 ). A large number of electrodes can be obtained from a single piece of standard dimensions (2.5 cm×7.5 cm) of paper, therefore minimizing the cost per unit. The electrochemical performance of the pyrolyzed paper was demonstrated by cyclic voltammetry, electrochemical impedance spectroscopy and by the determination of Zn, Cd, and Pb by square-wave anodic stripping voltammetry. The unmodified pyrolyzed paper showed excellent performance for Pb and Cd detection (LOD =0.19 and 0.16 ppb, respectively). In the presence of Bi 3+ (in-situ film formation), the simultaneous determination of Zn, Cd and Pb was also possible (LOD=0.26, 0.25, and 0.39 ppb, respectively). [ABSTRACT FROM AUTHOR]

Abstract: Lead (Pb) contamination in the black paper that recovers intraoral films (BKP) has been investigated. BKP samples were collected from the Radiology Clinics of the Dental School of Ribeirão Preto, University of São Paulo, Brazil. For sake of comparison, four different methods were used. The results revealed the presence of high lead levels, well above the maximum limit allowed by the legislation. Pb contamination levels achieved after the following treatments: paper digestion in nitric acid, microwave treatment, DIN38414-54 method and TCLP method were 997μgg−1, 189μgg−1, 20.8μgg−1, and 54.0μgg−1, respectively. Flame atomic absorption spectrometry (FAAS) and inductively coupled plasma mass spectrometry (ICP-MS) were employed for lead determination according to the protocols of the applied methods. Lead contamination in used BKP was confirmed by scanning electron microscopy coupled with energy dispersive X-ray microanalysis (SEM-EDS). All the SEM imaging was carried out in the secondary electron mode (SE) and backscattered-electron mode (QBSD) following punctual X-ray fluorescence spectra. Soil contamination derived from this product revealed the urgent need of addressing this problem. These elevated Pb levels, show that a preliminary treatment of BKP is mandatory before it is disposed into the common trash. The high lead content of this material makes its direct dumping into the environment unwise. [Copyright &y& Elsevier]