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The measurement of ultra-trace level of heavy metals in complex metrics is of great concern and challenge in life and environmental science. Herein, a novel thiol-functionalized covalent organic framework (COF) was prepared and achieved quantitative preconcentration of trace heavy metals in environmental water samples. The material was synthetized by two-step reactions, including a Schiff base reaction between 1,3,5-triformylphloroglucinol (Tp) and 2,5-divinyl-p-phenylenediamine (DvPa) to form preliminary COF (TpDvPa), and a thiol-ene “click” reaction between 1,2-ethanedithiol and the vinyl groups of TpDvPa to produce thiol-functionalized TpDvPa (TpDvPa-S-SH). By packing the material into a home-made SPE micro-column, and hyphenating the micro-column with inductively coupled plasma mass spectrometry (ICP-MS), trace level of Co2+, Ni2+ and Cd2+ in environmental waters could be successfully preconcentrated and measured, with LODs of 1.46, 1.38 and 0.10 ng L-1, respectively. The precisions were all less than 2.7%，with linear ranges extended from 5 to 1000 ng L-1. The proposed method was validated by the analysis of the certificated reference material (GBW08608), and measurement of Co2+, Ni2+ and Cd2+ in tap water, reservoir water, effluent of wastewater treatment plant and sea water, confirming the accuracy and feasibility of the method.

In this work, ZnO nanorods (ZnO NRs) with different sizes were hydrothermally grown on the surface of Whatman filter paper for the fabrication of a microfluidic paper-based device (μPAD) for the simultaneous detection of glucose and uric acid. As dual enzymatic reaction was employed for the colorimetric detection in this μPAD, the presence of ZnO NRs promoted the enzyme immobilization thus significantly enhancing the colorimetric signal. The coffee ring effect was effectively conquered by the uniform distribution of ZnO NR as well as a specialized double-layered μPAD design. Meanwhile, two color indicators with distinct colors were used to provide complementary results to better quantify the concentration of the analytes by naked eye. As a result, two linear calibration curves were obtained for the detection of glucose (0.01–10 mmol L−1) and uric acid (0.01–5 mmol L−1), along with a LOD of 3 μmol L−1 for glucose and 4 μmol L−1 for uric acid, respectively. The practical usefulness of the proposed μPAD was further validated by the simultaneous analysis of glucose and uric acid in serum samples and urine samples.