Co-immobilization strategies are available to improve the catalytic activity, stability and reusability of enzymes. It is applied in reactions involving multi-step catalysis to optimize the performance frequently in recent years....

Achieving direct electrochemical detection of 17β-estradiol (E2) at low concentrations remains a challenge due to the weak electrochemical activity of E2. In this study, we report a simple, cheap, and sensitive electrochemical sensor based on nanocomposite for the direct detection of E2 in wastewater. The nanocomposite sensing electrode was developed by electrochemical in-situ polymerization. Due to the π-π stacking and hydrogen bonding between poly-L-tyrosine (P(L-tyr)) with E2, we prepared P(L-tyr) electrode based on dopamine-modified multi-walled carbon nanotubes (PDA-CNTs) and gold nanoclusters (AuNCs). Then P(L-tyr)/AuNCs/PDA-CNTs/GCE sensing system was obtained. Meanwhile, the synergistic effect of fast electron transfer of AuNCs and the signal amplification effect of PDA-CNTs enables sensitive and direct detection of E2. The results showed that P(L-tyr)/AuNCs/PDA-CNTs/GCE sensor had a linear response to E2 concentration from 0.05 to 10 μmol·L−1 with a detection limit of 7.1 nmol·L−1. Then, the trace amount of E2 in pharmaceutical wastewater samples can be directly detected against several interferences from complex matrix, with recoveries from 91.0 to 107.5%. P(L-tyr)/AuNCs/PDA-CNTs/GCE showed good stability when placed at room temperature. Therefore, it can meet the requirements of the sensitive detection of E2 in complex matrix.

The illegal addition of progesterone to cosmetics could cause serious adverse reactions and pose a serious threat to human health. In this work, a simple, fast and sensitive method was developed by combining molecularly imprinted solid-phase extraction and high-performance liquid chromatography (MISPE–HPLC) for the selective determination of progesterone in cosmetics. Chitosan-modified silica is used as the carrier to provide binding sites for the effective conjugation of the target. The obtained molecularly imprinted polymers exhibited excellent adsorption capacity (36.2 mg·g−1), good selectivity and fast mass transfer rate for progesterone. Meanwhile, the prepared MISPE column could eliminate the interference of co-existing substances. Combined MISPE with HPLC, a selective and effective method for detecting progesterone in different cosmetics was achieved. Under the optimum conditions, the established MISPE–HPLC method was successfully used for the detection of progesterone in real samples. The linear range of this method was 1 to 200 μg·mL−1 with a limit of detection of 0.016 μg·mL−1. Therefore, this method could be used for the selective and effective detection of progesterone in different cosmetic samples with complex substrates. We provided an alternative method for the detection of illegal additions in cosmetics.

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