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Although the universal homogeneous G-quadruplex-DNAzyme based aptasensors have potentials to replace conventional biosensors,the high background induced by thermodynamic equilibrium may restrict their application.In this work,we took adenosine aptasensor as an example and found that the cation condition in buffer solution plays an important role in modulating the equilibrium between Watson-Crick structure and G-quadruplex sturcture,which in turn affects the background and response to target molecule.The combination of magnesium ion and potassium ion was proved to have better performance than commonly used sodium ion and potassium ion.By taking the advantages of chemiluminesce and microflow injection analysis,the optimized adenosine aptasensor can achieve a detection limit of 5 μM with consumption of only 4 μL adenosine sample.The aptasensor also showed satisfactory selectivity towards adenosine analogs.