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DNAzymes are DNA based catalysts that can undergo cleavage upon binding of the target analyte. The cleavage reaction is highly specific, and DNAzymes exists for a wide range of metal ions. The change of structure upon binding of a specific metal ion has given rise to many sensing strategies, but few exist with nanopore sensors. Resistive Pulse Sensing, RPS, is a platform that has emerged in recent years capable of identifying changes in DNA structure and sequence. Here we develop the use of DNAzymes with RPS technologies for the detection of Ca2+ ions in solution. Ca2+ plays an important role in biological processes, critical for cell signally, protein folding and catalysis. Extreme concentrations of Ca2+ within drinking water have also been linked to problems with corrosion, scaling and the taste of water. Using DNAzyme functionalised nanocarriers and RPS, it was possible follow the Ca2+ ions binding to the DNAzyme. The binding of Ca2+ caused a conformation change in the DNAzyme which was monitored as a change in translocation speed. By following the changes to the translocation speed, it is hypothesised that RPS can verify the changes in structure. In addition, the assay allowed the quantification of Ca2+ between 1 – 9 μM, and due its catalytic nature, increasing incubation time from 30 to 90 minutes allowed lower detection limits, down to 0.3 μM. We demonstrate that the speed changes are specific to Ca2+ in the presence of other metal ions, and we can quantify Ca2+ in tap and pond water samples.