Abstract: A method for identifying a target polymer (20) comprises translocating a target polymer (20) having detectable elements (22), such as fluorophores (22), through an analysing device (24) comprising a nanopore (28) having a detection window (40), wherein the analysing device (24) is capable of plasmon resonance to produce a localised electromagnetic field which defines the detection window (40) detecting the detectable elements (22) as they pass through the detection window (40) to produce a distribution profile of the detectable elements (22) along the target polymer (20) and identifying the target polymer (20) by comparing the distribution profile to a reference set of distribution profiles for known polymers. In a preferred embodiment the target polymer (20) is a nucleic acid and the detectable elements (22) are oligonucleotides complimentary to at least two adjacent nucleotides therein. Exemplified is the use of 6-mer oligonucleotides.