The invention discloses a detecting method for
divalent mercury ions. The principle for detecting mercury ions by using the method is as follows: a single-chain
DNA (
Deoxyribose Nucleic Acid) molecule B modified by
fluorescein contains a sequence which is complementary with a sequence of
a DNA catching needle (a single-chain
DNA molecule A) fixed on the surface of a probe, and also contains a T-T
base pair mismatch structure which can be combined with the
divalent mercury ions. During detection, the single-chain
DNA molecule B modified by the
fluorescein and the mercury ions are simultaneously input to the surface of an
optical fiber sensor probe for evanescent
waves, and the
divalent mercury ions are combined with the single-chain DNA molecule B modified by the
fluorescein by the DNA catching needle in a competition way. The more the concentration of the divalent mercury ions is, the fewer the single-chain DNA molecule B modified by the fluorescein and combined with the DNA catching needle on the
optical fiber sensor probe for evanescent
waves is, so that a
fluorescence intensity
signal detected by an optical detecting platform for evanescent
waves is weaker. An effective means is provided for the rapid on-site and real-time detection of heavy
metal mercury ions in the fields of foods, medicines and environments.