Analytical element and method for determination of magnesium ions.

摘要

An analytical element is used to determine magnesium ions at a pH of from 8.5 to 11. This element comprises an absorbent carrier material containing a magnesium ion complexing agent which is a 1,5-bis(2-hydroxyphenyl)-3-cyanoformazan compound. This compound is substituted in at least one of the 3-, 4- and 5-positions of either phenyl moiety. The substituents are chosen such that their cumulative Hammet-sigma value is greater than 0.23, provided that none of the substituents is carboxy. The assay is carried out in the presence of a calcium ion chelating agent and a suitable buffer. In preferred embodiments, the cyanoformazan is incorporated in the element in such a manner so as to be isolated from protein molecules which may be encountered in the assay.