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.
                            一种分析元件用于测定 pH 值为 8.5 至 11 的
镁离子。 该元件包括一种含有
镁离子络合剂的吸附载体材料,
镁离子络合剂是一种 1,5-双(2-羟基苯基)-3-
氰基甲臢化合物。 该化合物在苯基的 3-、4-和 5-位中至少有一个位被取代。 取代基的选择应使其累积哈美特-西格玛值大于 0.23,条件是取代基中没有一个是羧基。 该测定在有
钙离子螯合剂和适当缓冲液的情况下进行。 在优选的实施方案中,
氰基甲臢以这样一种方式加入元件中,以便与测定中可能遇到的蛋白质分子隔离。