Abstract: The present invention provides a combination of reagent compositions for measuring an electrolyte which are excellent in stability, precision and quantitativity and have high solution stability sufficient to withstand distribution. In the combination of the reagent compositions of the present invention, a chelating agent and an inactivated &agr;-amylase capable of being reversibly activated by the electrolyte are formulated separately from each other.

Abstract: A composition for determination of chloride ion, comprising a maltooligosaccharide derivative possessing modified or non-modified non-reducing terminal and modified reducing terminal, a metal chelating agent, .alpha.-amylase and an adjuvant enzyme, provided that the adjuvant enzyme may not be contained when the maltooligosaccharide derivative possesses reducing terminal with a modifying group bound in .alpha.-type, which does not require maintenance and control of special instruments and special treatment of waste liquors, affords good analytic efficiency, determination precision and linearity, and is capable of suppressing rise of reagent blank and giving accurate determination values from test samples showing high values.