Preservation conditions of pH standard solutions.

Abstract

The stability of borate and carbonate pH standard solutions has been investigated for long-term preservation. The material and volume of containers, preservation temperature and filling-up percent of solution were the factors examined. Experiments were performed based on statistical analysis using orthogonal array table. According to the preservation test for 17 months, differences of the container material, preservation temperature and filling-up precent of solution were significant for borate pH solution. Difference of container volume was not significant for the both solutions. Under the optimum conditions selected, variation of pH values in the lapse of 17 months were ±0.007 and ±0.010pH for borate and carbonate pH solutions, respectively.