测定方法如下:用电位滴定法测量浸入样品水溶液中的玻璃电极和参比电极之间的电位差。本方法仅适用于每种产品的特定标准中规定的情况。

The determination is carried out in the following way: Potentiometric measurement of the potential difference between a glass electrode and a reference electrode dipping in an aqueous solution of the sample. This method is only applicable when so indicated in the specific standard for each product.