We present here anion-exchange nanospheres as novel titration reagents for anions. The nanospheres contain a lipophilic cation for which the counterion is initially Cl–. Ion exchange takes place between Cl– in the nanospheres and a more lipophilic anion in the sample, such as ClO4– and NO3–. Consecutive titration in the same sample solution for ClO4– and NO3– were demonstrated. As an application, the concentration of NO3– in spinach was successfully determined using this method.