DIN 38402-62:2014-12

The testing of the ion balance in water samples for plausibility is a method within the framework of analytical quality assurance in order to detect errors during analysis of the major ions. For preparation of the ion balance, the sums of the equivalent concentrations of the anions and cations are calculated and compared. Due to the electroneutrality principle, the sum of the equivalent concentrations of the cations shall equal the sum of the equivalent concentrations of the anions. Since, in practice, analysis of the ions is always subject to measurement uncertainty, the sums of the equivalent concentrations of the cations and anions differ generally, however. The testing of the ion balance for plausibility is effected through comparison of the ion balance deviation with a target value. The standard applies for the preparation of the ion balance for the purpose of plausibility testing and is applicable for drinking, mineral, bathing, surface and ground waters in the pH range 3 to 10. The complexation of ionic species is not taken into account. For preparation of the ion balance, all anions and cations which are involved with at least 0,5 % in the cation or anion equivalent concentration sum shall be taken into account. Ions that contribute with less than 0,5 % can be neglected. For the waters indicated in the scope, this may generally include the following : natrium, potassium, calcium, magnesium, strontrium, aluminium, iron, manganese, ammonium, hydrogen ion as well as chloride, nitrate, sulphate, hydrogen carbonate (acid capacity up to pH of 4,3), nitrite, phosphate, hydroxide ion. This document has been prepared by Working Group NA 119-01-03-01-18 AK "Ionenbilanz" ("Ion budgets") of NA 119-01-03 AA "Wasseruntersuchung" ("Water examination") of the DIN Standards Committee Water Practice (NAW).