Instrumental methods for NaCl analysis in olive brines

Abstract

Aplicability of flame photometric and ion selective (sodium or chloride) methods to determinate NaCI concentration in olive brines in comparison with the official one (Volhard), which uses AgNO₃, is studied. According to the results using standard solutions or fermentative olive brines without previous lye treatment, no proportional systematic or constant systematic errors are detected and the percentaje of NaCl is evaluated by them with the same accuracy as by the reference. However, when the flame photometric or sodium ion-selective methods are used to determine this compound in Spanish olive brines, there is a deviation in comparison with the values obtained by the official one (Volhard) that is correlated with the combine acidity concentration of the solution. This fact is due to the presence of sodium organic salts, called combined acidity, that are formed during the lye treatment or "cocido" that these fruits are given before fermentation. Nevertheless, is does not represent any problem as there is a good correlation between such combined acidity and the magnitude of the deviation, that permit to calculate the corresponding correction factor. In addition these problems can be solved using the chloride selective ion method.