Sulphite quantification on damaged stones and mortars

An analytical procedure was developed for the simultaneous identification and quantification of the sulphite and main anions found in degradation patinas on historic buildings and monuments, as well as on stones and mortars exposed in simulation chamber and field tests. The quantification of anions was performed by means of ion chromatography (IC), after the stabilisation of sulphite with aD(−) fructose solution. The utilisation of two different chromatographic columns, connected in series, allowed the simultaneous determination of fluoride, acetate, formate, chloride, nitrite, bromide, iodide, oxyhalides, nitrate, phosphate, sulphite, sulphate and oxalate, in a time of approximately 25 min, without interference and with high reproducibility. Finally, the results show how in the majority of cases the formation of sulphite is an intermediate stage in the sulphation process affecting building materials exposed to the environment and needs to be measured together with sulphate, in order to obtain a correct interpretation of degradation mechanisms on such materials.