Migration processes of metal elements from carbon steel cylinders to food gases.

This study is aimed to provide a protocol for sampling and analysis of metal elements migrating from carbon steel cylinders, used for gas storage and distribution, to food gases, i.e. those gases, such as CO2, N2 and O2, employed by food and beverage industries. The concentrations of 23 selected elements, analysed by inductively coupled plasma mass spectrometry, in the three food gases collected from steel cylinders after a storage period of 50 days, were re-calculated considering (a) the initial concentrations (i.e. the concentrations of these elements in food gases before being packaged in carbon steel cylinders) and (b) a migration process of 5 years that proceeds in time following a linear trend. Computed data were compared with the limit concentrations for mineral waters (CEE/CEEA/CE no. 83,03-11-1998; D.Lgs no. 3, 2001; D.M. 29-12-2003),considering that the quantity of CO2 commonly added to 1 L of mineral water is 5 g. Although no reference values indicating the concentration limits of metal contaminants in food gases are currently promulgated, the results of this comparison have evidenced that the highest concentrations of the most abundant elements among those selected for the test, i.e. Al, Cd, Cr, Cu, Fe, Mn, Ni and Pb, are up to 4 orders of magnitude lower that the previously cited limits. This suggests that the effects of migration of contaminants from carbon steel cylinders do not have a significant influence on the quality of food gases, independently on the type of food gas and carbon steel composition.