Abstract: A comparison between the different proposed methods to perform the standard addition in an online way (flow injection analysis) is made. The different assemblies (reverse and conventional FIA) and the employed standards in every method are compared. Three analyzes were carried out, two of them were analyzes of samples of pH indicators (methylorange and chlorophenol red) prepared at an acid pH, while the standards were prepared at a basic pH. The third analysis was the analysis of chloride in different synthetic waters with a perfectly known composition for all the ions present in the samples. Besides a new method to perform the online standard addition is proposed, trying to reduce the consumption of reagents and sample. This new method makes use of a 6-port multiposition valve electrically actuated.