Standard addition method in FIA. Comparison between different assemblies

A comparison between the different proposed methods to perform the standard addition in an on-line way (flow injection analysis) is made. The differen t assemblies (reverse and conventional FIA) and the employed standards in e very method are compared. Three analyses were carried out, two of them were analyses of samples of pH indicators (methylorange and chlorophenol red) p repared 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 on-line standard addition is proposed, trying to reduce the consumption of reagents and sample. This new method m akes use of a 6-port multiposition valve electrically actuated. (C) 1999 El sevier Science B.V. All rights reserved.