Implementation of a generalized standard addition method in a flow injection system using merging-zones and gradient exploitation

A novel strategy for implementing a generalized standard addition method (G SAM) in a simple two-channel flow injection (FI) system and for correcting matrix effects and spectral interferences in multicomponent analysis is des cribed. The FI-GSAM system exploits the concentration gradients of the samp le and the standard solution, requires only one standard solution per analy te and provides several addition levels using a single simultaneous injecti on of the sample and of each standard solution. Because the matrix effects change at every addition level, a novel mathematical model for this FI-GSAM has been derived. The method was critically evaluated for simultaneous K, Ca and Na determinations by flame photometry in synthetic samples with diff erent ethanol or glycerol contents, added to the samples to promote matrix effects. The results show good agreement with the expected values, with the relative error and the overall relative standard deviation usually being < 5% (n=5) for 2.5 - 5.0 Na, 20.0 K and 1000 mg l(-1) Ca. The elapsed time fo r the simultaneous determination of three analytes was about 2 min, consumi ng 400 mu l of the sample and 100 mu l of each standard solution.