Analytical Sciences

Implementation of a Generalized Standard Addition Method in a Flow Injection System Using Merging-Zones and Gradient Exploitation

Edvan C. SILVA*, Valdomiro L. MARTINS**, Alessandro F. ARA��O**and Mt��o Csar U. ARA��O** ⁺

*Departamento de Quy��ca Fundamental, Universidade Federal de Pernambuco, Recife PE, Brazil
**Departamento de Quy��ca, Universidade Federal da Paray��, P. O. Box 5093, Zip code 58051-970, Jov��Pessoa PB, Brazil

A novel strategy for implementing a generalized standard addition method (GSAM) in a simple two-channel flow injec-tion(FI) system and for correcting matrix effects and spectral interferences in multicomponent analysis is described. The FI-GSAM system exploits the concentration gradients of the sample and the standard solution, requires only one standard solution per analyte and provides several addition levels using a single simultaneous injection of the sample and of each standard solution. Because the matrix effects change at every addition level, a novel mathematical model for this FI-GSAMhas been derived. The method was critically evaluated for simultaneous K, Ca and Na determinations by flame photometry in synthetic samples with different 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 for the simultaneous determination of three analytes was about 2 min, consuming 400 ml of the sample and 100 ml of each standard solution. (Keywords: Generalized standard addition method, flow injection system, gradient exploitation, emission spectrometry)

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