IJUP08 - Universidade do Porto

Single-standard calibration applied to SIA analytical system with
potentiometric detection
Leonel G. C. Soares 1 and Rui A.S. Lapa 1
1 REQUIMTE/CEQUP, Faculty of Pharmacy, University of Porto, Portugal.
The flow techniques provide a wide range of possibilities being calibration and dilution
schemes applicable to a variety of analytical methodologies [l, 2]. Among the flow
techniques, the Sequential Injection Analysis (SIA) analytical systems have been applied in
the refinement of calibration techniques to accompany the wide range of analytical
applications.
Different calibration methods has been proposed [3,4] and could be classified as: (a) the
conventional method (CM), (b) the indirect method (IM), (c) the internal standard method
(ISM) and (d) the dilution method (DM) [5].
The conventional calibration method is commonly used in analytical practice in two
modes: interpolative and extrapolative, which are usually termed ‘the calibration curve
method’ and ‘the standard addition method’, respectively [5]. In the first one, the
calibration graph is prepared with the use of a set of standard solutions prepared separately
from a sample; as a consequence, the signal measured for the sample is then related to the
calibration graph and the analytical results are interpolated. In the ‘the standard addition
method’ standard solutions are added to the sample, hence the calibration graph is limited
by the signal obtained for the sample and the analytical result can be evaluated exclusively
by extrapolation. The advantages of the extrapolative calibration process reside in the
compensation of the effect of the interferent species since the interpolative method presents
the effect of those interferences.
In the work, a simple extrapolative process applied to a SIA technique was developed to
generate a set of precisely diluted aliquots from a single standard and applied to the
determination of chloride in water sampled. An ion selective electrode sensitive to chloride
was used as detector.
References:
[1] - Ruzicka, J., and Hansen, E. H., Flow Injection Analysis, Wiley, New York, 2nd ed., 1988.
[2] - Ruzicka, J., Anal. Chem., 1983,55,1986.
[3] P. Koscielniak, Anal. Chim. Acta, 438 (2001) 323.
[4] P. Koscielniak, in: J. Niemiesnik, W. Chrzanowski (Eds.), New Horizons and Challenges in
Environmental Analysis and Monitoring, Centre of Excellence in Environmental Analysis and
Monitoring, Gdansk, 2003, 110.
[5] - Paweł Koscielniak, Marcin Wieczorek, Joanna Kozak, Małgorzata Herman, Analytica
Chimica Acta 600, 2007, 6.
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