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Evaluation of the Precision of the Flow Injection Doublet Peak Method
Analyst (1994)
  • Julian Tyson
  • Roger T. Echols
The factors affecting the precision of the flow injection
doublet peak method are discussed with particular reference
to the contribution from the uncertainty associated with the
calibration procedure. A single-line flow injection manifold
was used in which the concentration gradients were
generated by alternating helical reactors and the reaction
products were monitored by a simple detector incorporating
diodes as light source and intensity transducer. The
reactions between lanthanum and Methyl Thymol Blue and
between sodium hydroxide and hydrochloric acid in the
presence of Bromothymol Blue were used. Optimization
studies involved the method of steepest ascent, two figures of
merit (the slope of the calibration and the standard deviation
of a measured concentration) and two parameters (pump
speed setting and the number of segments in the alternating
helical reactor). The resulting minimum uncertainties, which
ranged from 3 to 9%, were found to be insensitive to
changes in experimental parameters. The major contribution
to the uncertainty in a determined concentration was found
to be the scatter of the points about the regression line fitted
to the calibration data. Alternative approaches to flow
injection peak width methods are discussed and it is pointed
out that the doublet peak method has the unique feature of
giving rise to an inherently linear calibration function,
because the reference points at which the time interval is
measured are not fixed at a particular value of the detector
response for all concentrations.
  • flow injection,
  • doublet peak method,
  • precision,
  • calibration,
  • uncertainty
Publication Date
Citation Information
Julian Tyson and Roger T. Echols. "Evaluation of the Precision of the Flow Injection Doublet Peak Method" Analyst Vol. 119 (1994) p. 2087 - 2091
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