A new software-controlled time-based system for sample or
reagent introduction in process flow injection analysis was developed. By
using a multi-syringe burette coupled with one multi-port selection valve,
the time-based injection of precise known volumes was accomplished.
Characteristics and performance of the injection system were studied by
injecting an indicator in a buffered carrier. Two multi-syringe time-based
injection (MS-TBI) systems were implemented: first, the injection of a
sample in a multiple-channel manifold where the sample would sequentially
merge and react with different reagents, and second, the sequential
injection of several solutions (sample and reagents) into a particular
flowing stream. The first system was applied to the spectrophotometric
determination of nickel(II) in diluted samples from the acidic
nickel ore leaching process, by using ammonium citrate as carrier, a
saturated solution of iodine as oxidizing agent and alkaline
dimethylglyoxime as chromogenic reagent. The sampling frequency attained
was 57 h−1. Determinations on process samples compared
well at the 95% confidence level with the reference values obtained by
ICP-OES. The second time-based injection system was applied to the
speciation of iron. Total iron and iron(II) concentrations were
separately and sequentially determined using 1,10-phenanthroline in acetic
buffer medium as reagent. The developed manifold allowed the optional use
of two different carrier solutions, containing or not containing ascorbic
acid, for performing the separate determinations. Also, in the sequential
procedure, plugs of reducing carrier were alternatively intercalated before
the sample injections used for total iron determinations. Sampling
frequencies of 68 injections per hour were routinely used. Accuracy was
assessed by analyzing synthetic known mixtures of Fe(III) and
Fe(II) standard solutions. Recoveries of 98–100.5% with a
maximum relative standard deviation of 3.6% were found. Results obtained
for various samples of fertilizers agreed well with those attained by the
standard batch procedure.
You have access to this article
Please wait while we load your content...
Something went wrong. Try again?