Abstract:
Flow injection analysis (FIA) was applied to the
determination of both chloride ion and mercury in water.
Conventional FIA was employed for the chloride study.
Investigations of the Fe3 +/Hg(SCN)2/CI-,450 nm
spectrophotometric system for chloride determination led to
the discovery of an absorbance in the 250-260 nm region when
Hg(SCN)2 and CI- are combined in solution, in the absence of
iron(III). Employing an in-house FIA system, absorbance
observed at 254 nm exhibited a linear relation from
essentially 0 - 2000 Jlg ml- 1 injected chloride. This linear
range spanning three orders of magnitude is superior to the
Fe3+/Hg(SCN)2/CI- system currently employed by laboratories
worldwide. The detection limit obtainable with the proposed
method was determin~d to be 0.16 Jlg ml- 1 and the relative
standard deviation was determined to be 3.5 % over the
concentration range of 0-200 Jig ml- 1. Other halogen ions
were found to interfere with chloride determination at 254 nm
whereas cations did not interfere. This system was
successfully applied to the determination of chloride ion in
laboratory water.
Sequential injection (SI)-FIA was employed for mercury
determination in water with the PSA Galahad mercury
amalgamation, and Merlin mercury fluorescence detection
systems. Initial mercury in air determinations involved
injections of mercury saturated air directly into the Galahad whereas mercury in water determinations involved solution
delivery via peristaltic pump to a gas/liquid separator, after
reduction by stannous chloride. A series of changes were made
to the internal hardware and valving systems of the Galahad
mercury preconcentrator. Sequential injection solution
delivery replaced the continuous peristaltic pump system and
computer control was implemented to control and integrate all
aspects of solution delivery, sample preconcentration and
signal processing. Detection limits currently obtainable with
this system are 0.1 ng ml-1 HgO.
