EurOCEAN 2000 - Vlaams Instituut voor de Zee

The reaction of 6-mercaptopurine, leading to the fluorescent (6-mercaptopurine)2 is still in
the stage of a badge process and we will concentrate here on the reaction of mercury with
thiamine.
A modified flow injection system was used for the determination of mercury with thiamine. In
the system, the highly fluorescent thiochrome was formed as a result of the redox interaction
of Hg with thiamine.
Thiochrome is retained on a solid support and its fluorescence is measured. Various resins have
been tested and the highest fluorescence intensities were obtained when using Amberlite
XAD-4. Moreover, different particle sizes of the packed resins were also investigated and
particle diameters between 0.080-0.160 mm were selected for further experiments.
Presently, the detection limit for Pb is 3.6 ng mL -1 ; the repeatability is +/- 3% and the response
time is 5 minutes.
IRON, COBALT, MANGANESE AND COPPER
The construction of the FI-CL system is outlined on the basis of the manifold for the
determination of dissolved Fe in seawater. For this purpose a FI-CL manifold based on the
Fe(II) catalysed oxidation of luminol has been developed (Bowie et al.). In the manifold, three
peristaltic pumps are used to deliver reagents, sample / buffer and wash solutions to the
injection valve, preconcentration column and CL detector. A six-port injection valve is used to
transport the sample to the detector. Three 3-way solenoid switching valves enable sample,
sample plus standard addition(s) and wash solutions to pass sequentially through the manifold.
In a first step, automation of the FI-CL system for the determination of Fe was provided via a
D/A device control interface card housed in a desktop PC, previously used successfully inhouse
for FI-CL systems. The detection system currently consists of a quartz glass spiral flow
cell mounted in front of an end-window photomultiplier tube, powered using a high voltage
supply. CL signals are recorded using a flat-bed chart recorder or an integrator.
FI-CL technologies for other trace elements (Co, Mn, Cu) are based on the above manifold
with minor modifications to suit the specific CL reaction system. Instrumentation is generic to
all systems.
The automation of the FI-CL system for the determination of Fe is achieved through a Labview
(National Instruments) environment run on a laptop PC. A digital i/o, 24 line TTL PCMCIA
card (DIO-24) enables full control of FI components (switching valve, injection valve, pumps,
autosampler), using a transformer box to modify 5 V signals generated by the card. A
multifunctional 16 analog input card is used for acquisition of CL signals generated from the
miniature photon counting head of the PMT detector. Signal output is modified through an inhouse
interface board into a frequency that could be acquired by the DAQ-700 card. The
chemiluminescence chemistries for the determination of Fe, Co, Mn and Cu are summarized in
table 2.
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