EurOCEAN 2000 - Vlaams Instituut voor de Zee

LUMINESCENCE EQUIPMENT
The equipment constructed by Edinburgh Instruments Ltd has been tested for steady and time
dependent fluorescence, for steady and time dependent phosphorescence ; it remains to be
tested for chemiluminesecence applications.
PRECONCENTRATION
The aim is to use immobilized quinolin-8ol for the preconcentration of seawater heavy metals.
Various immobilization supports, usable in a fluidised bed reactor were considered. Among
those, controlled pore glass (CPG) is found to be the most appropriate support material.
CPG supported oxine has been synthesized. The material displays quantitative removal from
the solution of most of the metals and shows suitable fluidisation behaviour.
A fluidised bed reactor using the selected material has been designed and tested. For all
examined metals the yield of preconcentration is around 50% and does not vary significantly
with flow rate
A first improvement consists in the addition of a vibrator mixer. The effect of this modification
is to increase the yield of trapping from ca. 50% to near 100%. The time required to obtain a
given preconcentration ratio has been reduced. A one hundred folds preconcentration ratio in
one hour is now possible. This results from the choice of a two-stage preconcentrator that
includes, in a first step, the removal of the solid and dissolved matrix by means of a fluidised
bed. In a second step, the heavy metals are concentrated by means of a classical packed column.
CADMIUM AND ZINC
The monitoring of the two metals is based on the enhanced fluorescence intensities and
modifications of the emission spectrum of aromatic-azamacrocycles systems induced by
cations (A.W.Czarnik, 1992). As an example, the structure of an anthrylazamacrocycle is given
in figure 1.
Fig. 1
Figure 1. Molecular structure of an anthrylazamacrocycle ; {1} is the molecule with five
nitrogens
In alkaline conditions, the fluorescence yield of {1} is very weak; when chelated to Zn or Cd
large but depending on the metal, dimension of the macrocycle and pH, chelation-enhanced
fluorescence is observed.
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NH
NH NH
N
NH