03.96 –
09.98
CO: J. Legrand
(IFREMER, FR)
RDs:
T.
Iskanderov (Nukus, Uzbekistan),
Scientific Objectives
prepare novel chemically modified materials with silica oxides as a support and
fluorescent dyes as selective component that covalently, ionically or other way
immobilised on the carrier surface.
test
the materials as sensitive matrixes for optical sensors development.
Investigate analytical properties and develop methodology of iron analysis in
diluted water solution with utilisation of silica supported
benzoilphenylhydroxylamine.
Obtain and study immobilised aminophosphonic acid for electrochemical analysis
The
analysis of the environment has some specific features, the most important being
that the toxicity of substances depends on their chemical form; from the point
of view there is a basic difference between free ions and ions bound in complex.
Most instrumental analytical methods are only capable of determining the overall
concentration of substances, and thus sensors' utilisation, yielding the
activity of the free ion content, is of a great importance in the study of ion
distribution among various chemical forms. Another characteristic feature in
environmental analyses is that it is important to compare the actual amount of a
pollutant with a certain critical value that is considered to be the toxicity
limit in the biosphere and is usually specified by a standard of law, rather
than to determine the absolute content of the substance. Sensors fitted very
well for this.
Besides utilisation of sensors for environmental monitoring have good prospects
because:
measurement with sensors is instrumentally and methodically simple,
permitting field work ,
the measurement is readily adapted to continuous monitoring of pollutants in
the biosphere (the atmosphere, rivers, wastewater, etc.).
Rapid (real-time) analysis can be made of many samples.
Sensors have the advantages of simpler operation, portability and small size,
no sample pre-treatment.
All these generally represent a major improvement over existing assays, and that
is why sensors become increasingly important for monitoring of environment.
Metal oxides with ligands covalently bonded to their surface constitute a new
class of 2 dimensional compounds. Metal oxides and particularly silicas with
monolayer of bonded groups are near to ideal object for development of sensitive
matrix for remote chemical sensors thanks to
high kinetic characteristics (it is an opportunity to use then in on-line
analysis),
large surface(it leads to effective analytical signal) and c)high chemical and
mechanical stability (they can be implanted in to a polymer membrane).
It is important that in case of it utilisation for optical sensoring analytical
signal can be evaluated both from diffuse reflectance (for thick tablets) and
transmission (for membranes) spectroscopy.
SUMMARY OF RESULTS
A
sets of materials (around 100 compounds) based on silica with immobilised
luminescent
dyes
have been obtained. The dyes was designed to be selective for important pH
region (6 – 9) and for interaction with toxic metal ions in water. Different
modified silicon oxide matrixes were used to improve stability, selectivity and
sensitivity of the dyes. For developing of optical sensors few configuration of
membrane that incorporate optically active materials were tested: transparent
films and bids, resistible slides and disks. Adsorption and fluorescent emission
spectra were recorded from the most perspective materials. It was shown that
fluorescent of some samples strongly depends form solution pH and contamination
of water by heavy metals. Chelating nature of modified silica increase
sensitivity of sensors. It can be used for increasing analytical signal in
diluted solutions.
As a prototype of
metal-selective chemical sensor
benzoilphenylhydroxylamine silica gel was used since correlation between iron
concentration in water and optical response of the sensor was found.
V.Skopenko (Kiev, Ukraine),
Dr. J.M. Slater (London, UK)