Letno poročilo 2005

Laboratorij za analizno kemijo
Analytical Chemistry Laboratory
predlaganega modela smo eksperimentalno
dokazali tako, da smo dolo~ili kemijsko
razpolo`ljivost sedmih kovin v standardnem
referen~nem materialu NIST 8704 (Buffalo
river sediment) za 1 mol l-1 NaOAc (pH 5) kot
ekstraktant. V {tudiji smo tudi pokazali na
omejitve modela linearne izoterme, ki so ga
uporabljali doslej.
- V okviru bilateralnega projekta smo z na{im
~e{kim partnerjem razvili elektrodo iz
ogljikove paste, ki je modificirana z bizmutovim
prahom (Bi-CPE). Ta elektroda je
primerna za dolo~evanje nekaterih te`kih
kovin v sledovih in je {e posebej uporabna
takrat, ko je in situ priprava tankoslojne
bizmutove elektrode neprimerna ali celo
nemogo~a (npr. okoljske meritve, in vivo
meritve). Poleg tega je Bi-CPE izredno
u~inkovita pri dolo~evanju v alkalnih medijih,
kjer je in situ priprava bizmutovih elektrod
manj ugodna.
- V sodelovanju z ameri{kim partnerjem smo
razvili elektrokemijski mikrosenzor za merjenje
pomembne biolo{ke spojine dopamin (`iv~ni
prena{alec) ob prisotnosti fiziolo{kih koncentracij
askorbata. Pripravljen je na osnavi
mikroelektrode iz ogljikovega vlakna, ki je
modificirana z ogljikovimi nanocevkami. Ta
mikrosenzor je primeren za dolo~evanje
nizkih koncentracij dopamina v mikrovolumskih
vzorcih in na mikro-lokacijah (npr.
za in vivo meritve)
- Izvedli smo {tudijo za pripravo in optimizacijo
ex situ bizmutove tankoslojne mikroelektrode,
primerne za uporabo v elektrokemijski
mikroanalizi nekaterih toksi~nih kovin
(npr. kobalta in niklja). Uvedli smo uporabo
bromidnih ionov in optimizirali ve~ parametrov,
pomembnih pri elektrolitskem
nana{anju bizmutovega sloja na povr{ino
ogljikovega vlakna. S tem smo dosegli
dolgotrajno mehansko in elektrokemijsko
stabilnost take mikroelektrode, kar je
pomembno za njeno uporabo npr. pri
meritvah te`kih kovin v (nizkovolumskih)
biolo{kih teko~inah.
66
reference material 8704 (Buffalo river sediment)
using 1 mol l-1 NaOAc (adjusted to pH
5) as an extractant. The limitations of an earlier
used linear isotherm model were demonstrated.
- Within the framework of a bilateral project
we prepared, in collaboration with our Czech
partner, a carbon paste electrode modified
with metallic bismuth powder (Bi-CPE) for
measurement of ultratrace heavy metals using
electrochemical stripping analysis. Its
application is particularly convenient in those
environments, where the in situ preparation
of bismuth film electrode is difficult or even
impossible (e.g. environmental monitoring,
in vivo measurements). Moreover, in contrast
to the bismuth film electrode, where the formation
of bismuth film at higher pH values
appears to be less favourable, we demonstrated
that the Bi-CPE even allowed measurements
in high alkaline media.
- We have developed an electrochemical
microsensor for measurement of a significant
biological compound, dopamine (a neurotransmitter),
in the presence of physiological
concentrations of ascorbate. The proposed
microsensor is based on a single carbon fiber
microelectrode that is modified with carbon
nanotubes. This microsensor holds great
promise for measurements of dopamine at
low levels in micro-volume samples and at
micro-locations, i.e. for in vivo measurements.
- We have performed an investigation on the
preparation and optimization of an ex situ
bismuth film microelectrode for use in
electrochemical microanalysis of some trace
toxic metals (e.g. cobalt and nickel). We have
introduced the addition of bromide ions and
optimized several parameters important in
the electrolytic deposition of the bismuth film
onto the surface of a carbon fiber. Based on
this work we achieved a long-term mechanical
and electrochemical stability of the proposed
microelectrode, which is very important
in applications such as e.g. the meas-