Researchers in Chemistry
http://hdl.handle.net/10566/1744
2024-03-28T14:43:18ZBioaccumulation of total mercury in the earthworm Eisenia andrei
http://hdl.handle.net/10566/2949
Bioaccumulation of total mercury in the earthworm Eisenia andrei
Shirley Le Roux; Priscilla Baker; Andrew Crouch
Earthworms are a major part of the total biomass of soil fauna and play a vital role
in soil maintenance. They process large amounts of plant and soil material and can
accumulate many pollutants that may be present in the soil. Earthworms have been
explored as bioaccumulators for many heavy metal species such as Pb, Cu and Zn but
limited information is available for mercury uptake and bioaccumulation in earth-
worms and very few report on the factors that influence the kinetics of Hg uptake by
earthworms. It is known however that the uptake of Hg is strongly influenced by the
presence of organic matter, hence the influence of ligands are a major factor contribut
-
ing to the kinetics of mercury uptake in biosystems. In this work we have focused on
the uptake of mercury by earthworms (
Eisenia andrei
) in the presence of humic acid
(HA) under varying physical conditions of pH and temperature, done to assess the role
of humic acid in the bioaccumulation of mercury by earthworms from soils. The study
was conducted over a 5-day uptake period and all earthworm samples were analysed
by direct mercury analysis. Mercury distribution profiles as a function of time, bioac-
cumulation factors (BAFs), first order rate constants and body burden constants for
mercury uptake under selected conditions of temperature, pH as well as via the dermal
and gut route were evaluated in one comprehensive approach. The results showed
that the uptake of Hg was influenced by pH, temperature and the presence of HA.
Uptake of Hg
2
+
was improved at low pH and temperature when the earthworms in
soil were in contact with a saturating aqueous phase. The total amount of Hg
2
+
uptake
decreased from 75 to 48
% as a function of pH. For earthworms in dry soil, the uptake
was strongly influenced by the presence of the ligand. Calculated BAF values ranged
from 0.1 to 0.8. Mercury uptake typically followed first order kinetics with rate constants
determined as 0.2 to 1
h
?
1
.
2016-01-01T00:00:00ZCorrection: Baker, P. et al. electrochemical aptasensor for endocrine disrupting 17β-estradiol based on a poly(3,4-ethylenedioxylthiopene)-gold nanocomposite platform. Sensors 2010, 10, 9872-9890
http://hdl.handle.net/10566/2480
Correction: Baker, P. et al. electrochemical aptasensor for endocrine disrupting 17β-estradiol based on a poly(3,4-ethylenedioxylthiopene)-gold nanocomposite platform. Sensors 2010, 10, 9872-9890
Olowu, Rasaq A.; Arotiba, Omotayo A.; Mailu, Stephen N.; Waryo, Tesfaye T.; Baker, Priscilla; Iwuoha, Emmanuel I.
Herewith please find corrected structures for Figure 8 in our paper published in Sensors in 2010.
2011-01-01T00:00:00ZElectrochemical aptasensor for endocrine disrupting 17β-estradiol based on a poly(3,4-ethylenedioxylthiopene)-gold nanocomposite platform
http://hdl.handle.net/10566/2479
Electrochemical aptasensor for endocrine disrupting 17β-estradiol based on a poly(3,4-ethylenedioxylthiopene)-gold nanocomposite platform
Olowu, Rasaq A.; Mailu, Stephen N.; Waryo, Tesfaye T.; Baker, Priscilla; Iwuoha, Emmanuel I.; Arotiba, Omotayo A.
A simple and highly sensitive electrochemical DNA aptasensor with high affinity for endocrine disrupting 17β-estradiol, was developed. Poly(3,4-ethylenedioxylthiophene) (PEDOT) doped with gold nanoparticles (AuNPs) was electrochemically synthesized and employed for the immobilization of biotinylated aptamer towards the detection of the target. The diffusion coefficient of the nanocomposite was 6.50 × 10−7 cm2 s−1, which showed that the nanocomposite was highly conducting. Electrochemical impedance investigation also revealed the catalytic properties of the nanocomposite with an exchange current value of 2.16 × 10−4 A, compared to 2.14 × 10−5 A obtained for the bare electrode. Streptavidin was covalently attached to the platform using carbodiimide chemistry and the aptamer immobilized via streptavidin—biotin interaction. The electrochemical signal generated from the aptamer–target molecule interaction was monitored electrochemically using cyclic voltammetry and square wave voltammetry in the presence of [Fe(CN)6]−3/−4 as a redox probe. The signal observed shows a current decrease due to interference of the bound 17β-estradiol. The current drop was proportional to the concentration of 17β-estradiol. The PEDOT/AuNP platform exhibited high electroactivity, with increased peak current. The platform was found suitable for the immobilization of the DNAaptamer. The aptasensor was able to distinguish 17β-estradiol from structurally similar endocrine disrupting chemicals denoting its specificity to 17β-estradiol. The detectable concentration range of the 17β-estradiol was 0.1 nM–100 nM, with a detection limit of 0.02 nM.
2010-01-01T00:00:00ZDetermination of anthracene on Ag-Au alloy nanoparticles/overoxidized-polypyrrole composite modified glassy carbon electrodes
http://hdl.handle.net/10566/2478
Determination of anthracene on Ag-Au alloy nanoparticles/overoxidized-polypyrrole composite modified glassy carbon electrodes
Mailu, Stephen N.; Waryo, Tesfaye T.; Ndangili, Peter M.; Ngece, Fanelwa R.; Baleg, Abd A.; Baker, Priscilla; Iwuoha, Emmanuel I.
A novel electrochemical sensor for the detection of anthracene was prepared by
modifying a glassy carbon electrode (GCE) with over-oxidized polypyrrole (PPyox) and
Ag-Au (1:3) bimetallic nanoparticles (Ag-AuNPs). The composite electrode
(PPyox/Ag-AuNPs/GCE) was prepared by potentiodynamic polymerization of pyrrole on
GCE followed by its overoxidation in 0.1 M NaOH. Ag-Au bimetallic nanoparticles were
chemically prepared by the reduction of AgNO3 and HAuCl4 using C6H5O7Na3 as the
reducing agent as well as the capping agent and then immobilized on the surface of the
PPyox/GCE. The nanoparticles were characterized by UV-visible spectroscopy technique
which confirmed the homogeneous formation of the bimetallic alloy nanoparticles.
Transmission electron microscopy showed that the synthesized bimetallic nanoparticles
were in the range of 20–50 nm. The electrochemical behaviour of anthracene at the
PPyox/Ag-AuNPs/GCE with Ag: Au atomic ratio 25:75 (1:3) exhibited a higher
electrocatalytic effect compared to that observed when GCE was modified with each
constituent of the composite (i.e., PPyox, Ag-AuNPs) and bare GCE. A linear relationship
between anodic current and anthracene concentration was attained over the range
of 3.0 × 10−6 to 3.56 × 10−4 M with a detection limit of 1.69 × 10−7 M. The proposed
method was simple, less time consuming and showed a high sensitivity.
2010-01-01T00:00:00Z