3 research outputs found
Ultrasensitive and Fast Voltammetric Determination of Iron in Seawater by Atmospheric Oxygen Catalysis in 500 μL Samples
A new
method based on adsorptive cathodic stripping voltammetry
with catalytic enhancement for the determination of total dissolved
iron in seawater is reported. It was demonstrated that iron detection
at the ultratrace level (0.1 nM) may be achieved in small samples
(500 μL) with high sensitivity, no need for purging, no added
oxidant, and a limit of detection of 5 pM. The proposed method is
based on the adsorption of the complex Fe/2,3-dihydroxynaphthalene
(DHN) exploiting the catalytic effect of atmospheric oxygen. As opposite
to the original method (Obata, H.; van den Berg, C. M. <i>Anal.
Chem.</i> 2001, <i>73</i>, 2522–2528), atmospheric
oxygen dissolved in solution replaced bromate ions in the oxidation
of the iron complex: removing bromate reduces the blank level and
avoids the use of a carcinogenic species. Moreover, the new method
is based on a recently introduced hardware that enables the determinations
to be performed in 500 μL samples. The analyses were carried
out on buffered samples (pH 8.15, HEPPS 0.01 M), 10 μM DHN and
iron quantified by the standard addition method. The sensitivity is
49 nA nM<sup>–1</sup> min<sup>–1</sup> with 30 s deposition
time and the LOD is equal to 5 pM. As a result, the whole procedure
for the quantification of iron in one sample requires around 7.5 min.
The new method was validated via analysis on two reference samples
(SAFe S and SAFe D2) with low iron content collected in the North
Pacific Ocean
Quantification of Iron in Seawater at the Low Picomolar Range Based on Optimization of Bromate/Ammonia/Dihydroxynaphtalene System by Catalytic Adsorptive Cathodic Stripping Voltammetry
A new analytical protocol for the challenging analysis
of total
dissolved iron at the low picomolar level in oceanic waters suitable
for onboard analysis is presented. The method is based on the revision
of the adsorptive properties of the iron/2,3-dihydroxynaphthalene
(Fe/DHN) complexes on the hanging mercury drop electrode with catalytic
enhancement by bromate ions. Although it was based on a previously
proposed reagent combination, we show here that the addition of an
acidification/alkalinization step is essential in order to cancel
any organic complexation, and that an extra increment of the pH to
8.6–8.8 leads to the definition of a preconcentration-free
procedure with the lowest detection limit described up to now. For
total dissolved iron analysis, samples were acidified to pH 2.0 in
the presence of 30 μM DHN and left to equilibrate overnight.
A 10 mL sample was subsequently buffered to a pH of ∼8.7 in
the presence of 20 mM bromate: a 60 s deposition at 0 V led to a sensitivity
of 34 nA nM<sup>–1</sup> min<sup>–1</sup>, a 4-fold
improvement over previous methods, that translated in a limit of detection
of 5 pM (2–20 fold improvement). Several tests proved that
a nonreversible reaction in the time scale of the analysis, triggered
by the acidification/alkalinization step, was behind the signal magnification.
The new method was validated onboard via the analysis of reference
material and via intercalibration against flow injection analysis-chemiluminescence
on Southern Ocean surface samples
Probing the Binding Site of Abl Tyrosine Kinase Using in Situ Click Chemistry
Modern combinatorial chemistry is used to discover compounds
with
desired function by an alternative strategy, in which the biological
target is directly involved in the choice of ligands assembled from
a pool of smaller fragments. Herein, we present the first experimental
result where the use of in situ click chemistry has been successfully
applied to probe the ligand-binding site of Abl and the ability of
this enzyme to form its inhibitor. Docking studies show that Abl is
able to allow the in situ click chemistry between specific azide and
alkyne fragments by binding to Abl-active sites. This report allows
medicinal chemists to use protein-directed in situ click chemistry
for exploring the conformational space of a ligand-binding pocket
and the ability of the protein to guide its inhibitor. This approach
can be a novel, valuable tool to guide drug design synthesis in the
field of tyrosine kinases