This blog has been set up for editors, reviewers, authors and readers of Elsevier's Analytical Chemistry Journals - all of which can be seen below. It will be updated from Monday to Friday with general news and announcements concerning the titles listed on this page. It should be noted that the views or claims made in the news items and feeds are not necessarily those of the Publisher.
World Congress on Biosensors 2014
Biosensors 2014
Tuesday, 24 July 2012
Just Published: Analytica Chimica Acta
A new issue of this journal has just
been published. To see abstracts of the papers it contains (with links through
to the full papers) click here:
Publication year:
2012 Source:Analytica Chimica Acta, Volume 739 Ricardo N.M.J.
Páscoa, Ildikó V. Tóth, António O.S.S. Rangel Incorporation of long path
length liquid waveguide capillary cell (LWCC or LCW) into spectrometric
detection systems can increase the sensitivity of these by orders of magnitude
(up to 500 times), and consequently can reduce the detection limits. The
combination of the long path length spectrophotometry with flow methodologies
can provide analytical solutions for various challenges in the field of
environmental, biochemical and food chemistry. In this present work, the
analytical applications of the long capillary cells are summarised and
critically discussed. A historical overview of the cell development is given;
applications in different areas are presented and grouped by analyte type. Major
improvements achieved based on the use of the LWCC in the analytical
characteristics (like sensitivity and detection limit) are emphasised while some
of the limitations are also discussed.
Graphical abstract
Graphical abstract Highlights
►
Advances in application of liquid core waveguide capillary cell are summarised
and critically discussed. ► Different flow strategies using the LWCC are
presented. ► Practical advantages and limitations in application are pointed
out.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 739 Zeid A. ALOthman,
Mohamed Dawod, Jihye Kim, Doo Soo Chung Single drop microextraction (SDME) is
a convenient and powerful preconcentration and sample cleanup method for
capillary electrophoresis (CE). In SDME, analytes are typically extracted from a
sample donor solution into an acceptor drop hanging at the inlet tip of a
capillary. The enriched drop is then introduced to the capillary for CE
analysis. Since the volume of the acceptor drop can be as small as a few
nanoliters, the consumption of solvents can be minimized and the
preconcentration effect is enhanced. In addition, by covering the acceptor phase
with an organic layer or by using an organic acceptor phase, inorganic ions such
as salts in the sample solution can be blocked from entering the acceptor phase,
providing desalting effects. Here, we describe the basic principles and
instrumentation for SDME and its coupling with CE. We also review recent
developments and applications of SDME-CE.
Graphical abstract
Graphical abstract Highlights
. ►
SDME is a convenient and powerful preconcentration and sample cleanup method for
CE. ► SDME-CE has been applied to the analysis of target analytes in complex
matrices. ► SDME-CE has been hyphenated with other on-line preconcentration
techniques in CE.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 739 Ping He, Wei Wang,
Licheng Du, Faqin Dong, Yuequan Deng, Tinghong Zhang A novel Cu-zeolite
A/graphene modified glassy carbon electrode for the simultaneous electrochemical
determination of dopamine (DA) and ascorbic acid (AA) has been described. The
Cu-zeolite A/graphene composites were prepared using Cu2+
functionalized zeolite A and graphene oxide as the precursor, and subsequently
reduced by chemical agents. The composites were characterized by X-ray
diffraction, Fourier transform infrared spectra and scanning electron
microscopy. Based on the Cu-zeolite A/graphene-modified electrode, the potential
difference between the oxidation peaks of DA and AA was over 200mV, which was
adequate for the simultaneous electrochemical determination of DA and AA. Also
the proposed Cu-zeolite/graphene-modified electrode showed higher
electrocatalytic performance than zeolite/graphene electrode or
graphene-modified electrode. The electrocatalytic oxidation currents of DA and
AA were linearly related to the corresponding concentration in the range of
1.0×10−7–1.9×10−5 M for DA and
2.0×10−5–2.0×10−4 M for AA. Detection limits (<!--
no-mfc -->S/N<!-- /no-mfc -->=3) were estimated to be
4.1×10−8 M for DA and 1.1×10−5 M for AA, respectively.
Graphical abstract
Graphical abstract Highlights
A novel Cu-zeolite
A/graphene-modified glassy carbon electrode was applied in the simultaneous
electrochemical determination of dopamine (DA) and ascorbic acid (AA). The
potential difference between the two oxidation peaks of DA and AA were over
200mV. The electrocatalytic oxidation currents of DA were linearly related to
the corresponding concentration in the range of
1.0×10−7–1.9×10−5 M. ► Cu
nanoparticles doped-zeolite A/graphene (CuZEA/RGO) modified electrode was
prepared. ► The composites of CuZEA/RGO were prepared via reduction of
Cu2+ functionalized zeolite A and graphene oxide in one pot. ► The
modified electrode was presented for the simultaneous determination of DA and
AA. ► The proposed electrode showed a higher electrocatalytic
performance.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 739 Tsze Yin Tan,
Chanbasha Basheer, Kai Perng Ng, Hian Kee Lee A simple and sensitive single
step electro membrane extraction (EME) procedure was demonstrated for biological
organic anions with determination by ion chromatography (IC). Nitrite, adipate,
oxalate, iodide, fumarate, thiocyanate and perchlorate were extracted from
aqueous donor solutions, across a supported liquid membrane (SLM) consisting of
methanol impregnated in the walls of a porous polypropylene membrane bag and
into an alkaline aqueous acceptor solution in the lumen of the propylene
envelope by the application of potential of 12V applied across the SLM. The
acceptor solution was analyzed by IC. Parameters affecting the extraction
performance such as type of SLM, extraction time, pH of the donor and acceptor
solution, and extraction voltage were studied. The most favorable EME conditions
were methanol as the SLM, extraction time of 5min, pH of acceptor and sample
solutions of 12 and 4, respectively, and a voltage of 12V. Portable 12V
batteries were used in the study. Under these optimized conditions, all anions
had enrichment factors ranging from 3.6 to 36.2 with relative standard
deviations (n =3) of between 6.6 and 17.5%. Good linearity ranging from 0.1 to
10μgmL−1 with coefficients of correlation (r) of between 0.9981 and
0.9996 were obtained. The limits of detection of the EME-IC method were from
0.01 to 0.14μgmL−1. The developed methodology was applied to amniotic
fluid samples to evaluate the feasibility of the method for real applications.
Graphical abstract
Graphical abstract Highlights
. Schematic of (a)
battery-operated electro membrane extraction, (b) proposed extraction mechanism
and (c) selected target anions. ► One-step
battery-operated electro membrane extraction of anions from biological samples.
► Extraction performance was compared with liquid-phase microextraction. ►
Simple and efficient analytical approach with low LODs, good linearity and
repeatability.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 739 Geraldine S.C.
Turner, Graham A. Mills, Peter R. Teasdale, Jonathan L. Burnett, Sean Amos, Gary
R. Fones Three adsorbents (Chelex-100, manganese dioxide [MnO2] and Metsorb),
used as binding layers with the diffusive gradient in thin film (DGT) technique,
were evaluated for the measurement of inorganic uranium species in synthetic and
natural waters. Uranium (U) was found to be quantitatively accumulated in
solution (10–100μgL−1) by all three adsorbents (uptake efficiencies
of 80–99%) with elution efficiencies of 80% (Chelex-100), 84% (MnO2) and 83%
(Metsorb). Consistent uptake occurred over pH (5–9), with only MnO2 affected by
pH<5, and ionic strength (0.001–1molL−1 NaNO3) ranges typical of
natural waters, including seawater. DGT validation experiments (5 days) gave
linear mass uptake over time (R 2 ≥0.97) for all three adsorbents in
low ionic strength solution (0.01M NaNO3). Validation experiments in artificial
sea water gave linear mass uptake for Metsorb (R 2 ≥0.9954) up to 12h
and MnO2 (R 2 ≥0.9259) up to 24h. Chelex-100 demonstrated no linear
mass uptake in artificial sea water after 8h. Possible interferences were
investigated with SO4 2− (0.02–200mgL−1) having little
affect on any of the three DGT binding layers. PO4 3− additions
(5μgL−1–5mgL−1) interfered by forming anionic uranyl
phosphate complexes that Chelex-100 was unable to accumulate, or by directly
competing with the uranyl species for binding sites, as with MnO2 and the
Metsorb. HCO3 − (0.1–500mgL−1) additions formed anionic
species which interfered with the performance of the Chelex-100 and the MnO2,
and the Ca2+ (0.1–500mgL−1) had the affect of forming
labile calcium uranyl species which aided uptake of U by all three resins. DGT
field deployments in sea water (Southampton Water, UK) gave a linear mass uptake
of U over time with Metsorb and MnO2 (4 days). Field deployments in fresh water
(River Lambourn, UK) gave linear uptake for up to 7 and 4 days for Metsorb and
MnO2 respectively. Field deployment of the Metsorb-DGT samplers with various
diffusive layer thicknesses (0.015–0.175cm) allowed accurate measurements of the
diffusive boundary layer (DBL) and allowed DBL corrected concentrations to be
determined. This DBL-corrected U concentration was half that determined when the
effect of the DBL was not considered. The ability of the DGT devices to measure
U isotopic ratios with no isotopic fractionation was shown by all three resins,
thereby proving the usefulness of the technique for environmental monitoring
purposes.
Graphical abstract
Graphical abstract Highlights
In situ field deployment of DGT
devices – manganese dioxide ( ) best suited for sea water monitoring (a) up to 7
days and Metsorb ( ) best suited for fresh water monitoring (b) of inorganic
uranium species up to 7 days. ► The adsorbents
Chelex-100, Metsorb and MnO2 were investigated for use with DGT. ► All three
adsorbents performed well in low ionic strength solutions. ► MnO2 resin was
found to be the most suitable for marine deployments. ► DGT is able to measure
isotopic ratios of U down to concentrations of 0.1μgL−1. ► DGT
underestimated U concentrations by at least 50% if the DBL was not taken into
account.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 739 S. Vo Duy, S.
Besteiro, L. Berry, C. Perigaud, F. Bressolle, H.J. Vial, I.
Lefebvre-Tournier Plasmodium falciparum is the causative agent of malaria, a
deadly infectious disease for which treatments are scarce and drug-resistant
parasites are now increasingly found. A comprehensive method of identifying and
quantifying metabolites of this intracellular parasite could expand the arsenal
of tools to understand its biology, and be used to develop new treatments
against the disease. Here, we present two methods based on liquid chromatography
tandem mass spectrometry for reliable measurement of water-soluble metabolites
involved in phospholipid biosynthesis, as well as several other metabolites that
reflect the metabolic status of the parasite including amino acids, carboxylic
acids, energy-related carbohydrates, and nucleotides. A total of 35 compounds
was quantified. In the first method, polar compounds were retained by
hydrophilic interaction chromatography (amino column) and detected in negative
mode using succinic acid-13C4 and fluorovaline as internal standards.
In the second method, separations were carried out using reverse phase (C18)
ion-pair liquid chromatography, with heptafluorobutyric acid as a volatile ion
pairing reagent in positive detection mode, using d9-choline and 4-aminobutanol
as internal standards. Standard curves were performed in P. falciparum-infected
and uninfected red blood cells using standard addition method (r 2
>0.99). The intra- and inter-day accuracy and precision as well as the
extraction recovery of each compound were determined. The lower limit of
quantitation varied from 50pmol to 100fmol/3×107 cells. These methods
were validated and successfully applied to determine intracellular
concentrations of metabolites from uninfected host RBCs and isolated Plasmodium
parasites.
Graphical abstract
Graphical abstract Highlights
►
Plasmodium falciparum is the causative agent of malaria. ► Two analytical
techniques using LC/MS/MS developed. ► 35 compounds were quantified. ► The
methods were validated and applied to determine intracellular concentrations of
metabolites.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 739 Wen-zhi Yang, Min
Ye, Xue Qiao, Chun-fang Liu, Wen-juan Miao, Tao Bo, Hai-yan Tao, De-an Guo To
discover new natural compounds from herbal medicines tends to be more and more
difficult. In this paper, a strategy integrating orthogonal column
chromatography and liquid chromatography/mass spectrometry (LC/MS) analysis was
proposed, and was applied for rapid discovery of new ginsenosides from Panax
ginseng (PG), Panax quinquefolium (PQ), and Panax notoginseng (PN). The
ginsenosides extracts were fractionated by MCI gel×silica gel orthogonal column
chromatography. The fractions were then separated on a C18 HPLC column, eluted
with a three-component mobile phase (CH3CN/CH3OH/3mM CH3COONH4 H2O), and
detected by electrospray ionization tandem mass spectrometry. The structures of
unknown ginsenosides were elucidated by analyzing negative and positive ion mass
spectra, which provided complementary information on the sapogenins and
oligosaccharide chains, respectively. A total of 623 comprising 437 potential
new ginsenosides were characterized from the ethanol extracts of PG, PQ and PN.
New acylations, diversified saccharide chains and C-17 side chains constituted
novelty of the newly identified ginsenosides. An interpretation guideline was
proposed for structural characterization of unknown ginsenosides by LC/MS. To
confirm reliability of this strategy, two targeted unknown trace ginsenosides
were obtained in pure form by LC/MS-guided isolation. Based on extensive NMR
spectroscopic analysis and other techniques, they were identified as
3-O-[6-O-(E)-butenoyl-β-d-glucopyranosyl(1,2)-β-d-glucopyranosyl]-20(S)-protopanaxadiol-20-O-β-d-glucopyranosyl(1,6)-β-d-glucopyranoside
(named ginsenoside IV) and
3-O-β-d-glucopyranosyl(1,2)-β-d-glucopyranosyl-3β,12β,20(S),24(R)-tetra
hydroxy-dammar-25-ene-20-O-β-d-glucopyranosyl(1,6)-β-d-glucopyranoside
(ginsenoside V), respectively. The fully established structures were consistent
with the MS-oriented structural elucidation. This study expanded our
understanding on ginsenosides of Panax species, and the proposed strategy was
proved efficient and reliable in the discovery of new minor compounds from
herbal extracts.
Graphical abstract
Graphical abstract Highlights
►
Orthogonal MCI and silica gel separation achieved enrichment of minor
ginsenosides. ► LC–(±)ESI-MS n analysis offered complementary
structure information of ginsenosides. ► 623 ginsenosides including 437 new ones
were identified from three Panax species. ► LC/MS guided isolation of P. ginseng
yielded two new ginsenosides. ► NMR analysis of two new ginsenosides was
consistent with LC/MS analysis.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 739 Franziska Hufsky,
Martin Rempt, Florian Rasche, Georg Pohnert, Sebastian Böcker The automated
fragmentation analysis of high resolution EI mass spectra based on a
fragmentation tree algorithm is introduced. Fragmentation trees are constructed
from EI spectra by automated signal extraction and evaluation. These trees
explain relevant fragmentation reactions and assign molecular formulas to
fragments. The method enables the identification of the molecular ion and the
molecular formula of a metabolite if the molecular ion is present in the
spectrum. These identifications are independent of existing library knowledge
and, thus, support assignment and structural elucidation of unknown compounds.
The method works even if the molecular ion is of very low abundance or hidden
under contaminants with higher masses. We apply the algorithm to a selection of
50 derivatized and underivatized metabolites and demonstrate that in 78% of
cases the molecular ion can be correctly assigned. The automatically constructed
fragmentation trees correspond very well to published mechanisms and allow the
assignment of specific relevant fragments and fragmentation pathways even in the
most complex EI-spectra in our dataset. This method will be very helpful in the
automated analysis of metabolites that are not included in common libraries and
it thus has the potential to support the explorative character of metabolomics
studies.
Graphical abstract
Graphical abstract Highlights
► We
present a method for de novo analysis of accurate mass EI mass spectra of small
molecules. ► This method identifies the molecular ion and thus the molecular
formula where the molecular ion is present in the spectrum. ► Fragmentation
trees are constructed by automated signal extraction and evaluation. ► These
trees explain relevant fragmentation reactions. ► This method will be very
helpful in the automated analysis of unknown metabolites.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 739 Fengming Chen, Zhen
Lin, Yongzan Zheng, Hulie Zeng, Hizuru Nakajima, Katsumi Uchiyama, Jin-Ming
Lin In this work, an automatic multi-channel ink-jet for chemiluminescence
(CL) analysis was developed. The four-channel ink-jet device was controlled by a
home-made circuit. Differing from the classic flow injection CL, the whole
procedure for CL analysis was automatically completed on a hydrophobic glass
side. CL reaction of luminal and hydrogen peroxide for the determination of
horseradish peroxidase (HRP) was selected as an application to automatic CL
analysis platform. All solutions delivered by different channels were precisely
ejected to the same position of the glass slide for the CL analysis. The
consumption of reaction solution was reduced to nanoliter level. The whole CL
analysis could be completed in less than 4min, which was benefited from the
prompt solution mixing in small size of droplet. The CL intensity increased
linearly with HRP concentration in the range from 0.01 to 0.5μgmL−1.
The limit of detection (LOD) (S/N=3) was 0.005μgmL−1. Finally, the
automatic CL system could also be used for the detection of HRP in HRP–protein
conjugates, which showed its practical application in immunoassay.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 739 Kai C.C. Johnson,
Francisco Mendez, Michael J. Serpe Poly (N-isopropylacrylamide)-co-acrylic
acid (pNIPAm-co-AAc) microgel-based etalons have been shown to have visible
color and unique spectral properties, which both depend on solution temperature
and pH. In this investigation, pNIPAm-co-AAc microgel-based etalons were
fabricated on the Au electrode of a quartz crystal microbalance (QCM), and the
resonant frequency of the QCM monitored as a function of temperature, at pH 3.0.
Furthermore, the resonant frequency at either pH 3.0 or 7.0 was monitored while
keeping the solution temperature constant at various temperatures. In all cases,
when the solution temperature was below the collapse transition for the
microgels (∼32°C), the resonant frequency at pH 3.0 was lower than at pH 7.0,
which we attribute to the film transitioning from a deswollen to swollen state,
respectively. It was observed that the magnitude of the resonant frequency
change increased as the solution temperature approached the collapse temperature
for the microgels. The overall sensitivity to pH was determined to be
1.3×10−8 M [H+]Hz−1 and a theoretical detection
limit of 390nM was obtained. This sensitivity will be exploited further for
future biosensing applications.
Graphical abstract
Graphical abstract Highlights
►
Color tunable materials on a QCM crystal can detect solution pH changes. ►
Sensitivity of 1.3×10−8 M [H+]Hz−1 is achieved
over a 2pH unit range. ► Detection limit of 390nM [H+] was
realized.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 739 Catarina L. Silva,
João L. Gonçalves, José S. Câmara A new approach based on microextraction by
packed sorbent (MEPS) and reversed-phase high-throughput ultra high pressure
liquid chromatography (UHPLC) method that uses a gradient elution and diode
array detection to quantitate three biologically active flavonols in wines,
myricetin, quercetin, and kaempferol, is described. In addition to performing
routine experiments to establish the validity of the assay to internationally
accepted criteria (selectivity, linearity, sensitivity, precision, accuracy),
experiments are included to assess the effect of the important experimental
parameters such as the type of sorbent material (C2, C8, C18, SIL, and C8/SCX),
number of extraction cycles (extract-discard), elution volume, sample volume,
and ethanol content, on the MEPS performance. The optimal conditions of MEPS
extraction were obtained using C8 sorbent and small sample volumes (250μL) in
five extraction cycle and in a short time period (about 5min for the entire
sample preparation step). Under optimized conditions, excellent linearity ( R
values 2 > 0.9963 ) , limits of detection of 0.006μgmL−1
(quercetin) to 0.013μgmL−1 (myricetin) and precision within 0.5–3.1%
were observed for the target flavonols. The average recoveries of myricetin,
quercetin and kaempferol for real samples were 83.0–97.7% with relative standard
deviation (RSD, %) lower than 1.6%. The results obtained showed that the most
abundant flavonol in the analyzed samples was myricetin
(5.8±3.7μgmL−1). Quercetin (0.97±0.41μgmL−1) and
kaempferol (0.66±0.24μgmL−1) were found in a lower concentration. The
optimized MEPSC8 method was compared with a reverse-phase solid-phase extraction
(SPE) procedure using as sorbent a macroporous copolymer made from a balanced
ratio of two monomers, the lipophilic divinylbenzene and the hydrophilic
N-vinylpyrrolidone (Oasis HLB) were used as reference. MEPSC8 approach offers an
attractive alternative for analysis of flavonols in wines, providing a number of
advantages including highest extraction efficiency (from 85.9±0.9% to 92.1±0.5%)
in the shortest extraction time with low solvent consumption, fast sample
throughput, more environmentally friendly and easy to perform.
Graphical abstract
Graphical abstract Highlights
► An
innovative methodology to pre-concentrate bioactive flavonols, MEPS. ► Rapid
screening for analysis of biological active flavonols in wines. ► MEPS reduced
the sample volume and the time necessary for the analysis. ► Limits the
consumption of organic solvents thus also reducing the testing cost. ► Good
results were obtained in terms of selectivity, precision, sensitivity and
accuracy.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 739 Ryan A. Picou, Indu
Kheterpal, S. Douglass Gilman A data treatment method is presented to detect
fluorescence anisotropy (FA) peaks in capillary electrophoresis
electropherograms. The data treatment method converts plots of fluorescence
anisotropy vs. time that contain no peaks that are distinguishable from the
noise of the anisotropy background into plots that show distinct fluorescence
anisotropy peaks. The method was demonstrated using laser-induced fluorescence
anisotropy data from individual Aβ (1–42) aggregates separated using capillary
electrophoresis. Applying this data treatment method enabled the detection of
anisotropy peaks for individual Aβ aggregate fluorescence peaks that were not
observed prior to the data treatment method. The data treatment method is not
specifically designed for Aβ aggregate analysis or capillary electrophoresis,
and it should be applicable to other applications and other separation methods
with FA detection.
Graphical abstract
Graphical abstract Highlights
► We
explain the absence of fluorescence anisotropy peaks for capillary separations.
► We developed a method to visualize fluorescence anisotropy peaks for
separations. ► This method was applied to a separation of amyloid beta peptide
aggregates.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 738 R. Dario Arrua,
Mohammad Talebi, Tim J. Causon, Emily F. Hilder In recent years the use of
monolithic polymers in separation science has greatly increased due to the
advantages these materials present over particle-based stationary phases, such
as their relative ease of preparation and good permeability. For these reasons,
these materials present high potential as stationary phases for the separation
and purification of large molecules such as proteins, peptides, nucleic acids
and cells. An example of this is the wide range of commercial available
polymer-based monolithic columns now present in the market. This review
summarizes recent developments in the synthesis of monolithic polymers for
separation science, such as the incorporation of nanostructures in the polymeric
scaffold as well as the preparation of hybrid structures. The different methods
used in the surface functionalization of monolithic columns are also reviewed.
Finally, we critically discuss the recent applications of this column technology
in the separation of large molecules under different chromatographic mode.
Graphical abstract
Graphical abstract Highlights
►
This review summarizes recent developments in the synthesis of polymer
monoliths. ► Alternative preparation methods still remain an important area of
research. ► The application of monoliths in the separation of large molecules is
discussed. ► The use of polymer monoliths in the separation of real samples is
still needed.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 738 Henryk H. Jeleń,
Małgorzata Majcher, Mariusz Dziadas Food flavor compounds due to the
complexity of food as a matrix, and usually their very low concentrations in a
product, as well as their low odor thresholds, create a challenge in their
extraction, separation and quantitation. Food flavor volatiles represent
compounds of different polarity, volatility and chemical character, which
determine method of extraction for their isolation from food. Microextraction
techniques, mainly SPME and SBSE have been used for food flavor compounds
analysis for two decades. Microextraction methods other than SPME and SBSE are
seldom used despite their analytical potential. The review discusses the nature
of food flavor compounds, and different approaches to food flavor analysis. It
summarizes the use of microextraction methods in food flavor compounds analysis
based on papers published in the last 5years, and discusses the potential of
microextraction methods in this field.
Graphical abstract
Graphical abstract Highlights
►
Microextraction methods in food flavors analysis based on 2006–2011 published
papers discussed. ► SPME, SBSE, LPME methods as dominating summarized in detail.
► Potential of other, less popular in this field microextraction methods
pronounced.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 738 Mingzhi Dai,
Stephanie Maxwell, Bryan D. Vogt, Jeffrey T. La Belle Two ordered,
soft-templated mesoporous carbon powders with cubic and hexagonal framework
structure and four different commercial, low cost methacrylate-based polymer
binders with widely varying physical properties are investigated as screen
printed electrodes for glucose sensors using glucose oxidase and ferricyanide as
the mediator. Both the chemistry and concentration of the binder in the
electrode formulation can significantly impact the performance.
Poly(hydroxybutyl methacrylate) as the binder provides hydrophilicity to enable
transport of species in the aqueous phase to the carbon surface, but yet is
sufficiently hydrophobic to provide mechanical robustness to the sensor. The
current from the mesoporous carbon electrodes can be more than an order of
magnitude greater than for a commercial printed carbon electrode (Zensor) with
improved sensitivity for model glucose solutions. Even when applying these
sensors to rabbit whole blood, the performance of these glucose sensors compares
favorably to a standard commercial glucose meter with the lower detection limit
of the mesoporous electrode being approximately 20mgdL−1 despite the
lack of a separation membrane to prevent non-specific events; these results
suggest that the small pore sizes and high surface areas associated with ordered
mesoporous carbons may effectively decrease some non-specific inferences for
electrochemical sensing.
Graphical abstract
Graphical abstract Highlights
. ►
We prepared screen printed glucose sensor with two different mesoporous carbons.
► We investigated low cost, fluorine-free methacrylate-based as polymer binders.
► Cubic structure carbon provided higher signal than hexagonal structure carbon.
► Hydrophilicity of the binder greatly impacted the performance of the sensor. ►
The best sensor accurately measured glucose level in rabbit
blood.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 738 Shuxian Mao, Weifeng
Li, Yumei Long, Yifeng Tu, Anping Deng We here reported a simple
electrochemical method for the detection of tryptophan (Trp) based on the Ag@C
modified glassy carbon (Ag@C/GC) electrode. The Ag@C core–shell structured
nanoparticles were synthesized using one-pot hydrothermal method and
characterized by scanning electron microscope (SEM), transmission electron
microscope (TEM), and Fourier transform-infrared spectroscopy (FTIR). The
electrochemical behaviors of Trp on Ag@C/GC electrode were investigated and
exhibited a direct electrochemical process. The favorable electrochemical
properties of Ag@C/GC electrode were attributed to the synergistic effect of the
Ag core and carbon shell. The carbon shell cannot only protect Ag core but also
contribute to the enhanced substrate accessibility and Trp-substrate
interactions, while nano-Ag core can display good electrocatalytic activity to
Trp at the same time. Under the optimum experimental conditions the oxidation
peak current was linearly dependent on the Trp concentration in the range of
1.0×10−7 to 1.0×10−4 M with a detection limit of
4.0×10−8 M (S/N=3). In addition, the proposed electrode was applied
for the determination of Trp concentration in real samples and satisfactory
results were obtained. The technique offers enhanced sensitivity and may trigger
the possibilities of the Ag@C nanocomposite towards diverse applications in
biosensor and electroanalysis.
Graphical abstract
Graphical abstract Highlights
Ag@C and Colloidal carbon sphere
modified glassy carbon electrodes were prepared. It was clear that the Ag@C/GCE
exhibited enhanced electrocatalytic activity towards Trp, which could result
from the synergistic effect between Ag core and carbon shell. The Ag@C/GCE
showed excellent analytical properties in the determination of Trp. ► The electrochemical behavior of Ag@C core–shell
nanocomposite was firstly proposed. ► Ag@C/GC electrode exhibited favorable
electrocatalytic properties towards Trp. ► The good electrocatalysis was due to
the synergistic effect of Ag-core and C-shell. ► The Ag@C/GC electrode displayed
excellent analytical properties in determining Trp.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 738 Ye Tian, Lianzhe Hu,
Shuang Han, Yali Yuan, Jianguo Wang, Guobao Xu Hydrogen evolution bothers
stripping analysis significantly. Dioctyl phthalate-based carbon paste electrode
exhibits extremely wide cathodic potential window. It is explored as a powerful
substrate electrode to solve the problem of hydrogen evolution and further
improve reproducibility for stripping analysis using bismuth-coated electrodes
for the first time. It was successfully applied to the simultaneous
determination of Zn2+, Cd2+, and Pb2+. Linear
responses are obtained for Zn2+ in the range of
10–100μgL−1 and for Pb2+ and Cd2+ in the range
of 5–100μgL−1. The detection limits for Zn2+,
Cd2+, and Pb2+ are 0.1μgL−1,
0.22μgL−1 and 0.44μgL−1, respectively. The method has been
successfully applied to the determination of Zn2+, Cd2+,
and Pb2+ in waste water samples. The detection strategy based on the
combination of dioctyl phthalate-based carbon paste electrode and bismuth-coated
electrodes holds great promise for stripping analysis.
Graphical abstract
Graphical abstract Highlights
. ►
Dioctyl phthalate-based CPE has extremely wide cathodic potential range. ► It
has been used for bismuth-based stripping analysis for the first time. ► It can
effectively avoid hydrogen evolution and improve reproducibility. ► It is
suitable for detecting more active metals such as zinc. ► It is a powerful
platform for bismuth-based electrochemical stripping analysis.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 738 Chaogui Chen, Yan
Du, Jing Li, Xiurong Yang, Erkang Wang In this work, we explored a novel
fabrication method to construct Au and Ag electrodes on chip, utilizing the
different solubility of gold and silver in different etching solutions. KI-I2
etching solution and 50% HNO3 were chosen to dissolve the metal layers
alternatively. Planar electrodes with gold and silver could be simultaneously
and accurately patterned on chip using photolithographic technique. The
as-prepared electrode could be directly served as integrated three-electrode
system for electrochemical measurement. Based on it, a sensing strategy has been
carried out using home-made electrochemical sensing (ECS) chip, which depended
on the competition of double strand DNA and Hg(II)-mediated T–T base pairs
(T-Hg(II)-T). Actually, a mercury specific oligonucleotide (MSO) was immobilized
onto the thus-fabricated gold working electrode and employed as the sensing
element. Chronocoulometry (CC) was chosen to monitor the differences of surface
charge volume and quantify the concentrations of Hg(II) ions with a low
detection limit down to 1nM. Therefore, a facile method to fabricate Au and Ag
electrodes has been demonstrated to simplify the production of ECS chip. The ECS
chip was finally used for constructing an effective sensing platform for
sensitive Hg(II) determination, which held promising potential for designing ECS
chip in lab-on-a-chip device or point-of-care diagnosis.
Graphical abstract
Graphical abstract Highlights
In this work, we explored a
novel method to fabricate multi-metallic planar electrodes and constructed
electrochemical sensing (ECS) chip for Hg(II) determination. Chronocoulometry
was carried out to measure the differences of surface charge volume owing to
specific activity of T-Hg(II)-T formation competed with double strand DNA. The
facile fabrication of multi-planar electrodes and sensing platform endowed the
ECS chip with great promise in environmental monitoring. ► A novel fabrication method was explored to prepare
multi-metallic planar electrodes. ► Electrochemical sensing (ECS) chip has been
constructed for Hg(II) analysis. ► Sensing strategy based on T-Hg(II)-T
formation competed with dsDNA has been built. ► Chronocoulometry (CC) was
carried out to measure the differences of surface charge. ► It resulted in a
high sensitive, high selective Hg(II) determination in practical samples.
No comments:
Post a Comment