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Monday 30 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 741 Joanne L. Holmes,
Frank Davis, Stuart D. Collyer, Séamus P.J. Higson Within this paper we
describe the use of scanning electrochemical microscopy (SECM) to fabricate a
dotted array of biotinylated polyethyleneimine which was then used to immobilise
first neutravidin and then a biotinylated antibody towards a relevant antigen of
interest (PSA, NTx, ciprofloxacin). These antigens were selected both for their
clinical relevance but also since they display a broad range of molecular
weights, to determine whether the size of the antigen used effects the
sensitivity of this approach. The SECM was then used to image the binding of
both complementary and non-complementary antigens in a label-free assay. Imaging
of the arrays before and following exposure to various concentrations of antigen
in buffer showed clear evidence for specific binding of the complementary
antigens to the antibody functionalised dots. Non-specific binding was also
quantified by control experiments with other antigens. This demonstrated
non-specific binding across the whole of the substrate, thereby confirming that
specific binding does occur between the antibody and antigen of interest at the
surface of the dots. The binding of ciprofloxacin was investigated both in
simple buffer solution and in a more complex media, bovine milk.
Graphical abstract
Graphical abstract Highlights
►
Employed scanning electrochemical microscopy for label-free detection of antigen
binding. ► Demonstrated selective and quantitative binding of three different
antigens. ► Detected antigens with a wide range of molecular weights. ►
Demonstrated detection of ciprofloxacin in bovine milk.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 741 Krystyna
Pyrzynska Determination of gold in environmental and geological samples
requires very often preconcentration and separation due to the high
concentration of interfering matrix components and the low content of this
metal. Solid phase extraction technique with different kind of solid sorbents
offers for this purpose high enrichment factor, rapid phase separation and the
ability of combination with different detection techniques. It can be easily
implemented and controlled in flow systems, The recent developments in this area
are presented and discussed.
Graphical abstract
Graphical abstract Highlights
►
Gold determination requires very often preconcentration and separation. ► Solid
phase extraction technique offers for this purpose high enrichment factor, rapid
phase separation and the ability of combination with different detection
techniques. ► The recent developments in this area were presented and
discussed.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 741 Cun Wang, Ruo Yuan,
Yaqin Chai, Shihong Chen, Fangxin Hu, Meihe Zhang A novel electrode was
developed through electrodepositing gold nanoparticles (GNPs) on
overoxidized-polyimidazole (PImox) film modified glassy carbon electrode (GCE).
The combination of GNPs and the PImox film endowed the GNPs/PImox/GCE with good
biological compatibility, high selectivity and sensitivity and excellent
electrochemical catalytic activities towards ascorbic acid (AA), dopamine (DA),
uric acid (UA) and tryptophan (Trp). In the fourfold co-existence system, the
peak separations between AA–DA, DA–UA and UA–Trp were large up to 186, 165 and
285mV, respectively. The calibration curves for AA, DA and UA were obtained in
the range of 210.0–1010.0μM, 5.0–268.0μM and 6.0–486.0μM with detection limits
(S/N=3) of 2.0μM, 0.08μM and 0.5μM, respectively. Two linear calibrations for
Trp were obtained over ranges of 3.0–34.0μM and 84.0–464.0μM with detection
limit (S/N=3) of 0.7μM. In addition, the modified electrode was applied to
detect AA, DA, UA and Trp in samples using standard addition method with
satisfactory results.
Graphical abstract
Graphical abstract Highlights
Electropolymerization of Im on
the GCE, the PIm modified electrode was denoted as PIm/GCE. Subsequently, the
PIm/GCE was washed with doubly distilled water, and then transferred to 0.1M PBS
(pH 4.0) for electrochemical oxidation at +1.8V for 250s. The obtained electrode
was denoted as PImox/GCE (Fig. A). Then, the deposition of GNPs on PImox/GCE was
carried out. The obtained electrode was described as GNPs/PImox/GCE (Fig. B).
► The electropolymerization of imidazole (Im) on GCE
was first reported. ► The PIm film can be overoxidized to form the overoxidized
polyimidazole (PImox). ► PImox allows dispersing of Au and generates additional
electrocatalytic sites. ► The overlapping voltammetric response of AA, DA, UA
and Trp is well-resolved.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 741 Irja Helm, Lauri
Jalukse, Ivo Leito A high-accuracy Winkler titration method has been
developed for determination of dissolved oxygen concentration. Careful analysis
of uncertainty sources relevant to the Winkler method was carried out and the
method was optimized for minimizing all uncertainty sources as far as practical.
The most important improvements were: gravimetric measurement of all solutions,
pre-titration to minimize the effect of iodine volatilization, accurate
amperometric end point detection and careful accounting for dissolved oxygen in
the reagents. As a result, the developed method is possibly the most accurate
method of determination of dissolved oxygen available. Depending on measurement
conditions and on the dissolved oxygen concentration the combined standard
uncertainties of the method are in the range of 0.012–0.018mgdm−3
corresponding to the k =2 expanded uncertainty in the range of
0.023–0.035mgdm−3 (0.27–0.38%, relative). This development enables
more accurate calibration of electrochemical and optical dissolved oxygen
sensors for routine analysis than has been possible before.
Graphical abstract
Graphical abstract Highlights
►
Probably the most accurate method available for dissolved oxygen concentration
measurement was developed. ► Careful analysis of uncertainty sources was carried
out and the method was optimized for minimizing all uncertainty sources as far
as practical. ► This development enables more accurate calibration of dissolved
oxygen sensors for routine analysis than has been possible
before.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 741 Hyun-Hee Lim,
Ho-Sang Shin A robotic method has been established for the determination of
bromate in sea water and drinking deep-sea water. Bromate in water was converted
into volatile derivative, which was measured with headspace solid-phase micro
extraction and gas chromatography–mass spectrometry (HS-SPME GC–MS).
Derivatization reagent and the HS-SPME parameters (selection of fibre,
extraction/derivatization temperature, heating time and; the morality of HCl)
were optimized and selected. Under the established conditions, the detection and
the quantification limits were 0.016μgL−1 and 0.051μgL−1,
respectively, and the intra- and inter-day relative standard deviation was less
than 7% at concentrations of 1.0 and 10.0μgL−1. The calibration curve
showed good linearity with r 2 =0.9998. The common ions
Cl−, NO3 −, SO4 2−, HPO4 2−, H2PO4
−, K+, Na+, NH4 +, Ca2+,
Mg2+, Ba2+, Mn4+, Mn2+,
Fe3+ and Fe2+ did not interfere even when present in
1000-fold excess over the active species. The method was successfully applied to
the determination of bromate in sea water and drinking deep-sea water.
Graphical abstract
Graphical abstract Highlights
►
This study is the first analysis method with HS SPME GC–MS of bromate. ►
Selection of reagent and fibre, reaction temperature/time and pH were optimized.
► The best reagent and fiber is 2,6-DMP and CAR-PDMS. ► LOD and LOQ in sea water
were 0.016 and 0.051μgL−1 and RSD was less than 7.0%.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 741 Kei Toda, Yuki
Ebisu, Kazutoshi Hirota, Shin-Ichi Ohira Underground fluids are important
natural sources of drinking water, geothermal energy, and oil-based fuels. To
facilitate the surveying of such underground fluids, a novel microchannel
extraction device was investigated for in-line continuous analysis and flow
injection analysis of sulfide levels in water and in oil. Of the four designs
investigated, the honeycomb-patterned microchannel extraction (HMCE) device was
found to offer the most effective liquid–liquid extraction. In the HMCE device,
a thin silicone membrane was sandwiched between two polydimethylsiloxane plates
in which honeycomb-patterned microchannels had been fabricated. The identical
patterns on the two plates were accurately aligned. The extracted sulfide was
detected by quenching monitoring of fluorescein mercuric acetate (FMA). The
sulfide extraction efficiencies from water and oil samples of the HMCE device
and of three other designs (two annular and one rectangular channel) were
examined theoretically and experimentally. The best performance was obtained
with the HMCE device because of its thin sample layer (small diffusion distance)
and large interface area. Quantitative extraction from both water and oil could
be obtained using the HMCE device. The estimated limit of detection for
continuous monitoring was 0.05μM, and sulfide concentrations in the range of
0.15–10μM could be determined when the acceptor was 5μM FMA alkaline solution.
The method was applied to natural water analysis using flow injection mode, and
the data agreed with those obtained using headspace gas chromatography-flame
photometric detection. The analysis of hydrogen sulfide levels in prepared oil
samples was also performed. The proposed device is expected to be used for real
time survey of oil wells and groundwater wells.
Graphical abstract
Graphical abstract Highlights
► We
have developed a membrane-based microchannel extraction (HMCE) device. ►
Extraction efficiency was examined theoretically and experimentally for this
device. ► Quantitative extraction can be performed with the HMCE device while
partial extraction with other conventional membrane-based devices. ► The HMCE
device was applied for the measurement of free sulfide or hydrogen sulfide
contained in water and oil samples. ► The presented device is expected to be
used for survey of underground fluid such as groundwater and oil in
future.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 741 Mathieu Dupré, Sonia
Cantel, Jean-Olivier Durand, Jean Martinez, Christine Enjalbal We report on
the simple deposition of Stöber silica nanoparticles (SiO2 NPs) on conventional
MALDI target plate for high throughput laser desorption/ionization mass
spectrometry (LDI-MS) analyses of peptide mixtures with sensitivity in the
femtomolar range. This low-cost easily prepared material allowed straightforward
LDI experiments by deposition of the studied samples directly onto a pre-spotted
MALDI plate. This analytical strategy can be performed in any laboratory
equipped with a MALDI-TOF instrument. All key benefits of organic matrix-free
technologies were satisfied while maintaining a high level of detection
performances (sensitivity and reproducibility/repeatability). In particular,
sample preparation was simple and detection in the low mass range was not
hampered by matrix ions. Imaging studies were undertaken to query sample
dispersion into the inert SiO2 NPs and to help into the search of the best
experimental conditions producing homogeneous analyte distribution within the
deposit. In contrast to commercial disposable LDI targets designed for single
use and requiring an adaptor such as NALDI™, the proposed SiO2 NPs pre-spotting
on a MALDI target plate allowed very easily switching between MALDI and LDI
experiments. They can be conducted either simultaneously (positions with an
organic matrix or SiO2 NPs) or in the row (support prepared in advance, stored
and washed after use). The overall cost and versatility of the methodology made
it very attractive to MALDI users in many domains (peptidomics, proteomics,
metabolomics).
Graphical abstract
Graphical abstract Highlights
► We
present a new pre-spotted MALDI target for peptide detection and sequencing. ►
The inert substrate consists of silica nanoparticles easily prepared by sol–gel
chemistry. ► This very efficient LDI-promoting support produces ions from few
femtomoles of mixtures of peptides. ► Rapid MS profiling and subsequent MS/MS
analyses are achieved.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 741 Emmanuel Njumbe
Ediage, Jose Diana Di Mavungu, Suquan Song, Aibo Wu, Carlos Van Peteghem, Sarah
De Saeger Detection of mycotoxin biomarkers in urine of humans and animals
provides a direct approach for assessing exposure to these mycotoxins as opposed
to the indirect approach of food analysis, which in most cases is affected by
the heterogeneity of the toxin in the food samples. Seven (7) mycotoxins and
their metabolites (total 18 analytes) were selected and an LC–MS/MS method for
their determination in human urine was developed and validated. The method
consisted of direct analysis of two mycotoxin conjugates,
deoxynivalenol-glucuronide and zearalenone-glucuronide without beta
glucuronidase digestion of the urine samples. Since high method sensitivity is
of utmost importance in such study, critical factors which could improve the
analyte recovery and method sensitivity were investigated by a D-optimal
experimental design. Urine samples (10mL) were first extracted with 15mL ethyl
acetate/formic acid (99/1, v/v) followed by SAX SPE clean-up of the acidified
aqueous fraction. Both extracts were combined and analyzed using an LC–MS/MS
system operated in the positive ionization mode. A total run time of 28min was
adopted with all the 18 analytes eluting within 15min. The method was validated
by taking into consideration the guidelines specified in Commission Decision
2002/657/EC and 401/2006/EC. Forty samples obtained from volunteers within the
laboratory research group were analyzed as part of a pilot study. All results
were expressed per mg creatinine. A total of 9 samples were found contaminated
with one or more of the following analytes: DON, OTA, OTα, 4-OH OTA, ZEN, CIT
and β-ZOL. One-eighth (5/40) of the samples were contaminated with DON in the
range of 3.7–67ngmg−1 creatinine. Samples with detectable levels of
DON did not show any co-occurrence of DON-3Glu. One sample was found to be
contaminated with 4-OH OTA (<LOQ), co-occurring with only OTA
(0.2ngmg−1 creatinine). OTα (up to 4.4ngmg−1 creatinine)
was detected in three other samples co-occurring with low levels of OTA (up to
0.3ngmg−1 creatinine) and no 4-OH OTA detected. ZEN was detected in
10% (4/40) of the samples analyzed. Three samples were contaminated with β-ZOL
(3.3–20ngmg−1 creatinine), co-occurring with ZEN
(<LOQ–10.8ngmg−1 creatinine). The ratio of ZEN/β-ZOL varied for
all the three samples. α-ZOL was not detected in any of the 40 samples. CIT was
detected in one sample at 4.5ngmg−1 creatinine. This is the first
study carried out with a small group of the Belgian population to assess
exposure to mycotoxins using biomarkers.
Graphical abstract
Graphical abstract Highlights
►
The method was established for analysis of mycotoxin biomarkers in human urine.
► LLE with acidified ethyl acetate was very efficient as extraction solvent. ►
Direct determination of the glucuronides was performed without enzyme digestion.
► Optimization of the analytical parameters was achieved with a D-optimal
design. ► The proposed sample preparation method is simple, cheaper and
robust.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 741 Nicole E. Oro, Randy
M. Whittal, Charles A. Lucy Normal phase high performance liquid
chromatography (HPLC) is used to separate a gas oil petroleum sample, and the
fractions are collected offline and analyzed on a high resolution Fourier
Transform Ion Cyclotron Resonance Mass Spectrometer (FT-ICR MS). The separation
prior to MS analysis dilutes the sample significantly; therefore the fractions
need to be prepared properly to achieve the best signal possible. The methods
used to prepare the HPLC fractions for MS analysis are described, with emphasis
placed on increasing the concentration of analyte species. The dilution effect
also means that contamination in the MS spectra needs to be minimized. The
contamination from molecular sieves, plastics, soap, etc. and interferences
encountered during the offline fraction collection process are described and
eliminated. A previously unreported MS contamination of iron formate clusters
with a 0.8 mass defect in positive mode electrospray is also described. This
interference resulted from the stainless steel tubing in the HPLC system.
Contamination resulting from what has tentatively been assigned as
palmitoylglycerol and stearoylglycerol was also observed; these compounds have
not previously been reported as contaminant peaks.
Graphical abstract
Graphical abstract Highlights
► We
collect HPLC fractions of gas oils offline for FT-ICR MS analysis. ► Optimized
sample preparation procedures are described. ► MS contamination encountered is
described and eliminated. ► Three new contaminants are identified, including
iron-formate clusters.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 741 Rosa M. Toledano,
Eva M. Díaz-Plaza, José M. Cortés, Inmaculada Blázquez, Ana Vázquez, Jesús
Villén, Jesús Muñoz-Guerra Anti-doping laboratories accredited by the WADA
(World Anti-Doping Agency) must have available methods capable of detecting
synthetic steroids at concentrations below 10ngmL−1 and, at the same
time, be able to quantify endogenous steroids with accuracy. The unequivocal
identification of the steroids must be carried out by GC–MS. In this manuscript
we describe a new method by on-line coupled liquid chromatography–gas
chromatography (LC–GC) using the Through Oven Transfer Adsorption Desorption
(TOTAD) interface and mass spectrometer (MS) detector. By this means, all the
analyte eluted in the LC stage are automatically transferred to the GC, avoiding
the contamination associated with manipulation of the sample. A newly designed
fraction collector is described for the first time. The collector permits the
different fractions eluted in LC to be stored and sent individually to the GC by
means of the TOTAD interface. The detection limits attained, measured in gas
chromatography–mass spectrometry (GC–MS) in SCAN mode, vary between 0.5 and
3.4ngmL−1, and the method, once the sample is derivatized, is
completely automatic.
Graphical abstract
Graphical abstract Highlights
► A
new method to analyze steroids in human urine by LC–GC–MS has been developed. ►
The TOTAD interface with a fraction collector is used in the on line coupling
LC–GC. ► A newly designed fraction collector, totally automated, is described
for the first time. ► Different LC fractions were analyzed in a sole injection
of sample. ► The sensitivity achieved permits the detection limits set by WADA
to be attained.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 741 Li-Yun Guan,
Yong-Qiang Li, Song Lin, Ming-Zhen Zhang, Jun Chen, Zhi-Ya Ma, Yuan-Di
Zhao In this paper, we prepared three types of transferrin-quantum dots
conjugates (QDs-Tf) using three different methods (electrostatic interaction,
1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) coupling,
denatured transferrin (dTf) coating). Fluorescence emission spectra, surface
characteristics, zeta potentials of quantum dots (QDs) and QDs-Tf fluorescent
probes were characterized by spectrophotometer, capillary electrophoresis, and
dynamic light scattering. Fluorescent imaging of HeLa cells was also performed
by QDs and QDs-Tf fluorescent probes. It was found that the fluorescence imaging
performances of QDs-Tf probes prepared by electrostatic interaction and EDC
coupling were better compared with the one prepared by dTf coating. Then a
real-time single cell detection system was established to quantitatively
evaluate cell labeling effects of QDs-Tf fluorescent probes. It was found that
for cell labeling efficiency, the proportion of cells labeled by quantum dot
probes to a group of cells, QDs-Tf probe prepared by EDC coupling showed the
highest labeling efficiency (85.55±3.88%), followed by electrostatic interaction
(78.86±9.57%), and dTf coating showed the lowest (40.09±10.2%). This efficiency
order was confirmed by flow cytometry results. This study demonstrated the
relationship between conjugation methods and the resultant QDs-Tf probes and
provided a foundation for choosing appropriate QDs-Tf probes in cell labeling.
Graphical abstract
Graphical abstract Highlights
► A
convenient method was designed to assess cell efficiency of QDs probes for
cellular labeling. ► The relationship between conjugation methods and
effectiveness was evaluated clearly. ► QDs-Tf probe synthesized by EDC coupling
had the highest labeling efficiency, followed by electrostatic interaction, and
dTf coating.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 741 Jun Ai, Tao Li,
Bingling Li, Yuanhong Xu, Dan Li, Zuojia Liu, Erkang Wang In this article, we
reported a novel approach for in situ labeling and imaging HeLa cancer cells
utilizing a bifunctional aptamer (AS1411) and its fluorescent ligand,
protoporphyrin IX (PPIX). In the presence of potassium ion, AS1411 folded to
G-quadruplex structure, binded fluorescent ligand (PPIX) with fluorescent
enhancement, and targeted the nucleolin overexpressed by cancer cells.
Consequently, bioimaging of cancer cells specifically were realized by laser
scanning confocal microscope. The bioimaging strategy with AS1411–PPIX complex
was capable to distinguish HeLa cancer cells from normal cells unambiguously,
and fluorescence imaging of cancer cells was also realized in human serum.
Moreover, the bioimaging method was very facile, effective and need not any
covalent modification. These results illustrated that the useful approach can
provide a novel clue for bioimaging based on non-covalent bifunctional aptamer
in clinic diagnosis.
Graphical abstract
Graphical abstract Highlights
In this work, we report a novel
approach to in situ labeling and imaging of a cellular protein nucleolin
utilizing a multifunctional anticancer aptamer combined with its fluorescent
ligand. ► AS1411 bind protoporphyrin IX and enhances
the fluorescence signal remarkably. ► According to LSCM experiment, HeLa cells
were imagined by AS1411–PPIX. ► Aptamer-based bioimaging plays an important role
for need not any covalent modification.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 741 Mei-Jun Chen,
Ying-Song Wu, Guan-Feng Lin, Jing-Yuan Hou, Ming Li, Tian-Cai Liu Quantum
dots (QDs) with novel photoproperties are not widely used in clinic diagnosis,
and homogeneous time-resolved fluorescence assays possess many advantages over
current methods for alpha-fetoprotein (AFP) detection. A novel QD-based
homogeneous time-resolved fluorescence assay was developed and used for
detection of AFP, a primary marker for many cancers and diseases. QD-doped
carboxyl-modified polystyrene microparticles (QPs) were prepared by doping
oil-soluble QDs possessing a 605nm emission peak. The antibody conjugates
(QPs-E014) were prepared from QPs and an anti-AFP monoclonal antibody, and
luminescent terbium chelates (LTCs) were prepared and conjugated to a second
anti-AFP monoclonal antibody (LTCs-E010). In a double-antibodies sandwich
structure, QPs-E014 and LTCs-E010 were used for detection of AFP, serving as
energy acceptor and donor, respectively, with an AFP bridge. The results
demonstrated that the luminescence lifetime of these QPs was sufficiently long
for use in a time-resolved fluoroassay, with the efficiency of time-resolved
Förster resonance transfer (TR-FRET) at 67.3% and the spatial distance of the
donor to acceptor calculated to be 66.1Å. Signals from TR-FRET were found to be
proportional to AFP concentrations. The resulting standard curve was log Y
=3.65786+0.43863·log X (R =0.996) with Y the QPs fluorescence intensity and X
the AFP concentration; the calculated sensitivity was 0.4ngmL−1. By
assaying test samples against the standard curve, the coefficient of variations
was <5%, indicating that QDs were suitable for this homogenous time-resolved
fluoroimmunoassay. This work extended the potential applications of QDs in
future homogeneous analytical bioassays. In the coming research, hepatitis B
surface antigen, another primary marker for hepatocellular carcinoma, will be
studied for practical detection using a QD-based homogenous multiplex
fluoroimmunoassay.
Graphical abstract
Graphical abstract Highlights
►
QDs-based homogeneous time-resolved fluoroimmunoassay was developed to detect
AFP. ► The conjugates were prepared with QDs-doped microspheres and anti-AFP
McAb. ► The conjugates were prepared with LTCs and another anti-AFP McAb. ►
Excess amounts of conjugates were used for detecting AFP without rinsing. ► The
wedding of QPs and LTCs was suitable for HTRFIA to detect AFP.
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