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World Congress on Biosensors 2014
Biosensors 2014
Wednesday 29 August 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 744 Poomrat Rattanarat,
Wijitar Dungchai, Weena Siangproh, Orawon Chailapakul, Charles S. Henry We
report the development of an electrochemical paper-based analytical device
(ePAD) for the selective determination of dopamine (DA) in model serum sample.
The ePAD device consists of three layers. In the top layer, SU-8 photoresist
defines a hydrophilic sample application spot on the filter paper. The middle
layer was made from transparency film and contained two holes, one for sample
preconcentration and the other for the surfactant to allow transfer to the third
layer. A screen-printed carbon electrode formed the bottom layer and was used
for electrochemical measurements. In the absence of the anionic surfactant,
sodium dodecyl sulfate (SDS), the oxidation peaks of DA, ascorbic acid (AA) and
uric acid (UA) overlapped. With the addition of SDS, the DA oxidation peak
shifted to more negative values and was clearly distinguishable from AA and UA.
The oxidation potential shift was presumably due to preferential electrostatic
interactions between the cationic DA and the anionic SDS. Indeed, whilst the
SDS-modified paper improved the DA current five-fold, the non-ionic Tween-20 and
cationic tetradecyltrimethylammonium bromide surfactants had no effect or
reduced the current, respectively. Furthermore, only the SDS-modified paper
showed the selective shift in oxidation potential for DA. DA determination was
carried out using square-wave voltammetry between −0.2 and 0.8V vs. Ag/AgCl, and
this ePAD was able to detect DA over a linear range of 1–100μM with a detection
limit (S/N=3) of 0.37μM. The ePAD seems suitable as a low cost, easy-to-use,
portable device for the selective quantitation of DA in human serum samples.
Graphical abstract
Graphical abstract Highlights
►
Selective detection of dopamine over uric acid and ascorbic acid in serum. ►
Multilayer electrochemical paper-based analytical device constructed for
preconcentration and detection of biological molecules in complex matrix. ►
Novel preconcentration mechanism based on electrostatic interactions between
dopamine and sodium dodecyl sulfate.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 744 Concepción Domingo,
Javier Saurina The analytical characterization of drug delivery systems
prepared by means of green manufacturing technologies using CO2 as a processing
fluid is here reviewed. The assessment of the performance of nanopharmaceuticals
designed for controlled drug release may result in a complex analytical issue
and multidisciplinary studies focused on the evaluation of physicochemical,
morphological and textural properties of the products may be required. The
determination of the drug content as well as the detection of impurities and
solvent residues are often carried out by chromatography. Assays on solid state
samples relying on X-ray, vibrational and nuclear magnetic resonance
spectroscopies are of great interests to study the composition and structure of
pharmaceutical forms. The morphology and size of particles are commonly checked
by microscopy and complementary chemical information can be extracted in
combination with spectroscopic accessories. Regarding the thermal behavior,
calorimetric and thermogravimetric techniques are applied to assess the thermal
transitions and stability of the samples. The evaluation of drug release
profiles from the nanopharmaceuticals can be based on various experimental
set-ups depending on the administration route to be considered. Kinetic curves
showing the evolution of the drug concentration as a function of time in various
physiological conditions (e.g., gastric, plasmatic or topical) are recorded
commonly by UV–vis spectroscopy and/or chromatography. Representative examples
are commented in detail to illustrate the characterization strategies.
Graphical abstract
Graphical abstract Highlights
►
Analytical evaluation of nanostructured drug delivery systems prepared by scCO2.
► Physicochemical characterization by chromatography and spectroscopy. ►
Particle characterization by microscopy and thermal analysis. ► Release
assessment by batch, continuous and diffusion devices.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 744 Guzel Ziyatdinova,
Endzhe Ziganshina, Herman Budnikov Effect of surfactant presence on
electrochemical generation of titrants has been evaluated and discussed for the
first time. Cationic (1-dodecylpyridinium and cetylpyridinium bromide), anionic
(sodium dodecyl sulfate) and nonionic (Triton X100 and Brij® 35)
surfactants as well as nonionic high molecular weight polymer (PEG 4000) do not
react with the electrogenerated bromine, iodine and hexacyanoferrate(III) ions.
The electrogenerated chlorine chemically interact with Triton X100 and
Brij® 35. The allowable range of surfactants concentrations providing
100% current yield has been found. Chain-breaking low molecular weight
antioxidants (ascorbic acid, rutin, α-tocopherol and retinol) were determined by
reaction with the electrogenerated titrants in surfactant media. Nonionic and
cationic surfactants can be used for the determination of antioxidants by
reaction with the electrogenerated halogens. On contrary, cationic surfactants
gives significantly overstated results of antioxidants determination with
electrogenerated hexacyanoferrate(III) ions. The use of surfactants in
coulometry of α-tocopherol and retinol provides their solubilization and allows
to perform titration in water media. Simple, express and reliable coulometric
approach for determination of α-tocopherol, rutin and ascorbic acid in
pharmaceuticals using surfactant media has been developed. The relative standard
deviation of the measurements does not exceed of 5%.
Graphical abstract
Graphical abstract Highlights
►
Applicability of surfactants in constant-current coulometry is shown for the
first time. ► Reactions of antioxidants with electrogenerated titrants in
surfactant media are investigated. ► Water insoluble antioxidants can be
determined in water media with addition of surfactants. ► Coulometric
determination of antioxidants in pharmaceutical dosage forms using surfactants
media is developed.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 744 Ulrich Lange,
Vladimir M. Mirsky Electroanalytical methods have been applied only in
conducting media. An application of conducting polymers allows to overcome this
limitation. If such material is in electrochemical equilibrium with dissolved
redox active species, its electrical conductivity depends on the redox potential
of these species. Therefore, conductometric measurements with conducting
polymers can provide about the same information as classical redox electrodes.
The approach was applied for redox titration. Equivalent points obtained by this
titration in aqueous and organic electrolytes were identical. Then the approach
was applied for determination of bromine number by redox titration in
non-conducting organic phase.
Graphical abstract
Graphical abstract Highlights
►
Electroanalytics in non-conducting media. ► Chemiresistors based on conducting
polymers as quantitative redox sensors. ► Simultaneous conductometry with
chemiresistor and redox potentiometry. ► A unique possibility to measure
redox-potential in gases and nonconducting liquids. ► An application for
redox-titration in non-conducting organic phase is demonstrated.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 744 Wenjing Wang, Lei
Bao, Jianping Lei, Wenwen Tu, Huangxian Ju A visible light induced
photoelectrochemical biosensing platform based on oxygen-sensitive near-infrared
quantum dots (NIR QDs) was developed for detection of glucose. The NIR QDs were
synthesized in an aqueous solution, and characterized with scanning electron
microscopy and X-ray photoelectron spectroscopy. The as-prepared NIR QDs were
employed to construct oxygen-sensitive photoelectrochemical biosensor on a
fluorine-doped tin oxide (FTO) electrode. The oxygen dependency of the
photocurrent was investigated at as-prepared electrode, which demonstrated the
signal of photocurrent is suppressed with the decreasing of oxygen. Coupling
with the consumption of oxygen during enzymatic reaction, a photoelectrochemical
strategy was proposed for the detection of substrate. Using glucose oxidase
(GOx) as a model enzyme, that is, GOx was covalently attached to the surface of
CdTe QDs, the resulting biosensor showed the sensitive response to glucose.
Under the irradiation of visible light of a wavelength at 505nm, the proposed
photoelectrochemical method could detect glucose ranging from 0.1mM to 11mM with
a detection limit of 0.04mM. The photoelectrochemical biosensor showed a good
performance with high upper detection limit, acceptable stability and accuracy,
providing an alternative method for monitoring biomolecules and extending the
application of near-infrared QDs.
Graphical abstract
Graphical abstract Highlights
►
The near-infrared QDs are synthesized in an aqueous solution. ► QDs-based
biosensor exhibits visible-light induced cathodic photocurrent. ► The oxygen
dependency of the photocurrent is verified. ► A photoelectrochemical strategy is
established by coupling with enzymatic reaction. ► Photoelectrochemical sensor
shows high upper detection limit, acceptable stability and
accuracy.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 744 Manzar Sohail,
Roland De Marco, Krystina Lamb, Eric Bakker A nitrate ion-selective electrode
(ISE) employing a permeable tubular membrane impregnated with a conventional ISE
cocktail has been used successfully in the coulometric analysis of nitrate in
fresh waters. The liquid ISE membrane comprising a nitrate ionophore
[tridodecylmethylammonium nitrate (TDMAN)], lipophilic electrolyte
[tetradodecyl-ammoniumtetrakis(4-chlorophenyl)borate (ETH 500)] and plasticizer
[bis(3-ethyl-hexyl)sebacate (DOS)] was supported on a porous polypropylene tube.
Coulometric analysis with the tubular membrane ISE showed that nitrate could be
detected in the range 10–100μM with a precision of 2.3% relative standard
deviation (RSD), limit of detection of 1.1μM and relative accuracy of 4.4%
compared to a certified reference material (CRM) Lake sample.
Graphical abstract
Graphical abstract Highlights
► A
tubular membrane nitrate ion-selective electrode is capable of the coulometric
analysis of nitrate in lake water. ► Exhaustive nitrate electrolysis in an
ion-selective coulometric sensor yielded a calibration free response. ► The
coulometric nitrate ion-selective electrode possesses a comparable precision and
accuracy to spectrophotometry.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 744 Yifen Li, Lateef
Syed, Jianwei Liu, Duy H. Hua, Jun Li We demonstrate the feasibility of a
label-free electrochemical method to detect the kinetics of phosphorylation and
dephosphorylation of surface-attached peptides catalyzed by kinase and
phosphatase, respectively. The peptides with a sequence specific to c-Src
tyrosine kinase and protein tyrosine phosphatase 1B (PTP1B) were first validated
with ELISA-based protein tyrosine kinase assay and then functionalized on
vertically aligned carbon nanofiber (VACNF) nanoelectrode arrays (NEAs).
Real-time electrochemical impedance spectroscopy (REIS) measurements showed
reversible impedance changes upon the addition of c-Src kinase and PTP1B
phosphatase. Only a small and unreliable impedance variation was observed during
the peptide phosphorylation, but a large and fast impedance decrease was
observed during the peptide dephosphorylation at different PTP1B concentrations.
The REIS data of dephosphorylation displayed a well-defined exponential decay
following the Michaelis–Menten heterogeneous enzymatic model with a specific
constant, k cat /K m, of (2.1±0.1)×107 M−1 s−1.
Consistent values of the specific constant was measured at PTP1B concentration
varying from 1.2 to 2.4nM with the corresponding electrochemical signal decay
constant varying from 38.5 to 19.1s. This electrochemical method can be
potentially used as a label-free method for profiling enzyme activities in fast
reactions.
Graphical abstract
Graphical abstract Highlights
► We
developed an electrochemical method to detect phosphorylation/dephosphorylation.
► Peptides were functionalized on carbon nanofiber nanoelectrode arrays. ►
Real-time electrochemical impedance spectroscopy (REIS) showed reversible
changes. ► The REIS data of phosphatase showed an exponential decay with a
consistent k cat /K m. ► The reaction was analyzed using the Michaelis–Menten
heterogeneous enzymatic model.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 744 Xu Zhang, Lu Yang,
Zoltan Mester A simple, rapid microwave digestion procedure for protein
hydrolysis preceding the determination of amino acids in yeast using gas
chromatography–mass spectrometry (GC–MS) is described. Protein hydrolysis was
performed in a focused microwave using 4M methanesulfonic acid (MAS). Amino
acids were derivatized with methyl chlorofomate (MCF) and extracted into
chloroform prior to GC–MS analysis. The microwave parameters, including power,
temperature and heating time, were optimized. It was found that temperature and
heating time were the most influential factors. A total of 17 amino acids were
determined in selenium-enriched yeast with use of standard addition calibration.
Limits of detection and quantitation (LODs/LOQs) of the amino acids measured
were in the sub-nmol range, suitable for monitoring of amino acids in yeast and
other food products.
Graphical abstract
Graphical abstract Highlights
Gas chromatography mass
spectrometry chromatogram of 18 amino acids extracted from selenium enriched
yeast. Microwave enhanced acid hydrolysis followed by methyl chlorofomate
derivatization was employed for sample preparation. ► A rapid microwave digestion procedure for protein
hydrolysis is described. ► A simple methyl chloroformate derivatization combined
with GC–MS determination was employed. ► A total of 17 amino acids were
determined. ► Limits of detection in the sub-nmol range, suitable for rapid
monitoring of amino acids in yeast.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 744 Jia-Ming Liu,
Xiao-Mei Huang, Li-Hong Zhang, Zhi-Yong Zheng, Xuan Lin, Xiao-Yang Zhang, Li
Jiao, Ma-Lin Cui, Shu-Lian Jiang, Shao-Qin Lin The present study proposed a
simple sensitive and specific immunoassay for the quantification of calcitonin
(CT) in human serum with water-soluble multi-walled carbon nanotubes (MWNTs).
The COOH group of MWNTs could react with the NH group of rhodamine S (Rhod.S)
molecules to form Rhod.S-MWNTs, which could emit room temperature
phosphorescence (RTP) on acetate cellulose membrane (ACM) and react with
Tween-80 to form micellar compound. Tween-80-Rhod.S-MWNTs (TRM), as a
phosphorescent labelling reagent, could dramatically enhance the RTP signal of
the system. The developed TRM phosphorescent reagent was used to label
anti-calcitonin antibody (AbCT) to form the TRM-AbCT labelling product, which
could take high specific immunoreaction with CT, and the ΔI p (= I p2 − I p1, I
p2 and I p1 were the phosphorescence intensity of the test solution and the
blank sample, respectively) of the system was linear to the content of CT.
Hence, a new solid substrate room temperature phosphorescence immunoassay
(SSRTPIA) was established for the determination of CT in human serum. This
sensitive (limit of quantification (LOQ) was 8.0×10−14
gmL−1), accurate, selective and precise method has been applied to
determine CT in human serum and predict primary osteoporosis and fractures, with
the results in good agreement with those obtained by chemiluminescence
immunoassay (CLIA). Simultaneously, the structure of MWNTs was characterized
with scanning electron microscopy (SEM) and infrared spectroscopy (IR), and the
reaction mechanisms of both labelling AbCT with TRM and SSRTPIA for the
determination of trace CT were discussed.
Graphical abstract
Graphical abstract Highlights
A new Tween-80-Rhodamine
S-water-soluble multi-walled carbon nanotubes (Tween-80-Rhod.S-MWNTs-EDC-NHS,
TRMEN) phosphorescent labelling reagent was developed. High sensitive solid
substrate room temperature phosphorescence immunoassay (SSRTPIA) for the
determination of calcitonin (CT) in human serum and the prediction of human
diseases based on the TRMEN could be used to label anti-calcitonin antibody
(AbCT) to form the TRMEN-AbCT labelling product, which could take high specific
immunoreaction with CT causing that the ΔI p of the system was linear to the
content of CT. Moreover, the reaction mechanisms of both labelling AbCT by TRMEN
and SSRTPIA for the determination of trace CT were discussed. This research not
only provides a new hormones analysis method, but also expands the application
field of MWNTs and promotes the development of SSRTP and IA. ► A Tween-80-Rhodamine S-multi-walled carbon nanotubes
labelling reagent was developed. ► The phosphorescence immunoassay was
established for the determination of calcitonin. ► This method has been applied
to determine CT and the prediction of diseases. ► The structure of MWNTs was
characterized with SEM and IR. ► The mechanisms for both determining trace CT
and labelling AbCT were discussed.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 744 Florian Meier,
Branka Schott, Denise Riedel, Boris Mizaikoff In molecular imprinting the
porogen plays a decisive role, as it not only affects the physical properties of
the resulting polymer including its porosity, the specific surface area, and the
swelling behavior, but also governs the stability of the prepolymerization
complex, which in turn decisively determines the recognition properties of the
resulting molecularly imprinted polymer (MIP). In this study, the influence of
the porogen on the selectivity of MIPs was investigated. Therefore, bulk MIPs
against 4-nitrophenol using 4-vinylpyridine (4-VP) as functional monomer and
ethylene glycol dimethacrylate (EDMA) as crosslinker were prepared in
acetonitrile and chloroform. The recognition properties of both MIPs were
evaluated during chromatographic studies using the respective porogenic solvents
as mobile phase for both MIPs. Along with the characterization of the morphology
of the obtained polymers via SEM and BET analysis, the beneficial nature of
chloroform as porogen for imprinting 4-NP was experimentally demonstrated and
verified by findings obtained from complementary molecular dynamics simulations.
Moreover, the application of chloroform as mobile phase for the MIP prepared in
acetonitrile and vice versa clearly demonstrated the dependence of the resulting
recognition properties on the selection of the mobile phase.
Graphical abstract
Graphical abstract Highlights
►
Influence of the porogenic solvent on the selectivity of MIPs was investigated.
► Recognition properties in different porogens were evaluated via
chromatography. ► Role of the porogen was studied via complementary molecular
dynamics simulations.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 744 Huamin Qiu, Chuannan
Luo, Min Sun, Fuguang Lu, Lulu Fan, Xiangjun Li A chemiluminescence (CL)
array sensor for determination of benzenediol isomers simultaneously using the
system of luminol–NaOH–H2O2 based on a graphene-magnetite-molecularly imprinted
polymer (GM-MIP) is described. Use of graphene in the GM-MIP thus prepared is
helpful to improve the adsorption capacity, while use of magnetite nanoparticles
can facilitate the isolation of GM-MIP at end of their synthesis, and rendering
easier the use of the polymers in the array sensor. The adsorption performance
and properties were characterized. The GM-MIP was used to increase the
selectivity in CL analysis. In addition, the sensor was reusable and of good
selectivity and adsorption capacity. The array sensor was finally used for the
determination of hydroquinone, resorcinol and catechol in waste water samples
simultaneously.
Graphical abstract
Graphical abstract Highlights
The sensor realized the
separation and determination of benzenediol isomers. ► Determination of benzenediol isomers at the same time. ► A
chemiluminescence (CL) array sensor was described. ►
Graphene-magnetite-molecularly imprinted polymer was used. ► The adsorption
capacity was improved.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 744 Yuanyuan Long, Haibo
Chen, Huaming Wang, Zhou Peng, Yufei Yang, Guoqing Zhang, Na Li, Feng Liu, Jian
Pei An electrospun nanofibrous explosive sensor was first constructed based
on a newly developed fluorescent conjugated polymer P containing heteroatom
polycyclic units. Electrospinning by doping polymer P as a fluorescent probe in
a polystyrene supporting matrix afforded a fluorescence nanofibrous film with
unique porous structures, and effectively avoided the aggregation of polymer P.
The novel explosive sensor exhibited stable fluorescence property, satisfactory
reversibility with less than 5% loss of signal intensity after four
quenching–regeneration cycles, and good reproducibility among three batches with
a relative standard deviation of 2.8%. Such fabricated sensor also showed
remarkable sensitivity toward a series of trace nitroaromatic explosive vapors,
including picric acid (parts-per-trillion level) and 2,4,6-trinitrotoluene vapor
(parts-per-billion level), as well as good selectivity with less than 10%
response to typical interferents. Therefore, the present strategy extends the
application of different kinds of conjugated polymers for the construction of
optical chemosensors.
Graphical abstract
Graphical abstract Highlights
► A
novel electrospun nanofibrous sensor was constructed for nitroaromatic
explosives. ► A new conjugated polymer P was developed as a fluorescent probe of
the sensor. ► The sensor exhibited remarkable sensitivity toward nitroaromatic
explosive vapors. ► The present strategy shows potentials in fabrication of
portable sensing devices.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 744 Dongyue Lin, Honglin
Liu, Kai Qian, Xia Zhou, Liangbao Yang, Jinhuai Liu This study found that
1,2-ethylenediamine (EDA) as a primary amine could be modified onto the surface
of citrate-stabilized gold nanoparticles (Au NPs), and the EDA-capped Au NPs
were successfully used as an ultrasensitive optical probe for TNT detection. The
strong donor–acceptor (D–A) interactions between EDA and trinitrotoluene (TNT)
at the Au NP/solution interface induced significant aggregation of the
EDA-capped Au NPs, and enabled to easily realize the direct colorimetric
detection of ultratrace TNT. The results showed that such a color change was
readily seen by the naked eye, and the colorimetric detection could be down to
400pM level of TNT with excellent discrimination against other nitro compounds.
UV–vis absorption spectroscopy was used to examine the TNT-induced changes in
local surface plasmon resonance (LSPR) of EDA-capped Au NPs, and a new LSPR band
at ca. 630nm arose along with the addition of TNT, which produced a detection
limit of TNT down to ca. 40pM. Furthermore, dynamic light scattering
measurements evidenced the ultratrace TNT-induced small changes in the size of
the EDA-capped Au NPs, and realized the quick and accurate detection of TNT in
0.4pM level. These results demonstrated the ultrahigh sensitivity of this
optical probe for TNT detection. Moreover, this optical probe is sample, stable,
low-cost, and these excellent properties make it quite promising for infield and
rapid detection of TNT.
Graphical abstract
Graphical abstract Highlights
►
EDA can interact with the citrate-stabilized Au NPs through electrostatic
attraction. ► EDA-capped Au NPs can be used as an ultrasensitive optical probe
for TNT detection. ► Direct colorimetric assays for TNT have a detection limit
of 400pM. ► DLS assays evidenced the aggregation of the probe induced by TNT in
0.4pM level. ► The probe has an excellent discrimination against other nitro
compounds.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 744 Chun-Chi Wang,
Jia-Ling Chen, Yen-Ling Chen, Hui-Ling Cheng, Shou-Mei Wu In this research, a
novel stacking capillary electrophoresis method, repetitive large volume sample
injection and sweeping MEKC (rLVSI-sweeping MEKC) were developed to analyze the
presence of three androgenic steroids considered as sport doping drugs,
testosterone (T), epitestosterone (E) and epitestosterone glucuronide (EG) in
urine. This method provides better sensitivity enhancement than the traditional
large volume sample stacking-sweeping strategies due to sensitivity enhancement
by repetitive injections. This multiple sampling method enhances sensitivity of
monitoring of urine samples by UV detection (254nm). Firstly, the phosphate
buffer was filled into an uncoated fused silica capillary and the samples were
injected into the capillary at 10psi for 20s, and then stacked at −10kV for 1min
using phosphate buffer containing SDS. The above injecting and stacking steps
were repeated five times. Finally, separation was performed at −20kV, using
phosphate buffer containing methanol, SDS and (2-hydroxypropyl)-β-cyclodextrin.
Method validation showed that calibration plots were linear (r ≧0.997) over a
range of 5–200ngmL−1 for T, 20–200ngmL−1 for E and
0.5–500ngmL−1 for EG. The limits of detection were
1.0ngmL−1 for T, 5.0ngmL−1 for E and
200.0pgmL−1 for EG. When evaluating precision and accuracy, values of
RSD and RE in intra-day (n =3) and inter-day (n =5) analysis were found to be
less than 10.0%. Compared with the simple LVSS-sweeping, which is also a
stacking strategy, this method further improves sensitivity up to 25 folds
(∼2500 folds with MEKC without preconcentration). This method was applied to
monitor 10 athletes’ urine, and did not detect any analyte. The novel stacking
method was feasible for monitoring of doping by sportsmen.
Graphical abstract
Graphical abstract Highlights
►
Testosterone, epitestosterone and epitestosterone glucuronide in urine were
analyzed. ► This rLVSI-CE method enhances sensitivity of monitoring of urine
samples by UV detection. ► This method could improve sensitivity up to 2500
folds.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 743 Liang Feng, Hui Li,
Xiao Li, Liang Chen, Zheng Shen, Yafeng Guan The analysis of anions in water
presents a difficult challenge due to their low charge-to-radius ratio, and the
ability to discriminate among similar anions often remains problematic. The use
of a 3×6 ratiometric indicator-displacement assay (RIDA) array for the
colorimetric detection and identification of ten anions in water is reported.
The sensor array consists of different combinations of colorimetric indicators
and metal cations. The colorimetric indicators chelate with metal cations,
forming the color changes. Upon the addition of anions, anions compete with the
indicator ligands according to solubility product constants (K sp). The
indicator–metal chelate compound changes color back dramatically when the
competition of anions wins. The color changes of the RIDA array were used as a
digital representation of the array response and analyzed with standard
statistical methods, including principal component analysis and hierarchical
clustering analysis. No confusion or errors in classification by hierarchical
clustering analysis were observed in 44 trials. The limit of detection was
calculated approximately, and most limits of detections of anions are well below
μM level using our RIDA array. The pH effect, temperature influence, interfering
anions were also investigated, and the RIDA array shows the feasibility of real
sample testing.
Graphical abstract
Graphical abstract Highlights
A colorimetric
indicator-displacement assay (IDA) array has been developed for the
determination of ten anions in water. The color changes in IDA array provide
facile identification of these anions with no misclassification. ► The RIDA array was developed to sense ten anions in
aqueous solution. ► No complicated molecular synthesis is needed. ► The
collected images were digitized for the semi-quantitative discriminations. ►
Array technologies and pattern-recognition were combined. ► The transparency
scan unit was used to avoid the light reflection.
Publication year:
2012 Source:Analytica Chimica Acta, Volume 743 Raghuram Dhumpa,
Michael G. Roper Microfluidic devices have found a unique place in cellular
studies due to the ease of fabrication, their ability to provide long-term
culture, or the seamless integration of downstream measurements into the
devices. The accurate and precise control of fluid flows also allows unique
stimulant profiles to be applied to cells that have been difficult to perform
with conventional devices. In this review, we describe and provide examples of
microfluidic systems that have been used to generate temporal gradients of
stimulants, such as waveforms or pulses, and how these profiles have been used
to produce biological insights into mammalian cells that are not typically
revealed under static concentration gradients. We also discuss the inherent
analytical challenges associated with producing and maintaining temporal
gradients in these devices.
Graphical abstract
Graphical abstract Highlights
►
Review article covering 2009–present. ► Topics include microfluidic devices
capable of producing gradients with a focus on mammalian cells. ► Also included
are selected examples of these waveforms on cell dynamics.
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