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Analytica Chimica Acta (v.626, #1)
Electrochemical detection of celecoxib at a polyaniline grafted multiwall carbon nanotubes modified electrode by Kalayil Manian Manesh; Padmanabhan Santhosh; Shanmugasundaram Komathi; Nam Hee Kim; Jong Wook Park; Anantha Iyengar Gopalan; Kwang-Pill Lee (pp. 1-9).
A modified electrode is fabricated by grafting polyaniline (PANI) chains onto multiwall carbon nanotubes (MWNTs) and utilized for the adsorptive reduction of celecoxib (CEL). PANI-g-MWNTs modified electrode appreciably enhances the sensitive detection of CEL in extremely lower concentrations (1×10−11M). Square wave stripping voltammogram (SWSV) shows a reduction peak at −1.08V with a high peak current for SW frequency of 100Hz, amplitude of 25mV and step height of 6mV. The high surface area of PANI-g-MWNTs is effectively utilized for the adsorption of CEL to preconcentrate at the electrode. The PANI chains covalently linked to MWNTs mediate the electron transfer processes. The present finding open-up the scope for extending on the use of other conducting polymers grafted MWNTs modified electrodes for the detection of compounds that do not have surface-active properties at conventional electrodes.
Keywords: Carbon nanotubes; Polyaniline; Electrochemical grafting; Modified electrode; Celecoxib; Square wave stripping voltammetry
Rapid determination of phenoxy acid residues in rice by modified QuEChERS extraction and liquid chromatography–tandem mass spectrometry by Urairat Koesukwiwat; Kunaporn Sanguankaew; Natchanun Leepipatpiboon (pp. 10-20).
A new method for the analysis of phenoxy acid herbicide residues in rice, based on the use of liquid extraction/partition and dispersive solid phase extraction (dispersive-SPE) followed by ultra-performance liquid chromatography–electrospray ionization tandem mass spectrometry (UPLC–ESI–MS/MS), is reported. 5% (v/v) formic acid in acetonitrile as the extraction solvent and inclusion of citrate buffer helped partitioning of all the analytes into the acetonitrile phase. The extract was then cleaned up by dispersive-SPE using C18 and alumina neutral as selective sorbents. Further optimization of sample preparation and determination allowed recoveries of between 45 and 104% for all 13 phenoxy acid herbicides with RSD values lower than 13.3% at 5.0μgkg−1 concentration level. Limit of detections (LODs) of 0.5μgkg−1 or below were attained for all 13 phenoxy acids. Quantitative analysis was done in the multiple-reaction monitoring (MRM) mode using two combinations of selected precursor ion and product ion transition for each compound. This developed method produced relatively higher recoveries of the acid herbicides with a smaller range of variation and less susceptibility to matrix effects, than the original QuEChERS (Quick,Easy,Cheap,Effective,Rugged, andS afe) method.
Keywords: Herbicide residues; Phenoxy acid; Qu; ick,; E; asy,; Ch; eap,; E; ffective,; R; ugged, and; S; afe; Ultra-performance liquid chromatography–mass spectrometry; Rice
Evaluation of working air quality by using semipermeable membrane devices by Francesc A. Esteve-Turrillas; Agustín Pastor; Miguel de la Guardia (pp. 21-27).
It has been evaluated the use of semipermeable membrane devices (SPMDs) as passive samplers of organophosphorus pesticides from air, in order to determine the contamination of working environments. Additionally, the use of SPMDs as portable samplers has been also considered. The analytical methodology for the determination of diazinon, chlorpyrifos-methyl, pirimiphos-methyl, chlorpyrifos and fenthion in SPMDs exposed to contaminated air was based on microwave-assisted extraction and gas chromatography with mass spectrometry determination. Limit of detection (LOD) values from 2 to 4ngSPMD−1 and repeatability from 2 to 7% were obtained by using the aforementioned methodology. Theoretical calculated sampling rates were employed for the estimation of the pesticide concentration in air, by using the pesticide mass retained in the deployed SPMD. The obtained LOD values, for a sampling time of 7 days, were from 1 to 2ngm−3. The evaluation of the air quality of a pesticide laboratory with an intensive use of diazinon and chlorpyrifos has been made in order to check the operation safety conditions.
Keywords: Semipermeable membrane devices; Pesticides; Organophosphorus compounds; Occupational exposure; Air quality
Development and application of ultra performance liquid chromatography–electrospray ionization tandem triple quadrupole mass spectrometry for determination of seven microcystins in water samples by Wei Xu; Qi Chen; Ting Zhang; Zengxuan Cai; Xiaofei Jia; Qing Xie; Yiping Ren (pp. 28-36).
In the present work, an ultra performance liquid chromatography (UPLC)–electrospray ionization tandem triple quadrupole/mass spectrometry (ESI-MS/MS) method was developed in selected reaction monitoring (SRM) mode to determine the amounts of seven/microcystin variants (MCYST-RR, -YR, -LR, -LA, -LY, -LW, -LF) in water samples. Solid phase extraction (SPE) or porous filter was used for sample cleaning-up and analyte enrichment. A C18 column enabled separation of 7 microcystins within 10min. Translation reaction ions including 995.6>134.9 (RR), 1045.8>135.1 (YR), 910.9>375.7 (LA), 1002.3>375.6 (LY), 520.1>135.0 (LR), 1025.8>891.7 (LW), 986.8>852.6 (LF) were set as quantitative ions and the enkephalin was the internal standard. Upon method validation, the limits of detection (LODs) and limits of quantification (LOQs) were found to be 0.06μgL−1 and 0.2μgL−1 (injection volume of 10μL), respectively, for all seven microcystin variants. The correlation coefficients were larger than 0.994 in all linear ranges and recoveries were in the range of 66.24–99.22%. The developed approach was highly sensitive and easy to perform. It generated accurate quantitative results for the analysis of microcystins in environmental water samples with a wide concentration range. The results showed that MC-RR and MC-LR widely existed in polluted water, while MC-LA and MC-LY were detected sporadically.
Keywords: Microcystins; Ultra performance liquid chromatography; Tandem triple quadrupole mass spectrometry; Selected reaction monitoring
Rapid and selective detection of cysteine based on its induced aggregates of cetyltrimethylammonium bromide capped gold nanoparticles by Jian Wang; Yuan Fang Li; Cheng Zhi Huang; Tong Wu (pp. 37-43).
A detection method of cysteine is reported in this contribution with water-soluble positively charged gold nanoparticles (Au-NPs) that were prepared by seed-mediated method and capped with cetyltrimethylammonium bromide (CTAB). In aqueous medium of pH 4.2, the CTAB-capped Au-NPs display greatly different features from those of generally prepared citrate-coated Au-NPs. It was found that in a medium of high salt concentration, the presence of cysteine could induce aggregation of CTAB-capped Au-NPs, while citrate-coated Au-NPs could get aggregation soon even if without the presence of cysteine. The cysteine-induced aggregates of CTAB-capped Au-NPs display strong plasmon resonance light scattering (PRLS) signals characterized at 566.0nm when excited by a light beam, and the PRLS intensities of the aggregates are in proportion to the concentration of cysteine in the range of 0.01–0.40μgmL−1 with the limit of detection (3 σ) being 2.9ngmL−1. No amino acids in the samples interfere with the detection, and cysteine in artificial samples could be detected with the recovery between 95.3% and 105.9%, and R.S.D. is less than 3.6%.
Keywords: Gold nanoparticles (Au-NPs); Cysteine (Cys); Plasmon resonance light scattering (PRLS); Cetyltrimethylammonium bromide (CTAB)
New sensitive layer based on pulsed plasma-polymerized aniline for integrated optical ammonia sensor by A. Airoudj; D. Debarnot; B. Bêche; F. Poncin-Epaillard (pp. 44-52).
A new integrated optical sensor based on plasma-polyaniline sensitive layer for ammonia detection is designed and developed. The sensor is based on polyaniline elaborated by the plasma technique (Plasma Enhanced Chemical Vapor Deposition, PECVD) and deposited on a small section of a single-mode planar SU-8 waveguide. The sensing properties of the integrated optical sensor to ammonia at room temperature are presented. A significant change in the guided light output power of the sensor is observed after exposition to ammonia gas. This new ammonia sensor exhibits fast response and recovery times, good reversibility and repeatability. The metrological parameters (sensitivity, response time and recovery time) of the sensor are strongly influenced by the interaction length (length of sensing region), the type of dopant and the light polarization. The sensor has a logarithmic linear optical response within the ammonia concentration range between 92 and 4618ppm.
Keywords: Polyaniline; Plasma polymerization; Planar waveguide; Integrated optical sensor; Ammonia sensor
Use of CdSe/ZnS luminescent quantum dots incorporated within sol–gel matrix for urea detection by Hong Dinh Duong; Jong Il Rhee (pp. 53-61).
In this work, urea detection techniques based on the pH sensitivity of CdSe/ZnS QDs were developed using three types of sol–gel membranes: a QD-entrapped membrane, urease-immobilized membrane and double layer consisting of a QD-entrapped membrane and urease-immobilized membrane. The surface morphology of the sol–gel membranes deposited on the wells in a 24-well microtiter plate was investigated. The linear detection range of urea was in the range of 0–10mM with the three types of sol–gel membranes. The urea detection technique based on the double layer consisting of the QD-entrapped membrane and urease-immobilized membrane resulted in the highest sensitivity to urea due to the Michaelis–Menten kinetic parameters. That is, the Michaelis–Menten constant ( Km=2.0745mM) of the free urease in the QD-entrapped membrane was about 4-fold higher than that ( Km=0.549mM) of the immobilized urease in the urease-immobilized membrane and about 12-fold higher than that ( Km=0.1698mM) of the immobilized urease in the double layer. The good stability of the three sol–gel membranes for urea sensing over 2 months showed that the use of sol–gel membranes immobilized with QDs or an enzyme is suitable for biomedical and environmental applications.
Keywords: Urea detection; Quantum dots; Sol–gel membranes; Microtiter plate; Urease; Immobilization
Fiber optic lifetime pH sensing based on ruthenium(II) complexes with dicarboxybipyridine by Helena M.R. Gonçalves; César D. Maule; Pedro A.S. Jorge; Joaquim C.G. Esteves da Silva (pp. 62-70).
The complexes of ruthenium(II) with phenanthroline (Phen), diphenylphenanthroline (Ph2Phen) and with 4,4′-dicarboxy-2,2′-bipyridine acid (Dcbpy) ([Ru(Phen)2Dcbpy]Cl2 and [Ru(Ph2Phen)2Dcbpy]Cl2) were synthesized and the variation of the correspondent fluorescence intensity and lifetime with the pH characterized. Luminescence intensity, emission wavelength and excited state lifetime all show a typical sigmoid variation with pH in the range 3–9, demonstrating the suitability of this complex for luminescence sensing applications. In aqueous solutions (28% ethanol) the complexes [Ru(Phen)2Dcbpy]Cl2 and [Ru(Ph2Phen)2Dcbpy]Cl2 show, respectively, the following properties: apparent p Ka of 3.6±0.4 and 3.7±0.4; lifetimes of the protonated species 0.46±0.01μs and 0.38±0.02μs and ionised species 0.598±0.001μs and 0.61±0.08μs. The [Ru(Phen)2Dcbpy]Cl2 complex was immobilised in the tip of optical fibers using a hybrid sol–gel procedure based on tetraethoxysilan and phenyltriethoxysilan enabling pH sensitive fiber probes. The immobilised complex shows the following lifetimes: protonated species 1.05±0.04μs and ionised species 1.16±0.04μs. These characteristics show that these ruthenium(II) complexes are good indicators for pH sensing, either in aqueous solution or immobilised in sol–gel, and are well suited for intensity and/or frequency domain interrogation.
Keywords: Fiber optic; Ruthenium(II) complexes; Fluorescence intensity; Lifetime measurements; pH sensor; Sol–gel technology
Novel method for evaluation of chemicals based on ligand-dependent recruitment of GFP labeled coactivator to estrogen receptor displayed on bacterial magnetic particles by Tomoko Yoshino; Chihiro Kaji; Makoto Nakai; Fumiyo Saito; Haruko Takeyama; Tadashi Matsunaga (pp. 71-77).
We established a novel method to evaluate endocrine disrupting chemicals (EDCs) by assembling the estrogen receptor–ligand binding domain (ERLBD) and GFP labeled coactivator on magnetic nanoparticles. EDC can promote or inhibit coactivator recruitment to the ligand–ERLBD complex. ERLBD was displayed on the surface of nano-sized bacterial magnetic particles (BacMPs) produced by the magnetic bacterium, Magnetospirillum magneticum AMB-1. Our method resulted in 38 molecules of ERLBD molecules on a BacMPs with diameter of 75nm. Furthermore, ligand-dependent recruitment assays of GFP labeled coactivator to ERLBD–BacMPs was performed by measuring the fluorescence intensity. 17β-estradiol (E2), estriol, diethylstilbestrol, zeralenone (full agonist), octylphenol (partial agonist) and ICI 182,780 (antagonist) were evaluated by this method. Full agonists tested showed increased fluorescence with increasing agonist concentration. Octylphenol had lower fluorescence intensity than E2. ICI 182,780 did not produce any fluorescence. The method developed in this study can evaluate the estrogenic potential of chemicals by discriminating whether they are an ER full agonist, partial agonist, or antagonist. Finally, this method is amenable adaptation into a high throughput format by using automated magnetic separation.
Keywords: Estrogen receptor; Coactivator; Ligand; Bacterial magnetic particles
A novel method for determination of low molecular weight dicarboxylic acids in background atmospheric aerosol using ion chromatography by Ying I. Tsai; Li-Ying Hsieh; Tzu-Hsiang Weng; Yu-Chien Ma; Su-Ching Kuo (pp. 78-88).
This paper describes a novel gradient elution ion chromatographic method using a Dionex AS11 system for the determination of low molecular weight dicarboxylic acids (low- Mw DCAs) in background atmospheric aerosol. Interference with the oxalic acid peak from sulfate in background PM2.5 aerosol, 15.8 times the oxalic acid concentration, was remedied by removing sulfate using a barium cartridge, whilst interference with the malonic acid peak from carbonate was reduced by using a carbonate removal device. An alternative remedy to sulfate interference was use of an AS14 system using isocratic eluent, and this produced good resolution of oxalic acid from a high sulfate peak. In both the AS11 and the AS14 system, linear correlation coefficients were at all times >0.9990 with excellent linear range, the recoveries ranged from 92.8 to 106%, with relative standard deviation of 3.67–6.30%, whilst method detection limits (MDLs) ranged from 0.36μgL−1 for malic acid to 3.87μgL−1 for maleic acid. These data indicate that the analytical methods developed herein produce excellent separation efficiency and good determination of low- Mw DCAs with satisfactory accuracy, recoveries, and MDLs. Samples left at room temperature (20°C) for 300min in a simulation of the ‘waiting time’ involved in the proposed IC analysis decayed to between 86% (oxalic acid) and 39% (succinic and malonic acids) of their original concentration, whilst at 4°C concentrations remained at 96–101% of original, indicating that maintaining samples at a low temperature prior to injection into the IC analyzer is vital for obtaining accurate results when analyzing low- Mw DCAs. Oxalic acid was found to be the most prevalent low- Mw DCA in background aerosol, comprising 57% of the total low- Mw DCAs and 0.959% of the PM2.5 aerosol mass, followed by succinic acid and malonic acid.
Keywords: Background aerosol; Dicarboxylic acids; Gradient elution; Interference; Effect of temperature
Analysis of the anti-Parkinson drug pramipexole in human urine by capillary electrophoresis with laser-induced fluorescence detection by Alessandro Musenga; Ernst Kenndler; Emanuele Morganti; Fabrizio Rasi; Maria Augusta Raggi (pp. 89-96).
A sensitive method based on capillary electrophoresis with laser-induced fluorescence detection has been developed for the analysis of the non-ergoline dopamine agonist pramipexole in human urine. Separation was carried out in uncoated fused silica capillaries (75μm internal diameter, 75.0 and 60.0cm total and effective length, respectively), with a background electrolyte composed of borate buffer (50mM, pH 10.3), tetrabutylammonium bromide (30mM), and acetone (15%, v/v). Applying a 20kV voltage, the electrophoretic run is completed within 12min. A sample pre-treatment procedure based on liquid/liquid extraction with ethyl acetate, followed by derivatisation of pramipexole with fluorescein isothiocyanate at pH 9, allows the complete removal of biological interferences, with extraction yields always higher than 94.5%. Method validation gave good linearity ( r2=0.9992) in the 25.0–1000ngmL−1 range; limit of detection and limit of quantitation were 10.0 and 25.0ngmL−1, respectively; precision was ≤6.8 R.S.D.%, accuracy expressed as recovery% was >90.0. The method was applied to the analysis of urine samples from patients undergoing therapy with pramipexole.
Keywords: Abbreviations; PRM; pramipexole; FITC; fluorescein isothiocyanate; TBAB; tetrabutyl ammonium bromide; LIF; laser-induced fluorescenceCapillary electrophoresis; Fluorescein isothiocyanate; Human urine; Laser-induced fluorescence; Pramipexole
On-chip fluorescence-activated particle counting and sorting system by Yuejun Kang; Xudong Wu; Yao-Nan Wang; Dongqing Li (pp. 97-103).
A fluorescence-activated particle counting and sorting system is developed for lab-on-a-chip applications. This system integrates the microfluidic chip, fluorescence excitation and detection, electronic power switch control, and optical visualization. The automatic sorting function is achieved by electrokinetic flow switching, which is triggered by a pre-set fluorescent threshold. A direct current electric pulse is generated to dispense the fluorescent particles to the collection reservoir. A user-friendly software interface is developed for automatic real-time counting, sorting and visualization. The design of the disposable microfluidic chip is simple and easy for integration. This system represents a promising prototype for development of affordable and portable flow cytometric instruments.
Keywords: Fluorescence-activated cell sorting; Microfluidics; Lab-on-a-chip; Electrokinetic flow switching; Particle dispensing
Analysis of selected carbonyl oxidation products in wine by liquid chromatography with diode array detection by Ryan J. Elias; V. Felipe Laurie; Susan E. Ebeler; Jon W. Wong; Andrew L. Waterhouse (pp. 104-110).
A high performance liquid chromatography (HPLC) method for the detection and quantitation of acetaldehyde, glyceraldehyde, pyruvic acid, 2-ketoglutaric acid, and formaldehyde in wine, based on the formation of the 2,4-dinitrophenylhydrazones, is presented. These carbonyl compounds often result from the chemical oxidation of major wine components, and are known to affect flavor and color stability. Their analysis in wine is complicated due to their instability and their tendency to react reversibly with bisulfite to form α-hydroxysulfonates. Published methods that break down the sulfonates for the quantitation of total carbonyls in wine involve alkaline hydrolysis of sulfite-bound carbonyls, but we show, for the first time, that this alkaline treatment step significantly increases the concentration of carbonyls during analysis. A solution based on oxygen exclusion is described. The technique offers good specificity, reproducibility (%RSD 0.45–10.6), and limits of detection (1.29–7.53μgL−1). The method was successfully used to monitor concentration changes of these compounds in both white and red wines.
Keywords: Carbonyl compounds; Aldehydes; 2,4-Dinitrophenylhydrazine; Wine; Oxidation; Sulfite