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Analytical Methods (v.3, #9)
Front cover (pp. 1915-1915).
The purpose of this work was to develop implantable curcumin-loaded poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) (PCL-PEG-PCL, PCEC) nanofibers, which might have potential application in cancer therapy. Curcumin was incorporated into biodegradable PCEC nanofibers by electrospinning method. The surface morphology of the composite nanofibers was characterized on Scanning Electron Microscope (SEM). The average diameter of the nanofibers was 2.3–4.5μm. In vitro release behavior of curcumin from the fiber mats was also studied in detail. The in vitro cytotoxicity assay showed that the PCEC fibers themselves did not affect the growth of rat Glioma 9L cells. Antitumor activity of the curcumin-loaded fibers against the cells was kept over the whole experiment process, while the antitumor activity of pure curcumin disappeared within 48 h. These results strongly suggested that the curcumin/PCEC composite nanofibers might have potential application for postoperative chemotherapy of brain cancers.
Inside front cover (pp. 1916-1916).
This paper discusses the importance of the transition between molecular compounds and nanocrystals. The boundary between molecular and nanocrystals/nanoclusters can be defined by the emergence of the bulk phase; atoms in the core of the nanoclusters that are not bound to ligands. This transition in dimensions and structural organization is important because it overlaps with the boundary between atomically defined moieties (molecules can be isolated with increasing purity) and mixtures (nanocrystals have a distribution of sizes, shapes, and defects; they cannot be easily separated into batches of structurally identical species). Passing through this boundary, as the size of a structure increases beyond a few nanometres, the information about the position of each atom gradually disappears. This loss of structural information about a chemical structure fundamentally compromises our ability to use it as a part of a complex chemical system. If we are to engineer complex functions encoded in a chemical language, we will need pure batches of atomically defined (truly monodisperse) nanoscale compounds, and we will need to understand how to make them and preserve them over a broad range of length scales, compositions, and timeframes. In this review we survey most classes of monodisperse nanomaterials (mostly nanoclusters) and highlight the recent breakthroughs in this area which might be spearheading the development of a chemistry of “nanoscale perfection”.
Contents (pp. 1917-1928).
Carbon nanotubes (CNTs) are interest to many different disciplines including chemistry, physics, biology, material science and engineering because of their unique properties and potential applications in various areas spanning from optoelectronics to biotechnology. However, one of the drawbacks associated with these materials is their insolubility which limits their wide accessibility for many applications. Various approaches have been adopted to circumvent this problem including modification of carbon nanotube surfaces by non-covalent and covalent attachments of solubilizing groups. Covalent approach modification may alter the intrinsic properties of carbon nanotubes and, in turn make them undesirable for many applications. On the other hand, a non-covalent approach helps to improve the solubility of CNTs while preserving their intrinsic properties. Among many non-covalent modifiers of CNTs, conjugated polymers are receiving increasing attention and highly appealing because of a number of reasons. To this end, the aim of this feature article is to review the recent results on the conjugated polymer-based non-covalent functionalization of CNTs with an emphasis on the effect of conjugated polymers in the dispersibility/solubility, optical, thermal and mechanical properties of carbon nanotubes as well as their usage in the purification and isolation of a specific single-walled nanotube from the mixture of the various tubes.
Nitrogen factors as a proxy for the quantitative estimation of high value flesh foods in compound products, a review and recommendations for future work by D. Thorburn Burns; Michael Walker; S. Elahi; P. Colwell (pp. 1929-1935).
It is often necessary to verify the quantity of high value flesh ingredients (meat and fish) in compound foods by analysis of the end product. The approach that has stood the test of time in this regard is that originally demonstrated by Stubbs and More who were working in the Laboratory of the Government Chemist (LGC). The method is based on the determination of the nitrogen content of a sample and its comparison, corrected for non-flesh nitrogen, with the species specific nitrogen concentration, the ‘Nitrogen Factor’. The available validated data for the nitrogen factors of meat, poultry and fish are reviewed from the first data, that of Stubbs and More published in the Analyst (1919), to date. In the main the only validated datasets for this important area of trade and enforcement are those of the Analytical Methods Committee of the Royal Society of Chemistry and the Association of Public Analysts, with input from LGC and trade laboratories. Recommendations are made for cost effective approaches to continue the generation of these datasets in the future.
Development and validation of a fast RP-HPLC method to determine the analogue of the thyroid hormone, 3,5,3′-triiodothyroacetic acid (TRIAC), in polymeric nanoparticles by Karen C. dos Santos; Maria Fátima G. F. da Silva; João B. Fernandes; Paulo C. Vieira; Igor Polikarpov; Valtencir Zucolotto; Moacir R. Forim (pp. 1936-1942).
The objective of this work was to develop and validate a rapid Reversed-Phase High-Performance Liquid Chromatography method for the quantification of 3,5,3′-triiodothyroacetic acid (TRIAC) in nanoparticles delivery system prepared in different polymeric matrices. Special attention was given to developing a reliable reproductive technique for the pretreatment of the samples. Chromatographic runs were performed on an Agilent 1200 Series HPLC with a RP Phenomenex® Gemini C18 (150 × 4, 6 mm i.d., 5 μm) column using acetonitrile and triethylamine buffer 0.1% (TEA) (40 : 60 v/v) as a mobile phase in an isocratic elution, pH 5.6 at a flow rate of 1 ml min−1. TRIAC was detected at a wavelength of 220 nm. The injection volume was 20 μl and the column temperature was maintained at 35 °C. The validation characteristics included accuracy, precision, specificity, linearity, recovery, and robustness. The standard curve was found to have a linear relationship (r 2 = 0.9996) over the analytical range of 5–100 μg ml−1. The detection and quantitation limits were 1.3 and 3.8 μg ml−1, respectively. The recovery and loaded TRIAC in colloidal system delivery was nearly 100% and 98%, respectively. The method was successfully applied in polycaprolactone, polyhydroxybutyrate, and polymethylmethacrylate nanoparticles.
Characterization of Japanese lacquer liquid and films by means of evolved gas analysis-ion attachment mass spectrometry by Masamichi Tsukagoshi; Yuki Kitahara; Seiji Takahashi; Takahisa Tsugoshi; Toshihiro Fujii (pp. 1943-1947).
We investigated the thermal decomposition of Japanese lacquer liquid and films, which are non-volatile complex natural materials, by means of evolved gas analysis-ion attachment mass spectrometry. The thermal decomposition products are identified by analysis of the mass spectra of degraded samples. The mass chromatogram (pyrogram) of the products generated at various temperatures with kinetic treatments is informative for the characterization of lacquer materials. The H2 O pyrogram (obtained in selected-ion-monitoring mode) of a Japanese lacquer film indicated two stages of water release—vaporization and intramolecular H2 O elimination—and the kinetics of these two processes were studied. Plots of temperature versus signal intensity at m /z 25 gave constant slopes and provided apparent activation energies of 41.4 and 171 kJ mol−1, respectively, for the two processes.
Highly sensitive and selective volatile organic compound gas sensors based on mesoporous nanocomposite monoliths by Nguyen Duc Hoa; Sherif A. El-Safty (pp. 1948-1956).
We introduce the use of highly ordered mesoporous silica/metal oxide (HOM/MO) nanocomposite monoliths for volatile organic compound (VOC) gas sensor applications. Monoliths with various loadings of semiconducting metal oxides (SnO2 , ZnO, NiO, CuO, and Fe2 O3 ) were prepared through instant direct-templating method. The dependence of the doping elements and doping levels on the mesoporous structure of monoliths was investigated. The results indicate that the monoliths retained their ordered porous structure at up to 40% doping by SnO2 . The high-resolution transmission electron microscopy and scanning transmission electron microscopy images revealed that the SnO2 nanocrystals were homogenously distributed in the matrix of the HOM monoliths up to 40% doping concentration. The gas-sensing properties of the HOM/SnO2 and HOM/ZnO monoliths to acetone, benzene, and ethanol were also investigated. Sensors based on the HOM/SnO2 nanocomposites showed highest sensitivity, selectivity, response rate, and response stability to acetone compared with the others. This finding provides interesting results on the large-scale synthesis of HOM/MO monoliths with the ability to control pore structure and opens a new strategy in the application of mesoporous nanocomposites for gas sensors. In addition, various HOM/MO nanocomposite monoliths are easily synthesized through this method. It expands the potential of HOM/MO nanocomposite monoliths to other applications, such as catalysis and adsorption.
Characterisation of plutonium species in alkaline liquors sampled from a UK legacy nuclear fuel storage pond by Colin R. Gregson; Jeremy J. Hastings; Howard E. Sims; Helen M. Steele; Robin J. Taylor (pp. 1957-1968).
Within the UK there are a number of nuclear legacy fuel storage ponds and silos that contain substantial volumes of corroding spent Magnox fuel pieces. The fuel and wastes within these ponds, including highly radioactive sludges, must be retrieved and processed during decommissioning. Sludges and other intermediate level wastes will then be encapsulated in a wasteform suitable for storage and disposal, whilst residual activity must be removed from pond liquors and process effluents prior to any authorised discharges. Understanding the nature and behaviour of the radionuclides in the ponds, including any potential for activity transfer from solid to solution phases, is critical in the environmental clean up of these nuclear legacy facilities. Plutonium isotopes (with 241Am) dominate the α-activity within these ponds. Herein, the Pu species in samples taken from a UK legacy fuel storage pond and downstream Holding Tank on the Sellafield site are shown to be predominantly associated with suspended solid phases. Analyses of the residual soluble Pu concentrations indicate differences in Pu solubility between different areas of the pond, which speciation studies suggest are related to differing Pu oxidation state distributions. The implication is that Pu redox chemistry varies across the pond and this controls Pu solubilities and, by implication, Pu behaviour during waste processing. Simple treatment methods to suppress soluble Pu-α are also suggested.
3D ordered gold nanoshell composite array as sensitive SERS nanosensor for detecting
Here we report a novel method for detecting 3,4-dihydroxyphenylalanine (l -DOPA) and tyrosinase (TR) activity based on surface-enhance Raman scattering (SERS) by employing a large-scale versatile three-dimensionally (3D) ordered nanocomposite (SiO2 /GNPs) array as a nanosensor. l -DOPA could reduce AuCl4 − to Au0 and enlarge the gold nanoparticles (GNPs) that attach on the surface of the SiO2 /GNPs array, the preadsorbed GNPs serve as nucleation sites for Au0 to deposit. As the concentration of l -DOPA increases, the surface coverage of resultant Au0 on silica cores increases accordingly until complete gold nanoshells (GNSs) are formed. During the growth procedure, the SERS-activity of the GNSs arrays correlate well with the concentration of l -DOPA, which indicates that this SiO2 /GNPs array is a potential nanosensor for detecting l -DOPA. As TR can catalyze the hydroxylation of l -tyrosine to form l -DOPA, this approach can also be employed to analyze the activity of TR, which possesses vast clinical and food industrial importance. Compounds such as cinnamic acid and p -hydroxybenzoic acid can inhibit the TR activity. Thus, the TR-triggered growth of the GNSs array system can also be used to detect the TR inhibited activity of inhibitors.
Indirect determination of sodium diclofenac, sodium dipyrone and calcium gluconate in injection drugs using digital image-based (webcam) flame emission spectrometric method by Wellington da Silva Lyra; Fátima Aparecida Castriani Sanches; Francisco Antônio da Silva Cunha; Paulo Henrique Gonçalves Dias Diniz; Sherlan Guimarães Lemos; Edvan Cirino da Silva; Mario Cesar Ugulino de Araujo (pp. 1975-1980).
This paper proposes a digital image-based flame emission spectrometric (DIB-FES) method for indirect determination of sodium diclofenac, sodium dipyrone and calcium gluconate in injectable forms. The proposed DIB-FES method uses digital images obtained from a webcam, based on the RGB (Red-Green-Blue) system. It offers a simple and inexpensive way to quantify these organic substances using the radiation emitted by the alkaline and earth-alkaline metals present in their formulae. Analytical curves were constructed on the basis of the relationship between RGB values and calibration solution concentrations. The results showed no statistical difference between the proposed and reference methods when applying the paired t -test at a 95% confidence level. The proposed DIB-FES method also performed well in terms of the figures of merit LOD, LOQ, linear range, precision, and the accuracy as revealed by recovery tests.
An ultra sensitive method for rapid
A novel approach for estimation of catalase activity in biological samples was developed using real-time signal averaging with LabVIEW based virtual instrumentation. The assay was performed by on-line monitoring of the increase in dissolved oxygen concentration due to the catalytic reaction of the enzyme with its substrate H2 O2 using a Clark type dissolved oxygen electrode. The electrode was interfaced with a computer using an op-amp based electronic circuit and LabVIEW based software for signal acquisition, data visualization and signal conditioning. Catalase activity in biological samples could be measured without pre-dilution and the method was not affected by interferences such as turbidity, viscosity and sample color. It was possible to increase the assay sensitivity from 0.5 U for the existing spectrophotometric method to 2.93 μU, with a sample size as little as 100 μl and response time as low as 9 s. Therefore, the proposed method shall find use in clinical assays, detection of pathogens and evaluation of catalase activity in cell cultures, neurological samples, milk and other food products.
Heat-shock transformation of
This work describes an improved method for monodispersed water-in-oil droplet formation and collection using a composite microfluidic device composed of a poly(dimethylsiloxane) (PDMS) microfluidic device and a commercially available quartz capillary. The application of the method to chemical heat-shock (CaCl2 -dependent) transformation of Escherichia coli (E. coli ) is also presented. With this approach, tunable and uniform different-sized droplets were generated and conveniently collected into a capillary for subsequent experiments. Characterization of droplet size and formation frequency exhibits that droplet behavior is strongly dependent on the ratio (R ) of aqueous phase flow rate (Q aq ) to oil phase flow rate (Q o ). An increase in R induces droplet size and droplet formation frequency increase, which agrees well with a theoretical calculation. To illustrate the application of this droplet-based device in biological fields, as a case study, we also apply this device to the study of heat-shock E. coli transformation. Results demonstrate that plasmid DNA can be effectively transformed into E. coli , and a similar transformation efficiency with the traditional tube-based method can be obtained. This technique provides a new way for droplet generation and easy collection, as well as functional genomics studies by taking advantage of the high throughput of droplet microfluidics.
A monoclonal antibody-based enzyme-linked immunosorbent assay for human urinary cotinine to monitor tobacco smoke exposure by Norihiro Kobayashi; Erika Banzono; Yuko Shimoda; Hiroyuki Oyama; Toshiomi Kunihiro; Izumi Morita; Mitsuhiro Ohta (pp. 1995-2002).
Immunoassays for human urinary cotinine [(S )-(−)-cotinine], a major nicotine metabolite, are useful to monitor the degree of tobacco smoke exposure. However, practical monoclonal antibodies for measuring urinary cotinine are not widely available. Here we generated a monoclonal antibody against a newly prepared cotinine–albumin conjugate and developed an enzyme-linked immunosorbent assay (ELISA). Splenocytes from a BALB/c mouse that had been immunized with the conjugate were fused with P3/NS1/1-Ag4-1 myeloma cells, and a hybridoma clone secreting the anti-cotinine antibody, Ab-CT#45 (IgG1κ ; amino acid sequences of the variable domains were determined), was established. This antibody was immobilized on microplates to generate an ELISA system in which biotin-labeled cotinine was used as the tracer molecule. After competitive reactions with analyte, the bound biotin residues were monitored colorimetrically with peroxidase-labeled streptavidin. This ELISA produced dose–response curves for cotinine ranging from 0.40–100 ng per assay and was able to discriminate nicotine, cotinine N -oxide, cotinine N -glucuronide (cross-reactivity was each <0.5%, taking cotinine as 100%), (3′R , 5′S )-3′-hydroxycotinine O -glucuronide (0.6%) and (R , S )-norcotinine (1.5%). Another major nicotine metabolite, (3′R , 5′S )-3′-hydroxycotinine, showed 8.4% cross-reactivity, but an analytical recovery test indicated that this metabolite did not result in a significant overestimation of the urinary cotinine levels. The present ELISA has been validated to allow the urine specimens to be “directly” (without pretreatment) measured in order to screen and monitor tobacco smoke exposure, and if necessary, to enable cotinine alone to be more specifically examined after the urine specimens are subjected to a simple chloroform extraction.
Robust TiO
A TiO2 /BDD heterojunction photoanode, utilizing the inherent properties of nanostructured titanium dioxide (TiO2 ) and boron-doped diamond (BDD), was prepared and used to determine chemical oxygen demand (COD) in wastewaters. The TiO2 nanoparticles were dip-coated on a BDD substrate and subject to calcination processes. A uniform, continuous and robust mixed-phase (anatase and rutile) TiO2 /BDD heterojunction electrode was obtained. The TiO2 /BDD heterojunction electrode was evaluated using a series of materials characterisation, electrical and electrochemical techniques. The preliminary results suggest the elevated photoelectrocatalytic activity over the oxidation of organic compounds stemmed from the formation of the p–n junction of the TiO2 /BDD electrode. The TiO2 /BDD electrode has an excellent resistance towards strong acid due to the use of BDD substrate, which is an added advantage for practical application. Under the optimized experimental conditions, the TiO2 /BDD electrode is capable of indiscriminately oxidizing a wide spectrum of organic compounds in a photoelectrochemical thin-layer cell. This bestows the photoelectrochemical system with the ability to measure the COD of synthetic and real samples in a fast, sensitive, reproducible and accurate fashion. In particular, a typical analysis time of 5 minutes, a practical detection limit of 0.12 mg L−1 COD, a RSD% value of 1.5% and a linear range of 0–300 mg L−1 were achieved. The TiO2 /BDD electrode can be an ideal sensor for online and in situ monitoring of organic pollutants in wastewaters.
Use of online rapid sampling microdialysis electrochemical biosensor for bowel anastomosis monitoring in swine model by Emma P. Córcoles; Samer Deeba; George B. Hanna; Paraskevas Paraskeva; Martyn G. Boutelle; Ara Darzi (pp. 2010-2016).
Bowel anastomosis ischemia carries a significant rise in morbidity and mortality after bowel surgery. Clinical measures of bowel ischemia are often non-specific and only become evident at a late stage. There is currently no method to continuously monitor, in real time, metabolic impairment at the anastomosis site. Our online rapid sampling microdialysis biosensor system has proved its efficacy in monitoring ischemia in the bowel. Selective glucose and lactate biosensors are coupled online to the microdialysis probe through a flow injection analysis (FIA) system, which performs in vivo bowel monitoring at high time resolution, typically every 30 seconds. The enzymatic reactors containing substrate oxidase (SOx) and horseradish peroxidase (HRP) are coupled to flow cell electrodes. The system was used to monitor ischemia at the bowel anastomosis level, by monitoring in vivo changes in the metabolic substrates, like glucose and lactate in the colon of swine models. The rapid decrease in glucose and increase in lactate 5 minutes post-clamping of the artery feeding the anastomosis highlights the vulnerability of the bowel to damage with surgical stress and previous ischemic insults.
Solid phase preconcentration and determination of mercury and uranyl ions using an itaconic acid functionalized adsorptive membrane by Y. Kalyan; Sadananda Das; A. K. Pandey; G. R. K. Naidu; P. K. Sharma; A. V. R. Reddy (pp. 2017-2024).
A potential sorbent for preconcentration and quantification of mercury and uranyl ions was developed by grafting cross-linked micro-gel in pores of the host polyethersulfone membrane. The micro-gel was formed by in situ photo-polymerization of itaconic acid (ICA) along with co-monomer acrylamide (AM) and crosslinker pentaerythritoltetraacrylate (PETA) in pores of the host membrane. The photo-polymerization was initiated by α,α′-dimethoxy-α′-phenyl acetophenone (DMPA) dissolved in polymerizing solution along with ICA, AM and PETA. Fourier Transform Infrared Spectroscopy and Gravimetry were used to confirm the anchoring of micro-gel in pores of the host membrane. The comparison of scanning electron microscopic images of blank and grafted membranes indicated that pores of membrane were completely blocked after grafting micro-gel in the membrane. The radiotracers and Energy Dispersive X-ray Fluorescence (EDXRF) were used to study the metal ion uptake efficiency of membrane as a function of pH of the aqueous samples. It was observed that only U(vi ) and Hg(ii ) sorbed with high efficiency (>80%) in the grafted membrane in the presence of other competing cations like Th(iv ), V(iv ), Eu(iii ), Fe(iii ), Cu(ii ), Pb(ii ) and Cd(ii ). It was also observed that desorption of Hg(ii ) and U(vi ) from the membrane sample is possible by 0.01 mol L−1 EDTA disodium salt and 0.5 mol L−1 Na2 CO3 , respectively. To explore analytical applications of the membrane, the concentrations of Hg2+ ions in the mining soil samples were determined by first preconcentrating mercury ions in the grafted membrane samples and then subjecting these membrane samples to cold vapour atomic absorption spectrophotometry (CV-AAS). The studies carried out in the present work demonstrated that the membrane developed in the present work could be used for removal of Hg2+ and UO2 2+ ions from waste streams as well as for their quanitative determinations in complex aqueous samples.
Ultra-performance liquid chromatographic assay coupled with two-dimensional separation for spectrometric determination of urinary
A gradient ultra-performance liquid chromatographic (UPLC) assay coupled with the two dimensional separation and diode array detection method was developed to determine S -phenylmercapturic acid (SPMA), a specific urinary metabolite of benzene. Gradient separation was performed on two C18 core–shell columns (2.6 and 1.7 μm, 50 × 2.1 mm i.d.) maintained at 40 and 20 °C. Among various solvents evaluated, dichloromethane which offered >85% recovery rates of both SPMA and d -benzylmercapturic acid (internal standard) was used for extraction. The yield of free-SPMA was maximized by hydrolyzing 200 μL of urine with 20 μL of 6 M HCl prior to dichloromethane extraction. The limit of detection was 1 μg L−1(s /n = 5) and the limit of quantification was 2 μg L−1. Using our method, a correlation of 0.99 was obtained with 10 specimens (range, 1.7 to 182 μg L−1) from the German External Quality Assessment Scheme. Among the 75 non-occupational exposure individuals, 61 (81%) had SPMA levels below the LOQ. Among the 26 male petroleum workers, 5 who were exposed to <0.04 ppm of benzene were found to have SPMA levels below the LOQ. The geometric means obtained from the other 15 non-smokers and 6 smokers who were exposed to <0.5 ppm of benzene were 5.05 and 6.65 μg g−1 creatinine, respectively. The proposed method can be useful for occupational benzene exposure surveillance.
Determination of some banned aromatic amines in waste water using micellar liquid chromatography by Sandeep-Kumar Mourya; Devasish Bose; Abhilasha Durgbanshi; Josep Esteve-Romero; Samuel Carda-Broch (pp. 2032-2040).
Aromatic amines are extensively used in industry but they are classified as a potential environment and health hazard. A new high performance liquid chromatography method has been developed and optimized, for the determination of eight banned aromatic amines: benzidine, o -anisidine, o -phenylenediamine, o -nitroaniline, 2-methoxy-5-methylaniline (p -cresidine), o -toluidine, p -toluidine and p -chloroaniline. The chromatographic conditions used were: C18 column, 0.085 M SDS, 3.2% (v/v) pentanol mobile phase buffered at pH 7.0, with detection at 280 nm. Under these conditions, the eight aromatic amines were separated and quantified in industrial waste waters in less than 16 min. Method validation studies were performed according to the ICH Guideline. The possibility of direct injection using micellar liquid chromatography reduces the cost and the total time of analysis, and decreases error sources owing to minimized risks of losses and chemical changes in the analytes. The proposed method is a good candidate for application in the routine analysis in the area of environmental monitoring.
A newly developed salicylanilide functionalized Amberlite XAD-16 chelating resin for use in preconcentration and determination of trace metal ions from environmental and biological samples by Aminul Islam; Akil Ahmad; Mohammad Asaduddin Laskar (pp. 2041-2048).
Salicylanilide has been incorporated into Amberlite XAD-16 through an azo spacer. Characterization of the synthesized resin was done on the basis of elemental analyses, infra-red spectral and thermal studies. The water regain value and hydrogen ion capacity were found to be 12.90 and 6.08 mmol g−1 respectively. The optimum pH values for the maximum sorption of analyte were 9.0 for Cu(ii ), Co(ii ), Ni(ii ), Zn(ii ), Cr(iii ), and 6.0 for Cd(ii ) and Pb(ii ), respectively, with the half-loading time, t 1/2 , ranging from 3.5 to 11.0 min. The breakthrough capacities for Cu(ii ), Co(ii ), Ni(ii ), Zn(ii ), Cr(iii ), Cd(ii ), and Pb(ii ) were found to be 697.91, 641.83, 629.32, 551.38, 531.72, 249.11 and 125.36 μmol g−1, respectively, with corresponding preconcentration factors of 440, 380, 380, 360, 280, 280 and 260. The detection limits were found to be 0.56, 0.64, 0.65, 0.70, 0.75, 0.88 and 1.17 μg L−1, respectively. Analysis of standard reference materials and recovery experiments were carried out for the validation of the method. Practical utility has been demonstrated by successfully determining metal ions in natural water, mango pulp, leafy vegetables and fish.
Development of a sequential injection gas diffusion system for the determination of ammonium in transitional and coastal waters by Ricardo Alves Segundo; Raquel Beatriz Ribeiro Mesquita; Maria Teresa Soares Oliveira Barbosa Ferreira; Catarina Fernanda Carvalho Pinheiro Teixeira; Adriano Agostinho Bordalo; António Osmaro Santos Silva Rangel (pp. 2049-2055).
This work describes the development of a sequential injection system for the ammonium determination in transitional and coastal waters with a wide salinity range. Estuarine waters are rather complex matrices as their characteristics change considerably along the salinity gradient, as well as the ammonium levels. The developed system effectively solves these issues by converting ammonium into ammonia and using a gas diffusion unit (GDU) for matrix removal. The ammonium determination in a wide quantification range (0.1–5.0 mg L−1) was obtained with small changes in the protocol sequence and was applied, not only to estuarine samples, but also well water samples (low salinity) and coastal waters (higher salinity). Spectrophotometry was the chosen detection system to measure the absorbance change in the bromothymol blue acid base indicator caused by the diffusion of ammonia through the GDU. Additionally, the developed system used a green chemistry approach, as there was no indicator reagent consumption per determination, still maintaining a good precision (relative standard deviation lower than 2%) and a low detection limit, 27 μg L−1 (1.5 μM).
Fabrication of adhesive coated swabs for improved swipe-based particle collection efficiency by Jessica L. Staymates; Jessica Grandner; Greg Gillen (pp. 2056-2060).
Improving particle collection efficiency for swipe-based sampling systems can provide a better chance of detection when screening for trace explosives or narcotics particles. A technique was developed to improve the particle collection efficiency of commercially-available collection swabs used for field sampling of trace contraband materials. A silicone adhesive was added to Teflon-coated fiberglass swabs to aid in collecting trace levels of contamination from surfaces. Since the swabs are typically used for ion mobility spectrometry (IMS) analysis, it is important for them to produce no chemical background when heated. Results show that the adhesive swabs had a higher particle collection efficiency compared to the untreated swabs by a factor of 12, without negatively interfering with the IMS analysis. It was also found that the adhesive swabs could be reused 10 times without significant reduction in collection efficiency. While it is possible that the adhesive swabs may not be suitable for all surface types due to loss of adhesive material after multiple uses, the benefits of higher particle collection efficiency are extremely promising.
Preparation and evaluation of a novel solid-phase microextraction fiber based on poly(3,4-ethylenedioxythiophene) for the analysis of OCPs in water by Mohammad Hossein Banitaba; Ali Ahmad Mohammadi; Saied Saeed Hosseiny Davarani; Ali Mehdinia (pp. 2061-2067).
A novel polymer coating, based on electropolymerization of poly(3,4-ethylenedioxythiophene) on gold wire is introduced for headspace-solid phase microextraction (HS-SPME) of OCPs and applied for the analysis of these compounds in different water samples by coupling to GC-micro-ECD and GC-MS. The proposed fiber shows good porosity, temperature resistance (up to 300 °C), life time (more than 50 times) and satisfactory extraction efficiency for OCPs. In the analysis of OCPs, the effects of different parameters influencing the extraction efficiency such as extraction temperature, extraction time, ionic strength, desorption time, stirring rate and headspace volume were investigated and optimized. Under optimized conditions, the limits of detection varied from 0.16 to 0.84 ng L−1 and the correlation coefficients (R 2) of the calibration curves ranged from 0.9908 to 0.9968 showing an acceptable linearity within 1–100 ng L−1. The single fiber repeatability and fiber-to-fiber reproducibility were <7.9 and <15.9%, respectively. The inter-day and intra-day precision of method were also evaluated to be <8.0 and <12.7%, respectively. The recoveries obtained in real sample analysis ranged from 63% to 126.7%.
Poly (Naphthol Green B) film based sensor for resolution of dopamine in the presence of uric acid: A voltammetric study by Umesh Chandra; B. E. Kumara Swamy; Ongera Gilbert; B. S. Sherigara (pp. 2068-2072).
A polymer film of Naphthol Green B was prepared on the surface of a graphite pencil electrode using cyclic voltammetry. This poly(Naphthol Green B) coated electrode exhibits an excellent electroanalytical activity towards the determination of dopamine and uric acid. The voltammogram obtained for dopamine at the modified electrode was reversible. The effect of concentration and also pH were investigated. The peak current and peak potential were recorded in a 0.2 M phosphate buffer solution of pH 7.0. The modified electrode shows the ability to detect the dopamine and uric acid separately. The interference study was done using differential pulse voltammetry. The modified electrode was also used for the detection of dopamine in injections.
A multiclass method for endocrine disrupting chemical residue analysis in human placental tissue samples by UHPLC–MS/MS by F. Vela-Soria; I. Jiménez-Díaz; R. Rodríguez-Gómez; A. Zafra-Gómez; O. Ballesteros; M. F. Fernández; N. Olea; A. Navalón (pp. 2073-2081).
The group of compounds commonly called endocrine-disrupting chemicals covers a wide range of synthetic and natural substances able to alter the normal hormone function of wildlife and humans, consequently causing adverse health effects. Bisphenol A (BPA) and its chlorinated derivatives, benzophenones (BPs) and parabens (PBs), belong to this group of compounds. In this work, we propose a multiclass ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC–MS/MS) method to determine BPA, its four chlorinated derivatives (monochloro-, dichloro-, trichloro- and tetrachloro-bisphenol A), six BPs (benzophenone-1, benzophenone-2, benzophenone-3, benzophenone-6, benzophenone-8 and 4-hidroxybenzophenone) and four PBs (methylparaben, ethylparaben, propylparaben and butylparaben) in human placental tissue samples. The method involves an extraction step of the analytes from the samples using ethyl acetate, followed by a clean-up step by centrifugation prior to their quantification by UHPLC–MS/MS using an atmospheric pressure chemical ionization (APCI) interface in the negative mode. Deuterated bisphenol A (BPA-d16 ) was used as surrogate. The limits of detection (LOD) found ranged from 0.03 to 0.6 ng g−1, the limits of quantification (LOQ) from 0.1 to 1.4 ng g−1, while inter- and intra-day variability was under 8%. The method was validated using matrix-matched calibration standard and a spike recovery assay. Recovery rates for spiked samples ranged from 95% to 106%. This method was satisfactorily applied to the determination of these compounds in 50 placental tissue samples collected from women who live in the province of Granada (Spain).
Graphene-Prussian blue/gold nanoparticles based electrochemical immunoassay of carcinoembryonic antigen by Guangfeng Wang; Ge Zhang; Hao Huang; Lun Wang (pp. 2082-2087).
A new electrochemical immunosensor for the determination of carcinoembryonic antigen (CEA) was developed with a Graphene (Gr)-Prussian blue (PB)/gold nanoparticles (GNP) immobilization platform. HRP-anti-CEA was immobilized on the platform and with the immunoreactions, the formed immunocomplex inhibited partly the bioactive center of the immobilized HRP, and decreased the HRP toward the reduction of H2 O2 , which was the base of the detection of CEA. The Gr-PB/GNP can be used not only as the electrochemical redox mediator but also to enhance the sensitivity. Under optimal experimental conditions, the proposed immunosensor for CEA was observed with an ultra low limit of detection equal to 3 pg mL−1 (at 3σ ), and the linear working range spanned from 0.01 to 1.0 and 1.0 to 60 ng mL−1. Moreover, the immunosensor was examined for use in the determination of CEA in real human serum specimens. The assayed results of serum samples with the sensor received an acceptable agreement with the reference values. Importantly, the methodology provides a promising ultra sensitive assay strategy for clinical applications.
Simple method for simultaneous detection of uric acid, xanthine and hypoxanthine in fish samples using a glassy carbon electrode modified with as commercially received multiwalled carbon nanotubes by Annamalai Senthil Kumar; Ranganathan Shanmugam (pp. 2088-2094).
A simple electrochemical sensor was designed, based on a glassy carbon electrode modified with “as commercially received” multiwalled carbon nanotubes (GCE/MWCNT), for the simultaneous detection of three purine bases: uric acid (UA), xanthine (X) and hypoxanthine (Hx) by differential pulse voltammetry (DPV). Comparison amongst various carbon nanotubes viz .; as commercially received-MWCNT, functionalized-MWCNT, purified-MWCNT and single walled carbon nanotubes for modified electrode preparation, and in turn for the simultaneous electrochemical detection of the purines by DPV, the “as received MWCNT” modified GCE showed the best performance in terms of well-separated peaks and higher peak current values. Scan rate experiments on discreet oxidations of UA, X and Hx suggested that the electron-transfer mechanism for both UA and X follows a mixed diffusion–adsorption controlled pathway, while in the case of Hx, a diffusion controlled route is followed. Calibration responses for the simultaneous detection of UA, X and Hx were linear up to 700, 200 and 150 μM respectively. Corresponding detection limit values were 141 nM, 134 nM and 2.87 μM. Finally analysis of UA, X and Hx content in three different fresh dead fish samples was successfully demonstrated with recoveries of around 100%.
Three-phase hollow fiber microextraction based on carrier-mediated transport combined with HPLC-UV for the analysis of dexamethasone sodium phosphate in biological samples by Homeira Ebrahimzadeh; Yadollah Yamini; Katayoun Mahdavi Ara; Fahimeh Kamarei (pp. 2095-2101).
A three-phase hollow fiber microextraction technique based on carrier mediated transport combined with high performance liquid chromatography-ultra violet detection (HPLC-UV) was applied in the extraction and determination of dexamethasone sodium phosphate in biological samples. Dexamethasone sodium phosphate (DSP) was extracted from 7.5 mL of acidic solution (source phase) of pH 3 into an organic phase (n -octanol containing 5% (w v−1) of Aliquate-336 as carrier) impregnated in the pores of a hollow fiber and finally back extracted into 24 μL of a basic solution (pH = 9.5) located inside the lumen of the hollow fiber (receiving phase). The extraction took place due to the gradient of the counter ion from the source to the receiving phase. In order to achieve maximum extraction efficiency, different parameters affecting the extraction conditions were optimized. Under the optimized conditions, a preconcentration factor of 276 and detection limit (LOD) of 0.2 μg L−1 were obtained. The calibration curve was linear (r 2 = 0.998) in the concentration range of 1–1000 μg L−1. Finally, the feasibility of the proposed method was successfully confirmed by extraction and determination of DSP in bovine milk, human plasma and urine samples in the range of microgram per liter and suitable results were obtained (RSDs < 7.2%).
Highly sensitive and selective fluorescent assay for quantitative detection of divalent copper ion in environmental water samples by Haiyan Cao; Wenbing Shi; Jianxin Xie; Yuming Huang (pp. 2102-2107).
It was found that Cu2+ has a great catalytic effect on p -cresol oxidation by hydrogen peroxide under alkaline conditions, leading to an intense fluorescence signal due to the fast formation of 2,2′-dihydroxy-5,5′-dimethylbiphenyl, an oxidation product of p -cresol. Investigation of the fluorescence spectra of the p -cresol–hydrogen peroxide system demonstrated the catalytic behavior of Cu2+. On this basis, a very simple, sensitive, and selective fluorescent method was established for the determination of trace copper in this study. Under the optimal conditions, the proposed system could respond down to 1.0 × 10−8 mol L−1 of Cu2+ with a linear calibration range of 3.0 × 10−7 mol L−1 to 5.0 × 10−5 mol L−1. The relative standard deviation (RSD) was 2.1% for 7.0 × 10−6 mol L−1 Cu2+ (n = 15). The proposed method was successfully applied in the determination of trace Cu2+ in lake, river and swimming pool water samples with satisfactory results. The results obtained by the proposed method are in good agreement with those obtained by a conventional atomic absorption spectroscopy method.
The HyperSep SCX micro-cartridge for on-line flow injection inductively coupled plasma atomic emission spectrometric determination of trace elements in biological and environmental samples by Aristidis N. Anthemidis; Georgia Giakisikli; George A. Zachariadis (pp. 2108-2114).
This work covers an investigation into the potential of developing an automated on-line column preconcentration system using the readily available micro-cartridge HyperSep SCX for fast simultaneous determination of trace Ag(i ), Cd(ii ), Co(ii ), Cr(iii ), Cu(ii ), Fe(iii ), Mn(ii ), Ni(ii ), Pb(ii ) and Zn(ii ) ions by inductively coupled plasma atomic emission spectrometry. The proposed method was based on the quantitative sorption of target elements onto the surface of the strong cation exchange resin at pH ∼2.0, and complete elution with 2.0 mol L−1 HCl. All factors affecting the performance of the system such as sample acidity, loading and elution flow rate, preconcentration time as well as radio frequency (RF) incident power and nebulizer gas flow rate were examined in detail. The noticeable reduced consumption of chemicals along with automatic manipulations enabled the realization of a simplified and relatively clean procedure with low detection limits in the range of 0.05 and 0.2 μg L−1. Under the optimal conditions, the developed method provided a sampling frequency of 24 h−1 for all 10 studied elements. The accuracy of the developed method was evaluated by analyzing certified reference materials and spiked environmental natural water samples.
Multi-element analysis of bread, cheese, fruit and vegetables by double-focusing sector-field inductively coupled plasma mass spectrometry by Rola Bou Khouzam; Ryszard Lobinski; Pawel Pohl (pp. 2115-2120).
An analytical method using double-focusing sector-field ICP MS was developed for the routine simultaneous multi-element analysis for essential and toxic elements (Ag, Al, As, Cd, Co, Cr, Cu, Fe, Hg, In, Li, Ni, Mn, Mo, Pb, Si, Sb, Se, Sn, V and Zn) in different food samples (bread, cheese, fruit and vegetables). Samples were hot-plate digested with a mixture of concentrated HNO3 and H2 O2 . Interfering ions involving matrix constituents were detected for several elements at the resolution of 300 (typical for a quadrupole analyzer) and could be separated at the 4000 and 10 000 resolution. The method was validated by the analysis of certified reference materials: wheat flour (NIST 1567a), non-fat milk powder (NIST 1549) and brown bread (BCR-IRMM 191). The method used in our laboratory over the period of one year for the analysis of over 300 samples showed a typical interday precision of 3–5% and intraday precision of 5–10% for virtually all the elements and investigated matrices.
A voltammetric sensor based on electrochemically activated glassy carbon electrode for simultaneous determination of hydroquinone and catechol by Yong Kong; Xiaohui Chen; Chao Yao; Mengjie Ma; Zhidong Chen (pp. 2121-2126).
A simple and reliable voltammetric sensor for simultaneous determination of hydroquinone (HQ) and catechol (CC) was developed on an electrochemically activated glassy carbon electrode (GCE). The cyclic voltammograms in a mixed solution of HQ and CC have shown that the oxidation peaks become well resolved and were separated by 108 mV, although the bare GCE gave a single broad oxidation peak. Moreover, the oxidation peak currents of both HQ and CC were remarkably increased at the electrochemically activated GCE, which makes it suitable for simultaneous determination of these isomers. In the presence of 5.0 × 10−5 mol L−1 isomer, the oxidation peak currents of square wave voltammograms are proportional to the concentration of HQ in the range of 1.0 × 10−6 to 1.0 × 10−4 mol L−1, and to that of CC in the range of 2.0 × 10−6 to 1.0 × 10−4 mol L−1. The corresponding detection limits for HQ and CC are as low as 1.8 × 10−8 and 3.2 × 10−8 mol L−1 (S/N = 3), respectively.
On-chip real-time nucleic acid sequence-based amplification for RNA detection and amplification by Maria-Nefeli Tsaloglou; Mahadji M. Bahi; Edward M. Waugh; Hywel Morgan; Matthew Mowlem (pp. 2127-2133).
Development of integrated systems for nucleic acid analyses is mainly driven by the requirement for fast and simple clinical and environmental diagnostics. The need for affordable and effective point-of-care diagnosis has inspired an entire field of biotechnology in micro and nano-fluidics. We are developing a microfluidic system that has individual sub-systems for performing cell concentration and lysis, RNA extraction/purification and real-time RNA detection. The system is being developed to analyse the rbcL gene of phytoplankton Karenia brevis , a species responsible for harmful algal blooms. This integrated system will perform sub-cellular analysis of RNA using nucleic acid sequence-based amplification and would be used in large scale biochemical analysis and experimentation. The device could potentially be used for the detection of any species with a known target nucleic acid sequence for in situ environmental monitoring, forensics or clinical diagnostics.
Improved sensitive detection of Pb2+ and Cd2+ in water samples at electrodeposited silver nanonuts on a glassy carbon electrode by S. Prakash; Vinod K. Shahi (pp. 2134-2139).
Silver nanonuts (AgNns) with controlled size were electrodeposited on a glassy carbon electrode (GCE) surface using a double pulse potentiostatic technique for simultaneous detection of Pb2+ and Cd2+ in water samples without removal of oxygen, surfactant and other metal ions. The AgNns decorated GCE electrode showed improved sensitivity and reproducibility in comparison with previously reported electrodes. The detection limits were 0.15 ppb and 0.10 ppb for Pb2+ and Cd2+, respectively. Finally, the practical application of the proposed method was verified in waste water samples taken from the Alang ship breaking yard located in Gujarat (India).
Dispersive liquid–liquid micro extraction of uranium(
A dispersive liquid–liquid microextraction (DLLME) method was developed for the determination of uranium(vi ) in groundwater/seawater by inductively coupled plasma–optical emission spectrometry (ICP–OES) and flow injection–inductively coupled plasma mass spectrometry (FI–ICPMS). This is the first report on the extraction of uranium(vi ) by a DLLME method. In this method, uranium(vi ) was complexed with ammonium pyrrolidine dithiocarbamate (APDC) in the presence of cetyltrimethyl ammonium bromide (CTAB), which enhanced the hydrophobicity of the ion–association complex resulting in improved extraction into chloroform. The extraction was carried out after adjusting the pH of the water sample to 1. The uranyl ion was back extracted from chloroform layer with nitric acid for determination by ICP–OES/FI–ICPMS. Some effective parameters for complex formation and extraction, such as volume of extraction and disperser solvent, extraction time, pH and concentration of the chelating agent and surfactant have been optimized using ICP–OES. Under optimum conditions, enrichment factors of 11 and 25 were obtained from 10 mL of water sample for determinations by ICP–OES and FI–ICPMS respectively. The calibration graphs were linear in the range of 5–200 μg L−1 and 50–5000 ng L−1 with limits of detection of 2.0 μg L−1 and 30 ng L−1 respectively for ICP–OES and FI–ICPMS. The method has been applied to a few groundwater and seawater samples. The recoveries obtained for uranium(vi ) in groundwater and seawater samples spiked to levels of 10 and 5 μg L−1 were 90–105% respectively. The results obtained by the proposed method have been cross validated by laser fluorimetry.
Tetrazolium salt based methods for high-throughput evaluation of anti-parasite chemotherapy by Cristina Henriques; Thiago Luiz B. Moreira; Claudia Maia-Brigagão; Andréa Henriques-Pons; Técia Maria U. Carvalho; Wanderley de Souza (pp. 2148-2155).
This study demonstrates the first standardization of the MTS/PMS tetrazolium-based method in T. cruzi and G. duodenalis , and its application for chemotherapy studies and drug screening. We improved the detection limit and compared the MTT, XTT/PMS and MTS/PMS methods, in T. cruzi epimastigotes, demonstrating that MTS/PMS is more reproducible, sensitive, faster and easier to manipulate than XTT/PMS and MTT. Oligomycin (10 μg ml−1) reduced T. cruzi epimastigote metabolic activity by 60% measured by the MTS/PMS method, which is in accordance with flow cytometry measurements. To validate the MTS/PMS method, an IC50 of 10.5 μM was estimated for the drug amiodarone in T. cruzi and an IC50 of 6.2 μM for metronidazole in G. duodenalis , corroborating the IC50 values found in the literature. In G. duodenalis , a protozoan that has remnant mitochondria, the MTS/PMS method displayed higher sensitivity than T. cruzi epimastigotes. The detection limit was 104 for G. duodenalis trophozoites and 2.5 × 105 for T. cruzi epimastigotes. The intensity of the colored MTS/PMS formazan derivative is proportional to the number of metabolically active protozoa, regardless of whether used in a mitochondrial or an “amitochondrial” organism.
Assay design considerations for use of affinity aptamer amplification in ultra-sensitive protein assays using capillary electrophoresis by Kris P. F. Janssen; Karel Knez; Jeroen Pollet; Scott J. Roberts; Jan Schrooten; Jeroen Lammertyn (pp. 2156-2159).
Affinity probe capillary electrophoresis (APCE) holds promise to be a powerful tool in diagnostic applications that rely on the selective and sensitive detection of proteins. Aptamers can serve to unlock the full potential of the technology since their use opens up possibilities to unite the immuno-sensing and separating strength of capillary electrophoresis with the signal enhancement power of nucleic acid amplification. To enable routine use of aptamer APCE, careful selection of the experimental conditions is crucial. Here it is shown how customization and careful consideration of the experimental parameters can significantly improve assay performance.
Gas chromatography-mass spectrometric determination of ivermectin following trimethylsilylation with application to residue analysis in biological meat tissue samples by Aya Sanbonsuge; Tsugiko Takase; Den-ichiro Shiho; Yoshitaka Takagai (pp. 2160-2164).
A gas chromatography-mass spectrometric (GC-MS) method utilizing electron impact ionization has been developed for the quantitation of the antiparasitic agent, ivermectin (IVM). The approach is based upon the pre-column derivatization of IVM by reaction with N ,O -bis(trimethylsilyl)tri-fluoroacetamide (BSTFA) in the presence of 1-methylimidazole as catalyst and carbon tetrachloride as solvent to form the trimethylsilyl (TMS) derivative of IVM (IVM-TMS) prior to injection into the GC-MS system. The derivatization reaction is complete within 5.0 min at room temperature and allows the GC-MS determination of IVM. A limit of detection for IVM of 0.67 ng g−1 was achieved (via monitoring the peak with m /z = 185 in the selective ion mode and benzophenone-d10 as the internal standard). The method was utilized with success for the determination of IVM in spiked horse meat samples yielding recoveries very similar to that obtained using a reference liquid chromatography-mass spectrometric method (LC-MS). In addition, this GC-MS method can be employed to determine not only IVM but also other related macrolide veterinary drugs such as eprinomectin and moxidectin which are often administered along with IVM. Detection limits of 3.72 and 5.44 ng g−1 were obtained for eprinomectin and moxidectin, respectively.
Back cover (pp. 2165-2166).
Uniform and crystalline nanofibers of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA), an insoluble organic semiconducting molecule, have been achieved by self-assembling the molecules using chemical reaction mediated conversion of an appropriately designed soluble precursor, perylene tetracarboxylic acid (PTCA) using carbodiimide chemistry.