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Analytica Chimica Acta (v.708, #1-2)

Editorial Board (pp. iii).

Microfluidics for the deposition of density gradients of immobilized oligonucleotide probes; developing surfaces that offer spatial control of the stringency of DNA hybridization by M. Omair Noor; Ulrich J. Krull (pp. 1-10).

Display Omitted► Mass transport reaction kinetics generate a density gradient of immobilized probes. ► Targets with similar sequence identified by spatial pattern of hybridization. ► Interactions of probes with surface ameliorated by temperature or use of formamide.A method for the development of continuous density gradients of immobilized oligonucleotide probes (20mer) along the length of microfluidic channels is demonstrated. The development of continuous density gradients was achieved using variable electrokinetic transport of probes in hybrid glass–polydimethylsiloxane microfluidic chips. The probes were terminated with an amine functional group, and were delivered by electrokinetic pumping to the flat glass channel wall after it had been densely coated with covalently immobilized aldehyde groups. This method provided probe immobilization densities ranging from 4.5(±0.8)×10¹³ to 2.5(±0.8)×10¹¹moleculescm⁻², with longitudinal dilution and differential mass transport of the injected plug of probes being the primary factors responsible for the gradient of density. The utility of the resulting density gradient of immobilized probes to control the selectivity of hybridization was demonstrated at room temperature by discrimination between a fully complementary oligonucleotide target, and a target strand containing 3 base pair mismatches (3BPM) based on the spatial pattern of hybridization for sub-picomole quantities of targets. Single nucleotide polymorphism (SNP) discrimination was possible when temperature control was implemented to improve resolution of the mismatch discrimination, allowing SNP discrimination at 35°C with a contrast ratio of almost 5 to 1.

Keywords: Hybridization; Microfluidics; Electrokinetic transport; Density gradient immobilized oligonucleotides

Applicability of multisyringe chromatography coupled to cold-vapor atomic fluorescence spectrometry for mercury speciation analysis by J.L. Guzmán-Mar; L. Hinojosa-Reyes; A.M. Serra; A. Hernández-Ramírez; V. Cerdà (pp. 11-18).

An automatic system, based on the applicability of multisyringe chromatography (MSC) coupled to cold-vapor atomic fluorescence spectrometry (CV/AFS) detection is developed for mercury speciation.Display Omitted► The on-line coupling of MSC to CV/AFS was developed for mercury speciation analysis. ► The speciation of MeHg⁺, Hg²⁺ and EtHg⁺ was achieved on a RP C18 monolithic column. ► The hyphenated system provided higher sample throughput compared to HPLC–CV/AFS. ► The limits of detection for mercury species were comparable or better than those reported by HPLC–CV/AFS. ► The developed method also provided low instrumental and operational costs.In this paper, a novel automatic approach for the speciation of inorganic mercury (Hg²⁺), methylmercury (MeHg⁺) and ethylmercury (EtHg⁺) using multisyringe chromatography (MSC) coupled to cold-vapor atomic fluorescence spectrometry (CV/AFS) was developed. For the first time, the separation of mercury species was accomplished on a RP C18 monolithic column using a multi-isocratic elution program. The elution protocol involved the use of 0.005% 2-mercapthoethanol in 240mM ammonium acetate (pH 6)–acetonitrile (99:1, v/v), followed by 0.005% 2-mercapthoethanol in 240mM ammonium acetate (pH 6)–acetonitrile (90:10, v/v). The eluted mercury species were then oxidized under post-column UV radiation and reduced using tin(II) chloride in an acidic medium. Subsequently, the generated mercury metal were separated from the reaction mixture and further atomized in the flame atomizer and detected by AFS. Under the optimized experimental conditions, the limits of detection (3 σ) were found to be 0.03, 0.11 and 0.09μgL⁻¹ for MeHg⁺, Hg²⁺ and EtHg⁺, respectively. The relative standard deviation (RSD, n=6) of the peak height for 3, 6 and 3μgL⁻¹ of MeHg⁺, Hg²⁺ and EtHg⁺ (as Hg) ranged from 2.4 to 4.0%. Compared with the conventional HPLC–CV/AFS hyphenated systems, the proposed MSC–CV/AFS system permitted a higher sampling frequency and low instrumental and operational costs. The developed method was validated by the determination of a certified reference material DORM-2 (dogfish muscle), and was further applied for the determination of mercury species environmental and biological samples.

Keywords: Multisyringe chromatography (MSC); Cold-vapor atomic fluorescence spectrometry (CV/AFS); Mercury speciation; Monolithic column

Quantitative trace analysis of benzene using an array of plasma-treated metal-decorated carbon nanotubes and fuzzy adaptive resonant theory techniques by Radouane Leghrib; Eduard Llobet (pp. 19-27).

Display Omitted► Oxygen plasma treated, metal decorated carbon nanotube gas sensors. ► Selective benzene detection when operated at room temperature. ► Benzene quantification possible in the presence of interfering species and humidity. ► Quantitative models use quantitative fuzzy adaptive resonance theory neural network.The functionalization of carbon nanotube sidewalls with metal nanoparticles is exploited here to improve the sensitivity and selectivity of gas sensors operated at room temperature. An array of sensors using oxygen plasma treated multiwalled carbon nanotubes (bare and decorated with Pt, Pd or Rh nanoparticles) is shown to selectively detect traces of benzene (i.e., 100ppb) in the presence of carbon monoxide, hydrogen sulfide or nitrogen dioxide at different humidity levels. Employing a quantitative fuzzy adaptive resonant theory (ART) network whose inputs are the responses of the sensor array, it is possible to accurately estimate benzene concentration in a changing background. The quantitative fuzzy ART is especially suited for compensating the nonlinear effects in sensor response caused by changes in ambient humidity, which explains why this method clearly outperforms partial least squares calibration models at estimating benzene concentration. These results open the way to design new affordable, wearable, sensitive and selective detectors aimed at the personal protection of workers subject to occupational exposure to benzene, toluene, ethyl benzene and xylenes.

Keywords: Carbon nanotubes; Room temperature gas sensing; Oxygen plasma treatment; Metal nanoparticle decoration; Quantitative trace analysis; Quantitative fuzzy artmap

Chemometric determination of the length distribution of single walled carbon nanotubes through optical spectroscopy by Rongmei Si; Ke Wang; Tao Chen; Yuan Chen (pp. 28-36).

Display Omitted► Optical spectroscopy is used as a convenient tool to analyze the length distribution of single walled carbon nanotubes. ► Advanced multivariate chemometric methods are compared, and the best methods can satisfactorily predict the length distribution. ► The entire length distribution, not just the mean, is modelled and calibrated.Current synthesis methods for producing single walled carbon nanotubes (SWCNTs) do not ensure uniformity of the structure and properties, in particular the length, which is an important quality indicator of SWCNTs. As a result, sorting SWCNTs by length is an important post-synthesis processing step. For this purpose, convenient analysis methods are needed to characterize the length distribution rapidly and accurately. In this study, density gradient ultracentrifugation was applied to prepare length-sorted SWCNT suspensions containing individualized surfactant-wrapped SWCNTs. The length of sorted SWCNTs was first determined by atomic force microscope (AFM), and their absorbance was measured in ultraviolet–visible near-infrared (UV–vis-NIR) spectroscopy. Chemometric methods are used to calibrate the spectra against the AFM-measured length distribution. The calibration model enables convenient analysis of the length distribution of SWCNTs through UV–vis-NIR spectroscopy. Various chemometric techniques are investigated, including pre-processing methods and non-linear calibration models. Extended inverted signal correction, extended multiplicative signal correction and Gaussian process regression are found to provide good prediction of the length distribution of SWCNTs with satisfactory agreement with the AFM measurements. In summary, spectroscopy in conjunction with advanced chemometric techniques is a powerful analytical tool for carbon nanotube research.

Keywords: Chemometrics; Density gradient ultracentrifugation; Jensen–Shannon divergence; Length distribution; Multivariate calibration; Single walled carbon nanotube

Electrochemical sensors based on molecularly imprinted polymers grafted onto gold electrodes using click chemistry by Tanyu Wang; Curtis Shannon (pp. 37-43).

Display Omitted► Click chemistry was used to graft molecularly imprinted polymers onto Au electrodes. ► The detection limit of the clicked-on MIP sensor was found to be four times lower than a coated-on MIP sensor. ► The sensitivity of the clicked-on MIP sensor was three times greater than the coated-on MIP sensor. ► The improved performance arises from the favorable mass transfer characteristics of the clicked-on MIP sensing membrane.We have developed a three-step method to graft molecularly imprinted polymer (MIP) thin films onto Au electrodes. In the first step, propargyl acrylate is clicked onto an azidoundecanethiol (N₃(CH₂)₁₁SH)/decanethiol mixed self-assembled monolayer (SAM). Then, by applying UV light (365nm) in the presence of N, N′-methylenebis(acrylamide) (MAAM) and azobisisobutyronitrile (AIBN) as the radical initiator, polymerization was carried out directly on the electrode surface in the presence of an electroactive template molecule, hydroquinone (HQ). Detection of HQ using the clicked-on MIP sensor was studied using chronoamperometry and its behavior was compared to that of a sensor prepared by drop-coating MIPs onto Au. The detection limit of the clicked-on MIP sensor for HQ was found to be 1.21±0.56μM, about four times lower than what was observed using the coated-on MIP sensor. In addition, the sensitivity of the clicked-on MIP sensor was found to be approximately three times greater than the coated-on MIP sensor. Apparent diffusion coefficients determined using chronoamperometry suggest that the improved performance is likely due to the favorable mass transfer characteristics of the clicked-on MIP sensing membrane.

Keywords: Molecularly imprinted polymers; Amperometry; Click chemistry; Electrochemical sensors

A sensitive enzymeless hydrogen-peroxide sensor based on epitaxially-grown Fe₃O₄ thin film by Jiang Yang; Hua Xiang; Li Shuai; Sundaram Gunasekaran (pp. 44-51).

Display Omitted► Simple material synthesis, easy preparation and conducive for mass production. ► High sensitivity (432.2μAmM⁻¹cm⁻²) and low detection limit (1.0μM at S/N=3). ► Fast response (≤5s), good specificity, stability, and accuracy in real samples.A novel and facile approach has been developed to synthesize thin films of magnetite (Fe₃O₄) with epitaxial needle-like columnar grains on titanium nitride (TiN) buffered substrate using DC magnetron reactive sputtering. TiN buffer layer was first sputtered onto a substrate at 550°C as a preferable substrate for growth following sputtering of epitaxial crystalline Fe₃O₄ at 300°C. The as-synthesized epitaxial Fe₃O₄ was extensively characterized. The electrocatalytic activity of the epitaxial Fe₃O₄ thin-film sensor against hydrogen peroxide (H₂O₂) reduction was rapid with a response time less than 5s. The sensor also exhibited an acceptable stability, a satisfying sensitivity of 432.2μAmM⁻¹cm⁻², good specificity to the substrate, a dynamic working range of up to 0.7mM and a low detection limit of 1.0μM. The sensor performance correlated well ( R²=0.996) with results obtained using a commercial HPLC-UV device. The sensor performance was robust and accurate in measuring H₂O₂ in some complex matrices. The advantages of relative simplicity and ease of mass production make the epitaxial Fe₃O₄ thin film promising candidate for use in sensing applications.

Keywords: Epitaxial; Fe; ₃; O; ₄; film; Hydrogen peroxide; Electrochemical sensor

Optimization and evaluation of mixed-bed chemisorbents for extracting fission and activation products from marine and fresh waters by Bryce E. Johnson; Peter H. Santschi; Raymond Shane Addleman; Matt Douglas; Joe Davidson; Glen E. Fryxell; Jon M. Schwantes (pp. 52-60).

Display Omitted► We evaluate mixtures of chemisorbents for extracting radionuclides from water. ► We compare performance of traditional and nanostructured chemisorbents. ► We provide method for simultaneous extraction of Co, Zr, Ru, Ag, Te, Sb, Ba, Cs, Ce, Eu, Pa, Np, and Th. ► We discuss operational optimizations for extraction of radionuclides from water.Chemically selective chemisorbents are needed to monitor natural and engineered waters for anthropogenic releases of stable and radioactive contaminants. Here, a number of individual and mixtures of chemisorbents were investigated for their ability to extract select fission and activation product elements from marine and coastal waters, including Co, Zr, Ru, Ag, Te, Sb, Ba, Cs, Ce, Eu, Pa, Np, and Th. Conventional manganese oxide and cyanoferrate sorbents, including commercially available Anfezh and potassium hexacyanocobalt(II) ferrate(II) (KCFC), were tested along with novel nano-structured surfaces (known as Self Assembled Monolayers on Mesoporous Supports or SAMMS) functionalized with a variety of moieties including thiol, diphosphonic acid (DiPhos-), methyl-3,4 hydroxypyridinone (HOPO-), and cyanoferrate. Extraction efficiencies were measured as a function of salinity, organic content, temperature, flow rate and sample size for both synthetic and natural fresh and saline waters under a range of environmentally relevant conditions. The effect of flow rate on extraction efficiency, from 1 to 70mLmin⁻¹, provided some insight on rate limitations of mechanisms affecting sorption processes. Optimized mixtures of sorbent–ligand chemistries afforded excellent retention of all target elements, except, Ba and Sb. Mixtures of tested chemisorbents, including MnO₂/Anfezh and MnO₂/KCFC/Thiol (1–3mm)-SAMMS, extracted 8 of the 11 target elements studied to better than 80% efficiency, while a mixture of MnO₂/Anfezh/Thiol (75–150μm)-SAMMS mixture was able to extract 7 of the 11 target elements to better than 90%. Results generated here indicate that flow rate should be less of a consideration for experimental design if sampling from fresh water containing variable amounts of DOM, rather than collecting samples from salt water environments. Relative to the capability of any single type of chemisorbent tested, optimized mixtures of several sorbents are able to increase the number of elements that can be efficiently and simultaneously extracted from natural waters.

Keywords: Chemisorbent; Radionuclides; Manganese dioxide; Cyanoferrate; Nanoporous; Self assembled monolayers

Graphene-assisted matrix solid-phase dispersion for extraction of polybrominated diphenyl ethers and their methoxylated and hydroxylated analogs from environmental samples by Qian Liu; Jianbo Shi; Jianteng Sun; Thanh Wang; Lixi Zeng; Nali Zhu; Guibin Jiang (pp. 61-68).

Display Omitted► Graphene was used as a new sorbent material in matrix solid-phase dispersion. ► The method was used to extract PBDEs, MeO- and OH-PBDEs from environmental samples. ► The method offered satisfactory analytical performance. ► The method compared favorably with other materials and extraction techniques. ► The method was successfully applied to different real environmental matrices.In this work, we developed a novel graphene-assisted matrix solid-phase dispersion (GA-MSPD) method for extraction of polybrominated diphenyl ethers (PBDEs) and their methoxylated (MeO–) and hydroxylated (OH–) analogs from environmental samples. We found that grinding the solid sample with chemically converted graphene (CCG) powder yielded a tight contact and sufficient dispersion of the sample matrix due to the large surface area and flexible nanosheet morphology of CCG. The resultant blend was eluted using a two-step elution strategy: PBDEs and MeO-PBDEs were eluted firstly by hexane/dichloromethane and analyzed by GC–ECD, and then OH-PBDEs were eluted by acetone and determined by LC–ESI-MS/MS. The GA-MSPD conditions were optimized in detail. Better recoveries were obtained with GA-MSPD than with other sorbents (C18 silica, Florisil and carbon nanotubes) and other extraction techniques (Soxhlet and accelerated solvent extraction). Other advantages of GA-MSPD, including reduced consumption of sorbent and solvent, good selectivity and short extraction time, were also demonstrated. In analysis of soil samples, the method detection limits of five PBDEs, ten MeO-PBDEs and ten OH-PBDEs were in the range of 5.9–28.7, 14.3–46.6, and 5.3–212.6pgg⁻¹ dry weight, respectively. The proposed method was successfully applied to the extraction of PBDEs, MeO-PBDEs and OH-PBDEs from different kinds of spiked environmental samples, including soil, tree bark and fish.

Keywords: Graphene; Matrix solid-phase dispersion; Extraction; Polybrominated diphenyl ether; Methoxylated polybrominated diphenyl ether; Hydroxylated polybrominated diphenyl ether

Determination of trace impurities in cosmetic intermediates by ion mobility spectrometry by David Zamora; Manel Alcalà; Marcelo Blanco (pp. 69-74).

Display Omitted► Simple, inexpensive and highly expeditious method for DMAPA determination. ► High sensitivity in complex samples. ► Identification and characterization of oligomers of amidoamines.The cosmetic and pharmaceutical industries are continuously demanding fast, efficient, cost-effective analytical methods to monitor production processes and assure end-product quality. The presence of residual reagents or impurities formed during a synthetic process can have an adverse impact on product quality, assurance of which requires using increasingly sensitive analytical methods to facilitate the detection and/or determination of toxic compounds with potentially hazardous effects on consumer's health. In this work, we assessed the potential of ion mobility spectrometry (IMS) for the detection and quantitation of dimethylaminopropylamine (DMAPA) residues in stearamidopropyldimethylamine (SAPDA) production samples. The influence of instrumental variables including solvent, solution drying time, injected volume and volatilization temperature was examined. The ensuing analytical method takes less than 1min per analysis and uses only a few microlitres of sample. The calibration curve was linear over the DMAPA concentration range 0.030–0.500μgmL⁻¹. The proposed method was validated for use in control processes. The complex plasmagram for amidoamines allows the origin of cosmetic oils to be easily, expeditiously identified. Based on the results, IMS holds great promise for the qualitative and quantitative determination of the studied amide and various others in cosmetic products.

Keywords: Ion mobility spectrometry; 3-Dimethylaminopropylamine; Amidoamine; Cosmetics

Nanoparticle assembled microcapsules for application as pH and ammonia sensor by Arlin Jose Amali; Nour H. Awwad; Rohit Kumar Rana; Digambara Patra (pp. 75-83).

HPTS encapsulated nanoparticle assembled microcapsule is exploited as dual excitations ratiometic pH sensor. This nanoparticle assembled microcapsule based fluorescence sensor can determine ammonia and offers a robust, simple and fast sensing material.Display Omitted► A novel HPTS encapsulated nanoparticle assembled microcapsule is developed. ► Its dual excitation facilitates a ratiometic pH sensor. ► It is successfully applied for the determination of ammonia. ► It provides a robust, simple and fast sensing material.The encapsulation of molecular probes in a suitable nanostructured matrix can be exploited to alter their optical properties and robustness for fabricating efficient chemical sensors. Despite high sensitivity, simplicity, selectivity and cost effectiveness, the photo-destruction and photo-bleaching are the serious concerns while utilizing molecular probes. Herein we demonstrate that hydroxy pyrene trisulfonate (HPTS), a pH sensitive molecular probe, when encapsulated in a microcapsule structure prepared via the assembly of silica nanoparticles mediated by poly-l-lysine and trisodium citrate, provides a robust sensing material for pH sensing under the physiological conditions. The temporal evolution under continuous irradiation indicates that the fluorophore inside the silica microcapsule is extraordinarily photostable. The fluorescence intensity alternation at dual excitation facilitates for a ratiometic sensing of the pH, however, the fluorescence lifetime is insensitive to hydrogen ion concentration. The sensing scheme is found to be robust, fast and simple for the measurement of pH in the range 5.8–8.0, and can be successfully applied for the determination of ammonia in the concentration range 0–1.2mM, which is important for aquatic life and the environment.

Keywords: Poly-; l; -Lysine; HPTS; Nanoparticles; Microcapsules; pH sensor; Ammonia

Simple and fast fluorescence detection of benzoyl peroxide in wheat flour by N-methoxy rhodamine-6G spirolactam based on consecutive chemical reactions by Wei Chen; Wen Shi; Zhao Li; Huimin Ma; Yang Liu; Jinghua Zhang; Qingjun Liu (pp. 84-88).

A simple and fast method for fluorescence detection of benzoyl peroxide in wheat flour by N-methoxy rhodamine-6G spirolactam (1) is proposed based on consecutive chemical reactions.Display Omitted► Benzoyl peroxide can oxidize Fe²⁺ into Fe³⁺. ► Fe³⁺ selectively induces the opening of rhodamine spirolactam ring. ► The two reactions led to the development of a new fluorescent method for benzoyl peroxide. ► The method is simple and fast, and is used to detect benzoyl peroxide in wheat flour.Benzoyl peroxide (BPO) as a brightener is often added to wheat flour, and excessive use of this food additive is receiving increasing concern. Herein, a simple and fast method for fluorescence detection of BPO is proposed based on consecutive chemical reactions. In this approach, BPO first oxidizes Fe²⁺ into Fe³⁺ and the resulting Fe³⁺ then induces the opening of the spirolactam ring of a new rhodamine derivative, N-methoxy rhodamine-6G spirolactam, switching on fluorescence of the detection system. More importantly, the fluorescence response of the reaction system to BPO is rather rapid and sensitive, with a detection limit of 6mgkg⁻¹ ( k=3), which makes it to be of great potential use in food safety analysis. The applicability of the proposed method has been successfully demonstrated on the determination of BPO in wheat flour samples.

Keywords: Fluorescence detection; Benzoyl peroxide; Wheat flour; N; -Methoxy rhodamine-6G spirolactam; Consecutive chemical reactions

Silver nanoparticle-treated filter paper as a highly sensitive surface-enhanced Raman scattering (SERS) substrate for detection of tyrosine in aqueous solution by Min-Liang Cheng; Bo-Chan Tsai; Jyisy Yang (pp. 89-96).

Display Omitted► Silver nanoparticles (AgNPs) doped filter papers as substrates for SERS measurements. ► Highly sensitive for detection of analyte in aqueous solution. ► Raman enhancement reaches 7 orders of magnitude.Highly sensitive SERS substrates based on deposition of silver nanoparticles on commercially available filter paper were prepared in this work, and used to overcome problems found in analyses of aqueous samples. To prepare silver nanoparticle- (AgNP) doped filter substrates, a silver mirror reaction was used. The procedures for substrate preparation were systematically optimized. Pretreatment of filter paper, reaction time, temperature, and concentration of reagents for silver mirror reactions were studied. The morphologies of the resulting substrates were characterized by field-emission scanning electron microscopy (FE-SEM) and correlated with the SERS signals by probing with p-nitrothiophenol (pNTP). Filter papers with different pretreatments were found to have different sizes and distributions of AgNPs. The best performance was found when filter paper was pre-treated with ammonia solution before growth of AgNPs. Based on the SEM images, the resulting AgNPs had roughly spherical shape with a high degree of uniformity. The silver-coated filter paper substrates provide much higher SERS signals compared to glass substrates and the reproducibility was improved significantly. Based on statistical analyses, the relative standard deviations for substrate-to-substrate and spot-to-spot were both were less than 8% and the enhancement factors for the substrates were, in general, higher than 107. The SERS substrates were used to selectively detect tyrosine in aqueous solution. Results indicate that filter-based SERS substrates are highly suited to detection of tyrosine. Compared to glass-based SERS substrates, 50 times more SERS signal was observed in detection of tyrosine. The linear range can be up to 100μM with a detection limit of 625nM (SN⁻¹=3).

Keywords: Raman spectroscopy; Silver nanoparticles; Surface enhancement; Filter paper

Synthesis and characterisation of immunogens for the production of antibodies against small hydrophobic molecules with biosignature properties by Manisha Sathe; Mariliza Derveni; Gillian Broadbent; Anne Bodlenner; Keith Charlton; Bindu Ravi; Michel Rohmer; Mark R. Sims; David C. Cullen (pp. 97-106).

Display Omitted► Synthesis of derivatives of apolar hapten targets for generation of immunogens. ► Production and characterisation of immunogens for atypical apolar hapten targets. ► Demonstration of immune response to immunogens of atypical apolar immunogens.In the present study, five different classes of small hydrophobic molecular targets, atypical for antibody generation, were structurally modified in order to introduce suitable reactive functionalities and/or spacers which allow covalent coupling to a carrier protein resulting in a stable carrier–hapten complex. These targets were chosen to serve as markers of extant and/or extinct life in the context of the development of the Life Marker Chip (LMC), an antibody-based instrument, which is being developed by a UK-led international consortium for flight to Mars on board the joint ESA/NASA Mars exploration ExoMars mission. The hapten–protein conjugates were designed to be used as immunogens for antibody generation and immunoassay reagents in subsequent stages of the LMC development. The extent of protein modification due to covalent attachment of hapten was determined by two independent methods, i.e. trinitrobenzenesulfonic acid (TNBSA) titrations of remaining protein reactive groups and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) of the resultant hapten–protein conjugates. In a further quality validation step, the conjugates were presented to an animal's immune system and polyclonal antibody titres with moderate specificity were obtained. These results suggest that conjugates synthesized as described herein can successfully be used in the generation of antibodies targeting small hydrophobic molecules.

Keywords: Hapten; Life Marker Chip; Bioconjugation; Mars; Antibody generation; Hydrophobic molecules

Selective recognition of monohydrogen phosphate by fluorescence enhancement of a new cerium complex by Mohammad Reza Ganjali; Morteza Hosseini; Zahra Memari; Farnoush Faridbod; Parviz Norouzi; Hassan Goldooz; Alireza Badiei (pp. 107-110).

Display Omitted► Finding a new fluorescent enhancing chemosensor for phosphate ions. ► Synthesis of a new complex (bis(8-hydroxy quinoline-5-solphonate) cerium(III) chloride (Ce(QS)₂Cl)) as a practical fluorescent probe. ► Analysis of phosphate content in three kinds of fertilizers, mixed fertilizer (N–P–K), triple super phosphate (TSP), and single super phosphate (SSP) (from Zarrin Kood Co., Tehran, Iran).Bis(8-hydroxy quinoline-5-solphonate) cerium(III) chloride (Ce(QS)₂Cl) (L) was synthesized and then used as a novel fluorescent sensor for anion recognition. Preliminarily study showed that fluorescence of L enhanced selectively in the presence of HPO₄²⁻ ion. This enhancement is attributed to a 1:1 complex formation between L and HPO₄²⁻ anion. The association constant of 1:1 complex ofl-HPO₄²⁻ was calculated as 3.0×10⁶. Thus, L was utilized as a basis for a selective detection of HPO₄²⁻ anion in solution. The linear response range of the proposed fluorescent chemo-sensor covers a concentration range of HPO₄²⁻ from 3.3×10⁻⁷ to 5.0×10⁻⁶molL⁻¹ with a detection limit of 2.5×10⁻⁸molL⁻¹. L showed selective and sensitive fluorescence enhancement response toward HPO₄²⁻ ion in comparison with I₃⁻, NO₃⁻, CN⁻, CO₃²⁻, Br⁻, Cl⁻, F⁻, H₂PO₄⁻ and SO₄²⁻ ions. It was probably attributed to the higher stability of the inorganic complex between HPO₄²⁻ ion and L. The method was successfully applied for analysis of phosphate ions in some fertilizers samples.

Keywords: Fluorescent sensor; Monohydrogen phosphate; Enhancement; Hydroxy quinoline

Terbium hybrid particles with spherical shape as luminescent probe for detection of Cu²⁺ and Fe³⁺ in water by Qianming Wang; Chaoliang Tan (pp. 111-115).

A novel luminescent terbium hybrid material possessing intense green luminescence in water was successfully fabricated. Interestingly, we noticed that not only Cu²⁺ but also Fe³⁺ can give rise to emission quenching to this target material in comparison with K⁺, Na⁺, Mn²⁺, Pd²⁺, Cd²⁺ and Co²⁺.Display Omitted► A novel inorganic–polymeric terbium material possessing intense green luminescence in water was successfully designed. ► The spherical micro-meter shape of the materials was controllable. ► We noticed that not only Cu²⁺ but also Fe³⁺ can give rise to emission quenching to this target material in comparison with other tested cations.A novel green emissive terbium inorganic–polymeric hybrid particle was designed and this material could detect cations in water. Polyvinyl alcohol as an amphiphilic surfactant rendered the powders dispersible in water with regular round shape (10–20μm). Interestingly, we noticed that not only Cu²⁺ (detection limit 10⁻⁴M) but also Fe³⁺ (detection limit 10⁻⁴M) can give rise to emission quenching to this target material in comparison with K⁺, Na⁺, Fe²⁺, Mn²⁺, Pd²⁺, Cd²⁺ and Co²⁺ (10⁻³molL⁻¹). We regarded that the coordination interactions between ligand and metal ions resulted in these quenching processes. Additionally, it was found that the sensing material can be repeatedly used at least 5 cycles. More importantly, this novel material demonstrated higher thermal-stability in aqueous media than pure silica hybrid material.

Keywords: Luminescent; Copper ion; Iron ion; Terbium

Development of a highly sensitive and robust Cor a 9 specific enzyme-linked immunosorbent assay for the detection of hazelnut traces by Stanislav A. Trashin; Tatiana Cucu; Bart Devreese; Annemie Adriaens; Bruno De Meulenaer (pp. 116-122).

Display Omitted► The antibodies against a purified allergen result in the robust and highly sensitive hazelnut ELISA. ► An amperometric biosensor was fabricated using tetramethylbenzidine as an electrochemical mediator. ► The colorimetric ELISA was highly sensitive and the amperometric ELISA was fast.Allergy to tree nuts represents an acute health problem. Sensitized people can be inadvertently exposed to hidden allergens resulting from cross-contamination of foods. For this reason, reliable and highly sensitive analytical methods are needed to be developed for control and labeling of food ingredients and products. In the present paper we have proposed a new allergen specific sandwich-ELISA for hazelnut operated in optical and electrochemical modes. The ELISA was based on chicken egg yolk antibodies raised against a major hazelnut allergen, Cor a 9. The developed ELISA has a limit of detection in phosphate buffer of 4ngmL⁻¹. No significant cross-reactivity with peanut, wheat or other food ingredients has been detected. Extracts of blank control cookies did not show any false positive response and the limit of detection in cookies was estimated to be 0.1μg of hazelnut protein per g of food (0.1ppm). The ELISA protocol was successfully adapted to operate in electrochemical mode and it was applied for the detection of hazelnut traces in cookies

Keywords: Allergen; 11S globulin-like; Sandwich ELISA; Amperometry; Biosensor

A simple, rapid and high-throughput fluorescence polarization immunoassay for simultaneous detection of organophosphorus pesticides in vegetable and environmental water samples by Zhen-Lin Xu; Qiang Wang; Hong-Tao Lei; Sergei A. Eremin; Yu-Dong Shen; Hong Wang; Ross C. Beier; Jin-Yi Yang; Ksenia A. Maksimova; Yuan-Ming Sun (pp. 123-129).

Display Omitted► A broad-specificity FPIA for organophosphorus pesticides (OPs) was developed. ► The effect of tracer structure and several physicochemical parameters were studied. ► The FPIA can detect 5 OPs simultaneously with a limit of detection below 10ngmL⁻¹. ► Recovery tests from vegetable and environmental water samples were studied. ► Good accuracy and reproducibility were obtained.A simple, rapid and high-throughput fluorescent polarization immunoassay (FPIA) for simultaneous determination of organophosphorus pesticides (OPs) using a broad-specificity monoclonal antibody was developed. The effects of tracer structure, tracer concentration, antibody dilution, methanol content and matrix effect on FPIA performance were studied. The FPIA can detect 5 OPs simultaneously with a limit of detection below 10ngmL⁻¹. The time required for the equilibrium of antibody–antigen interaction was less than 10min. The recovery from spiked vegetable and environmental samples ranged from 71.3% to 126.8%, with the coefficient of variations ranging from 3.5% to 14.5%. The developed FPIA was applied to samples, followed by confirmation with high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) analysis. The developed FPIA demonstrated good accuracy and reproducibility, and is suitable for rapid and high-throughput screening for OP contamination with high-efficiency and low cost.

Keywords: Fluorescent polarization immunoassay; Organophosphorus pesticides; Monoclonal antibody; High-throughput

A colorimetric probe for online analysis of sulfide based on the red shifts of longitudinal surface plasmon resonance absorption resulting from the stripping of gold nanorods by Jia-Ming Liu; Xin-Xing Wang; Fei-Ming Li; Li-Ping Lin; Wen-Lian Cai; Xuan Lin; Li-Hong Zhang; Zhi-Ming Li; Shao-Qin Lin (pp. 130-133).

A nonaggregation-based colorimetric gold nanorods (GNRs) probe has been developed for the detection of sulfide based on the fact that the longitudinal surface plasmon resonance absorption wavelength (LPAW) of GNRs red shifts (Δ λ) and the color of the solution distinctly changes on account of the faster stripping of GNRs along longitudinal axis than transverse axis in the process of GNRs reacting with S²⁻ ions in solution to form Au₂S complexes on the GNRs surfaces. The proposed colorimetric probe can be used to visibly detect S²⁻ in water samples on line in 15min with the results agreeing well with methylene blue trihydrate method, showing its great practicality. Moreover, the detection mechanism of the probe is also discussed. This research not only provides a new on-line detection technology for S²⁻, but also expands the application field of GNRs and promotes the development of colorimetric probes.Display Omitted► A nonaggregation-based colorimetric gold nanorods (GNRs) probe has been developed for the detection of sulfide. ► This probe has the sensitive response to red shift of longitudinal surface plasmon resonance absorption wavelength of GNRs. ► The GNRs probe exhibits highly sensitive and selective response toward S²⁻ with a wide linear range from 10.0 to 10000.0μM. ► The probe can be used to visibly detect S²⁻ with the results agreeing well with methylene blue trihydrate method. ► The detection mechanism of the probe was discussed, which promoted the development of colorimetric probes.A gold nanorods (GNRs) nonaggregation-based colorimetric probe has been developed for the detection of S²⁻ based on that the longitudinal surface plasmon resonance absorption wavelength (LPAW) of GNRs red shifts (Δ λ) and the color of the solution distinctly changes on account of the faster stripping of GNRs along longitudinal axis than transverse axis in the process of GNRs reacting with S²⁻ ions to form Au₂S complexes on the GNRs surfaces. The GNRs probe exhibits highly sensitive and selective response toward S²⁻ with a wide linear range from 10.0 to 10000.0μM. The proposed colorimetric probe can be used to visibly detect S²⁻ in water samples on line in 15min with the results agreeing well with those of the optical sensor, showing its great practicality. Moreover, the detection mechanism of the probe is also discussed.

Keywords: Gold nanorods; Colorimetric probe; Longitudinal surface plasmon resonance absorption wavelength; On-line analysis; Sulfide

Synthesis in aqueous solution and characterisation of a new cobalt-doped ZnS quantum dot as a hybrid ratiometric chemosensor by Wen-sheng Zou; Jun-qin Qiao; Xin Hu; Xin Ge; Hong-zhen Lian (pp. 134-140).

Display Omitted► CoD ZnS QDs were synthesised in aqueous solution and characterised. ► Phosphorescence lifetime of the synthesised CoD ZnS QDs was 3.0ms. ► CoD ZnS QDs has great potential as a hybrid colorimetric assay for sensing TNT. ► This colorimetric probe can detect down to 25nM TNT.In this paper, cobalt (Co²⁺)-doped (CoD) ZnS quantum dots (QDs) are synthesised in aqueous solution and characterised for the first time.l-Cysteine (l-Cys) ligands on the surface of CoD ZnS QDs can bind 2,4,6-trinitrotoluene (TNT) to form Meisenheimer complexes (MHCs) mainly through acid–base pairing interactions between TNT andl-Cys and the assistance of hydrogen bonding and electrostatic co-interactions amongl-Cys intermolecules. The aggregation of inter-dots induced by MHCs greatly influenced the light scattering property of the QDs in aqueous solution, and Rayleigh scattering (RS) enhancement at the defect-related emission wavelengths as well as its left side was observed with the excitation of CoD ZnS QDs by violet light. RS enhancement, combining with the quenching of the orange transition emission induced by TNT anions, resulted in a change in the ratiometric visualisation of the system being investigated. A novel CoD ZnS QD-based hybrid ratiometric chemosensor has therefore been developed for simple and sensitive analysis of TNT in water. This ratiometric probe can assay down to 25nM TNT in solution without interference from a matrix of real water sample and other nitroaromatic compounds. Because of the excellent electron-accepting ability and strong affinity of TNT tol-Cys on the surface of CoD ZnS QDs, the CoD photoluminescent nanomaterials reported here are well suited for detecting ultra-trace TNT and for distinguishing different nitro-compounds in aqueous solution.

Keywords: Cobalt-doped (CoD) ZnS QDs; 2,4,6-Trinitrotoluene (TNT); Rayleigh scattering (RS); Hybrid ratiometric chemosensor; Room-temperature phosphorescence (RTP)

Sensitivity evaluation of rhodamine B hydrazide towards nitric oxide and its application for macrophage cells imaging by Chi-Ming Wu; Yen-Hao Chen; Kasala Dayananda; Tsun-Wei Shiue; Chen-Hsiung Hung; Wen-Feng Liaw; Po-Yu Chen; Yun-Ming Wang (pp. 141-148).

Display Omitted► RH shows good stability over a broad pH range. ► RH possesses excellent linearity between fluorescence intensity and NO concentration. ► RH shows ca. 1000-fold fluorescence enhancement after reacting with 5equiv. NO. ► RH can be used to detect exogenous NO and to trace endogenous NO.A colorless and non-fluorescent rhodamine derivative, rhodamine B hydrazide (RH), is applied to detect nitric oxide and form fluorescent rhodamine B (RB). The reaction mechanism of RH with NO is proposed in this study. The probe shows good stability over a broad pH range (pH>4). Furthermore, fluorescence intensity of RH displays an excellent linearity to the NO concentration and the detection limit is as low as 20nM. A 1000-fold fluorescence turn-on from a dark background was observed. Moreover, the selectivity study indicated that the fluorescence intensity increasing in the presence of NO was significantly higher than those of other reactive oxygen/nitrogen species. In exogenously generated NO detection study, clear intracellular red fluorescence was observed in the presence of S-nitroso- N-acetyl-D,L-penicillamine (SNAP, a kind of NO releasing agent). In endogenously generated NO detection study, increasing incubation time of RH with lipopolysaccharied (LPS) pre-treated cells could obtain a highly fluorescent cell image. These cell imaging results demonstrated that RH can efficiently penetrate into Raw 264.7 cells and be used for detection of exogenously and endogenously generated nitric oxide.

Keywords: Nitric oxide; Fluorescent probe; Cell imaging; Rhodamine

Development of a polymerase chain reaction and capillary gel electrophoresis method for the detection of chicken or turkey meat in heat-treated pork meat mixtures by Juan F. Hernández-Chávez; Aarón F. González-Córdova; Roberto Rodríguez-Ramírez; Belinda Vallejo-Cordoba (pp. 149-154).

A polymerase chain reaction and capillary gel electrophoresis (PCR-CGE) method with ultraviolet (UV) or laser induced fluorescence detection (LIF) was established for the detection of chicken or turkey in heat-treated pork meat mixtures. Mitochondrial DNA samples extracted from heat treated meat were amplified with their corresponding specific primers yielding PCR products between 200 and 300bp. LIF detection was superior than UV detection in terms of precision and sensitivity for the study of DNA fragments. The CGE-LIF method was highly reproducible and accurate for determining DNA fragment size. The PCR-CGE-LIF was sensitive since a significant fluorescent signal was obtained at the minimum admixture level employed of 1% in meat mixtures. Thus, the PCR-CGE-LIF method established was useful for the detection of chicken or turkey in heat treated meat mixtures and may prove to be useful for the detection of poultry meat in pork processed products.

Keywords: Identification; Meat species; Capillary electrophoresis; Polymerase chain reaction

Determination of triazine herbicides in environmental water samples by high-performance liquid chromatography using graphene-coated magnetic nanoparticles as adsorbent by Guangying Zhao; Shuangju Song; Chun Wang; Qiuhua Wu; Zhi Wang (pp. 155-159).

Effect of the amount of the magnetic nanoparticles (NPs) on the peak area of the triazines. Extraction conditions: sample volume, 250mL; extraction time, 30min; sample pH, 6.2; desorption solvent, 0.5mL acetone; concentration of analytes, 5ngmL⁻¹.Display Omitted► A graphene-coated Fe₃O₄ magnetic nanoparticles (G-Fe₃O₄ MNPs) was used for the extraction of triazines from water samples. ► The extraction conditions by the G-Fe₃O₄ MNPs were investigated. ► The G-Fe₃O₄ MNPs proved to be an effective adsorbent.In this paper, a graphene-based Fe₃O₄ magnetic nanoparticles (G-Fe₃O₄ MNPs) was used as the adsorbent for the magnetic solid-phase extraction of some triazine herbicides (atrazine, prometon, propazine and prometryn) in environmental water samples followed by high performance liquid chromatography-diode array detection (HPLC-DAD). After the extraction, the adsorbent can be conveniently separated from the aqueous samples by an external magnet. The main factors influencing the extraction efficiency including the amount of the MNPs, the extraction time, the pH of sample solution, and desorption conditions were studied and optimized. Under the optimized experimental conditions, a good linearity was observed in the range of 0.1–50.0ngmL⁻¹ for all the analytes, with the correlation coefficients ( r) ranging from 0.9996 to 0.9999. The limits of detection of the method ranged between 0.025 and 0.040ngmL⁻¹. Good reproducibility was obtained with the relative standard deviations below 5.2%. The developed method was applied to the analysis of the triazine herbicides in different water samples (lake, river and reservoir). The recoveries of the method were in the range between 89.0% and 96.2%.

Keywords: Graphene; Magnetic nanoparticles; Triazine herbicides; Water samples; High performance liquid chromatography

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Analytica Chimica Acta (v.708, #1-2)

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Analytica Chimica Acta (v.708, #1-2)