Simultaneous determination of four trace level endocrine disrupting compounds in environmental samples by solid-phase microextraction coupled with HPLC

Publication date: 1 September 2015
Source:Talanta, Volume 142
Author(s): Lingling Wang , Zhenzhen Zhang , Xu Xu , Danfeng Zhang , Fang Wang , Lei Zhang
A simple, rapid, sensitive and effective method for the simultaneous determination of four endocrine disrupting compounds (EDCs) (bisphenol A (BPA), bisphenol F (BPF), bisphenol AF (BPAF) and bisphenol AP (BPAP)) in environment water samples based on solid-phase microextraction (SPME) coupled with high performance liquid chromatography (HPLC) was developed. Multi-wall carbon nanotubes (MWCNTs) adsorbents showed a good affinity to the target analytes. These compounds were rapidly extracted within 10min. Various experimental parameters that could affect the extraction efficiencies had been investigated in detail. Under the optimum conditions, the enrichment factors of the method for the target EDCs were found to be 500. Satisfactory precision and accuracy of the method were obtained in a low concentration range of 2.0–500.0ngmL1. The method detection limits were in the range of 0.10–0.30ngmL1. The high pre-concentration rate and efficiency of the method ensure its successful application in extraction of trace EDCs from large volumes of environmental water samples. The extraction recoveries in real samples ranged from 85.3% to 102.5% with the relative standard deviations (n=5) less than 3.74%.

Graphical abstract

image



Microchip electrophoretic separation and fluorescence detection of chelerythrine and sanguinarine in medicinal plants

Publication date: 1 September 2015
Source:Talanta, Volume 142
Author(s): Yue Sun , Yuanyuan Li , Jiajian Zeng , Qixian Lu , Paul C.H. Li
A new method has been developed for separation of chelerythrine and sanguinarine in medicinal plants used in traditional Chinese medicine (TCM). The separation is achieved by microchip electrophoresis (CE) using laser-induced fluorescence detection. The CE separation is achieved by using a hydro-organic medium as the electrolyte buffer. The experimental results are consistent with the prediction by theory in terms of resolution and migration speed because of the low Joule heat generated in microchip CE. In addition, formamide was found to have a potential for separation of molecules with similar chemical structures. Based on these findings, a run buffer containing 50% formamide was used to separate chelerythrine (CHE) and sanguinarine (SAN). The influencing factors, such as solvent of run buffer, pH of buffer, separation distance, and separation voltage, were optimized. Baseline separation of chelerythrine and sanguinarine was achieved within 120s under an electrical voltage of 1.8kV. Good linearity was observed in the concentration range of 0.15–550μgmL−1 (r=0.9993) for CHE and in the range of 0.3–600μgmL−1 (r=0.9998) for SAN. A low limit of detection (LOD) was achieved because of the high sensitivity achieved by laser-induced fluorescence detection (i.e. 5.0ngmL−1 and 2.0ngmL−1 for CHE and SAN, respectively). The contents of CHE are found to be 641.8±7.5 and 134.0±2.3mg/kg in extracts of Macleaya cordata and Chelidonium majus, respectively, with good recovery of above 99%. The corresponding values for SAN found in these Chinese herbal extracts are 681.8±7.9mg/kg and 890.5±8.9mg/kg, respectively.

Graphical abstract

image



HPLC–UV method validation for the identification and quantification of bioactive amines in commercial eggs

Publication date: 1 September 2015
Source:Talanta, Volume 142
Author(s): Tadeu Chaves de Figueiredo , Débora Cristina Sampaio de Assis , Liliane Denize Miranda Menezes , Guilherme Resende da Silva , Isabela Pereira Lanza , Luiz Guilherme Dias Heneine , Silvana de Vasconcelos Cançado
A quantitative and confirmatory high-performance liquid chromatography with ultraviolet detection (HPLC–UV) method for the determination of bioactive amines in the albumen and yolk of commercial eggs was developed, optimized and validated by analyte extraction with trichloroacetic acid and pre-column derivatization with dansyl chloride. Phenylethylamine, putrescine, cadaverine, histamine, tyramine, spermidine and spermine standards were used to evaluate the following performance parameters: limit of detection (LoD), limit of quantification (LoQ), selectivity, linearity, precision, recovery and ruggedness. The LoD of the method was defined from 0.2 to 0.3mgkg−1 for the yolk matrix and from 0.2 to 0.4mgkg−1 for the albumen matrix; the LoQ was from 0.7 to 1.0mgkg−1 for the yolk matrix and from 0.7 to 1.1mgkg−1 for the albumen matrix. The validated method exhibited excellent selectivity and separation of all amines with coefficients of determination higher than 0.99. The obtained recovery values were from 90.5% to 108.3%, and the relative standard deviation (RSD) was lower than 10% under repeatability conditions for the studied analytes. The performance parameters show the validated method to be adequate for the determination of bioactive amines in egg albumen and yolk.

Graphical abstract

image



Solvent bar micro-extraction: Improving hollow fiber liquid phase micro-extraction applicability in the determination of Ni in seawater samples

Publication date: 1 September 2015
Source:Talanta, Volume 142
Author(s): Juan J. Pinto , Mabel Martín , Belén Herce-Sesa , José A. López-López , Carlos Moreno
During the last decade, hollow fiber liquid phase micro-extraction (HF-LPME) has become an attractive alternative in sample treatment for the analysis of trace metals in seawater. If compared with other similar methodologies, its main advantages are associated to a higher stability of the organic solution contained into the pores of the fiber, which acts as a lipophilic membrane during the extraction process. However there are some remaining problems that makes its use difficult, mostly related to the need of increasing the rate of analysis and improving portability.In this paper a novel three phase solvent bar micro-extraction (3PSBME) for the fiber device has been proposed. Its main advantage is that the 3PSBME device can be left free in the sample. This way the system is portable, and no special support is needed leading to the possibility of simultaneous extraction of several samples.In this work, multivariate central composite design of experiment has been carried out to optimize Ni pre-concentration using di-2-ethylhexyl phosphoric acid (DEHPA) as extractant and HNO3 as acceptor agent. Factors influencing extraction have been the pH in the sample and the fiber length. For seawater samples, Ni can be pre-concentrated 11 times in 140min. The method presents RSD 9.42% and limit of detection 44ngL−1, using GFAAS for instrumental determination. It has been applied for determination of Ni in seawater, including a reference material CRM-403 proving its applicability.

Graphical abstract

image



Determination of malachite green in fish based on magnetic molecularly imprinted polymer extraction followed by electrochemiluminescence

Publication date: 1 September 2015
Source:Talanta, Volume 142
Author(s): Baomei Huang , Xibin Zhou , Jing Chen , Guofan Wu , Xiaoquan Lu
A novel procedure for selective extraction of malachite green (MG) from fish samples was set up by using magnetic molecularly imprinted polymers (MMIP) as the solid phase extraction material followed by electrochemiluminescence (ECL) determination. MMIP was prepared by using Fe3O4 magnetite as magnetic component, MG as template molecule, methacrylic acid (MAA) as functional monomer and ethylene glycol dimethacrylate (EGDMA) as crosslinking agent. MMIP was characterized by SEM, TEM, FT-IR, VSM and XRD. Leucomalachite green (LMG) was oxidized in situ to MG by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). And then MMIP was successfully used to selectively enrich MG from fish samples. Adsorbed MG was desorbed and determined by ECL. Under the optimal conditions, calibration curve was good linear in the range of 0.29–290μg/kg and the limit of detection (LOD) was 7.3ng/kg (S/N=3). The recoveries of MMIP extraction were 77.1–101.2%. In addition, MMIP could be regenerated. To the best of our knowledge, MMIP coupling with ECL quenching of Ru(bpy)32+/TPA for the determination of MG has not yet been developed.

Graphical abstract

image



Designing valid and optimised standard addition calibrations: Application to the determination of anions in seawater

Publication date: 1 September 2015
Source:Talanta, Volume 142
Author(s): Joana Rodrigues , Ricardo J.N. Bettencourt da Silva , M. Filomena G.F.C. Camões , Cristina M. Oliveira
A strategy for designing valid standard addition calibrations and for optimising their uncertainty is presented. The design of calibrations involves the development of models of the sensitivity and precision of the instrumental signal, in a wide range of analyte concentration (or any other studied quantity), and the definition of sample dilution and standard addition procedures that allow fulfilling the assumptions of the linear unweighted regression model in, typically, a smaller range of standard addition calibrations. Calibrators are prepared by diluting the sample and adding analyte with negligible uncertainty to fit in a concentration range where signals are homoscedastic. The minimisation of the uncertainty is supported on detailed measurement uncertainty models function of the calibrators preparation procedure and of analytical instrumentation performance. The number of collected signals replicates is defined by balancing their impact on the estimated expanded uncertainty, the resources needed and the target (maximum) uncertainty for the intended use of measurements.The calibration design strategy was successfully applied to the determination of the mass concentration (mgL−1) of Cl, Br, NO3- and SO4-2 in seawater by ion chromatography. A target expanded uncertainty of 20% was defined for the determination of Cl, NO3- and SO4-2, or 40% for the determination of the smaller mass concentration of Br. The developed measurement model produced reliable predictions of the measurement uncertainty from approximate concentration of the analyte in the sample, before its accurate quantification, thus proving optimisation is effective. Predictions are more prone to the variability of the measurement uncertainty estimation if based on low number of calibrators signals. The reported relative expanded uncertainty ranged from 7.1% to 49%.

Graphical abstract

image



Simultaneous speciation of inorganic arsenic, selenium and tellurium in environmental water samples by dispersive liquid liquid microextraction combined with electrothermal vaporization inductively coupled plasma mass spectrometry

Publication date: 1 September 2015
Source:Talanta, Volume 142
Author(s): Ying Liu , Man He , Beibei Chen , Bin Hu
A new method based on dispersive liquid liquid microextraction (DLLME) combined with electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) was developed for the simultaneous speciation of inorganic arsenic (As), selenium (Se) and tellurium (Te) with sodium diethyldithiocarbamate (DDTC) as both chelating reagent and chemical modifier. As(III), Se(IV) and Te(IV) were transformed into DDTC-chelates at pH 7 and extracted into the fine droplets formed by injecting the binary solution of bromobenzene (extraction solvent) and methanol (dispersive solvent) into the sample solution. After phase separation by centrifugation, As(III), Se(IV) and Te(IV) preconcentrated in the organic phase were determined by ETV-ICP-MS. Total inorganic As, Se and Te were obtained by reducing As(V), Se(VI) and Te(VI) to As(III), Se(IV) and Te(IV) with l-cysteine, which were then subjected to the same DLLME-ETV-ICP-MS process. The concentration of As(V), Se(VI), Te(VI) were calculated by subtracting the concentration of As(III), Se(IV) and Te(IV) from the total inorganic As, Se and Te, respectively. The main factors affecting the microextraction efficiency and the vaporization behavior of target species were investigated in detail. Under the optimal conditions, the limits of detection were 2.5, 8.6 and 0.56ngL−1 for As(III), Se(IV) and Te(IV), respectively, with the relative standard deviations (n=7) of 8.5–9.7%. The developed method was applied to the speciation of inorganic As, Se and Te in Certified Reference Materials of GSBZ50004-88, GBW(E)080395 and GBW(E)080548 environmental waters, and the determined values are in good agreement with the certified values. The method was also successfully applied to the simultaneous speciation of inorganic As, Se and Te in different environmental water samples with the recoveries in the range of 86.3–107% for the spiked samples.

Graphical abstract

image



Novel and rapid method for determination of organophosphorus pesticide residues in edible fungus using direct gas purge microsyringe extraction coupled on-line with gas chromatography–mass spectrometry

Publication date: 1 September 2015
Source:Talanta, Volume 142
Author(s): Jingxi Nan , Juan Wang , Xiangfan Piao , Cui Yang , Xue Wu , Maurizio Quinto , Donghao Li
In this work a new analytical method for a rapid and simultaneous determination of 28 organophosphorus pesticides (OPPs) residues in edible fungus using gas purge microsyringe extraction (GP-MSE), coupled with on-line gas chromatography–mass spectrometry (GP-MSE-GC-MS) has been developed and optimized. GP-MSE, a novel gas flow liquid-phase microextraction technique, has been then fruitfully used as innovative and one-step extraction procedure, allowing a direct injection into the gas chromatograph coupled with a mass spectrometry detector (GC–MS) system without any further cleaning step. Once optimized, the GP-MSE-GC-MS analysis procedure showed reproducibility values, resolutions, linear responses, detection and quantification limits that allowed to consider this method suitable for the analysis of the 28 OPPs in real samples. Furthermore, OPP recoveries and the relative standard deviations (RSDs) ranged from 85.26% to 100.21%, and from 1.6% to 6.9%, respectively. This procedure was then used for the analysis of real samples and the obtained results were compared with those of ultrasonic extraction–solid phase extraction. Among the 28 OPPs, 14 of them were found in Lentinus edodes and Enoki mushrooms fungus samples, with a total concentrations of 112.7 and 210.7μgkg1, respectively. This work demonstrated then that GP-MSE-GC-MS provided a highly efficient, solvent-saving, accurate and sensitive quantitative analysis method for a rapid determination of OPPs in edible fungus.

Graphical abstract

image



Prediction of the distillation temperatures of crude oils using 1H NMR and support vector regression with estimated confidence intervals

Publication date: 1 September 2015
Source:Talanta, Volume 142
Author(s): Paulo R. Filgueiras , Luciana A. Terra , Eustáquio V.R. Castro , Lize M.S.L. Oliveira , Júlio C.M. Dias , Ronei J. Poppi
This paper aims to estimate the temperature equivalent to 10% (T10%), 50% (T50%) and 90% (T90%) of distilled volume in crude oils using 1H NMR and support vector regression (SVR). Confidence intervals for the predicted values were calculated using a boosting-type ensemble method in a procedure called ensemble support vector regression (eSVR). The estimated confidence intervals obtained by eSVR were compared with previously accepted calculations from partial least squares (PLS) models and a boosting-type ensemble applied in the PLS method (ePLS). By using the proposed boosting strategy, it was possible to identify outliers in the T10% property dataset. The eSVR procedure improved the accuracy of the distillation temperature predictions in relation to standard PLS, ePLS and SVR. For T10%, a root mean square error of prediction (RMSEP) of 11.6°C was obtained in comparison with 15.6°C for PLS, 15.1°C for ePLS and 28.4°C for SVR. The RMSEPs for T50% were 24.2°C, 23.4°C, 22.8°C and 14.4°C for PLS, ePLS, SVR and eSVR, respectively. For T90%, the values of RMSEP were 39.0°C, 39.9°C and 39.9°C for PLS, ePLS, SVR and eSVR, respectively. The confidence intervals calculated by the proposed boosting methodology presented acceptable values for the three properties analyzed; however, they were lower than those calculated by the standard methodology for PLS.

Graphical abstract

image



Portable gliadin-immunochip for contamination control on the food production chain

Publication date: 1 September 2015
Source:Talanta, Volume 142
Author(s): Maria Serena Chiriacò , Francesco de Feo , Elisabetta Primiceri , Anna Grazia Monteduro , Giuseppe Egidio de Benedetto , Antonio Pennetta , Ross Rinaldi , Giuseppe Maruccio
Celiac disease (CD) is one of the most common digestive disorders caused by an abnormal immune reaction to gluten. So far there are no available therapies, the only solution is a strict gluten-free diet, which however could be very challenging as gluten can be hidden in many food products. Furthermore an additional problem is related to cross-contamination of nominal gluten-free foods with gluten-based ones during manufacturing. Here we propose a lab on chip platform as a powerful tool to help food manufacturers to evaluate the real amount of gluten in their products by an accurate in-situ control of the production chain and maybe to specify the real gluten content in packages labeling. Our portable gliadin-immunochips, based on an electrochemical impedance spectroscopy transduction method, were first calibrated and then validated for both liquid and solid food matrixes by analyzing different beers and flours. The high specificity of our assay was also demonstrated by performing control experiments on rice and potatoes flours containing prolamin-like proteins. We achieved limit of quantification of 0.5ppm for gliadin that is 20 times lower than the worldwide limit established for gluten-free food while the method of analysis is faster and cheaper than currently employed ELISA-based methods. Moreover our results on food samples were validated through a mass spectrometry standard analysis.

Graphical abstract

image



A label-free impedimetric immunosensor for direct determination of the textile dye Disperse Orange 1

Publication date: 1 September 2015
Source:Talanta, Volume 142
Author(s): Jing Yang , Carolina Gomes da Rocha , Shengfu Wang , Antonio Aparecido Pupim Ferreira , Hideko Yamanaka
A strategy for a label-free impedimetric immunosensor is described for detection of the textile dye Disperse Orange 1 (DO1). The compounds 1,12-diaminododecane (DADD) and then 1,7-diaminoheptane (DAH) were firstly successively grafted onto a glassy carbon electrode (GCE) surface by electro-oxidation of one amino group, while the other terminal amino group was modified with the antibody anti-DO1. The construction process of the immunosensor was characterized by cyclic voltammetry, electrochemical impedance spectroscopy and capacitance measurements. The electron transfer resistance (Rct) exhibited an effective response to the affinity between the immobilized antibody and the antigen in solution. The linear range for the target compound was from 5.0nmolL−1 to 0.5μmolL−1 (R=0.9980), and the limit of detection (LOD) was 7.56nmolL−1. The proposed impedimetric immunosensor has the advantages of simplicity, cost-effectiveness, and sensitivity.

Graphical abstract

image



Dielectric barrier discharge-assisted one-pot synthesis of carbon quantum dots as fluorescent probes for selective and sensitive detection of hydrogen peroxide and glucose

Publication date: 1 September 2015
Source:Talanta, Volume 142
Author(s): Duhong He , Chengbin Zheng , Qiang Wang , Chunlin He , Yong-Ill Lee , Li Wu , Xiandeng Hou
In this work, we proposed a dielectric barrier discharge (DBD)-assisted one-pot strategy to fabricate carbon quantum dots (CQDs) using only one reagent N, N-dimethylformamide (DMF) at atmospheric pressure and room temperature. The experimental conditions were carefully investigated, and the prepared CQDs were characterized by using UV–vis spectrophotometer, fluorescence spectrophotometer, Fourier transform infrared (FTIR) spectrometer, transmission electron microscopy (TEM) and X-ray photoelectron spectrometer (XPS). The CQDs have an average size of 3.6nm in diameter with narrow size distribution, and can be used as highly selective and sensitive fluorescence probes for hydrogen peroxide and glucose, with limits of detection of 3.8μM and 3.5μM, respectively.

Graphical abstract

image



Rapid screening of aflatoxin B1 in beer by fluorescence polarization immunoassay

Publication date: 1 September 2015
Source:Talanta, Volume 142
Author(s): N.V. Beloglazova , S.A. Eremin
This manuscript describes the development of a sensitive, fast and easily-performed fluorescence polarization immunoassay (FPIA) for the mycotoxin aflatoxin B1 (AFB1) in various beer samples, both lager and dark. The highest sensitivity was determined for six poly- and monoclonal antibodies selective towards aflatoxins. The sample pretreatment design was emphasized since beer samples are characterized by extremely diverse matrices. Herein, the choice of sorbent for effective removal of matrix interferences prior to analysis was crucial. The samples were diluted with a borate buffer solution containing 1% PEG 6000 and passed through the clean-up column packed with NH2-derivated silica. This sample pretreatment technique was perfectly suitable for the FPIA of lager beer samples, but for dark beer and ale it did not suffice. An artificial matrix was constructed to plot a calibration curve and quantify the results of the latter samples. The developed immunoassay was characterized by a limit of detection of 1ngmL−1. Apparent recovery values of 89–114% for lager and 80–125% for dark beer were established. The FPIA data for AFB1 was characterized by elevated linear regression coefficients, 0.9953 for spiked lager and 0.9895 for dark beer samples respectively.

Graphical abstract

image



A categorical review on electroanalytical determination of non-narcotic over-the-counter abused antitussive drugs

Publication date: 1 September 2015 Source:Talanta, Volume 142 Author(s): Neeta Thapliyal , Harun Patel , Rajshekhar Karpoormath , Rajendra N. Goyal , Rajkumar Patel Dextromethorphan (DXM) and diphenhydramine (DPH) are two commonly…



Immunochromatographic assay for quantitative and sensitive detection of hepatitis B virus surface antigen using highly luminescent quantum dot-beads

Publication date: 1 September 2015
Source:Talanta, Volume 142
Author(s): Jun Shen , Yaofeng Zhou , Fen Fu , Hengyi Xu , Jiaofeng Lv , Yonghua Xiong , Andrew Wang
Hepatitis B virus infection is one of the major causes of hepatitis, liver cirrhosis and liver cancer. In this study, we used highly luminescent quantum dot-beads (QBs) as signal amplification probes in the sandwich immunochromatographic assay (ICA) for ultrasensitive and quantitative detection of hepatitis B virus surface antigen (HBsAg) in human serum. Various parameters that influenced the sensitivity and stability of the QB-based ICA (QB-ICA) sensor were investigated. Two linear independent regression equations for detection of serum HBsAg were expressed with Y=0.3361X−0.0059 (R2=0.9983) for low HBsAg concentrations between 75pgmL−1 and 4.8ngmL−1, and Y=0.8404 X−2.9364 (R2=0.9939) for high HBsAg concentrations in the range from 4.8ngmL−1 to 75ngmL−1. The detection limit of the proposed ICA sensor achieved was 75pgmL−1, which is much higher than that of the routinely-used gold nanoparticle based ICA. The intra- and inter-assays recovery rates for spiked serum samples at HBsAg concentrations of 75pgmL−1, 3.75ngmL−1 and 18.75ngmL−1 ranged from 90.14% to 97.6%, and coefficients of variation were all below 7%, indicating that the QB-ICA sensor has an acceptable accuracy for HBsAg detection. Additionally, the quantitative method developed showed no false positive results in an analysis of 49 real HBsAg-negative serum samples, and exhibited excellent agreement (R2=0.9209) with a commercial chemiluminescence immunoassay kit in identifying 47 HBsAg-positive serum samples. In summary, due to its high fluorescence intensity, the sandwich QB-ICA sensor is a very promising point-of-care test for rapid, simple and ultrasensitive detection of HBsAg, as well as other disease-related protein biomarkers.

Graphical abstract

image



One-pot green synthesis of oxygen-rich nitrogen-doped graphene quantum dots and their potential application in pH-sensitive photoluminescence and detection of mercury(II) ions

Publication date: 1 September 2015 Source:Talanta, Volume 142 Author(s): Bingfang Shi , Liangliang Zhang , Chuanqing Lan , Jingjin Zhao , Yubin Su , Shulin Zhao Nitrogen doping has been a powerful method to modulate the propertie…



Preparation and properties of a new solid state arsenate As(V) ion selective electrode and its application

Publication date: 1 September 2015
Source:Talanta, Volume 142
Author(s): Güler Somer , Ummihan T. Yilmaz , Şükrü Kalaycı
In this study a new solid-state ion selective electrode which is easy to prepare and sensitive to arsenate ion concentration is prepared. The solid salts used in the electrode composition were Cu2S, Ag3AsO4 and Ag2S. The principal component of the electrode was Ag3AsO4. The measurements were made in constant ionic strength using 0.1M NaNO3 and at room temperature. The potentiometric response of electrodes prepared in various compositions was investigated against arsenate ion concentration. The highest slope was obtained with 40% Ag3AsO4, 30% Cu2S and 30% Ag2S. This electrode showed linear response for arsenate ion in the 10−5–10−1M concentration range. An analytically useful potential change occurred, from 1×10−6 to 1×10−1M arsenate. The slope of the linear portion was about 19±2mV/10-fold change in arsenate concentration. The lifetime of the electrode was more than two years, when used at least 4–5 times a day, and the response time was about 20–30s depending on the concentration changes. The interference of most common ions and the effect of pH (6–10) have been investigated. This electrode has been used for the determination of arsenate ion in beer sample.

Graphical abstract

image



Use of ZIF-8-derived nanoporous carbon as the adsorbent for the solid phase extraction of carbamate pesticides prior to high-performance liquid chromatographic analysis

Publication date: 1 September 2015
Source:Talanta, Volume 142
Author(s): Lin Hao , Xingli Liu , Juntao Wang , Chun Wang , Qiuhua Wu , Zhi Wang
In this work, a chemically and thermally robust and highly porous zeolite-type metal–organic framework, zeolitic imidazolate framework-8 (ZIF-8), was used as both a precursor and a template and furfuryl alcohol as a second precursor to synthesize a nanoporous carbon. The prepared ZIF-8-derived nanoporous carbon was used as the solid-phase extraction adsorbent for the extraction of carbamate pesticides from cabbage and water samples. The adsorbed analytes were eluted with acetonitrile for the determination by high performance liquid chromatography–ultraviolet detection. The high surface area, high porosity, good stability and fast adsorption/desorption kinetics of the material enabled it to have a high adsorption capacity and good adsorption performance. Under optimum conditions, good linearity for the analytes in the range of 0.5–100ngg−1 and 0.05–20ngmL−1 existed for cabbage and water samples with the correlation coefficients of 0.9968–0.9980 and 0.9990–0.9995, respectively. The limits of detection (S/N=3) for the analytes were in the range of 0.25–0.1ngg−1 and 0.01–0.02ngmL−1 for the cabbage and water samples, respectively. The relative standard deviations (RSDs) for intra-day and the inter-day determinations of the analytes were below 7.0% and 12.5%, respectively.

Graphical abstract

image



Editorial Board

Publication date: 1 September 2015 Source:Talanta, Volume 142



Design of a dual-function peptide probe as a binder of angiotensin II and an inducer of silver nanoparticle aggregation for use in label-free colorimetric assays

Publication date: 1 September 2015
Source:Talanta, Volume 142
Author(s): Mina Okochi , Masashi Kuboyama , Masayoshi Tanaka , Hiroyuki Honda
Label-free colorimetric assays using metallic nanoparticles have received much recent attention, for their application in simple and sensitive methods for detection of biomolecules. Short peptide probes that can bind to analyte biomolecules are attractive ligands in molecular nanotechnology; however, identification of biological recognition motifs is usually based on trial-and-error experiments. Herein, a peptide probe was screened for colorimetric detection of angiotensin II (Ang II) using a mechanism for non-crosslinking aggregation of silver nanoparticles (AgNPs). The dual-function peptides, which bind to the analyte and induce AgNP aggregation, were identified using a two-step strategy: (1) screening of an Ang II-binding peptide from an Ang II receptor sequence library, using SPOT technology, which enable peptides synthesis on cellulose membranes via an Fmoc method and (2) selection of peptide probes that effectively induce aggregation of AgNPs using a photolinker modified peptide array. Using the identified peptide probe, KGKNKRRR, aggregation of AgNPs was detected by observation of a pink color in the absence of Ang II, whereas AgNPs remained dispersed in the presence of Ang II (yellow). The color changes were not observed in the presence of other hormone molecules. Ang II could be detected within 15min, with a detection limit of 10µM, by measuring the ratio of absorbance at 400nm and 568nm; the signal could also be observed with the naked eye. These data suggest that the peptide identified here could be used as a probe for simple and rapid colorimetric detection of Ang II. This strategy for the identification of functional peptides shows promise for the development of colorimetric detection of various diagnostically important biomolecules.

Graphical abstract

image