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Analytica Chimica Acta (v.747, #)

Editorial Board (pp. iii).

Investigating the interactions between cations, peroxidation substrates and G-quadruplex topology in DNAzyme peroxidation reactions using statistical testing by Shizuka Nakayama; Herman O. Sintim (pp. 1-6).

Display Omitted► G-quadruplex peroxidation rate depends on the cation present. ► NH₄⁺ is best cation amongst Li⁺, Na⁺, K⁺, Cs⁺, Rb⁺, Sr²⁺, Br²⁺, Pb²⁺ and Tb³⁺. ► ANOVA reveals cation effect is dependent on DNAzyme topology and peroxidation substrate.Cations affect the topology and enzymatic proficiency of most macromolecular catalysts but the role of cations in DNAzyme peroxidation reactions remains unresolved. Herein, we use statistical methods (ANOVA, t-test and Wilcoxon Mann–Whitney non-parametric test) to demonstrate that there are strong associations between cations, DNAzyme topology, peroxidation substrate and peroxidation rates of G-quadruplex peroxidises. Ammonium cation was found to be superior to all tested cations, including potassium. A t-test indicated that NH₄⁺ was better than K⁺ with a p-value=0.05. Interestingly, the nature of the peroxidation substrate employed affected the dependence of peroxidation rate on the cation present and of the three substrates tested, 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid (ABTS), tyramine and 3,3′,5,5′-tetramethylbenzidine (TMB), ABTS was the most sensitive to the nature of cation present.

Keywords: G-quadruplex; Peroxidase; Cation; Topology; Peroxidation substrate; Statistical testing

Versatile nanocomposites in phosphoproteomics: A review by Muhammad Najam-ul-Haq; Fahmida Jabeen; Dilshad Hussain; Adeela Saeed; Syed Ghulam Musharraf; Christian W. Huck; Günther K. Bonn (pp. 7-18).

Display Omitted► Protein phosphorylation, the most important post-translational modification. ► Enrichment of phosphopeptides for mapping protein phosphorylation sites. ► Versatile nanocomposites of different materials. ► The nanocomposites include magnetic, coated, embedded as well as chemically derivatized materials. ► Different base materials such as polymers, carbon based and metal oxides.Protein phosphorylation is one of the most important post-translational modifications. Phosphorylated peptides are present in low abundance in blood serum but play a vital role in regulatory mechanisms and may serve as casual factors in diseases. The enrichment and analysis of phosphorylated peptides directly from human serum and mapping the phosphorylation sites is a challenging task. Versatile nanocomposites of different materials have been synthesized using simple but efficient methodologies for their enrichment. The nanocomposites include magnetic, coated, embedded as well as chemically derivatized materials. Different base materials such as polymers, carbon based and metal oxides are used. The comparison of nanocomposites with respective nanoparticles provides sufficient facts about their efficiency in terms of loading capacity and capture efficiency. The cost for preparing them is low and they hold great promise to be used as chromatographic materials for phosphopeptide enrichment. This review gives an overview of different nanocomposites in phosphoproteomics, discussing the improved efficiency than the individual counterparts and highlighting their significance in phosphopeptide enrichment.

Keywords: Nanocomposites; Phosphorylation; Phosphopeptide enrichment; Biomarkers; Microspheres; Metal oxide affinity chromatography

Ordered mesoporous carbon for electrochemical sensing: A review by Jean Chrysostome Ndamanisha; Li-ping Guo (pp. 19-28).

Display Omitted► The preparation and functionalization of ordered mesoporous carbon. ► Their applications as electrochemical sensors with high electrocatalytic activity. ► A promising electrode material based on its interesting properties.With its well-ordered pore structure, high specific surface area and tunable pore diameters in the mesopore range, ordered mesoporous carbon (OMC) is suitable for applications in catalysis and sensing. We report recent applications of OMC in electrochemical sensors and biosensors. After a brief description of the electrochemical properties, the functionalization of the OMC for improvement of the electrocatalytic properties is then presented. We show how the ordered mesostructure of OMC is very important in those applications. The high density of edge plane-like defective sites (EDSs), oxygen-containing groups and a large surface area on OMC may provide many favorable sites for electron transfer to compounds, which makes OMC a potential novel material for an investigation of the electrochemical behavior of substances. Moreover, the structural capabilities of OMC at the scale of a few nanometers agree with immobilization of other electrocataytic substances. Interesting properties of this material may open up a new approach to study the electrochemical determination of other biomolecules.

Keywords: Ordered mesoporous carbon; Electrochemical properties; Sensors; Biosensors; Functionalization; Edge plane-like defective sites

Magnetic solid-phase extraction of sulfonylurea herbicides in environmental water samples by Fe₃O₄@dioctadecyl dimethyl ammonium chloride@silica magnetic particles by Zeying He; Donghui Liu; Ranhong Li; Zhiqiang Zhou; Peng Wang (pp. 29-35).

Display Omitted► A novel adsorbent was prepared for magnetic solid phase extraction. ► Varieties of experiment factors were optimized and selected. ► Good enrichment factors (1200–1410) were obtained. ► This method has been successfully applied in the analysis of real water samples.A magnetic solid phase extraction (MSPE) method coupled with high-performance liquid chromatography (HPLC) was proposed for the determination of five sulfonylurea herbicides (bensulfuron-methyl, prosulfuron, pyrazosulfuron-ethyl, chlorimuron-ethyl and triflusulfuron-methyl) in environmental water samples. The magnetic adsorbent was prepared by incorporating Fe₃O₄ nanoparticles and surfactant into a silica matrix according to a sol–gel procedure, which can provide surfactant free extracts during the eluting step to avoid chromatographic interference. The prepared adsorbent was used to extract the sulfonylurea herbicides in several kinds of water samples. The main factors affecting the extraction efficiency, including desorption conditions, extraction time, sample volume, and sample solution pH were optimized. Under the optimum conditions, good linearity was obtained within the range of 0.2–50.0μgL⁻¹ for all analytes, with correlation coefficients ranging from 0.9993 to 0.9999. The enrichment factors were between 1200 and 1410, and the limits of detection were between 0.078 and 0.10μgL⁻¹. The proposed method was successfully applied in the analysis of sulfonylurea herbicides in environmental samples (tap, reservoir, river, and rice field). The recoveries of the method ranged between 80.4% and 107.1%. This study reported for the first time the use of MSPE procedure in the preconcentration of sulfonylurea herbicides in environmental samples. The procedure proved to be efficient, environmentally friendly, and fast.

Keywords: Magnetic solid phase extraction; Surfactant; Sulfonylurea herbicides; Environmental water

The use of copper(II) isonicotinate-based micro-solid-phase extraction for the analysis of polybrominated diphenyl ethers in soils by You-Ya Zhou; Chao-Yan Zhang; Zeng-Guang Yan; Ke-Ji Li; Lin Wang; Ya-Bo Xie; Fa-Sheng Li; Zhou Liu; Jin Yang (pp. 36-41).

Display Omitted► A Cu(4-C₅H₄N-COO)₂(H₂O)₄-based μ-SPE device was developed for determining PBDEs. ► Extraction parameters for determination of PBDEs using μ-SPE in soils were optimized. ► The μ-SPE showed a high selectivity to PBDEs, especially lower brominated PBDEs. ► The μ-SPE is a promising microextraction technique for monitoring PBDEs in soils.A micro-solid-phase extraction (μ-SPE) device was developed by filling copper(II) isonicotinate coordination polymer (Cu(4-C₅H₄N-COO)₂(H₂O)₄) into a porous polypropylene envelope, and the μ-SPE, coupling with gas chromatography (GC) with a micro-cell electron capture detector (μ-ECD), was used for extraction and determination of PBDEs in soils. Variables affecting extraction procedures, including temperature, water volume, extraction time, and desorption time, were investigated in a spiked soil, and the parameters were optimized. Under the optimal experimental conditions, the method detection limits for seven PBDEs (BDE-28, 47, 99, 100, 153, 154, and 183) were in the range of 0.026–0.066ngg⁻¹, and the reproducibility was satisfactory with the relative standard deviation in range of 1.3–10.1%. Good linear relationship between PBDEs concentrations and GC signals (defined as peak area) was obtained in the range between 0.1 and 200ngg⁻¹. The recovery of the seven PBDEs by μ-SPE varied from 70 to 90%, which was comparable to that determined by accelerated solvent extraction method. Finally, the proposed method was used to determine PBDEs in several field-contaminated soils, and it was suggested that the μ-SPE is a promising alternative microextraction technique for the detection of PBDEs in soils.

Keywords: Copper(II) isonicotinate; Micro-solid-phase extraction; Polybrominated diphenyl ethers; Soil

Impact of the sample matrix composition on the signal enhancement in the capillary electrophoretic separation of poliovirus samples by Iuliana Oita; Hadewych Halewyck; Bert Thys; Bart Rombaut; Yvan Vander Heyden (pp. 42-50).

The effect of the small increase in sample matrix conductivity on the electrophoretic profile of the poliovirus suspensions. Separation conditions: uncoated fused silica capillary 40cm effective length; 100mM borate buffer pH 8.3 with 25mM SDS; detection wavelength 205nm. Sample: highly purified poliovirus suspension after matrix removal and concentration by ultrafiltration, diluted using the borate buffer pH 8.3 of specified concentration, injected as 12% plug.Display Omitted► First study of the sample matrix impact on the CE signal enhancement of viruses. ► The effect of sample matrix variations from growth and purification is discussed. ► Sample matrix importance for the CE sensitivity of poliovirus separations is shown. ► Influence of the sample matrix on the preconcentration mechanism is examined. ► Approaches for repeatable and reliable CE separations of poliovirus are indicated.The development of capillary electrophoretic applications aiming to provide reliable stability assessment of viral suspensions, to detect subviral particles from cell extracts or to study the interactions between virus particles and various biomolecules, cannot be done without a thorough understanding of the sample matrix contribution to the observed electrophoretic behaviour. The present study thoroughly investigates the effect of the sample matrix on the electrophoretic behaviour of poliovirus injected as sample plugs of 1%, 5% and 12% effective capillary length. The effect of the sample matrix for three different poliovirus batches was evaluated. Additionally, simulated samples, obtained from concentrated poliovirus suspensions of high purity and diluted with commonly used lab buffers in order to obtain samples with either high or low conductivities, were also investigated. The goal of the study was to obtain a better understanding of the effect of the sample matrix on the signal enhancement, in order to define a general approach allowing a repeatable capillary electrophoretic (CE) separation of poliovirus from complex samples. This study clearly demonstrates that the sample matrix has an important influence on the sensitivity of the CE poliovirus separations. Translation of these observations into routine practice involves several compromises and a set of rules in order to reduce day-to-day variation and to maximize sensitivity.

Keywords: Capillary electrophoresis; Poliovirus; Sensitivity improvement; Signal enhancement; Virus quantitation

Tracing phenolic biosynthesis in Vitis vinifera via in situ C-13 labeling and liquid chromatography–diode-array detector–mass spectrometer/mass spectrometer detection by Alexander W. Chassy; Douglas O. Adams; V. Felipe Laurie; Andrew L. Waterhouse (pp. 51-57).

Display Omitted►l-Phenyl-¹³C₆-alanine was incorporated into grape berries, intact on the vine, at two stages of maturity. ► Labeled anthocyanins were synthesized by the berry and quantified by LC–UV/Vis–MS/MS. ► Extremely tight regulation of phenylpropanoid pathways was observed.Phenolic compounds in Vitis vinifera contribute important flavor, functionality, and health qualities to both table and wine grapes. The plant phenolic metabolic pathway has been well characterized, however many important questions remain regarding the influence of environmental conditions on pathway regulation. As a diagnostic for this pathway's regulation, we present a technique to incorporate a stable-isotopic tracer,l-phenyl-¹³C₆-alanine (Phe¹³), into grape berries in situ and the accompanying high throughput analytical method based on LC–DAD–MS/MS to quantify and track the label into phenylalanine metabolites. Clusters of V. vinifera cv. Cabernet Sauvignon, either near the onset of ripening or 4weeks later, were exposed to Phe¹³ in the vineyard. Phe¹³ was present in berries 9days afterwards as well as labeled flavonols and anthocyanins, all of which possessed a molecular ion shift of 6amu. However, nearly all the label was found in anthocyanins, indicating tight regulation of phenolic biosynthesis at this stage of maturity. This method provides a framework for examining the regulation of phenolic metabolism at different stages of maturity or under different environmental conditions. Additionally, this technique could serve as a tool to further probe the metabolism/catabolism of grape phenolics.

Keywords: Anthocyanin; Stable-isotope; Metabolism; Flavonoid

A reliable solid phase microextraction-gas chromatography–triple quadrupole mass spectrometry method for the assay of selenomethionine and selenomethylselenocysteine in aqueous extracts: Difference between selenized and not-enriched selenium potatoes by Emanuela Gionfriddo; Attilio Naccarato; Giovanni Sindona; Antonio Tagarelli (pp. 58-66).

Display Omitted► A SPME-GC–QqQ MS approach was developed for free SeAA quantification in aqueous extracts. ► Possibility to use an available commercial instrument as GC–QqQ MS for analyzing SeAA. ► Application to commercial samples of selenized and not selenium enriched potatoes. ► The Se fertilization increases the concentration of studied SeAA in selenized potatoes.A new analytical approach is exploited in the assay of selenium speciation in selenized and not selenium enriched potatoes based on the widely available solid-phase microextraction (SPME) coupled to-GC–triple quadrupole mass spectrometry (SPME-GC–QqQ MS) method.The assay of selenomethionine (SeMet) and selenomethylselenocysteine (SeMeSeCys) in potatoes here reported provides clues to the effectiveness of SPME technique combined with gas chromatography–tandem mass spectrometry, which could be of general use. For the exploitation of the GC method, the selected analytes were converted into their N( O, S)-alkoxycarbonyl alkyl esters derivatives by direct treatment with alkyl chloroformate in aqueous extracts. The performance of five SPME fibers and three chloroformates were tested in univariate mode and the best results were obtained using the divinylbenzene/carboxen/polydimethylsiloxane fiber and propylchloroformate. The variables affecting the efficiency of SPME analysis were optimized by the multivariate approach of design of experiment (DoE) and, in particular, a central composite design (CCD) was applied. Tandem mass spectrometry in selected reaction monitoring (SRM) has allowed the elimination of matrix interferences, providing reconstructed chromatograms with well-resolved peaks and the achievement of very satisfactory detection and quantification limits. Both precision and recovery of the proposed protocol tested at concentration of 8 and 40μgkg⁻¹ (dry matter), offered values ranging from 82.3 to 116.3% and from 8.5 to 13.1% for recovery and precision, respectively. The application of the method to commercial samples of selenized and not selenium enriched potatoes proved that the Se fertilization increases significantly the concentration of these bioavailable selenoamino acids.

Keywords: Selenoamino acids; Selenized potatoes; SPME; Tandem mass spectrometry; Selenium speciation; Alkyl chloroformates

Analytical performance of a triple quadrupole mass spectrometer compared to a high resolution mass spectrometer for the analysis of polybrominated diphenyl ethers in fish by Susan A. Mackintosh; Alicia Pérez-Fuentetaja; Lisa R. Zimmerman; Grazina Pacepavicius; Mark Clapsadl; Mehran Alaee; Diana S. Aga (pp. 67-75).

Display Omitted► A GC–QQQ-MS/MS method was developed for the analysis of PBDE congeners in fish. ► This method was directly compared with a GC–HR-MS analysis of the same samples. ► Limits of detection were found to be comparable between the two instruments. ► GC–QQQ-MS/MS results were not statistically different from the GC–HR-MS results. ► Findings support the suitability of GC–QQQ-MS/MS for analysis of PBDEs in fish.Polybrominated diphenyl ethers (PBDEs) are a class of flame retardants used globally in many consumer products and industrial applications. Traditionally, gas chromatography–high resolution mass spectrometry (GC–HR-MS) is the method of choice for analysis of PBDEs in environmental samples because it offers high sensitivity and selectivity, resulting in less interferences. However, the specificity offered by gas chromatography-triple quadrupole tandem mass spectrometry (GC–QQQ-MS/MS), operated in selected reaction monitoring mode, provides a more affordable alternative to GC–HR-MS for the analysis of PBDEs in complex environmental samples. In this study, an analytical method was developed for the analysis of 41 PBDE congeners in fish using GC–QQQ-MS/MS. Results from the analysis of three fish species [lake trout ( Salvelinus namaycush), yellow perch ( Perca flavescens), and round goby ( Neogobius melanostomus)] using GC–QQQ-MS/MS were compared with those obtained by GC–HR-MS. These species were selected because they represent varying levels of lipid-rich matrix and contaminant loads. Instrumental limits of detection for the GC–QQQ-MS/MS ranged from 0.04pg to 41pg, whereas those for the GC–HR-MS ranged from 5pg to 85pg. The PBDE values obtained from these two methods were highly correlated, R² values >0.7, for all three fish species, supporting the suitability of GC–QQQ-MS/MS for analysis of PBDEs in fish with varying fat content.

Keywords: Polybrominated diphenyl ethers; Triple quadrupole mass spectrometry; High-resolution mass spectrometry; Fish; Brominated flame retardants; Methods

Quality evaluation and species differentiation of Rhizoma coptidis by using proton nuclear magnetic resonance spectroscopy by Gang Fan; Meng Ying Zhang; Xiang Dong Zhou; Xian Rong Lai; Qing Hong Yue; Ce Tang; Wei Zao Luo; Yi Zhang (pp. 76-83).

Display Omitted► We report a qNMR method for the determination of six alkaloids in Rhizoma coptidis. ► The results of the qNMR method are reliable by comparison with a HPLC method. ► The proposed method has good selectivity, precision, repeatability and accuracy. ► This method coupled with chemometrics can distinguish three Rhizoma coptidis species. Rhizoma coptidis, a broadly used traditional Chinese medicine, derives from the dried rhizomes of Coptis chinensis Franch, Coptis deltoidea C.Y. Cheng et Hsiao and Coptis teeta Wall. Quantitative determination of protoberberine alkaloids in R. coptidis is critical for controlling its quality. In this study, a rapid, simple and accurate quantitative¹H NMR (qNMR) method was developed for simultaneous determination of berberine, jatrorrhizine, epiberberine, coptisine, palmatine and columbamine in R. coptidis from the three species. Method validation was performed in terms of selectivity, precision, repeatability, stability, accuracy, robustness and linearity. The average recoveries obtained were in the range of 96.9–102.4% for all the six alkaloids. In addition, the qNMR data were analyzed with analysis of variance (ANOVA), hierarchical clustering analysis (HCA) and principal component analysis (PCA), and the results showed that the contents of the active alkaloids have significant difference among the three species. Compared with the conventional HPLC approach, the proposed qNMR method was demonstrated to be a powerful tool for quantifying the six alkaloids due to its unique advantages of high robustness, rapid analysis time and no need of standard compounds for calibration curves preparation. These findings indicate that this method has potential as a reliable method for quality evaluation of herb medicines, especially for protoberberine alkaloid-containing ones.

Keywords: Proton nuclear magnetic resonance; Rhizoma coptidis; Protoberberine alkaloids; Quantitative analysis; Species differentiation

Grafted Azure A modified electrodes as disposable β-nicotinamide adenine dinucleotide sensors by M. Revenga-Parra; C. Gómez-Anquela; T. García-Mendiola; E. Gonzalez; F. Pariente; E. Lorenzo (pp. 84-91).

Display Omitted► Electrografting of Azure A diazonium salt onto screen-printed electrodes is described. ► These modified electrodes are electrochemically characterized. ► Modified electrodes shows a persistent catalytic activity toward NADH oxidation. ► Rapid, sensitive, selective, robust, stable and disposable NADH sensors are described.We report the in situ generation of aryl diazonium cations of Azure A, a redox-active phenothiazine dye, by reaction between the corresponding aromatic aminophenyl group and sodium nitrite in 0.1M HCl. The subsequent electrochemical reduction of these dye diazonium salts gives rise to conductive electrografted films onto screen-printed carbon (SPC) electrodes. The resulting Azure A films have a very stable and reversible electrochemical response and exhibit potent and persistent electrocatalytic behavior toward NADH oxidation. We have optimized the electrografting conditions in order to obtain SPC modified electrodes with high and stable electrocatalytic response. The kinetic of the reaction between the NADH and the redox active centers in the Azure A film has been characterized using cyclic voltammetry and single step chronoamperometry. The catalytic currents were proportional to the concentration of NADH giving rise to linear calibration plots up to a concentration of 0.5mM with a detection limit of 0.57±0.03μM and a sensitivity of 9.48Amolcm⁻²μM⁻¹. The precision of chronoamperometric determinations was found to be 2.3% for five replicate determinations of 3.95μM NADH. The great stability of such modified electrodes makes them ideal for their application in the development of biosensing platforms based on dehydrogenases.

Keywords: Diazotization reaction; Azure A dye; Electrochemical surface modification; β-Nicotinamide adenine dinucleotide sensors

“Oxidative etching-aggregation” of silver nanoparticles by melamine and electron acceptors: An innovative route toward ultrasensitive and versatile functional colorimetric sensors by Guang-Li Wang; Xiao-Ying Zhu; Huan-Jun Jiao; Yu-Ming Dong; Xiu-Ming Wu; Zai-Jun Li (pp. 92-98).

Display Omitted► A novel concept for colorimetric sensing of MA based on non-crosslinking of AgNPs. ► The detection mechanism was based on “oxidative etching-aggregation” of unmodified AgNPs. ► This method was simple, selective and ultrasensitive. ► The detection limit for MA was as low as 0.08nM when using H₂O₂ as electron acceptor. ► The method also enabled the detection of H₂O₂ with a detection limit of 0.2nM.An innovative and versatile functional colorimetric sensor for melamine (MA) and H₂O₂ was developed with simplicity, excellent selectivity and ultrasensitivity. The detection mechanism was based on the “oxidative etching-aggregation” of silver nanoparticles (AgNPs) by the cooperation effect of MA and electron acceptors such as H₂O₂, ozone or Fe(NO₃)₃. The detection limits of this method for MA could reach as low as 0.08nM, 0.16nM and 3nM when H₂O₂, ozone or Fe(NO₃)₃ was used as an electron acceptor, respectively. When using H₂O₂ as a typical electron acceptor, the method enabled the detection of H₂O₂ with a detection limit of 0.2nM. This proposed method offered a new way to design MA and H₂O₂ sensors and might be easily extended to detect other nucleophilic reagents and electron acceptors based on colorimetric sensors.

Keywords: Colorimetric sensor; Melamine; Silver nanoparticles; Oxidative etching-aggregation

A highly sensitive label-free resonance light scattering assay of carcinoembryonic antigen based on immune complexes by Zhanguang Chen; Yulong Lei; Zhisen Liang; Fengji Li; Lidong Liu; Changlong Li; Fang Chen (pp. 99-105).

A novel label-free resonance light scattering (RLS) spectral CEA assay was developed based on the combination of highly selective CEA immunoreaction and ultrasensitive RLS technique. The specific immunoreaction between CEA antigen and mouse anti-CEA formed immune complexes which had a maximum RLS spectral peak at 389.0nm. Under the optimal conditions, the magnitude of enhanced RLS intensity ( I_RLS) was proportional to the concentration of CEA. This new assay was successfully used to detect CEA in 20 serum specimens and it has many satisfying merits including sensitivity, label-free and high selectivity.Display Omitted► Carcinoembryonic antigen is an important tumor marker for clinical diagnosis of tumor. ► The immunoreaction between CEA and mouse anti-CEA resulted in the enhanced RLS. ► The RLS characteristics, immune response and optimum conditions have been studied. ► This developed RLS assay was successfully applied to detect CEA in 20 serum samples. ► The assay possesses the merits of label-free, sensitivity and high selectivity.As a kind of glycoprotein, carcinoembryonic antigen (CEA) is the important tumor marker for clinical diagnosis of the presence or recurrence of cancer. In this work, a novel label-free resonance light scattering (RLS) spectral CEA assay was developed based on the combination of highly selective immunoreaction and ultrasensitive RLS technique. In Tris–HCl buffer solution (pH 7.5), the specific immunoreaction between CEA antigen and mouse anti-CEA formed immune complexes which had a maximum RLS spectral peak at 389.0nm, with the existence of physiological saline and polyethylene glycol 20,000 (PEG 20,000). Under the optimal conditions, the magnitude of enhanced RLS intensity (Δ I_RLS) was proportional to the concentration of CEA in the range from 0.1 to 60ngmL⁻¹, with a detection limit (LOD, 3 σ) of 0.03ngmL⁻¹. The characteristics of RLS, the CEA immunocomplex, the immune response, the ratio of CEA antigen and mouse anti-CEA, and the optimum conditions of the immunoreaction have been investigated. The CEA concentrations of 20 serum specimens detected by the developed assay showed consistent results in comparison with those obtained by commercially available enzyme-linked immunosorbent assay (ELISA) kit. And this method has many satisfying merits including label-free, sensitivity and high selectivity.

Keywords: Tumor marker; Carcinoembryonic antigen; Resonance light scattering; Immunoreaction

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Analytica Chimica Acta (v.747, #)