Analytical and Bioanalytical Chemistry (v.410, #7)

Successfully navigating the early years of a faculty position by Michelle L. Kovarik; Christopher R. Harrison; Thomas J. Wenzel (1855-1861).
is Assistant Professor of Chemistry at Trinity College in Hartford, Connecticut. Her research interests include microfluidics, single-cell measurements, and the use of fluorescently labeled peptides for enzyme assays. She is also involved in scholarly activity to develop materials for the undergraduate analytical chemistry curriculum that emphasize active learning and engage students with the primary literature. is Associate Professor of Chemistry at San Diego State University. His research focus centers around the separation of biomolecules via capillary electrophoresis, with a particular emphasis on developing new methods for athlete anti-doping tests, and exploring the fundamentals of electroosmotic flow control. He has also been active in incorporating digitals tools and methods in his teaching, and developing active learning materials for analytical chemistry education. is the Charles A. Dana Professor of Chemistry at Bates College in Lewiston, Maine. He currently carries out research with the aid of undergraduate students in the area of chiral NMR shift reagents. His research accomplishments were recognized with the 2010 American Chemical Society Award for Research at an Undergraduate Institution. He is active in efforts to reform the undergraduate analytical chemistry curriculum to include inquiry- and project-based experiences.

is the Head of the Clinical Research Center at the Department of Laboratory Medicine in the Third Affiliated Hospital of Chongqing Medical University of China. Presently his research interests mainly include clinic immunoassay and early disease diagnostics. received his B.S. degree in 2013 from North Sichuan Medical University, China. He is now a graduate student in Chongqing Medical University and conducting research related to liquid biopsy and its clinical application. received his B.S. degree in 2015 from Wenzhou Medical University, China, and was then trained in metabolic inflammation and lipid metabolism at University of Nebraska, Lincoln, as a visiting scholar for two years. His research interests include metabolic inflammation, gut microbiota regulating host metabolism and biosensor technology. A new homogeneous electrochemical sensing system was developed for sensitive detection of microRNA-21 (miRNA-21) based on target-induced glucose release from propylamine-functionalized mesoporous silica nanoparticle (MSN) with glucometer readout. Glucose molecules (as the signal tracers) were initially gated into the pores through the interaction of the negatively charged anchor DNA with the aminated MSN. Upon addition of target miRNA, the analyte competitively hybridized with anchor DNA to form the RNA-DNA duplex, thus resulting in detachment of anchor DNA from the MSN accompanying the pore opening. The loaded glucose molecules released out from the pores because of concentration gradients, which could be detected by using a portable personal glucometer (PGM). Experimental results indicated that the PGM signal increased with the increasing miRNA level, and exhibited a good linear dependence on the miRNA-21 concentration from 50 pM to 5.0 nM with a detection limit of 19 pM under optimum conditions. Additionally, multifunctional mesoporous silica nanoparticles also showed good stability and favorable selectivity, and satisfactory accuracy for the miRNA detection in cell lysates with quantitative real-time polymerase chain reaction (qRT-PCR). Such good analytical performance endows it as a promising scheme for the efficient and convenient detection of miRNA in clinical diagnosis and therapy. Graphical abstractAn electrochemical sensing system is designed for detection of microRNA-21 based on target-induced glucose release from propylamine-functionalized mesoporous silica nanoparticle with glucometer readout.
Keywords: Electrochemical assay; MicroRNA-21; Multifunctional mesoporous silica nanoparticles; Personal glucometer; Competitive displacement reaction

Metabolomic spectral libraries for data-independent SWATH liquid chromatography mass spectrometry acquisition by Tobias Bruderer; Emmanuel Varesio; Anita O. Hidasi; Eva Duchoslav; Lyle Burton; Ron Bonner; Gérard Hopfgartner (1873-1884).
obtained his PhD under the supervision of Prof. Gérard Hopfgartner at the University of Geneva. He is an analytical chemist with focus on high-resolution mass spectrometry. His current research aims to develop molecular breath analysis for asthma preschool diagnosis and early infection screening in cystic fibrosis patients in the Moeller group at the Children’s University Hospital Zurich and the Zenobi group at ETH Zurich. is a senior lecturer at the School of Pharmaceutical Sciences and Executive Director of the Mass Spectrometry core facility of the Faculty of Sciences at University of Geneva. Besides his interest in new MS-based techniques and strategies like data-independent acquisition, he likes to teach and implement such new tools at the core facility to support scientists in their research. is a postdoctoral associate in the Life Sciences Mass Spectrometry group in the Department of Inorganic and Analytical Chemistry at the University of Geneva. She is a biochemist with experience in toxicology, molecular biology, and bioanalytics including LC-MS-based omics approaches, furthermore working with the animal model zebrafish (Danio rerio) embryo. She is interested in exploring biomarkers of chemical exposures and diseases. Her current research focuses on data-independent acquisition and electron-based dissociation in metabolomics. works as a senior staff research scientist at SCIEX, focusing on new mass spectrometry data collection and processing concepts, enabling automation of small molecule qualitative applications, such as identification of endogenous and exogenous metabolites and characterization and profiling of lipids. is a senior research scientist at Sciex and is based near Toronto, Canada. He is interested in many aspects of LC-MS data processing to extract useful information from raw data with a particular focus on the areas of metabolomics, biologics, and quantitative data analysis. is the Principal of Ron Bonner Consulting which he started following a 40-year career in mass spectrometry research. He continues to explore mass spectrometry applications such as metabolomics and proteomics and is particularly interested in the analysis and interpretation of complex data and in compound identification. is Professor for Analytical Chemistry and Mass Spectrometry at the Department of Analytical and Inorganic Chemistry of the University of Geneva. His research interests focus on the development and application of novel hyphenated mass spectrometry in the field of life sciences. High-quality mass spectral libraries have become crucial in mass spectrometry-based metabolomics. Here, we investigate a workflow to generate accurate mass discrete and composite spectral libraries for metabolite identification and for SWATH mass spectrometry data processing. Discrete collision energy (5–100 eV) accurate mass spectra were collected for 532 metabolites from the human metabolome database (HMDB) by flow injection analysis and compiled into composite spectra over a large collision energy range (e.g., 10–70 eV). Full scan response factors were also calculated. Software tools based on accurate mass and predictive fragmentation were specially developed and found to be essential for construction and quality control of the spectral library. First, elemental compositions constrained by the elemental composition of the precursor ion were calculated for all fragments. Secondly, all possible fragments were generated from the compound structure and were filtered based on their elemental compositions. From the discrete spectra, it was possible to analyze the specific fragment form at each collision energy and it was found that a relatively large collision energy range (10–70 eV) gives informative MS/MS spectra for library searches. From the composite spectra, it was possible to characterize specific neutral losses as radical losses using in silico fragmentation. Radical losses (generating radical cations) were found to be more prominent than expected. From 532 metabolites, 489 provided a signal in positive mode [M+H]+ and 483 in negative mode [M-H]. MS/MS spectra were obtained for 399 compounds in positive mode and for 462 in negative mode; 329 metabolites generated suitable spectra in both modes. Using the spectral library, LC retention time, response factors to analyze data-independent LC-SWATH-MS data allowed the identification of 39 (positive mode) and 72 (negative mode) metabolites in a plasma pool sample (total 92 metabolites) where 81 previously were reported in HMDB to be found in plasma. Graphical abstractLibrary generation workflow for LC-SWATH MS, using collision energy spread, accurate mass, and fragment annotation.
Keywords: MS/MS libraries; High-resolution LC-MS; Data-independent acquisition; SWATH; Metabolomics

Extraction and detection of bisphenol A in human serum and urine by aptamer-functionalized magnetic nanoparticles by Yu Su; Chenggang Shao; Xielin Huang; Jinxia Qi; Renshan Ge; Huaqin Guan; Zhenkun Lin (1885-1891).
A new type of magnetic nanoparticles (MNPs), as the absorbents of bisphenol A (BPA), was prepared by functionalization of Fe3O4@SiO2 with BPA-specific aptamer in this work. ssDNA aptamer was immobilized on the Fe3O4@SiO2 surface through biotin-avidin interactions, playing a role of the specific probe for BPA. The resultant materials (Apt-MNPs) exhibited outstanding magnetic responsibility and can be separated efficiently by the magnetic field. Experimental results also showed that Apt-MNPs had large adsorption capacity and high competitive selectivity for the targeted compound BPA. Furthermore, Apt-MNPs were adopted as the specific absorbents to extract and enrich BPA from human serum and urine samples. Therefore, an efficient detection method of BPA was developed in combination with high-performance liquid chromatography (HPLC). The linearity of the method was over a range of 5–10,000 ng mL−1 with a correlation coefficient of 0.99997, and the limit of detections (LODs) for serum and urine were 2.0 and 1.0 ng mL−1, respectively. The recoveries of BPA in the spiked human serum and urine samples were 90.8 ± 7.3% (RSD) and 92.3 ± 1.5%, respectively. Our results demonstrated that Apt-MNPs were high-performance adsorbents for extracting and enriching BPA, resulting in fast and efficient detection of BPA in serum and urine samples. Graphical abstractAptamer-MNPs were effective for BPA separation from serum and urine
Keywords: ssDNA aptamer; Magnetic nanoparticles; Bisphenol A; Serum; Urine

Hexachlorobutadiene (HCBD) was listed as a new controlling persistent organic pollutant in the Stockholm Convention because of its wide industrial applications and potential genotoxicity and carcinogenicity. However, only limited information exists on the release of HCBD from unintentional sources, such as waste incineration. Identification and quantification of HCBD in fly ash, one of the major outputs of waste incineration, is imperative. This work presents a simple method for determining HCBD in waste incineration fly ash based on ultrasonic extraction coupled with a silica gel–Florisil column cleanup followed by gas chromatography–mass spectrometry detection. Two typical persistent organic pollutants, pentachlorobenzene (PeCB) and hexachlorobenzene (HCB), were measured simultaneously. The parameters that influence the extraction efficiency and the quality of instrument detection were studied. Under the optimum experimental conditions, high sensitivity (detection limit 0.25–0.53 ng g-1), acceptable recoveries (64.0–71.4%) at spiking levels of 5–500 ng g-1, and good repeatability [relative standard deviation (n = 3) of 14% or less] were achieved for all target analytes. The validation of this method was performed by analysis of six real fly ash samples from different waste incinerators in eastern China. The concentrations of HCBD detected in these samples (1.39–97.6 ng g-1) were comparable to those of PeCB (1.22–150 ng g-1) and HCB (0.82–120 ng g-1), indicating that the residual HCBD as well as PeCB and HCB in waste incineration fly ash should not be ignored. The results confirm for the first time that waste incineration is an unintentional source of HCBD in China. Graphical abstractAn analytical method for hexachlorobutadiene, pentachlorobenzene, and hexachlorobenzene in fly ash from waste incineration. GC-MS gas chromatography–mass spectrometry, Ph-d10 phenanthrene-d 10
Keywords: Persistent organic pollutants; Hexachlorobutadiene; Pentachlorobenzene; Hexachlorobenzene; Waste incineration fly ash; Ultrasonic extraction

Multiplex highly sensitive immunochromatographic assay based on the use of nonprocessed antisera by Nadezhda A. Byzova; Alexandr E. Urusov; Anatoly V. Zherdev; Boris B. Dzantiev (1903-1910).
The format of an immunochromatographic multiassay is first proposed with native antisera and a universal conjugate of antispecies antibodies with gold nanoparticles. This format allows (1) the exclusion of purification and conjugation stages for specific antibodies and (2) significant reduction of the concentration of specific antibodies in the system. The independent use of specific antibodies and a conjugated marker provided a low detection limit and high signal intensity. The proposed format was implemented for the simultaneous detection of two herbicides. The instrumental limits for the detection of atrazine and chlorsulfuron were 0.1 and 0.7 ng/mL, respectively, and the analysis time was 20 min. The suitability of the test system for monitoring these herbicides in nontreated apple and blackcurrant juices is shown. The assay technique is simple, sensitive, and easily transferrable to any other antigen. Graphical abstractThe proposed format of the immunochromatographic multiassay is based on the use of native antisera and a universal conjugate of antispecies antibodies with gold nanoparticles. In this way purification and conjugation stages for specific antibodies are excluded, and the concentrations of specific antibodies and the conjugated marker can be varied independently to obtain a low detection limit.
Keywords: Immunoassay; Lateral flow assay; Test strips; Gold nanoparticles; Indirect labeling; Herbicides

Spatially resolved chemical analysis of cicada wings using laser-ablation electrospray ionization (LAESI) imaging mass spectrometry (IMS) by Jessica K. Román; Callee M. Walsh; Junho Oh; Catherine E. Dana; Sungmin Hong; Kyoo D. Jo; Marianne Alleyne; Nenad Miljkovic; Donald M. Cropek (1911-1921).
Laser-ablation electrospray ionization (LAESI) imaging mass spectrometry (IMS) is an emerging bioanalytical tool for direct imaging and analysis of biological tissues. Performing ionization in an ambient environment, this technique requires little sample preparation and no additional matrix, and can be performed on natural, uneven surfaces. When combined with optical microscopy, the investigation of biological samples by LAESI allows for spatially resolved compositional analysis. We demonstrate here the applicability of LAESI-IMS for the chemical analysis of thin, desiccated biological samples, specifically Neotibicen pruinosus cicada wings. Positive-ion LAESI-IMS accurate ion-map data was acquired from several wing cells and superimposed onto optical images allowing for compositional comparisons across areas of the wing. Various putative chemical identifications were made indicating the presence of hydrocarbons, lipids/esters, amines/amides, and sulfonated/phosphorylated compounds. With the spatial resolution capability, surprising chemical distribution patterns were observed across the cicada wing, which may assist in correlating trends in surface properties with chemical distribution. Observed ions were either (1) equally dispersed across the wing, (2) more concentrated closer to the body of the insect (proximal end), or (3) more concentrated toward the tip of the wing (distal end). These findings demonstrate LAESI-IMS as a tool for the acquisition of spatially resolved chemical information from fragile, dried insect wings. This LAESI-IMS technique has important implications for the study of functional biomaterials, where understanding the correlation between chemical composition, physical structure, and biological function is critical. Graphical abstractPositive-ion laser-ablation electrospray ionization mass spectrometry coupled with optical imaging provides a powerful tool for the spatially resolved chemical analysis of cicada wings
Keywords: Laser-ablation electrospray ionization; Imaging; Mass spectrometry; Cicada wings; Spatial resolution; Insect hydrocarbons

Magnetofluorescent nanocomposites with optimal magnetic and fluorescent properties were prepared and characterized by combining magnetic nanoparticles (iron oxide@polymethyl methacrylate) with fluorescent nanoparticles (rhodamine 6G@mSiO2). Experimental parameters were optimized to produce nanocomposites with high magnetic susceptibility and fluorescence intensity. The detection of a model biomarker (alpha-fetoprotein) was used to demonstrate the feasibility of applying the magnetofluorescent nanocomposites combined with quantum dots and using magnetic fluorescence-linked immunoassay. The magnetofluorescent nanocomposites enable efficient mixing, fast re-concentration, and nanoparticle quantization for optimal reactions. Biofunctional quantum dots were used to confirm the alpha-fetoprotein (AFP) content in sandwich immunoassay after mixing and washing. The analysis time was only one third that required in ELISA. The detection limit was 0.2 pg mL−1, and the linear range was 0.68 pg mL−1–6.8 ng mL−1. This detection limit is lower, and the linear range is wider than those of ELISA and other methods. The measurements made using the proposed method differed by less than 13% from those obtained using ELISA for four AFP concentrations (0.03, 0.15, 0.75, and 3.75 ng mL−1). The proposed method has a considerable potential for biomarker detection in various analytical and biomedical applications. Graphical abstractMagnetofluorescent nanocomposites combined with fluorescent quantum dots were used in magnetic fluorescence-linked immunoassay.
Keywords: Magnetofluorescent nanocomposites; Quantum dots; Magnetic fluorescence-linked immunoassay

Performance of combined fragmentation and retention prediction for the identification of organic micropollutants by LC-HRMS by Meng Hu; Erik Müller; Emma L. Schymanski; Christoph Ruttkies; Tobias Schulze; Werner Brack; Martin Krauss (1931-1941).
In nontarget screening, structure elucidation of small molecules from high resolution mass spectrometry (HRMS) data is challenging, particularly the selection of the most likely candidate structure among the many retrieved from compound databases. Several fragmentation and retention prediction methods have been developed to improve this candidate selection. In order to evaluate their performance, we compared two in silico fragmenters (MetFrag and CFM-ID) and two retention time prediction models (based on the chromatographic hydrophobicity index (CHI) and on log D). A set of 78 known organic micropollutants was analyzed by liquid chromatography coupled to a LTQ Orbitrap HRMS with electrospray ionization (ESI) in positive and negative mode using two fragmentation techniques with different collision energies. Both fragmenters (MetFrag and CFM-ID) performed well for most compounds, with average ranking the correct candidate structure within the top 25% and 22 to 37% for ESI+ and ESI− mode, respectively. The rank of the correct candidate structure slightly improved when MetFrag and CFM-ID were combined. For unknown compounds detected in both ESI+ and ESI−, generally positive mode mass spectra were better for further structure elucidation. Both retention prediction models performed reasonably well for more hydrophobic compounds but not for early eluting hydrophilic substances. The log D prediction showed a better accuracy than the CHI model. Although the two fragmentation prediction methods are more diagnostic and sensitive for candidate selection, the inclusion of retention prediction by calculating a consensus score with optimized weighting can improve the ranking of correct candidates as compared to the individual methods. Graphical abstractConsensus workflow for combining fragmentation and retention prediction in LC-HRMS-based micropollutant identification
Keywords: LC-HRMS; Environmental contaminants; Structure elucidation; Fragmentation prediction; Retention prediction; Micropollutants

Cherry stems have been used in traditional medicine mostly for the treatment of urinary tract infections. Extraction with subcritical water, according to its selectivity, efficiency and other aspects, differs substantially from conventional extraction techniques. The complexity of plant subcritical water extracts is due to the ability of subcritical water to extract different chemical classes of different physico-chemical properties and polarities in a single run. In this paper, dispersive liquid-liquid microextraction (DLLME) with simultaneous derivatisation was optimised for the analysis of complex subcritical water extracts of cherry stems to allow simple and rapid preparation prior to gas chromatography-mass spectrometry (GC-MS). After defining optimal extracting and dispersive solvents, the optimised method was used for the identification of compounds belonging to different chemical classes in a single analytical run. The developed sample preparation protocol enabled simultaneous extraction and derivatisation, as well as convenient coupling with GC-MS analysis, reducing the analysis time and number of steps. The applied analytical protocol allowed simple and rapid chemical screening of subcritical water extracts and was used for the comparison of subcritical water extracts of sweet and sour cherry stems. Graphical abstractDLLME GC MS analysis of cherry stem extracts obtained by subcritical water
Keywords: Subcritical water extraction; Cherry stems; Dispersive liquid-liquid microextraction; GC-MS

A sensitive method using SPME pre-concentration for the quantification of aromatic amines in indoor air by Vincent Lucaire; Jean-Jacques Schwartz; Olivier Delhomme; Ruben Ocampo-Torres; Maurice Millet (1955-1963).
Monitoring the levels of aliphatic and aromatic amines (AA) in indoor air is important to protect human health because of exposure to these compounds through diet and inhalation. A sampling and analytical method using XAD-2 cartridges and gas chromatography coupled to mass spectrometry used for assessing 25 AA in different smoking and non-smoking indoor environment was developed. After sampling and delivering 1 m3 of air (6–8 h sampling), an adsorbent was ultrasonically extracted with acetonitrile, concentrated to 1 mL and diluted in 25 mL of water (pH = 9; 5% NaCl), and then extracted for 40 min at 80 °C using a divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber and injected in a GC/MS system. With this method, 22 of the 25 AA can be analyzed with detection limits up to five times lower than that of classic liquid injection. Benzylamine, 3-aminophenol, and 4-aminophenol were not detected with the solid-phase micro-extraction (SPME) method. It can be assumed that aminophenols required a derivatization step for their analysis by GC as these molecules were not detected regardless of the injection mode used. Graphical abstractAnalysis of aromatic amines in indoor air by SPME-GC/MS
Keywords: Aromatic amines; SPME; Indoor air

Comprehensive targeted and non-targeted lipidomics analyses in failing and non-failing heart by Ganesh V. Halade; Anela Dorbane; Kevin A. Ingle; Vasundhara Kain; Jean-Marie Schmitter; Boutayna Rhourri-Frih (1965-1976).
Myocardial infarction (MI) and subsequent progressive heart failure pathology is the major cause of death worldwide; however, the mechanism of this pathology remains unclear. The present work aimed at testing the hypothesis whether the inflammatory response is superimposed with the formation of bioactive lipid resolving molecules at the site of the injured myocardium in acute heart failure pathology post-MI. In this view, we used a robust permanent coronary ligation model to induce MI, leading to decreased contractility index with marked wall thinning and necrosis of the infarcted left ventricle. Then, we applied mass spectrometry imaging (MSI) in positive and negative ionization modes to characterize the spatial distribution of left ventricle lipids in the infarcted myocardium post-MI. After micro-extraction, liquid chromatography coupled to tandem mass spectrometry was used to confirm the structures of the imaged lipids. Statistical tools such as principal component analysis were used to establish a comprehensive visualization of lipid profile changes in MI and no-MI hearts. Resolving bioactive molecules such as resolvin (Rv) D1, RvD5, RvE3, 17-HDHA, LXA4, and 18-HEPE were detected in negative ion mode MSI, whereas phosphatidyl cholines (PC) and oxidized derivatives thereof were detected in positive ion mode. MSI-based analysis demonstrated a significant increase in resolvin bioactive lipids with comprehensive lipid remodeling at the site of infarction. These results clearly indicate that infarcted myocardium is the primary location of inflammation-resolution pathomechanics which is critical for resolution of inflammation and heart failure pathophysiology. Graphical abstractApplied scheme to determine comprehensive lipidomics in failing and non-failing heart.
Keywords: Myocardial infarction; Lipids; Ischemic myocardium; Resolution of inflammation; Bioactive lipid molecules

Trace analysis of pesticide residues in sediments using liquid chromatography–high-resolution Orbitrap mass spectrometry by Christina I. Nannou; Vasiliki I. Boti; Triantafyllos A. Albanis (1977-1989).
The present study describes the optimization and validation of an analytical method based on quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction and purification with dispersive solid-phase extraction (dSPE) before analysis, followed by ultrahigh-performance liquid chromatography–high-resolution linear ion trap/Orbitrap (LTQ Orbitrap) mass spectrometry for the determination of 18 pesticides in sediment. To optimize process efficiency, parameters such as pH, extraction salts, sediment amount, and cleanup sorbents were evaluated. Identification was based on both accurate mass and retention time, and further confirmation was achieved by mass spectrometry fragmentation. The optimized analytical method demonstrated good validation characteristics, such as accuracy (recoveries from 70.8% to 106.2%), method quantification limits (below 10 ng g-1 for 89% of the pesticides selected), linearity (coefficient of determination greater than 0.9921 in all cases), precision (repeatability and reproducibility with standard deviations below 18% and 21%, respectively), and matrix effect (signal suppression was exhibited for almost all analytes). The overall method performance, expressed as process efficiency, ranged from 58.8% to 102.1%. The validated method was successfully applied to real samples collected along two rivers in northwestern Greece, revealing the presence of three selected pesticides but at levels below the method quantification limit.
Keywords: Pesticides; Sediments; Trace analysis; QuEChERS; Liquid chromatography–LTQ Orbitrap mass spectrometry

G-quadruplex aptamer selection using capillary electrophoresis-LED-induced fluorescence and Illumina sequencing by Audrey Ric; Vincent Ecochard; Jason S. Iacovoni; Audrey Boutonnet; Frédéric Ginot; Varravaddheay Ong-Meang; Véréna Poinsot; Laurent Paquereau; François Couderc (1991-2000).
One of the major difficulties that arises when selecting aptamers containing a G-quadruplex is the correct amplification of the ssDNA sequence. Can aptamers containing a G-quadruplex be selected from a degenerate library using non-equilibrium capillary electrophoresis (CE) of equilibrium mixtures (NECEEM) along with high-throughput Illumina sequencing? In this article, we present some mismatches of the G-quadruplex T29 aptamer specific to thrombin, which was PCR amplified and sequenced by Illumina sequencing. Then, we show the proportionality between the number of sequenced molecules of T29 added to the library and the number of sequences obtained in Illumina sequencing, and we find that T29 sequences from this aptamer can be detected in a random library of ssDNA after the sample is fractionated by NECEEM, amplified by PCR, and sequenced. Treatment of the data by the counting of double-stranded DNA T29 sequences containing a maximum of two mismatches reveals a good correlation with the enrichment factor (f E). This factor is the ratio of the number of aptamer sequences found in the collected complex sample divided by the total number of sequencing reads (aptamer and non-aptamer) plus the quantity of T29 molecules (spiked into a DNA library) injected into CE.
Keywords: Aptamer; Capillary electrophoresis; Biomolecule; Thrombin

A near-infrared fluorescent sensor with large Stokes shift for rapid and highly selective detection of thiophenols in water samples and living cells by Rongjin Zeng; Qian Gao; Fenmin Cheng; Yunshan Yang; Peisheng Zhang; Shu Chen; Heping Yang; Jian Chen; Yunfei Long (2001-2009).
The development of simple methods with high sensitivity and selectivity to differentiate toxic aromatic thiols (thiophenols) from aliphatic thiols (cysteine, homocysteine, and glutathione) and hydrogen sulfide (H2S) is of great significance. Herein, we report on the fabrication of a novel near-infrared (NIR) fluorescent sensor for rapid and highly selective detection of thiophenols through the photoinduced electron transfer (PET) mechanism. In the presence of the thiophenols, an obvious enhancement of NIR fluorescence at 658 nm could be visualized with the aid of nucleophilic aromatic substitution (SNAr) reaction. The sensor displays large Stokes shift (~ 227 nm), fast response time (< 30 s), high sensitivity (~ 8.3 nM), and good biocompatibility. Moreover, the as-prepared sensor possesses an excellent anti-interference feature even when other possible interferents exist (aliphatic thiols and H2S) and has been successfully utilized for thiophenol detection in both water samples and living cells. Graphical abstractIllustration of the sensor for thiophenol imaging in living cells
Keywords: Thiophenols; NIR fluorescence; Live cell imaging

Simultaneous quantification of endogenous and exogenous plasma glucose by isotope dilution LC-MS/MS with indirect MRM of the derivative tag by Lingling Yu; Chao Wen; Xing Li; Shiqi Fang; Lichuan Yang; Tony Wang; Kaifeng Hu (2011-2018).
Quantification of endogenous and exogenous plasma glucose can help more comprehensively evaluate the glucose metabolic status. A ratio-based approach using isotope dilution liquid chromatography tandem mass spectrometry (ID LC-MS/MS) with indirect multiple reaction monitoring (MRM) of the derivative tag was developed to simultaneously quantify endo-/exogenous plasma glucose. Using diluted D-[13C6] glucose as tracer of exogenous glucose, 12C6/13C6 glucoses were first derivatized and then data were acquired in MRM mode. The metabolism of exogenous glucose can be tracked and the concentration ratio of endo/exo-genous glucose can be measured by calculating the endo-/exo-genous glucose concentrations from peak area ratio of specific daughter ions. Joint application of selective derivatization and MRM analysis not only improves the sensitivity but also minimizes the interference from the background of plasma, which warrants the accuracy and reproducibility. Good agreement between the theoretical and calculated concentration ratios was obtained with a linear correlation coefficient (R) of 0.9969 in the range of D-glucose from 0.5 to 20.0 mM, which covers the healthy and diabetic physiological scenarios. Satisfactory reproducibility was obtained by evaluation of the intra- and inter-day precisions with relative standard deviations (RSDs) less than 5.16%, and relative recoveries of 85.96 to 95.92% were obtained at low, medium, and high concentration, respectively. The method was successfully applied to simultaneous determination of the endo-/exogenous glucose concentration in plasma of non-diabetic and type II diabetic cynomolgus monkeys. Graphical AbstractThe scheme of the proposed ratio-based approach using isotope dilution LC-MS/MS with indirect MRM of the derivative tag for simultaneous quantification of endogenous and exogenous plasma glucose.
Keywords: Derivatization; Diabetes; Endogenous glucose; Exogenous glucose; LC-MS/MS

In this work, high-performance non-enzymatic catalysts based on 3D hierarchical hollow porous Co3O4 nanododecahedras in situ decorated on carbon nanotubes (3D Co3O4-HPND/CNTs) were successfully prepared via direct carbonizing metal-organic framework-67 in situ grown on carbon nanotubes. The morphology, microstructure, and composite of 3D Co3O4-HPND/CNTs were characterized by scanning electron microscopy, transmission electron microscopy, micropore and chemisorption analyzer, and X-ray diffraction. The electrochemical characterizations indicated that 3D Co3O4-HPND/CNTs present considerably catalytic activity toward glucose oxidation and could be promising for constructing high-performance electrochemical non-enzymatic glucose sensors and glucose/O2 biofuel cell. When used for non-enzymatic glucose detection, the 3D Co3O4-HPND/CNTs modified glassy carbon electrode (3D Co3O4-HPND/CNTs/GCE) exhibited excellent analytical performance with high sensitivity (22.21 mA mM−1 cm−2), low detection limit of 0.35 μM (S/N = 3), fast response (less than 5 s) and good stability. On the other hand, when the 3D Co3O4-HPND/CNTs/GCE worked as an anode of a biofuel cell, a maximum power density of 210 μW cm−2 at 0.15 V could be obtained, and the open circuit potential was 0.68 V. The attractive 3D hierarchical porous structural features, the large surface area, and the excellent conductivity based on the continuous and effective electron transport network in 3D Co3O4-HPND/CNTs endow 3D Co3O4-HPND/CNTs with the enhanced electrochemical performance and promising applications in electrochemical sensing, biofuel cell, and other energy storage and conversion devices such as supercapacitor. Graphical abstractHigh-performance non-enzymatic catalysts for enzymeless glucose sensing and biofuel cell based on 3D hierarchical hollow porous Co3O4 nanododecahedras anchored on carbon nanotubes were successfully prepared via direct carbonizing metal-organic framework-67 in situ grown on carbon nanotubes.
Keywords: Metal-organic frameworks; Co3O4 nanododecahedras; Carbon nanotubes; In situ fabrication; Non-enzymatic glucose detection; Biofuel cells

In this work, the suitability of Fe3O4 nanoparticles coated with polydopamine was evaluated as sorbent for the extraction of a group of 21 compounds with oestrogenic activity including seven phytoestrogens, six mycotoxins as well as four synthetic and four natural oestrogens from different types of milk, including sheep milk, in which the evaluation of oestrogenic compounds have never been developed before. Extraction was carried out using magnetic micro-dispersive solid-phase extraction after a previous deproteinisation step. Separation, determination and quantification of the target analytes were achieved by ultra-high-performance liquid chromatography coupled to triple quadrupole-tandem mass spectrometry. The methodology was validated for five milk samples using 17β-estradiol-2,4,16,16,17-d5 as internal standard for natural and synthetic oestrogens, β-zearalanol-10,10,11,12,12-d5 for mycotoxins and prunetin for phytoestrogens. Recovery values ranged from 70 to 120% for the five types of matrices with relative standard deviation values lower than 18%. Limits of quantification of the method were in the range 0.55–11.8 μg L−1 for all samples. Graphical abstractGeneral scheme of the multiresidue analysis of oestrogenic compounds in milk using core-shell polydopamine coated magnetic nanoparticles as extraction sorbent in μ-dSPE
Keywords: Oestrogenic compounds; Magnetic nanoparticles; Micro-dispersive solid-phase extraction; Milk; Ultra-high-performance liquid chromatography; Tandem mass spectrometry

The authors would like to call the reader’s attention to the fact that unfortunately during a recent cross-check of the experimental record, they found that the positions of intercept and slope were reversed in Table 1 in the original manuscript. The authors apologize for the mistake.