Analytical and Bioanalytical Chemistry (v.410, #25)

Fading lemonade challenge by Hervé This (6339-6340).

Solution to best food reference material challenge by Melissa Phillips (6341-6342).

Instrumental analysis of microplastics—benefits and challenges by Sven Huppertsberg; Thomas P. Knepper (6343-6352).
is a PhD student working on the German national project Microplastic in the Freshwater Cycle (MiWa) at Hochschule Fresenius, University of Applied Sciences. His research focusses, besides microplastic analysis via FT-IR, on the investigation of the sorption behavior of organic chemicals to microplastic particles. is Vice President for Research and Research Funding of Hochschule Fresenius, University of Applied Sciences, Germany, and Director of the Institute for Analytical Research. He and his group have been working in the analytical field of synthetic polymers in the environment for more than 15 years. There is a high demand for easy, cheap, comparable, and robust methods for microplastic (MP) analysis, due to the ever-increasing public and scientific interest in (micro-) plastic pollution in the environment. Today, a multitude of methodologies for sampling, sample preparation, and analysis of MPs are in use. This feature article deals with the most prominent detection methods as well as with sampling strategies and sample preparation techniques. Special emphasis is on their benefits and challenges. Thus, spectroscopic methods, coupled with microscopy, require time-consuming sample preparation and extended measurement times, whereas thermo-analytical methods are faster but lack the ability to determine the size distribution in samples. To that effect, most of the described methods are applicable depending on the defined analytical question. Graphical abstractᅟ
Keywords: Microplastic; Spectrometry; Thermo-analytical methods

Electromigration separation techniques often demand certain compounds in the electrolyte to achieve the required selectivity and efficiency. These compounds, including the electrolyte itself, ampholytes, polymeric compounds for sieving, complexing agents, tensides, etc. are often non-volatile. Thus, interference with the electrospray ionization process is a common issue, impeding direct coupling of such electrolyte systems to mass spectrometry. Still, several options exist to obtain mass spectra after separation, including offline fractionation, alternative ionization, dilution, or the change to volatile constituents. In the first part of this article, these methods are discussed. However, all of these options are a compromise of separation performance and sensitivity of mass spectrometric detection. Two-dimensional capillary electrophoresis-mass spectrometry (CE-CE-MS) systems represent a promising alternative to the aforementioned challenges, as they allow the use of existing methods with best separation performance in combination with sensitive mass characterization. In this context, the second part of this article is dedicated to the advantages, limitations, and applications of this approach. Finally, an outlook towards future developments is given.
Keywords: Capillary electrophoresis; Electrospray ionization; Two-dimensional separation; Interference-free mass spectrometry; Pharmaceutical analysis; 2D interface

Where are modern flow techniques heading to? by Burkhard Horstkotte; Manuel Miró; Petr Solich (6361-6370).
This article aims to provide an overview on the transition from earlier laboratory automation using analytical flow approaches toward today’s applications of flow methodologies, recent developments, and future trends. The article is directed to flow practitioners while serving as a valuable reference to newcomers in the field in providing insight into flow techniques and conceptual differences in operation across the distinct flow generations. In the focus are the recently developed and complementary techniques Lab-On-Valve and Lab-In-Syringe. In the following, a brief comparison of the different application niches and contributions of flow techniques to past and modern analytical chemistry is given, including (i) the development of sample pretreatment approaches, (ii) the potential applicability for in-situ/on-site monitoring of environmental compartments or technical processes, (iii) the ability of miniaturization of laboratory chemistry, (iv) the unique advantages for implementation of kinetic assays, and finally (v) the beneficial online coupling with scanning or separation analytical techniques. We also give a critical comparison to alternative approaches for automation based on autosamplers and robotic systems. Finally, an outlook on future applications and developments including 3D prototyping and specific needs for further improvements is given. Graphical abstractᅟ
Keywords: Flow techniques; Automation and miniaturization; Lab-On-Valve and Lab-In-Syringe; Sample pretreatment; Monitoring and surveillance; Hyphenation

Lifestyle optimizations are implementable changes that can have an impact on health and disease. Nutrition is a lifestyle optimization that has been shown to be of great importance in cancer initiation, progression, and metastasis. Dozens of clinical trials are currently in progress that focus on the nutritional modifications that cancer patients can make prior to and during medical care that increase the efficacy of treatment. In this review, we discuss various nutritional inventions for cancer patients and the analytical approaches to characterize the downstream molecular effects. We first begin by briefly explaining the many different forms of nutritional intervention currently being used in cancer treatment as well as their motivating biology. The forms of nutrient modulation described in this review include calorie restriction, the different practices of fasting, and carbohydrate restriction. The review then shifts to explain how proteomics is used to determine biomarkers of cancer and how it can be utilized in the future to determine the metabolic phenotype of a tumor, and inform physicians if nutritional intervention should be recommended for a cancer patient. Nutrigenomics aims to understand the relationship of nutrients and gene expression and can be used to understand the downstream molecular effects of nutrition restriction, partially through proteomic analysis. Proteomics is just beginning to be used as cancer diagnostic and predictive tools. However, these approaches have not been used to their full potential to understand nutritional intervention in cancer. Graphical abstractᅟ
Keywords: Cancer; Nutrition; Fasting; Mass spectrometry; Nutritional proteomics

Over the past decade, mass spectrometry (MS)-based “shotgun lipidomics” has emerged as a powerful tool for quantitative and qualitative analysis of the complex lipids in the biological system. The aim of this critical review is to give the interested reader a concise overview of the current state of the technology, focused on lipidomic analysis by mass spectrometry. The pros and cons, and pitfalls associated with each available “shotgun lipidomics” method are discussed; and the new strategies for improving the current methods are described. A list of important papers and reviews that are sufficient rather than comprehensive, covering all the aspects of lipidomics including the workflow, methodology, and fundamentals is also compiled for readers to follow. Graphical abstractᅟ
Keywords: Lipidomics; Mass spectrometry; Electrospray ionization; MALDI; Collision induced dissociation; Lipid

Non-volatile compounds in exhaled breath condensate: review of methodological aspects by Elaheh Rahimpour; Maryam Khoubnasabjafari; Vahid Jouyban-Gharamaleki; Abolghasem Jouyban (6411-6440).
In contrast to bronchial and nasal lavages, the analysis of exhaled breath condensate (EBC) is a promising, simple, non-invasive, repeatable, and diagnostic method for studying the composition of airway lining fluid with the potential to assess lung inflammation, exacerbations, and disease severity, and to monitor the effectiveness of treatment regimens. Recent investigations have revealed the potential applications of EBC analysis in systemic diseases. In this review, we highlight the analytical studies conducted on non-volatile compounds/biomarkers in EBC. In contrast to other related articles, this review is classified on the basis of analytical techniques and includes almost all the applied methods and their methodological limitations for quantification of non-volatile compounds in EBC samples, providing a guideline for further researches. The studies were identified by searching the SCOPUS database with the keywords “biomarkers,” “non-volatile compounds,” “determination method,” and “EBC.”
Keywords: Exhaled breath condensate; Non-volatile compounds; Biomarkers; Analytical methods

Supercritical fluid chromatography (SFC), which employs pressurized carbon dioxide as the major component of the mobile phase, has been known for several decades but has faced a significant resurgence of interest in the recent years, thanks to the development of modern instruments to comply with current expectations in terms of robustness and sensitivity. This review is focused on the recent literature, specifically since the introduction of modern systems but in relation to older literature, to identify the changing trends in application domains. Typically, natural products, bioanalysis, food science, and environmental analyses are all strongly increasing. Together with reduced extra-column volumes in the instruments, the advent of sub-2-μm particles and superficially porous particles in the stationary phases is favoring ultra-high-performance SFC (UHPSFC) allowing for improved resolution and faster analyses, but without the constraints of viscous liquids encountered in ultra-high-performance liquid chromatography (UHPLC). Hyphenation to mass spectrometry is also more frequent and opened the way to new application domains, and raises different issues from liquid chromatography mobile phases, especially due to decompression of carbon dioxide. It is also shown that the frontiers between SFC and HPLC are fading, as switching from one method to the other, even within the course of a single analysis, is facilitated my modern instruments. The present review is not intended to be exhaustive but rather giving a snapshot of recent trends in supercritical fluid chromatography, based on the observation of about 500 papers published in English-written peer-reviewed journals from 2014 to 2018. Graphical abstractᅟ
Keywords: Convergence chromatography; Hyphenation to mass spectrometry; Supercritical fluid chromatography; Ultra-high-performance supercritical fluid chromatography

Selective non-enzymatic total bilirubin detection in serum using europium complexes with different β-diketone-derived ligands as luminescence probes by Wei Yang; Jinfeng Xia; Guohong Zhou; Danyu Jiang; Qiang Li; Shiwei Wang; Xiaohong Zheng; Xi Li; Yibo Shen; Xin Li (6459-6468).
Three europium(III) complexes, Eu(ectfd)3 (Hectfd = 1-(9-ethyl-9H-carbazol-7-yl)-4,4,4-trifluorobutane-1,3-dione), Eu(tta)3 (Htta = 4,4,4-trifluoro-1-(thiophen-2-yl)-butane-1,3-dione), and Eu(dbt)3 (Hdbt = 2-(4',4',4'-trifluoro-1',3'-dioxobutyl)dibenzothiophene), were synthesized and employed to detect total bilirubin (BR) in blood-serum samples. UV-visible absorption and fluorescence (FL) spectroscopies were used to evaluate the selectivity of each europium (III) fluorescence probe to BR, which was shown to remarkably reduce the luminescence intensities of the europium(III) complexes at a wavelength of 612 nm. The luminescence intensity of each complex is linearly related to BR concentration. Eu(tta)3 was shown to be the more-appropriate fluorescence probe for the sensitive and reliable detection of total BR in blood serum samples than either Eu(ectfd)3 or Eu(dbt)3. This observation can be ascribed to special σ-hole bonding between Htta and BR. In addition, the optimal pH test conditions for the detection of BR in human serum by the Eu(tta)3 probe were determined. Sensitivity was shown to be dramatically affected by the pH of the medium. The experimental results reveal that pH 7.5 is optimal for this probe, which coincides with the pH of human serum. Furthermore, BR detection using the Eu(tta)3 luminescence probe is simple, practical, and relatively free of interference from coexisting substances; it has a minimum detection limit (DL) of 68 nM and is a potential candidate for the routine assessment of total BR in serum samples. Graphical Abstractᅟ
Keywords: Total bilirubin; Europium(III) complex; Biosensor; Fluorescence quenching; σ-hole

Evaluation of accuracy dependence of Raman spectroscopic models on the ratio of calibration and validation points for non-invasive glucose sensing by Surya P. Singh; Soumavo Mukherjee; Luis H. Galindo; Peter T. C. So; Ramachandra Rao Dasari; Uzma Zubair Khan; Raghuraman Kannan; Anandhi Upendran; Jeon Woong Kang (6469-6475).
The authors would like to bring to the reader’s attention that the Clarke error grid plot presented in Fig. 3 was generated using codes adapted from following reference.Optical monitoring of blood glucose levels for non-invasive diagnosis is a growing area of research. Recent efforts in this direction have been inclined towards reducing the requirement of calibration framework. Here, we are presenting a systematic investigation on the influence of variation in the ratio of calibration and validation points on the prospective predictive accuracy of spectral models. A fiber-optic probe coupled Raman system has been employed for transcutaneous measurements. Limit of agreement analysis between serum and partial least square regression predicted spectroscopic glucose values has been performed for accurate comparison. Findings are suggestive of strong predictive accuracy of spectroscopic models without requiring substantive calibration measurements. Graphical abstract
Keywords: Diabetes; Raman spectroscopy; Glucose sensing; Partial least squares regression

Subcellular mapping of living cells via synchrotron microFTIR and ZnS hemispheres by K. L. Andrew Chan; Pedro L. V. Fale; Ali Atharawi; Katia Wehbe; Gianfelice Cinque (6477-6487).
FTIR imaging is a label-free, non-destructive method valuably exploited in the study of the biological process in living cells. However, the long wavelength/low spatial resolution and the strong absorbance of water are still key constrains in the application of IR microscopy ex vivo. In this work, a new retrofit approach based on the use of ZnS hemispheres is introduced to significantly improve the spatial resolution on live cell FTIR imaging. By means of two high refractive index domes sandwiching the sample, a lateral resolution close to 2.2 μm at 6 μm wavelength has been achieved, i.e. below the theoretical diffraction limit in air and more than twice the improvement (to ~λ/2.7) from our previous attempt using CaF2 lenses. The ZnS domes also allowed an extended spectral range to 950 cm−1, in contrast to the cut-off at 1050 cm−1 using CaF2. In combination with synchrotron radiation source, microFTIR provides an improved signal-to-noise ratio through the circa 12 μm thin layer of medium, thus allowing detailed distribution of lipids, protein and nucleic acid in the surround of the nucleus of single living cells. Endoplasmic reticula were clearly shown based on the lipid ν(CH) and ν(C=O) bands, while the DNA was imaged based on the ν(PO2 ) band highlighting the nucleus region. This work has also included a demonstration of drug (doxorubicin) in cell measurement to highlight the potential of this approach. Graphical abstract
Keywords: FT-IR imaging; Fourier transform infrared; High definition; Cell systems/single cell analysis; Immersion objective; Anti-cancer drugs

Spectrofluorometric determination of berberine using a novel Au nanocluster with large Stokes shift by Aoli Wen; Xiaoxiao Peng; Pingping Zhang; Yunfei Long; Huiming Gong; Qingru Xie; Ming Yue; Shu Chen (6489-6495).
Berberine hydrochloride (BHC), a natural isoquinoline alkaloid, is widely applied as a an agent in traditional Chinese medicine. Almost all the traditional methods for BHC detection require complicated preprocessing steps or expensive instruments. In this article, we report a simple, rapid, sensitive, and selective method for BHC detection using fluorescent gold nanoclusters (F-AuNCs) as the fluorescent probe with a large Stokes shift of 237 nm. The F-AuNCs prepared with citrate-stabilized stannous chloride and hydrogen tetrachloroaurate(III) as raw materials in an aqueous medium display strong and stable fluorescence at 566 nm. When F-AuNCs are mixed with BHC, the fluorescence of F-AuNCs is effectively quenched. Under optimized conditions, this method allows sensitive and selective measurements of BHC in a concentration ranging from 1.0 × 10-6 to 1.0 × 10-4 mol L-1 with a detection limit of 7.5 × 10-8 mol L-1, which is relatively low among reported spectral methods. This method provides excellent selectivity for the detection of BHC against inorganic anions and natural amino acids. In addition, the BHC content in two different types of berberine tablets was successfully determined by this method and the results showed high accuracy. Graphical Abstractᅟ
Keywords: Berberine hydrochloride; Gold nanoclusters; Fluorescent; Stokes shift

Quantification of Hv1-induced proton translocation by a lipid-coupled Oregon Green 488-based assay by Benjamin Gerdes; Rebecca M. Rixen; Kristina Kramer; Enrico Forbrig; Peter Hildebrandt; Claudia Steinem (6497-6505).
Passive proton translocation across membranes through proton channels is generally measured with assays that allow a qualitative detection of the H+-transfer. However, if a quantitative and time-resolved analysis is required, new methods have to be developed. Here, we report on the quantification of pH changes induced by the voltage-dependent proton channel Hv1 using the commercially available pH-sensitive fluorophore Oregon Green 488-DHPE (OG488-DHPE). We successfully expressed and isolated Hv1 from Escherichia coli and reconstituted the protein in large unilamellar vesicles. Reconstitution was verified by surface enhanced infrared absorption (SEIRA) spectroscopy and proton activity was measured by a standard 9-amino-6-chloro-2-methoxyacridine assay. The quantitative OG488-DHPE assay demonstrated that the proton translocation rate of reconstituted Hv1 is much smaller than those reported in cellular systems. The OG488-DHPE assay further enabled us to quantify the K D-value of the Hv1-inhibitor 2-guanidinobenzimidazole, which matches well with that found in cellular experiments. Our results clearly demonstrate the applicability of the developed in vitro assay to measure proton translocation in a quantitative fashion; the assay allows to screen for new inhibitors and to determine their characteristic parameters. Graphical abstractᅟ
Keywords: ACMA assay; Lipid-coupled fluorophore; pH-sensitive dye; Proton channel; SEIRA

Synthesis and application of ratio fluorescence probe for chloride by Chen Ma; Fengyuan Zhang; Yaya Wang; Xinyue Zhu; Xiaoyan Liu; Chunyan Zhao; Haixia Zhang (6507-6516).
As chloride ions (Cl) play a vital role in maintaining normal physiological activity, detection of chloride ions is quite urgent. Hence, we developed chloride fluorescence probes to highly selectively and sensitively monitor chloride ions. The probe M2 with single emission has a high fluorescence quantum yield (Φ = 45%), and it is capable of quantitative detection of Cl under physiological conditions (pH = 7.4) and pH = 5.0 with a linear range of 0.1–4.0 mM; nevertheless, it is of the switch-off type. We further synthesized a ratiometric fluorescent probe MY with M2 as raw material, which featured excellent selectivity and anti-interference, and large two-photon cross section (555 GM). The probe is conveniently used to detect Cl in water samples and biological samples including human sweat, serum, and urine samples, indicating it holds great promise for chloride detection and biological application. Graphical abstractᅟ
Keywords: Chloride ion; Ratio fluorescence; Biological detection

Clustering-based preprocessing method for lipidomic data analysis: application for the evolution of newborn skin surface lipids from birth until 6 months by Rime Michael-Jubeli; Ali Tfayli; Caroline Baudouin; Jean Bleton; Dominique Bertrand; Arlette Baillet-Guffroy (6517-6528).
After life in utero and birth, the skin is submitted to an important process of adaptation to a relatively dry gaseous environment. Skin surface lipids (SSLs) contribute actively to the protection of the skin barrier. Within this context, our objective was to study the evolution of each lipid compound during the postnatal period. SSLs were collected from six newborns a few days after birth until the age of 6 months. Seventy samples were analyzed using high-temperature gas chromatography coupled to mass spectrometry (HT-GC/MS). The use of separative techniques coupled to mass spectrometry for the analysis of samples containing complex mixtures of lipids generates a large volume of data which renders the results interpretation very difficult. In this study, we propose a new approach to handle the raw data, a clustering-based preprocessing method (CB-PPM), in order to achieve (1) volume reduction of data provided by each chromatogram without loss of information, (2) alignment of time retention shift between different runs, (3) clustering of mass spectra of the same molecule in one qualitative group, (4) and integration of all data into a single matrix to be explored by chemometric tools. This approach allowed us to gather data variations in 256 qualitative groups and therefore enabled us to highlight the variation of compounds including those of low intensity. Moreover, the representation of all data gathered in one matrix rendered reading of the results rapid and efficient. Thus, using this approach, we have demonstrated an increase of cholesterol esterification with epidermal fatty acids (C20 to C25) with age. This epidermis participation in SSL production at a molecular level in the first period of life has not been previously shown. These data can be very interesting for the development and improvement of products destined for the protection of infant skin. Graphical abstractᅟ
Keywords: Lipidomic; Preprocessing data; Clustering-based preprocessing method (CB-PPM); HT-GC/MS; Skin surface lipids (SSLs); Epidermis lipids

ZnO flower-rod/g-C3N4-gold nanoparticle-based photoelectrochemical aptasensor for detection of carcinoembryonic antigen by Zhizhong Han; Min Luo; Qinghua Weng; Li Chen; Jinghua Chen; Chunyan Li; Ying Zhou; Long Wang (6529-6538).
A highly sensitive and selective photoelectrochemical (PEC) aptasensor was constructed for carcinoembryonic antigen (CEA) detection based on ZnO flower-rods (ZnO FRs) modified with g-C3N4-Au nanoparticle (AuNP) nanohybrids. The nanohybrids of g-C3N4-AuNPs can improve the visible light absorbance of ZnO FRs and enhance the PEC property. We designed a sandwichlike structure formed with DNA hybridization of NH2-probe1, CEA aptamer, and CuS-NH2-probe2 to detect CEA. The p-type semiconductor CuS nanocrystals (NCs) at the terminational part of sandwichlike structure work as electron traps to capture photogenerated electrons and consequently lead to a magnified photocurrent change. The results indicate that the photocurrent is increased when CEA antigen (Ag) is introduced. Since the sandwichlike structure is destroyed, CuS NCs are restricted to capture photogenerated electron. The PEC aptasensor for CEA determination is ranged from 0.01 ng·mL−1 to 2.5 ng·mL−1 with a detection of 1.9 pg·mL−1. The proposed aptasensor exhibits satisfactory PEC performances with rapid detection, great sensitivity and specificity. Specially, this PEC aptasensor shows a reliable result for the determination of CEA in invalid human serum compared with the ELISA method. The designed aptasensor may provide a new idea for a versatile PEC platform to determine various molecules. Graphical abstractᅟ
Keywords: Photoelectrochemical aptasensor; ZnO flower-rods; g-C3N4-Au nanoparticles; CuS; Carcinoembryonic antigen

An efficient analytical method based on molecularly imprinted solid-phase extraction (MISPE) coupled with high-performance liquid chromatography-diode array detection (HPLC-DAD) was established for the determination of iridoid glycosides (IGs) in Di-huang pills. As the solid-phase extraction medium, superhydrophilic molecularly imprinted polymers (MIPs) with high affinity and selectivity to IGs in water media were fabricated using divinyl galactose as a single cross-linking monomer. The structure, porosity, and hydrophilicity of MIPs were characterized. The properties involving dynamic adsorption, kinetic adsorption, and selectivity were evaluated. Under optimal conditions the MISPE-HPLC-DAD based method was applied for loganin, morroniside, cornin, and sweroside determination in three kinds of Di-huang pills. The limits of detection of four IGs were 0.002–0.003 mg g−1. Furthermore, the proposed method exhibited some merits including good linearity, excellent precision, and desirable accuracy. The established MISPE-HPLC-DAD method has great potential for the selective determination of IGs in Chinese patent drugs. Graphical Abstractᅟ
Keywords: Superhydrophilic molecularly imprinted polymers; Single cross-linking monomer; Solid-phase extraction; Iridoid glycosides; Di-huang pills

An optimized band-target entropy minimization for mass spectral reconstruction of severely co-eluting and trace-level components by Chun Kiang Chua; Bo Lu; Yunbo Lv; Xiao Yu Gu; Ai Di Thng; Hua Jun Zhang (6549-6560).
Gas chromatography-mass spectrometry (GC-MS) is a versatile analytical method but its data is usually complicated by the presence of severely co-eluting and trace-level components. In this work, we introduce an optimized band-target entropy minimization approach for the analysis of complex mass spectral data. This new approach enables an automated mass spectral analysis which does not require any user-dependent inputs. Moreover, the approach provides improved sensitivity and accuracy for mass spectral reconstruction of severely co-eluting and trace-level components. The accuracy of our approach is compared to the automatic mass spectral deconvolution and identification system (AMDIS) with two controlled mixtures and a sample of Eucalyptus essential oil. Our approach was able to putatively identify 130 compounds in Eucalyptus essential oil, which was 46% in excess of that identified by AMDIS. This new approach is expected to benefit GC-MS analysis of complex mixtures such as biological samples and essential oils, in which the data are often complicated by co-eluting and trace-level components. Graphical abstractᅟ
Keywords: Gas chromatography; Mass spectrometry; Entropy minimization; Spectral deconvolution

Separation of sub-micron particles from micron particles using acoustic fluid relocation combined with acoustophoresis by Gayatri P. Gautam; Rubi Gurung; Frank A. Fencl; Menake E. Piyasena (6561-6571).
Acoustophoresis has gained increasing attention as a gentle, non-contact, and high-throughput cell and particle separation technique. It is conveniently used to isolate and enrich particles that are greater than 2 μm; however, its use in manipulating particles smaller than 2 μm is limited. In this work, we present an alternative way of using acoustic forces to manipulate sub-micrometer particles in continuous flow fashion. It has been shown that acoustic forces can be employed to relocate parallel laminar flow streams of two impedance-mismatched fluids. We demonstrate the separation of sub-micron particles from micron particles by the combination of acoustophoresis and acoustic fluid relocation. The micron particles are focused into the middle of the flow channel via primary acoustic forces while sub-micron particles are moved to the side via drag forces created by the relocating fluid. We demonstrate the proof of the concept using binary mixtures of particles comprised of sub-micron/micron particles, micron/micron particles, and bovine red blood cells with E. coli. The efficiency of the particle enrichment is determined via flow cytometry analysis of the collected streams. This study demonstrates that by combining acoustic fluid relocation with acoustophoresis, sub-micron particles can be effectively separated from micron particles at high flow rates and it can be further implemented to separate binary mixtures of micron particles if the volumetric ratio of two particles is greater than 10 and the larger particle diameter is about 10 μm. The combined method is more appropriate to use than acoustophoresis in situations where acoustic streaming and differences in acoustic impedance of fluids can be of concern. Graphical abstractIn the presence of a resonance acoustic field, the clean high-density fluid (dark gray) and the low-density sample fluid are relocated. During this process, E. coli are separated from the red blood cells (RBCs).
Keywords: Acoustophoresis; Acoustic fluid relocation; Particle separation; Microfluidics

The toxicity of nitrofuran drugs has attracted great attention, and the reported electroanalytical methods suffered limited sensitivity. In this work, a sensitive electrochemical assay in the cathodic region is developed to determine four nitrofuran derivatives, including nitrofurantoin (NFT), nitrofurazone (NFZ), furaltadone (FTD), and furazolidone (FZD). The screen-printed carbon electrode (SPCE) was used as the electrode substrate, and the sensing surface was composed of multi-walled carbon nanotube (MWCNT) and conducting poly(melamine) (PME). The overoxidation-pretreated MWCNTs affect the surface morphology of the electrodeposited PME and, thus, the interaction with nitrofuran drugs. The characteristics of the nanocomposite-modified electrode surfaces were well characterized by field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and surface water contact angle experiments. The nanocomposite-modified electrodes exhibited excellent adsorption and electrochemical reduction of nitrofurans by cyclic voltammetry. The proposed assay exhibited a linear range of sub-micro to micro molar concentrations for the four drugs under the optimized differential pulse voltammetric (DPV) technique. The detection limits were found to be in the nanomolar ranges. The developed assay was applied to detect NFT in two real samples, and the results showed good recoveries that ranged from 99.0 to 104.8% and 98.0 to 103.2% for milk and lake water samples, respectively. Graphical abstractᅟ
Keywords: Nitrofurans; Multi-walled carbon nanotubes; Poly(melamine); Adsorption; Differential pulse voltammetry

HILIC/ESI-MS determination of gangliosides and other polar lipid classes in renal cell carcinoma and surrounding normal tissues by Roman Hájek; Miroslav Lísa; Maria Khalikova; Robert Jirásko; Eva Cífková; Vladimír Študent Jr; David Vrána; Lukáš Opálka; Kateřina Vávrová; Marcel Matzenauer; Bohuslav Melichar; Michal Holčapek (6585-6594).
Negative-ion hydrophilic liquid chromatography-electrospray ionization mass spectrometry (HILIC/ESI-MS) method has been optimized for the quantitative analysis of ganglioside (GM3) and other polar lipid classes, such as sulfohexosylceramides (SulfoHexCer), sulfodihexosylceramides (SulfoHex2Cer), phosphatidylglycerols (PG), phosphatidylinositols (PI), lysophosphatidylinositols (LPI), and phosphatidylserines (PS). The method is fully validated for the quantitation of the studied lipids in kidney normal and tumor tissues of renal cell carcinoma (RCC) patients based on the lipid class separation and the coelution of lipid class internal standard with the species from the same lipid class. The raw data are semi-automatically processed using our software LipidQuant and statistically evaluated using multivariate data analysis (MDA) methods, which allows the complete differentiation of both groups with 100% specificity and sensitivity. In total, 21 GM3, 28 SulfoHexCer, 26 SulfoHex2Cer, 10 PG, 19 PI, 4 LPI, and 7 PS are determined in the aqueous phase of lipidomic extracts from kidney tumor tissue samples and surrounding normal tissue samples of 20 RCC patients. S-plots allow the identification of most upregulated (PI 40:5, PI 40:4, GM3 34:1, and GM3 42:2) and most downregulated (PI 32:0, PI 34:0, PS 36:4, and LPI 16:0) lipids, which are primarily responsible for the differentiation of tumor and normal groups. Another confirmation of most dysregulated lipids is performed by the calculation of fold changes together with T and p values to highlight their statistical significance. The comparison of HILIC/ESI-MS data and matrix-assisted laser desorption/ionization mass spectrometric imaging (MALDI-MSI) data confirms that lipid dysregulation patterns are similar for both methods. Graphical abstractᅟ
Keywords: Lipids; Lipidomics; Gangliosides; Mass spectrometry; HILIC; Renal cell carcinoma; Tumor tissues

Over the centuries, oak wood has been used in the maturation process of alcoholic beverages imparting aroma and flavor notes. Whereas several studies have dealt with the impact of oak wood on the chemical composition of, for example, wine aroma, only limited information is available on the odorant composition of unmodified and raw oak wood itself. To close this gap, a combination of human sensory and chemo-analytical techniques was applied for the elucidation of the chemical composition of oak odor, comprising extraction of the volatile fraction of oak wood by means of solvent-assisted flavor evaporation (SAFE) and subsequent mild concentration of the distillate. Odor extract dilution analysis (OEDA), which is based on gas chromatography-olfactometry (GC-O), was then applied for the targeted characterization of the odor-active compounds. Overall, a total of 97 odorants was identified via gas chromatography-mass spectrometry/olfactometry (GC-MS/O) and heart-cut two-dimensional gas chromatography-mass spectrometry/olfactometry (2D-GC-MS/O). The majority of these odorants comprised a series of terpenes, mainly mono- and sesquiterpenes, aldehydes, acids, and lactones, as well as a number of odorants containing a phenolic core moiety. Several odorants are reported here for the first time as volatile organic compounds in oak wood. Identification of the molecular composition of oak wood odor helps to establish a better understanding of the distinctive smell of oak wood, and offers the basis for unveiling its potential effects on humans when being exposed to oak wood smell in daily life. Graphical abstractᅟ
Keywords: Volatile; Odor extract dilution analysis (OEDA); Gas chromatography olfactometry (GC-O); Heart-cut two-dimensional gas chromatography-mass spectrometry/olfactometry; Odorant

Detection of organic compounds in impact glasses formed by the collision of an extraterrestrial material with the Libyan Desert (Africa) and Tasmania (Australia) by Leticia Gómez-Nubla; Julene Aramendia; Silvia Fdez-Ortiz de Vallejuelo; Kepa Castro; Juan Manuel Madariaga (6609-6617).
Impact glasses are rich silica melted formed at high temperature and pressure by the impact of an extraterrestrial body on Earth. Here, Libyan Desert glasses (LDGs) and Darwin glasses (DGs) were studied. Two non-destructive analytical techniques were used to detect and characterize organic compounds present in their inclusions: Raman spectroscopy and scanning electron microscopy coupled to energy-dispersive X-ray spectroscopy (SEM-EDS). Phytoliths, humboldtine, palmitic acid, myristic acid, oleic acid, 4-methyl phthalic acid, and S-H stretching vibrations of amino acids were identified. The presence of these particular organic compounds in such materials has not been reported so far, providing information about (a) the ancient matter of the area where the impact glasses were formed, (b) organic matter belonging to the extraterrestrial body which impacted on the Earth, or (c) even to current plant or bacterial life, which could indicate an active interaction of the LDG and DG with the surrounding environment. Moreover, the identification of fullerene allowed us to know a pressure (15 GPa) and temperatures (670 K or 1800–1900 K) at which samples could be subjected.
Keywords: Impact glass; Libyan Desert glass; Darwin glass; Organic compounds; Raman spectroscopy

In this work, a variety of highly porous metal organic framework/chitosan (MOF/CS) foams (MIL-53(Al)/CS, MIL-53(Fe)/CS, MIL-101(Cr)/CS, MIL-101(Fe)/CS, UiO-66(Zr)/CS, and MIL-100(Fe)/CS) were designed and prepared by an ice-templating process. The introduction of MOFs made these foams achieve excellent inherent characters in terms of strength, stability, and adsorption ability. The MOFs incorporated in the foams retained their unique properties. Additionally, the foams were durable and their adsorption abilities had only a little loss after being recycled several times. MIL-53(Al)/CS foam was selected as an adsorbent candidate to develop an ultrasound-assisted solid-phase extraction (UA-SPE) method for the first time, owing to its particularly noteworthy performance among the prepared MOF/CS foams. The method was then successfully applied to extract trace amount of five parabens (methylparaben, ethylparaben, propylparaben, butylparaben, benzylparaben) in water samples, followed by ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS) detection. Several experimental parameters were investigated. Under the optimal conditions, the linear ranges were 0.5–200 μg/L with regression coefficients (r 2) from 0.9948 to 0.9983. The method detection limits were between 0.09 and 0.45 μg/L. The recoveries ranged from 78.75 to 102.1% with relative standard deviations (RSDs) < 7.4%. Furthermore, the molecular interactions and free binding energies between MOFs and parabens were calculated by means of molecular docking to explain the adsorption mechanism deeply. The novel method proposed in this work exhibited many benefits such as easy operation, high enrichment efficiency, less solvent consuming, and higher sensitivity. Such a strategy would expand the application prospect of MOFs in sample pretreatment. Graphical abstractᅟ
Keywords: Metal organic framework/chitosan foams; Ultrasound-assisted solid-phase extraction; Parabens; Water samples

Strong and oriented conjugation of nanobodies onto magnetosomes for the development of a rapid immunomagnetic assay for the environmental detection of tetrabromobisphenol-A by Jinxin He; Jiesheng Tian; Junjie Xu; Kai Wang; Ji Li; Shirley J. Gee; Bruce D. Hammock; Qing X. Li; Ting Xu (6633-6642).
Variable domain of heavy chain antibody (nanobody, Nb) derived from camelids is an efficient reagent in monitoring environmental contaminants. Oriented conjugates of Nbs and bacterial magnetic particles (BMPs) provide new tools for the high-throughput immunoassay techniques. An anti-tetrabromobisphenol-A (TBBPA) Nb genetically integrated with an extra cysteine residue at the C terminus was immobilized onto BMPs enclosed within the protein membrane, using a heterobifunctional reagent N-succinimidyl-3-(2-pyridyldithiol) propionate, to form a solid BMP-Nb complex. A rapid and sensitive enzyme-linked immunosorbent assay (ELISA) based on the combination of BMP-Nb and T5-horseradish peroxidase was developed for the analysis of TBBPA, with a total assay time of 30 min and a half-maximum signal inhibition concentration (IC50) of 1.04 ng/mL in PBS (pH 10, 10% methanol and 0.137 moL/L NaCl). This assay can even be performed in 100% methanol, with an IC50 value of 44.3 ng/mL. This assay showed quantitative recoveries of TBBPA from spiked canal water (114–124%) and sediment (109–113%) samples at 1.0–10 ng/mL (or ng/g (dw)). TBBPA residues determined by this assay in real canal water samples were below the limit of detection (LOD) and in real sediments were between
Keywords: Oriented conjugation; Nanobody; Bacterial magnetic particles; Immunomagnetic assay; Tetrabromobisphenol-A; Environmental detection

Application of polyethyleneimine-modified attapulgite for the solid-phase extraction of chlorophenols at trace levels in environmental water samples by Mengsa Chai; Yihui Chen; Rongrong Xuan; Junfeng Ma; Zhenfeng Jin; Tingting Wang; Dan Qiu; Lihua Zhang; Yukui Zhang (6643-6651).
A polyethyleneimine (PEI)-modified attapulgite was employed as a new adsorbent for solid-phase extraction (SPE) of chlorophenols (CPs) from environmental water samples. Key factors pivotal to extraction efficiency, such as organic additive, pH, salt, sample loading volume, elution volume, and sample loading flow rate, were investigated. The maximum adsorption capacity of CPs reached 38 mg/g, and the adsorption behavior could be described with the Langmuir isotherm model. The developed SPE procedure was then tested on river water samples. Of this cartridge, 0.4 g could be used to treat up to 100 mL of the water sample, with high recoveries achieved. The limit of detection (S/N = 3) and the limit of quantification (S/N = 10) were in range of 0.08–0.56 and 0.27–1.88 ng/mL, respectively. The mean recoveries of CPs spiked in river water samples ranged from 84.4 to 96.8% with relative standard deviations for the intra-day and inter-day less than 6.30%. The developed SPE method exhibited high sensitivity, high selectivity, excellent accuracy, and good repeatability to the analysis of trace CPs in complicated aqueous matrices. Graphical abstract Graphical abstract contains poor quality and small text inside the artwork. Please do not re-use the file that we have rejected or attempt to increase its resolution and re-save. It is originally poor, therefore, increasing the resolution will not solve the quality problem. We suggest that you provide us the original format. We prefer replacement figures containing vector/editable objects rather than embedded images. Preferred file formats are eps, ai, tiff and pdf.The separated figures were attached, which named Graphical abstract.ᅟ
Keywords: Attapulgite; Chlorophenols; Environmental water samples; Solid-phase extraction

In this work, poly(glycidyl methacrylate-ethyleneglycol dimethacrylate) monolith functionalized with copper tetra(N-carbonylacrylic) aminephthalocyanine and iminodiacetic acid was successfully synthesized. Owing to hydrogen bonding and hydrophilic interactions, the monolith exhibited good performance for glycopeptide enrichment. When the tryptic digests of horseradish peroxidase were enriched by the developed monolith, a total of 20 glycopeptides could be captured and identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis with a detection limit as low as 0.5 fmol μL−1. With the mixture of bovine serum albumin and horseradish peroxidase digests (200:1, m/m) as the sample, 14 glycopeptides were identified after enrichment, showing the high selectivity of the monolith. Moreover, the functionalized monolith exhibited good stability and reproducibility. It was successfully applied to enrich glycopeptides from human serum, demonstrating its potential applications in selective and efficient capture of glycopeptides in complex biological samples. Graphical abstractᅟ
Keywords: Monolith; Phthalocyanine; Enrichment; Glycopeptide; Mass spectrometry

Optimization, performance, and application of a pyrolysis-GC/MS method for the identification of microplastics by Ludovic Hermabessiere; Charlotte Himber; Béatrice Boricaud; Maria Kazour; Rachid Amara; Anne-Laure Cassone; Michel Laurentie; Ika Paul-Pont; Philippe Soudant; Alexandre Dehaut; Guillaume Duflos (6663-6676).
Plastics are found to be major debris composing marine litter; microplastics (MP, < 5 mm) are found in all marine compartments. The amount of MPs tends to increase with decreasing size leading to a potential misidentification when only visual identification is performed. These last years, pyrolysis coupled with gas chromatography/mass spectrometry (Py-GC/MS) has been used to get information on the composition of polymers with some applications on MP identification. The purpose of this work was to optimize and then validate a Py-GC/MS method, determine limit of detection (LOD) for eight common polymers, and apply this method on environmental MP. Optimization on multiple GC parameters was carried out using polyethylene (PE) and polystyrene (PS) microspheres. The optimized Py-GC/MS method require a pyrolysis temperature of 700 °C, a split ratio of 5 and 300 °C as injector temperature. Performance assessment was accomplished by performing repeatability and intermediate precision tests and calculating limit of detection (LOD) for common polymers. LODs were all below 1 μg. For performance assessment, identification remains accurate despite a decrease in signal over time. A comparison between identifications performed with Raman micro spectroscopy and with Py-GC/MS was assessed. Finally, the optimized method was applied to environmental samples, including plastics isolated from sea water surface, beach sediments, and organisms collected in the marine environment. The present method is complementary to μ-Raman spectroscopy as Py-GC/MS identified pigment containing particles as plastic. Moreover, some fibers and all particles from sediment and sea surface were identified as plastic. Graphical abstractᅟ
Keywords: Microplastics; Pyrolysis; Gas chromatography; Method; Environmental samples

We report the development and characterization of digital microfluidic (DMF) immobilized enzyme reactors (IMERs) for studying cytochrome P450 (CYP)-mediated drug metabolism on droplet scale. The on-chip IMERs consist of porous polymer (thiol-ene) monolith plugs prepared in situ by photopolymerization and functionalized with recombinant CYP1A1 isoforms (an important detoxification route for many drugs and other xenobiotics). The DMF devices also incorporate inexpensive, inkjet-printed microheaters for on-demand regio-specific heating of the IMERs to physiological temperature, which is crucial for maintaining the activity of the temperature-sensitive CYP reaction. For on-chip monitoring of the CYP activity, the DMF devices were combined with a commercial well-plate reader, and a custom fluorescence quantification method was developed for detection of the chosen CYP1A1 model activity (ethoxyresorufin-O-deethylation). The reproducibility of the developed assay was examined with the help of ten parallel CYP-IMERs. All CYP-IMERs provided statistically significant difference (in fluorescence response) compared to any of the negative controls (including room-temperature reactions). The average (n = 10) turnover rate was 20.3 ± 9.0 fmol resorufin per minute. Via parallelization, the concept of the droplet-based CYP-IMER developed in this study provides a viable approach to rapid and low-cost prediction of the metabolic clearance of new chemical entities in vitro.
Keywords: Digital microfluidics; Drug metabolism; Cytochrome P450; Microheater; Microreactor; Enzyme immobilization