Analytical and Bioanalytical Chemistry (v.410, #11)

Cutting the cord: virtual machines for real instrumental analysis not just at the instrument by Rosina M. Georgiadis; Kristina Streu; Norman C. Lee (2657-2662).
is an associate professor of chemistry at Boston University. Her research in experimental physical and bioanalytical chemistry has been funded by NSF, including an NSF Career Award, and NIH. At BU, she developed an entirely new advanced laboratory course and has been actively developing resources to help students who use (and instructors who teach with) research-caliber analytical instrumentation. is a postdoctoral faculty fellow in the Chemistry Department at Boston University. Her research interests include developing computational approaches to identifying macrocyclic inhibitors that target protein–protein interactions, along with her research faculty mentor Adrian Whitty. Since 2016, she has taught an instrumental methods of analysis laboratory course with her teaching faculty mentor Rosina Georgiadis. She also teaches introductory chemistry courses and participates in outreach with the Boston University Women in Chemistry organization. is the director of the Chemical Instrumentation Center (CIC) at Boston University, where some of the VM instrumentation is located. He actively participates in instructional activities and research projects with instructors and faculty, and has over 15 years of experience with a broad range of analytical instrumentation. The CIC is a core facility which has received instrumentation awards from NSF and NIH in recent years.

Sensitive paper-based analytical device for fast colorimetric detection of nitrite with smartphone by Xiu-Xiu Zhang; Yi-Zhen Song; Fang Fang; Zhi-Yong Wu (2665-2669).
On-site rapid monitoring of nitrite as an assessment indicator of the environment, food, and physiological systems has drawn extensive attention. Here, electrokinetic stacking (ES) was combined with colorimetric reaction on a paper-based device (PAD) to achieve colorless nitrite detection with smartphone. In this paper, nitrite was stacked on the paper fluidic channel as a narrow band by electrokinetic stacking. Then, Griess reagent was introduced to visualize the stacking band. Under optimal conditions, the sensitivity of nitrite was 160-fold increased within 5 min. A linear response in the range of 0.075 to 1.0 μg mL−1 (R 2 = 0.99) and a limit of detection (LOD) of 73 ng mL−1 (0.86 μM) were obtained. The LOD was 10 times lower than the reported PAD, and close to that achieved by a desktop spectrophotometer. The applicability was demonstrated by nitrite detection from saliva and water with good selectivity, adding 100 times more concentrated co-ions. High recovery (91.0~108.7%) and reasonable intra-day and inter-day reproducibility (RSD < 9%) were obtained. This work shows that the sensitivity of colorless analyte detection-based colorimetric reaction can be effectively enhanced by integration of ES on a PAD. Graphical abstractSchematic of the experimental setups (left) and the corresponding images (right) of the actual portable device.
Keywords: Paper-based analytical device; Nitrite; Colorimetry; Electrokinetic stacking; Smartphone

is pursuing a Doctor's degree at College of Marine Life Sciences, Ocean University of China, Qingdao, China. His current research interests focus on separation and analysis of trace environmental and food pollutants. is an Associate Professor of Environmental Ecology in College of Marine Life Sciences, Ocean University of China, Qingdao, China. His research interests include environmental toxicology and biological monitoring. is Head of Biological and Ecological Department of Marine Environment Monitoring Center of Shandong Province, Shandong Marine Resource and Environment Research Institute, Yantai, China. His current research interests include analysis of marine biology and marine biology diversity changes under long-term climate change, phytoplankton classification, and relationship with environmental factors. is a researcher of Biological and Ecological Department of Marine Environment Monitoring Center of Shandong Province, Shandong Marine Resource and Environment Research Institute, Yantai, China. His current research interests include analysis of marine biology and marine biology diversity changes. is a Professor of Soil Science and Biogeochemistry in the Department of Land, Air, and Water Resources, Davis, University of California, USA. His principal research interest is watershed-scale biogeochemistry, including interactions of hydrological, geochemical, and biological processes in regulating groundwater and surface water chemistry. is pursuing a Master's degree at College of Marine Life Sciences, Ocean University of China, Qingdao, China. His current research interests focus on ecotoxicology, antibody, and colloidal gold preparation. is a professor of Environmental Ecology in College of Marine Life Sciences, Ocean University of China, Qingdao, China. His current research interests include biological screening methods and damage mechanism on aquatic organisms. is currently a researcher in College of Public Health and Management, Wenzhou Medical University, Wenzhou, China. He is also an Associate Dean of the Key Laboratory of Watershed Sciences and Health of Zhejiang Province. His current research interests focus on development of green analytical techniques and ecological restoration of pollutants. This study developed a new effervescence-assisted switchable fatty acid-based microextraction combined with solidification of a floating organic-droplet (EA-SFAM-SFO) for simple and rapid determination of fluoroquinolones and tetracyclines in seawater, sediment, and seafood. Five medium-chain fatty acids (pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, and nonanoic acid) were tested as an extraction solvent, given their ability to change between hydrophobic and hydrophilic forms by pH adjustment. As nonanoic acid had the highest extraction recovery (>92%) for the six antibiotics and the ability to transform from liquid to a solidified floating state at low temperature, it was selected as the optimum extraction solvent. The prominent advantages of the newly developed method are: (1) reaction between the procedures salt and fatty acid changed extraction solvent from the hydrophobic to hydrophilic state; (2) bubbling with CO2 greatly increased the contact area between fatty acid and analytes resulting in improved extraction recovery; and (3) solidification of the fatty acid at a low temperature provided good separation and avoided the use of specialized equipment. Single-factor screening and optimization of the main factors were conducted using Plackett-Burman design and central composite design, respectively. The main parameters were optimized as follows: 258 μL fatty acid, 406 μL H2SO4 (98%), 3.9 min vortex time, and 354 μL Na2CO3 (2 mol L-1). Under optimized conditions, limits of detection were 0.007–0.113 μg L-1 or μg kg-1 and extraction recoveries were 82.2%–116.7% for six fluoroquinolone and tetracycline antibiotics in seawater, sediments, and seafood. The newly developed method combines the advantages of effervescence-assisted dispersion, hydrophobic/hydrophilic switchable solvent, and liquid/solid transition induced by low temperature. Overall, the new method is simple, quick, and environment-friendly with low detection limits and high recoveries. Thus, the newly developed method has excellent prospects for sample pretreatment and analysis of antibiotics in marine environmental and food samples. Graphical Abstractᅟ
Keywords: Fluoroquinolones; Tetracyclines; Medium-chain saturated fatty acids; Effervescence-assisted switchable fatty acid-based microextraction combined with solidification of floating organic droplet (EA-SFAM-SFO); Marine environmental samples

MCEE: a data preprocessing approach for metabolic confounding effect elimination by Yitao Li; Mengci Li; Wei Jia; Yan Ni; Tianlu Chen (2689-2699).
is a graduate student in the Center for Translational Medicine of Shanghai Jiao Tong University Affiliated Sixth People’s Hospital. He mainly engages in the study of metabolomics and bioinformatics. is a PhD candidate of the Center for Translational Medicine at Shanghai Jiao Tong University Affiliated Sixth People's Hospital and the School of Biomedical Engineering and Med-X Research Institute at Shanghai Jiao Tong University in Shanghai, China. She majors in bioinformatics, including development of metabolomics and metagenomics softs and database as well as x-omics data analysis. is the Associate Director for Shared Resources of the University of Hawaii Cancer and Director of the Center for Translational Medicine of Shanghai Jiao Tong University Affiliated Sixth People’s Hospital. His research interest involves carbon source metabolism and its regulation in cancer cells as well as the molecular mechanisms that link metabolic disruptions in gut microbial-host co-metabolism to metabolic disorders and gastrointestinal cancer. is an assistant specialist of Cancer Epidemiology Program and Metabolomics Shared Resources at the University of Hawaii Cancer Center. She has been working for over 10 years in the field of mass spectrometry-based metabolomics and its applications. is an associate researcher of the Center for Translational Medicine of Shanghai Jiao Tong University Affiliated Sixth People’s Hospital. Her research interest involves chemometrics and biological/medical information mining, especially metabolic diseases-related x-omics data processing and management. It is well recognized that physiological and environmental factors such as race, age, gender, and diurnal cycles often have a definite influence on metabolic results that statistically manifests as confounding variables. Currently, removal or controlling of confounding effects relies heavily on experimental design. There are no available data processing techniques focusing on the compensation of their effects. We therefore proposed a new method, Metabolic confounding effect elimination (MCEE), to remove the influence of specified confounding factors and make the data more accurate. The method consists of three steps: metabolites grouping, confounder-related metabolites selection, and metabolites modification. Its effectiveness and advantages were evaluated comprehensively by several simulated models and real datasets, and were compared with two typical methods, the principal component analysis (PCA)- and the direct orthogonal signal correction (DOSC)-based methods. MCEE is simple, effective, and safe, and is independent of sample number, association degree, and missing value. Hence, it may serve as a good complement to existing metabolomics data preprocessing methods and aid in better understanding the metabolic and biological status of interest. Graphical AbstractAlgorithm flow and demo performance of MCEE
Keywords: Metabolomics; Confounding factor; Generalized linear model; Principal component analysis; Direct orthogonal signal correction

A novel and simple method utilizing a chromogenic reaction on filter paper is introduced for the rapid screening of banned aromatic amines released from azo dyes. The proposed method involves the sample preparation protocols outlined by the current standard method and the chromogenic reaction of extracted aromatic amines on filter paper. Based on the principle of the reaction between primary amines and aldehydes, p-dimethylaminobenzaldehyde (DMAB) was used as the chromogenic reagent for the rapid screening of 24 carcinogenic aromatic amines and aniline without any chromatographic instruments under optimized experimental conditions. The detection limit for all the aromatic amines in this study was less than 15 mg/kg. A total of 727 dyed textile samples were analyzed using both the present standard method and the proposed method simultaneously. Using the proposed method, a total of 471 samples did not require further instrumental analysis, which can dramatically save instrumental detection time (61.2%), can decrease instrumental detection costs, and can avoid the use of large amounts of toxic reagents. The proposed method has been applied to detect banned aromatic amines in some inspection institutions and dye factories and has large social and economic benefits. Graphical abstractChromogenic reaction methods
Keywords: Aromatic amines; Textiles; Chromogenic reaction; Screening

Phase identification of individual crystalline particles by combining EDX and EBSD: application to workplace aerosols by Torunn Kringlen Ervik; Nathalie Benker; Stephan Weinbruch; Asbjørn Skogstad; Yngvar Thomassen; Dag G. Ellingsen; Balázs Berlinger (2711-2721).
This paper discusses the combined use of electron backscatter diffraction (EBSD) and energy dispersive X-ray microanalysis (EDX) to identify unknown phases in particulate matter from different workplace aerosols. Particles of α-silicon carbide (α-SiC), manganese oxide (MnO) and α-quartz (α-SiO2) were used to test the method. Phase identification of spherical manganese oxide particles from ferromanganese production, with diameter less than 200 nm, was unambiguous, and phases of both MnO and Mn3O4 were identified in the same agglomerate. The same phases were identified by selected area electron diffraction (SAED) in transmission electron microscopy (TEM). The method was also used to identify the phases of different SiC fibres, and both β-SiC and α-SiC fibres were found. Our results clearly demonstrate that EBSD combined with EDX can be successfully applied to the characterisation of workplace aerosols. Graphical abstractSecondary electron image of an agglomerate of manganese oxide particles collected at a ferromanganese smelter (a). EDX spectrum of the particle highlighted by an arrow (b). Indexed patterns after dynamic background subtraction from three particles shown with numbers in a (c)
Keywords: Aerosols/particulates; Workplace; Electron backscatter diffraction; Phase identification; Electron microscopy

Combined untargeted and targeted fingerprinting by comprehensive two-dimensional gas chromatography: revealing fructose-induced changes in mice urinary metabolic signatures by Davide Bressanello; Erica Liberto; Massimo Collino; Fausto Chiazza; Raffaella Mastrocola; Stephen E. Reichenbach; Carlo Bicchi; Chiara Cordero (2723-2737).
This study exploits the information potential of comprehensive two-dimensional gas chromatography configured with a parallel dual secondary column-dual detection by mass spectrometry and flame ionization (GC×2GC-MS/FID) to study changes in urinary metabolic signatures of mice subjected to high-fructose diets. Samples are taken from mice fed with normal or fructose-enriched diets provided either in aqueous solution or in solid form and analyzed at three stages of the dietary intervention (1, 6, and 12 weeks). Automated Untargeted and Targeted fingerprinting for 2D data elaboration is adopted for the most inclusive data mining of GC×GC patterns. The UT fingerprinting strategy performs a fully automated peak-region features fingerprinting and combines results from pre-targeted compounds and unknowns across the sample-set. The most informative metabolites, with statistically relevant differences between sample groups, are obtained by unsupervised multivariate analysis (MVA) and cross-validated by multi-factor analysis (MFA) with external standard quantitation by GC-MS. Results indicate coherent clustering of mice urine signatures according to dietary manipulation. Notably, the metabolite fingerprints of mice fed with liquid fructose exhibited greater derangement in fructose, glucose, citric, pyruvic, malic, malonic, gluconic, cis-aconitic, succinic and 2-keto glutaric acids, glycine acyl derivatives (N-carboxy glycine, N-butyrylglycine, N-isovaleroylglycine, N-phenylacetylglycine), and hippuric acid. Untargeted fingerprinting indicates some analytes which were not a priori pre-targeted which provide additional insights: N-acetyl glucosamine, N-acetyl glutamine, malonyl glycine, methyl malonyl glycine, and glutaric acid. Visual features fingerprinting is used to track individual variations during experiments, thereby extending the panorama of possible data elaboration tools. Graphical abstractᅟ
Keywords: Comprehensive two-dimensional gas chromatography-mass spectrometry; Parallel dual secondary column-dual detection; Fructose-induced metabolic derangements; Urine metabolic profiling; Untargeted and targeted fingerprinting

Specific and robust ion chromatographic determination of hypothiocyanite in saliva samples by Harald Below; Romy Baguhl; Wiebke Geßner; Axel Kramer; Elke Below; Heike Kahlert; Alexander Welk (2739-2749).
The enzymatic system in saliva, consisting of salivary peroxidase (SPO), hydrogen peroxide (H2O2), and thiocyanate (SCN), produces hypothiocyanite (OSCN) as a high effective antibacterial compound. OSCN is of great importance for the natural non-specific antibacterial resistance in the oral cavity. However, no analytical method currently exists to selectively quantify OSCN in saliva samples. A robust and specific analytical method for the determination of OSCN was developed based on ion chromatography with combined UV and electrochemical detection. Calibration was achieved by calculating a derived calibration factor based on the known ratio of molar extinction coefficients of SCN and OSCN. Thus, the specific quantification of OSCN in saliva samples is possible, as demonstrated here. The median value of 200 saliva samples was determined to be 0.56 mg L−1 (median), with a maximum of 3.9 mg L−1; the minimum value was below the detection limit (< 0.09 mg L−1). The recovery rate in individual saliva samples was 95 ± 8%.
Keywords: Hypothiocyanite; Thiocyanate; Ion chromatography; Saliva peroxidase

Development of a sensitive and quantitative capillary LC-UV method to study the uptake of pharmaceuticals in zebrafish brain by Stanislav Kislyuk; Wannes Van den Bosch; Erwin Adams; Peter de Witte; Deirdre Cabooter (2751-2764).
The present study explores the potential of 10-day-old zebrafish (Danio rerio) as a predictive blood-brain-barrier model using a set of 7 pharmaceutical agents. For this purpose, zebrafish were incubated with each of these 7 drugs separately via the route of immersion and the concentration reaching the brain was determined by applying a brain extraction procedure allowing isolation of the intact brain from the head of the zebrafish larvae. Sample analysis was performed utilizing capillary ultra-high performance liquid chromatography (cap-UHPLC) on a Pepmap RSLC C18 capillary column (150 mm × 300 μm, d p = 2 μm) coupled to a variable wavelength UV detector. Gradient separation was performed in 28 min at a flow rate of 5 μL/min and the optimal injection volume was determined to be 1 μL. The brain extraction procedure was established for the zebrafish strain TG898 exhibiting red fluorescence of the brain, allowing control of the integrity of the extracted parts. Quantitative experiments carried out on pooled samples of six zebrafish (n = 6) demonstrated the selective semipermeable nature of the blood-brain barrier after incubating the zebrafish at the maximum tolerated concentration for the investigated pharmaceuticals. The obtained brain-to-trunk ratios ranged between 0.3 for the most excluded compound and 1.2 for the pharmaceutical agent being most accumulated in the brain of the fish. Graphical abstractWorkflow of brain extraction to study the uptake of pharmaceuticals in the brain of zebrafish larvae
Keywords: Zebrafish; Blood-brain barrier; Capillary UHPLC; Method development; Sample preparation

A study was initiated to investigate a fast and reliable method for the determination of selected systemic insecticides in water matrixes and to evaluate potential sources of bias in their analysis. Acetamiprid, clothianidin, desnitro-imidacloprid, dinotefuran, fipronil, imidacloprid, nitenpyram, thiacloprid, and thiamethoxam were amenable to analysis via on-line sample enrichment hyphenated to ultra-high-performance liquid chromatography tandem mass spectrometry. The selection of on-line solid-phase extraction parameters was dictated by a multicriterion desirability approach. A 2-mL on-line injection volume with a 1500 μL min−1 loading flow rate met the objectives sought in terms of chromatographic requirements, extraction efficiency, sensitivity, and precision. A total analysis time of 8 min per sample was obtained with method limits of detection in the range of 0.1–5 ng L−1 for the scope of targeted analytes. Automation at the sample concentration step yielded intraday and interday precisions in the range of 1–23 and 2–26%, respectively. Factors that could affect the whole method accuracy were further evaluated in matrix-specific experiments. The impact of the initial filtration step on analyte recovery was evaluated in ultra-pure water, tap water, and surface water. Out of the nine membranes tested, glass fiber filters and polyester filters appeared as the most appropriate materials. Sample storage stability was also investigated across the three matrix types; the targeted analytes displayed suitable stability during 28 days at either 4 °C or − 20 °C, with little deviations (± 10%) with respect to the initial T 0 concentration. Method applicability was demonstrated in a range of tap water and surface water samples from the province of Québec, Canada. Results from the present survey indicated a predominance of thiamethoxam (< 0.5–10 and 3–61 ng L−1 in tap water and river water, respectively), clothianidin (< 0.5–6 and 2–88 ng L−1 in tap water and river water, respectively), and imidacloprid (< 0.1–1 and 0.8–38 ng L−1 in tap water and river water, respectively) among the targeted analytes. Graphical abstractᅟDevelopment of solid-phase extraction coupled on-line to UHPLC-MS/MS for the rapid screening of systemic insecticides in water.
Keywords: Systemic pesticides; Neonicotinoids; On-line solid-phase extraction; Water analysis; Filtration; Storage stability

Tuning of gold nanoclusters sensing applications with bovine serum albumin and bromelain for detection of Hg2+ ion and lambda-cyhalothrin via fluorescence turn-off and on mechanisms by Jigna R. Bhamore; Sanjay Jha; Hirakendu Basu; Rakesh Kumar Singhal; Z. V. P. Murthy; Suresh Kumar Kailasa (2781-2791).
Herein, fluorescent gold nanoclusters (Au NCs) were obtained by one-pot synthetic method using bovine serum albumin (BSA) and bromelain as templates. As-synthesized fluorescent Au NCs were stable and showed bright red fluorescence under UV lamp at 365 nm. The fluorescent Au NCs exhibit the emission intensity at 648 nm when excited at 498 nm. Various techniques were used such as spectroscopy (UV-visible, fluorescence, and Fourier-transform infrared), high-resolution transmission electron microscopy, and dynamic light scattering for the characterization of fluorescent Au NCs. The values of I 0/I at 648 nm are proportional to the concentrations of Hg2+ ion in the range from 0.00075 to 5.0 μM and of lambda-cyhalothrin in the range from 0.01 to 10 μM with detection limits of 0.0003 and 0.0075 μM for Hg2+ ion and lambda-cyhalothrin, respectively. The practical application of the probe was successfully demonstrated by analyzing Hg2+ ion and lambda-cyhalothrin in water samples. In addition, Au NCs used as probes for imaging of Simplicillium fungal cells. These results indicated that the as-synthesized Au NCs have proven to be promising fluorescent material for the sensing of Hg2+ ion and lambda-cyhalothrin in environmental and for imaging of microorganism cells in biomedical applications.
Keywords: Au NCs; BSA; Bromelain; Hg2+ ion; Lambda-cyhalothrin; Optical spectroscopy

Rapid two-dimensional ALSOFAST-HSQC experiment for metabolomics and fluxomics studies: application to a 13C-enriched cancer cell model treated with gold nanoparticles by Martina Palomino Schätzlein; Johanna Becker; David Schulze-Sünninghausen; Antonio Pineda-Lucena; José Raul Herance; Burkhard Luy (2793-2804).
Isotope labeling enables the use of 13C-based metabolomics techniques with strongly improved resolution for a better identification of relevant metabolites and tracing of metabolic fluxes in cell and animal models, as required in fluxomics studies. However, even at high NMR-active isotope abundance, the acquisition of one-dimensional 13C and classical two-dimensional 1H,13C-HSQC experiments remains time consuming. With the aim to provide a shorter, more efficient alternative, herein we explored the ALSOFAST-HSQC experiment with its rapid acquisition scheme for the analysis of 13C-labeled metabolites in complex biological mixtures. As an initial step, the parameters of the pulse sequence were optimized to take into account the specific characteristics of the complex samples. We then applied the fast two-dimensional experiment to study the effect of different kinds of antioxidant gold nanoparticles on a HeLa cancer cell model grown on 13C glucose-enriched medium. As a result, 1H,13C-2D correlations could be obtained in a couple of seconds to few minutes, allowing a simple and reliable identification of various 13C-enriched metabolites and the determination of specific variations between the different sample groups. Thus, it was possible to monitor glucose metabolism in the cell model and study the antioxidant effect of the coated gold nanoparticles in detail. Finally, with an experiment time of only half an hour, highly resolved 1H,13C-HSQC spectra using the ALSOFAST-HSQC pulse sequence were acquired, revealing the isotope-position-patterns of the corresponding 13C-nuclei from carbon multiplets. Graphical abstractFast NMR applied to metabolomics and fluxomics studies with gold nanoparticles
Keywords: Fast NMR; HSQC; Metabolomics; Fluxomics; Gold nanoparticles

Quantification of cardiac troponin I in human plasma by immunoaffinity enrichment and targeted mass spectrometry by Nicole A. Schneck; Karen W. Phinney; Sang Bok Lee; Mark S. Lowenthal (2805-2813).
Quantification of cardiac troponin I (cTnI), a protein biomarker used for diagnosing myocardial infarction, has been achieved in native patient plasma based on an immunoaffinity enrichment strategy and isotope dilution (ID) liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. The key steps in the workflow involved isolating cTnI from plasma using anti-cTnI antibody coupled to magnetic nanoparticles, followed by an enzymatic digestion with trypsin. Three tryptic peptides from cTnI were monitored and used for quantification by ID-LC-MS/MS via multiple reaction monitoring (MRM). Measurements were performed using a matrix-matched calibration system. NIST SRM 2921 Human Cardiac Troponin Complex acted as the calibrant and a full-length isotopically labeled protein analog of cTnI was used as an internal standard. The method was successfully demonstrated on five patient plasma samples, with cTnI concentrations measuring between 4.86 μg/L and 11.3 μg/L (signifying moderate myocardial infarctions). LC-MS/MS measurement precision was validated by three unique peptides from cTnI and two MRM transitions per peptide. Relative standard deviation (CV) from the five plasma samples was determined to be ≤14.3%. This study has demonstrated that quantification of cTnI in native plasma from myocardial infarction patients can be achieved based on an ID-LC-MS/MS method. The development of an ID-LC-MS/MS method for cTnI in plasma is a first step for future certification of matrix-based reference materials, which may be used to help harmonize discordant cTnI clinical assays. Graphical abstractA schematic of the workflow for measuring cardiac troponin I (cTnI), a low-abundant protein biomarker used for diagnosing myocardial infarction, in human plasma by isotope-dilution LC-MS/MS analysis.
Keywords: Protein biomarker; Cardiac troponin I; Mass spectrometry; Isotope dilution; Quantification; Multiple reaction monitoring

MALDI imaging facilitates new topical drug development process by determining quantitative skin distribution profiles by David Bonnel; Raphaël Legouffe; André H. Eriksson; Rasmus W. Mortensen; Fabien Pamelard; Jonathan Stauber; Kim T. Nielsen (2815-2828).
Generation of skin distribution profiles and reliable determination of drug molecule concentration in the target region are crucial during the development process of topical products for treatment of skin diseases like psoriasis and atopic dermatitis. Imaging techniques like mass spectrometric imaging (MSI) offer sufficient spatial resolution to generate meaningful distribution profiles of a drug molecule across a skin section. In this study, we use matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) to generate quantitative skin distribution profiles based on tissue extinction coefficient (TEC) determinations of four different molecules in cross sections of human skin explants after topical administration. The four drug molecules: roflumilast, tofacitinib, ruxolitinib, and LEO 29102 have different physicochemical properties. In addition, tofacitinib was administrated in two different formulations. The study reveals that with MALDI-MSI, we were able to observe differences in penetration profiles for both the four drug molecules and the two formulations and thereby demonstrate its applicability as a screening tool when developing a topical drug product. Furthermore, the study reveals that the sensitivity of the MALDI-MSI techniques appears to be inversely correlated to the drug molecules’ ability to bind to the surrounding tissues, which can be estimated by their Log D values. Graphical abstract
Keywords: Mass spectrometry imaging; MALDI-MSI; Human skin; Quantification; Drug distribution; Skin penetration

Development of an analytical method to assess the occupational health risk of therapeutic monoclonal antibodies using LC-HRMS by Lars M. H. Reinders; Martin D. Klassen; Martin Jaeger; Thorsten Teutenberg; Jochen Tuerk (2829-2836).
Monoclonal antibodies are a group of commonly used therapeutics, whose occupational health risk is still discussed controversially. The long-term low-dose exposure side effects are insufficiently evaluated; hence, discussions are often based on a theoretical level or extrapolating side effects from therapeutic dosages. While some research groups recommend applying the precautionary principle for monoclonal antibodies, others consider the exposure risk too low for measures taken towards occupational health and safety. However, both groups agree that airborne monoclonal antibodies have the biggest risk potential. Therefore, we developed a peptide-based analytical method for occupational exposure monitoring of airborne monoclonal antibodies. The method will allow collecting data about the occupational exposure to monoclonal antibodies. Thus, the mean daily intake for personnel in pharmacies and the pharmaceutical industry can be determined for the first time and will help to substantiate the risk assessment by relevant data. The introduced monitoring method includes air sampling, sample preparation and detection by liquid chromatography coupled with high-resolution mass spectrometry of individual monoclonal antibodies as well as sum parameter. For method development and validation, a chimeric (rituximab), humanised (trastuzumab) and a fully humanised (daratumumab) monoclonal antibody are used. A limit of detection between 1 μg per sample for daratumumab and 25 μg per sample for the collective peptide is achieved. Graphical abstractDemonstration of the analytical workflow, from the release of monoclonal antibodies to the detection as single substances as well as sum parameter.
Keywords: Monoclonal antibody; Occupational exposure; Sensitising; High-resolution mass spectrometry; Airborne; Sum parameter

Asymmetric flow field-flow fractionation coupled with use of ultraviolet–visible, multiangle light scattering (MALLS), and dynamic light scattering (DLS) detectors was used for separation and characterization of biologically synthesized silver composites in two liquid compositions. Moreover, to supplement the DLS/MALLS information, various complementary techniques such as transmission electron spectroscopy, Fourier transform infrared spectroscopy, and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) were used. The hydrodynamic diameter and the radius of gyration of silver composites were slightly larger than the sizes obtained by transmission electron microscopy (TEM). Moreover, the TEM results revealed the presence of silver clusters and even several morphologies, including multitwinned. Additionally, MALDI-TOF MS examination showed that the particles have an uncommon cluster structure. It can be described as being composed of two or more silver clusters. The organic surface of the nanoparticles can modify their dispersion. We demonstrated that the variation of the silver surface coating directly influenced the migration rate of biologically synthesized silver composites. Moreover, this study proves that the fractionation mechanism of silver biocolloids relies not only on the particle size but also on the type and mass of the surface coatings. Because silver nanoparticles typically have size-dependent cytotoxicity, this behavior is particularly relevant for biomedical applications. Graphical abstractWorkflow for asymmetric flow field-flow fractionation of natural biologically synthesized silver nanocomposites
Keywords: Biologically synthesized silver composites; Asymmetric flow field-flow fractionation; Fractionation; Organic deposit; Matrix-assisted laser desorption ionization mass spectrometry; Silver clusters

Quantification of elemental area densities in multiple metal layers (Au/Ni/Cu) on a Cr-coated quartz glass substrate for certification of NMIJ CRM 5208-a by Tomoko Ariga; Yanbei Zhu; Mika Ito; Toshiko Takatsuka; Shinya Terauchi; Akira Kurokawa; Kazumi Inagaki (2849-2857).
Area densities of Au/Ni/Cu layers on a Cr-coated quartz substrate were characterized to certify a multiple-metal-layer certified reference material (NMIJ CRM5208-a) that is intended for use in the analysis of the layer area density and the thickness by an X-ray fluorescence spectrometer. The area densities of Au/Ni/Cu layers were calculated from layer mass amounts and area. The layer mass amounts were determined by using wet chemical analyses, namely inductively coupled plasma mass spectrometry (ICP-MS), isotope-dilution (ID-) ICP-MS, and inductively coupled plasma optical emission spectrometry (ICP-OES) after dissolving the layers with diluted mixture of HCl and HNO3 (1:1, v/v). Analytical results of the layer mass amounts obtained by the methods agreed well with each another within their uncertainty ranges. The area of the layer was determined by using a high-resolution optical scanner calibrated by Japan Calibration Service System (JCSS) standard scales. The property values of area density were 1.84 ± 0.05 μg/mm2 for Au, 8.69 ± 0.17 μg/mm2 for Ni, and 8.80 ± 0.14 μg/mm2 for Cu (mean ± expanded uncertainty, coverage factor k = 2). In order to assess the reliability of these values, the density of each metal layer calculated from the property values of the area density and layer thickness measured by using a scanning electron microscope were compared with available literature values and good agreement between the observed values and values obtained in previous studies.
Keywords: Area density; Certified reference material; Elemental determination; Multiple metal layers; Uncertainty

The authors would like to call the reader’s attention to the fact that unfortunately in the original article Steptococcus suis was introduced as gram-negative bacteria. Steptococcus suis is gram positive. The authors apologize for the mistake.