Analytical and Bioanalytical Chemistry (v.409, #17)
Pink tea challenge by Lucia D’Ulivo (4111-4112).
Solution to redox titration challenge by Tadeusz Michałowski; Anna Maria Michałowska-Kaczmarczyk; Juris Meija (4113-4115).
European analytical column number 45 by Wolfgang Buchberger; Slavica Razic (4117-4118).
Infrared laser ablation sample transfer of tissue DNA for genomic analysis by Kelin Wang; Fabrizio Donnarumma; Scott W. Herke; Patrick F. Herke; Kermit K. Murray (4119-4126).
is a doctoral candidate at Louisiana State University in the Department of Chemistry. She received a B.S. degree in applied chemistry at Liaoning Shihua University in Fushun, China and a M.S. in chemistry at Western Kentucky University. Her research, under the supervision of Prof. Kermit K. Murray, focuses on applications of infrared laser ablation for sampling and imaging of complex biological samples for mass spectrometry and genomic analysis. received his M. Pharm. degree in pharmaceutical chemistry and technology at the University of Modena and Reggio Emilia in Italy and a Ph.D. degree in pharmaceutical sciences at the University of Graz in Austria. He is currently a postdoctoral researcher in the Murray Group at LSU and his research interests include laser ablation techniques for biomedical and forensic applications as well as the development of liquid chromatography mass spectrometry assays and mass spectrometry imaging techniques. completed his M.S. degree in zoology at the University of Maine, Orono, in 1988, and worked for the U.S. Army Corps of Engineers, New England Division, until 1993. He received a Ph.D. in Biological Sciences in 1999 at LSU. Since 2006, he has managed the Genomics Core Facility for the LSU College of Science. His current interests are focused on client-based troubleshooting and optimization of genomics research methods, such as those used in Sanger sequencing and next-generation sequencing. is an honors student at the Baton Rouge Magnet High School (BRHMS), and he has participated in several research projects at the Genomics Core Facility of LSU. His efforts to optimize the facility’s Sanger sequencing procedures resulted in significant time savings as well as improvements in data quality. In addition to scientific pursuits, he plays the viola in the BRMHS Advanced Orchestra and the Louisiana Youth Orchestra. is the Roy Paul Daniels Professor of Chemistry at Louisiana State University. He received a B.S. in chemistry from the University of California at Berkeley in 1982 and a Ph.D. in chemical physics at the University of Colorado in 1988. His research at LSU concentrates on the fundamentals and applications of laser desorption ionization mass spectrometry and laser ablation for biological sampling and imaging. Infrared (IR) laser ablation was used to remove material from tissue sections mounted on microscope slides, with subsequent capture in a solvent-containing microcentrifuge tube. Experiments conducted with a 3200-bp double-stranded plasmid DNA template demonstrated IR-laser ablation transfer of intact DNA. The transfer efficiency and the molecular integrity of the captured DNA were evaluated using Sanger sequencing, gel electrophoresis, and fluorimetric analysis. The plasmid DNA was reproducibly transferred with an efficiency of 59 ± 3% at laser fluences of between 10 and 20 kJ/m2 at a wavelength of 3 μm. IR laser ablation sample transfer was then used to ablate and capture DNA from 50-μm-thick rat brain and kidney tissue sections. DNA was extracted from the captured material using five commercial DNA extraction kits that employed significantly divergent methodologies, with all kits recovering sufficient DNA for successful amplification by polymerase chain reaction (PCR). Four sets of primers were employed, targeting one region of the CYP 11b2 gene (376 bp) and three different regions of the Snn1g gene (298, 168, and 281 bp). The PCR results were not consistently reliable when using unpurified ablation samples; however, after extraction, all samples produced PCR products of the expected size. This work expands the sampling capabilities of IR laser ablation, demonstrating that DNA can be isolated from tissue samples for genomic assays. Due to the small size of the ablation regions (1 mm2), this technique will be useful for sampling discrete cell populations from tissue sections. Graphical abstract Infrared laser ablation transfer of intact DNA from a tissue section.
Keywords: Nucleic acids (DNA | RNA); Laser ablation; Localized sampling; Genomics; Tissue nucleic acids (DNA | RNA); Laser ablation; Localized sampling; Genomics; Tissue
Analysis of honeybush tea (Cyclopia spp.) volatiles by comprehensive two-dimensional gas chromatography using a single-stage thermal modulator by Gaalebalwe Ntlhokwe; Andreas G. J. Tredoux; Tadeusz Górecki; Matthew Edwards; Jochen Vestner; Magdalena Muller; Lené Erasmus; Elizabeth Joubert; J. Christel Cronje; André de Villiers (4127-4138).
The applicability of comprehensive two-dimensional gas chromatography (GC×GC) using a single-stage thermal modulator was explored for the analysis of honeybush tea (Cyclopia spp.) volatile compounds. Headspace solid phase micro-extraction (HS-SPME) was used in combination with GC×GC separation on a non-polar × polar column set with flame ionisation (FID) detection for the analysis of fermented Cyclopia maculata, Cyclopia subternata and Cyclopia genistoides tea infusions of a single harvest season. Method optimisation entailed evaluation of the effects of several experimental parameters on the performance of the modulator, the choice of columns in both dimensions, as well as the HS-SPME extraction fibre. Eighty-four volatile compounds were identified by co-injection of reference standards. Principal component analysis (PCA) showed clear differentiation between the species based on their volatile profiles. Due to the highly reproducible separations obtained using the single-stage thermal modulator, multivariate data analysis was simplified. The results demonstrate both the complexity of honeybush volatile profiles and the potential of GC×GC separation in combination with suitable data analysis techniques for the investigation of the relationship between sensory properties and volatile composition of these products. The developed method therefore offers a fast and inexpensive methodology for the profiling of honeybush tea volatiles. Graphical abstract Surface plot obtained for the GC×GC-FID analysis of honeybush tea volatiles
Keywords: Comprehensive two-dimensional gas chromatography (GC×GC); Honeybush tea; Thermal modulation; Multivariate data analysis; Volatiles
Rapid electrochemical quantification of Salmonella Pullorum and Salmonella Gallinarum based on glucose oxidase and antibody-modified silica nanoparticles by Yiheng Luo; Wenchao Dou; Guangying Zhao (4139-4147).
In this article, a facile and sensitive electrochemical method for quantification of Salmonella Pullorum and Salmonella Gallinarum (S. Pullorum and S. Gallinarum) was established by monitoring glucose consumption with a personal glucose meter (PGM). Antibody-functionalized magnetic nanoparticles (IgG-MNPs) were used to capture and enrich S. Pullorum and S. Gallinarum, and IgG-MNPs-S. Pullorum and IgG-MNPs-S. Gallinarum complexes were magnetically separated from a sample using a permanent magnet. The trace tag was prepared by loading polyclonal antibodies and high-content glucose oxidase on amino-functionalized silica nanoparticles (IgG-SiNPs-GOx). With a sandwich-type immunoassay format, IgG-SiNPs-GOx were added into the above mixture solution and conjugated to the complexes, forming sandwich composites IgG-MNPs/S. Pullorum and S. Gallinarum/IgG-SiNPs-GOx. The above sandwich composites were dispersed in glucose solution. Before and after the hydrolysis of glucose, the concentration of glucose was measured using PGM. Under optimal conditions, a linear relationship between the decrease of glucose concentration and the logarithm of S. Pullorum and S. Gallinarum concentration was obtained in the concentration range from 1.27 × 102 to 1.27 × 105 CFU mL−1, with a detection limit of 7.2 × 101 CFU mL−1 (S/N = 3). This study provides a portable, low-cost, and quantitative analytical method for bacteria detection; thus, it has a great potential in the prevention of disease caused by S. Pullorum and S. Gallinarum in poultry. Graphical abstract A schematic illustration of the fabrication process of IgG-SiNPs-GOD nanomaterials (A) and IgG-MNPs (B) and experimental procedure of detection of S. Pullorum and S. Gallinarum using GOD-functionalized silica nanospheres as trace tags based on PGM (C).
Keywords: Silica nanoparticle; Glucose oxidase; Magnetic nanoparticles; Personal glucose meter; Salmonella Pullorum and Salmonella Gallinarum
High-throughput analysis of sub-visible mAb aggregate particles using automated fluorescence microscopy imaging by Albert Jesuran Paul; Fabian Bickel; Martina Röhm; Lisa Hospach; Bettina Halder; Nina Rettich; René Handrick; Eva Maria Herold; Hans Kiefer; Friedemann Hesse (4149-4156).
Aggregation of therapeutic proteins is a major concern as aggregates lower the yield and can impact the efficacy of the drug as well as the patient’s safety. It can occur in all production stages; thus, it is essential to perform a detailed analysis for protein aggregates. Several methods such as size exclusion high-performance liquid chromatography (SE-HPLC), light scattering, turbidity, light obscuration, and microscopy-based approaches are used to analyze aggregates. None of these methods allows determination of all types of higher molecular weight (HMW) species due to a limited size range. Furthermore, quantification and specification of different HMW species are often not possible. Moreover, automation is a perspective challenge coming up with automated robotic laboratory systems. Hence, there is a need for a fast, high-throughput-compatible method, which can detect a broad size range and enable quantification and classification. We describe a novel approach for the detection of aggregates in the size range 1 to 1000 μm combining fluorescent dyes for protein aggregate labelling and automated fluorescence microscope imaging (aFMI). After appropriate selection of the dye and method optimization, our method enabled us to detect various types of HMW species of monoclonal antibodies (mAbs). Using 10 μmol L−1 4,4′-dianilino-1,1′-binaphthyl-5,5′-disulfonate (Bis-ANS) in combination with aFMI allowed the analysis of mAb aggregates induced by different stresses occurring during downstream processing, storage, and administration. Validation of our results was performed by SE-HPLC, UV-Vis spectroscopy, and dynamic light scattering. With this new approach, we could not only reliably detect different HMW species but also quantify and classify them in an automated approach. Our method achieves high-throughput requirements and the selection of various fluorescent dyes enables a broad range of applications.
Keywords: Protein aggregation; Fluorescence microscopy; Monoclonal antibody; Fluorescent dyes; Automatization
Molecularly imprinted polymers based stir bar sorptive extraction for determination of cefaclor and cefalexin in environmental water by Jun Peng; Donghao Liu; Tian Shi; Huairu Tian; Xuanhong Hui; Hua He (4157-4166).
Although stir bar sportive extraction was thought to be a highly efficiency and simple pretreatment approach, its wide application was limited by low selectivity, short service life, and relatively high cost. In order to improve the performance of the stir bar, molecular imprinted polymers and magnetic carbon nanotubes were combined in the present study. In addition, two monomers were utilized to intensify the selectivity of molecularly imprinted polymers. Fourier transform infrared spectroscopy, scanning electron microscopy, and selectivity experiments showed that the molecularly imprinted polymeric stir bar was successfully prepared. Then micro-extraction based on the obtained stir bar was coupled with HPLC for determination of trace cefaclor and cefalexin in environmental water. This approach had the advantages of stir bar sportive extraction, high selectivity of molecular imprinted polymers, and high sorption efficiency of carbon nanotubes. To utilize this pretreatment approach, pH, extraction time, stirring speed, elution solvent, and elution time were optimized. The LOD and LOQ of cefaclor were found to be 3.5 ng · mL–1 and 12.0 ng · mL–1, respectively; the LOD and LOQ of cefalexin were found to be 3.0 ng · mL–1 and 10.0 ng · mL–1, respectively. The recoveries of cefaclor and cefalexin were 86.5 ~ 98.6%. The within-run precision and between-run precision were acceptable (relative standard deviation <7%). Even when utilized in more than 14 cycles, the performance of the stir bar did not decrease dramatically. This demonstrated that the molecularly imprinted polymeric stir bar based micro-extraction was a convenient, efficient, low-cost, and a specific method for enrichment of cefaclor and cefalexin in environmental samples.
Keywords: Molecularly imprinted polymers; Magnetic carbon nanotubes; Cephalosporins; Environmental water; Stir bar sorption microextraction
Analysis of cellular autofluorescence in touch samples by flow cytometry: implications for front end separation of trace mixture evidence by M. Katherine Philpott; Cristina E. Stanciu; Ye Jin Kwon; Eduardo E. Bustamante; Susan A. Greenspoon; Christopher J. Ehrhardt (4167-4179).
The goal of this study was to survey optical and biochemical variation in cell populations deposited onto a surface through touch or contact and identify specific features that may be used to distinguish and then sort cell populations from separate contributors in a trace biological mixture. Although we were not able to detect meaningful biochemical variation in touch samples deposited by different contributors through preliminary antibody surveys, we did observe distinct differences in red autofluorescence emissions (650–670 nm), with as much as a tenfold difference in mean fluorescence intensities observed between certain pairs of donors. Results indicate that the level of red autofluorescence in touch samples can be influenced by a donor’s contact with specific material prior to handling the substrate from which cells were collected. In particular, we observed increased red autofluorescence in cells deposited subsequent to handling laboratory gloves, plant material, and certain types of marker ink, which could be easily visualized microscopically or using flow cytometry, and persisted after hand washing. To test whether these observed optical differences could potentially be used as the basis for a cell separation workflow, a controlled two-person touch mixture was separated into two fractions via fluorescence-activated cell sorting (FACS) using gating criteria based on intensity of 650–670 nm emissions and then subjected to DNA analysis. Genetic analysis of the sorted fractions provided partial DNA profiles that were consistent with separation of individual contributors from the mixture suggesting that variation in autofluorescence signatures, even if driven by extrinsic factors, may nonetheless be a useful means of isolating contributors to some touch mixtures. Graphical Abstract Conceptual workflow diagram. Trace biological mixtures containing cells from multiple individuals are analyzed by flow cytometry. Cells are then physically separated into two populations based on intensity of red autofluorescence using Fluorescence Activated Cell Sorting. Each isolated cell fraction is subjected to DNA analysis resulting in a DNA profile for each contributor.
Keywords: Biological mixtures; Flow cytometry; Touch; Trace; FACS; Epithelial cells; Mixture interpretation; STR profiling; Autofluorescence
A new carbon-based magnetic material for the dispersive solid-phase extraction of UV filters from water samples before liquid chromatography–tandem mass spectrometry analysis by Susy Piovesana; Anna Laura Capriotti; Chiara Cavaliere; Giorgia La Barbera; Roberto Samperi; Riccardo Zenezini Chiozzi; Aldo Laganà (4181-4194).
Magnetic solid-phase extraction is one of the most promising new extraction methods for liquid samples before ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) analysis. Several types of materials, including carbonaceous ones, have been prepared for this purpose. In this paper, for the first time, the preparation, characterization, and sorption capability of Fe3O4-graphitized carbon black (mGCB) composite toward some compounds of environmental interest were investigated. The synthesized mGCB consisted of micrometric GCB particles with 55 m2 g−1 surface area bearing some carbonyl and hydroxyl functionalities and the surface partially decorated by Fe3O4 microparticles. The prepared mGCB was firstly tested as an adsorbent for the extraction from surface water of 50 pollutants, including estrogens, perfluoroalkyl compounds, UV filters, and quinolones. The material showed good affinity to many of the tested compounds, except carboxylates and glucoronates; however, some compounds were difficult to desorb. Ten UV filters belonging to the chemical classes of benzophenones and p-aminobenzoates were selected, and parameters were optimized for the extraction of these compounds from surface water before UHPLC–MS/MS determination. Then, the method was validated in terms of linearity, trueness, intra-laboratory precision, and detection and quantification limits. In summary, the method performance (trueness, expressed as analytical recovery, 85–114%; RSD 5–15%) appears suitable for the determination of the selected compounds at the level of 10–100 ng L−1, with detection limits in the range of 1–5 ng L−1. Finally, the new method was compared with a published one, based on conventional solid-phase extraction with GCB, showing similar performance in real sample analysis. Graphical Abstract Workflow of the analytical method based on magnetic solid-phase extraction followed by LC-MS/MS determination
Keywords: Magnetic graphitized carbon black; UV filters; Water samples; Magnetic solid-phase extraction; LC–MS/MS
In vitro anti-thrombotic and anti-coagulant properties of blacklip abalone (Haliotis rubra) viscera hydrolysate by Hafiz Ansar Rasul Suleria; Paul P. Masci; Rama Addepalli; Wei Chen; Glenda C. Gobe; Simone A. Osborne (4195-4205).
Abalone viscera contain sulphated polysaccharides with anti-thrombotic and anti-coagulant activities. In this study, a hydrolysate was prepared from blacklip abalone (Haliotis rubra) viscera using papain and bromelain and fractionated using ion exchange and size exclusion chromatography. Hydrolysates and fractions were investigated for in vitro thrombin inhibition mediated through heparin cofactor II (HCII) as well as anti-coagulant activity in plasma and whole blood. On the basis of sulphated polysaccharide concentration, the hydrolysate inhibited thrombin through HCII with an inhibitor concentration at 50% (IC50) of 16.5 μg/mL compared with 2.1 μg/mL for standard heparin. Fractionation concentrated HCII-mediated thrombin inhibition down to an IC50 of 1.8 μg/mL and improved anti-coagulant activities by significantly delaying clotting time. This study confirmed the presence of anti-thrombotic and anti-coagulant molecules in blacklip abalone viscera and demonstrated that these activities can be enriched with a simple chromatography regime. Blacklip abalone viscera warrant further investigation as a source of nutraceutical or functional food ingredients. Graphical abstract Schematic showing preparation of bioactive extracts and fractions from blacklip abalone
Keywords: Anti-coagulant; Anti-thrombotic; Blacklip abalone; Viscera; Marine processing waste
Dual-mode immunoassay based on shape code and infrared absorption fingerprint signals of silica nanorods by Pengfei Zhao; Ran Ni; Kexin Wang; Xia Hong; Yadan Ding; Tie Cong; Junping Liu; Huiying Zhao (4207-4213).
Silica nanorods were synthesized through a simple one-pot emulsion-droplet-based growth method, in which tetraethylorthosilicate (TEOS) was used as the silica source, ammonia as the catalyst, and polyvinylpyrrolidone (PVP) as the structure-directing agent and stabilizer. By controlling hydrolysis and condensation in the reaction process, we regulated the aspect ratios and the infrared (IR) absorption fingerprint signals (the transverse optical and the longitudinal optical phonon modes) of the silica nanorods. Based on this, a dual-mode immunoassay was performed for detecting model target analyte, human IgG. The shape code of the silica nanorods was used for simple, rapid qualitative, and sensitive semi-quantitative immunoassay by using a conventional optical microscope. The characteristic IR absorption fingerprint signals of the silica nanorods allowed for reliable quantitative immunoassay with good selectivity and high specificity. The detection limit and the linear range were found out to be 0.5 pM and 1 pM–10 nM, respectively. We expect that such dual-mode immunoassay could be applied for the detection of other analytes, such as protein, nucleic acids, bacteria, viruses, explosives, toxins, and so on. Graphical abstract A simple dual-mode immunoassay was performed using the shape code and infrared absorption fingerprint signals of silica nanorods as detection signals.
Keywords: Silica nanorods; IR fingerprint signals; Shape code; Immunoassay
Complexation-mediated electromembrane extraction of highly polar basic drugs—a fundamental study with catecholamines in urine as model system by Elena Fernández; Linda Vårdal; Lorena Vidal; Antonio Canals; Astrid Gjelstad; Stig Pedersen-Bjergaard (4215-4223).
Complexation-mediated electromembrane extraction (EME) of highly polar basic drugs (log P < −1) was investigated for the first time with the catecholamines epinephrine, norepinephrine, and dopamine as model analytes. The model analytes were extracted as cationic species from urine samples (pH 4), through a supported liquid membrane (SLM) comprising 25 mM 4-(trifluoromethyl)phenylboronic acid (TFPBA) in bis(2-ethylhexyl) phosphite (DEHPi), and into 20 mM formic acid as acceptor solution. EME was performed for 15 min, and 50 V was used as extraction voltage across the SLM. TFPBA served as complexation reagent, and selectively formed boronate esters by reversible covalent binding with the model analytes at the sample/SLM interface. This enhanced the mass transfer of the highly polar model analytes across the SLM, and EME of basic drugs with log P in the range −1 to −2 was shown for the first time. Meanwhile, most matrix components in urine were unable to pass the SLM. Thus, the proposed concept provided highly efficient sample clean-up and the system current across the SLM was kept below 50 μA. Finally, the complexation-mediated EME concept was combined with ultra-high performance liquid chromatography coupled to tandem mass spectrometry and evaluated for quantification of epinephrine and dopamine. Standard addition calibration was applied to a pooled human urine sample. Calibration curves using standards between 25 and 125 μg L−1 gave a high level of linearity with a correlation coefficient of 0.990 for epinephrine and 0.996 for dopamine (N = 5). The limit of detection, calculated as three times signal-to-noise ratio, was 5.0 μg L−1 for epinephrine and 1.8 μg L−1 for dopamine. The repeatability of the method, expressed as coefficient of variation, was 13% (n = 5). The proposed method was finally applied for the analysis of spiked pooled human urine sample, obtaining relative recoveries of 91 and 117% for epinephrine and dopamine, respectively.
Keywords: Electromembrane extraction; Polar analytes; Urine samples; Catecholamines
Cobalt oxyhydroxide nanoflakes with intrinsic peroxidase catalytic activity and their application to serum glucose detection by Yu-Min Wang; Jin-Wen Liu; Jian-Hui Jiang; Wenwan Zhong (4225-4232).
Cobalt oxyhydroxide (CoOOH) nanoflakes, an emerging type of two-dimensional nanomaterial, show great potential for use in molecular detection. Previous assays utilizing such materials have largely been based on their outstanding fluorescence quenching ability and oxidizing power. Herein, we report the intrinsic peroxidase-like activity of cobalt oxyhydroxide (CoOOH) nanoflakes, and we show how this activity can be employed for glucose detection. We found that, in the presence of hydrogen peroxide (H2O2), the nanoflakes accelerated the conversion of peroxidase substrates such as 3,3′,5,5′-tetramethylbenzidine (TMB) into colored products. By combining the CoOOH nanoflakes with the biological enzyme glucose oxidase (GOx), we developed a colorimetric method for the detection of glucose within the concentration range 5.3–500 μM. The proposed method was applied to detect elevated blood glucose levels in diabetic patients, and the intense color change induced by elevated glucose levels was found to be readily apparent to the naked eye, proving the utility of our assay for point-of-care testing. Graphical abstract The intrinsic peroxidase-like activity of cobalt oxyhydroxide (CoOOH) nanoflakes was exploited to enable the direct visualization of elevated glucose levels in sera from diabetic patients
Keywords: CoOOH nanoflakes; Peroxidase; Hydrogen peroxide; Glucose; Bioassay
Chemical characterisation of the whole plant cell wall of archaeological wood: an integrated approach by Luca Zoia; Diego Tamburini; Marco Orlandi; Jeannette Jacqueline Łucejko; Anika Salanti; Eeva-Liisa Tolppa; Francesca Modugno; Maria Perla Colombini (4233-4245).
Wood artefacts undergo complex alteration and degradation during ageing, and gaining information on the chemical composition of wood in archaeological artefacts is fundamental to plan conservation strategies. In this work, an integrated analytical approach based on innovative NMR spectroscopy procedures, gel permeation chromatography and analytical pyrolysis coupled with gas chromatography/mass spectrometry (Py-GC-MS) was applied for the first time on archaeological wood from the Oseberg collection (Norway), in order to evaluate the chemical state of preservation of the wood components, without separating them. We adopted ionic liquids (ILs) as non-derivatising solvents, thus obtaining an efficient dissolution of the wood, allowing us to overcome the difficulty of dissolving wood in its native form in conventional molecular solvents. Highly substituted lignocellulosic esters were therefore obtained under mild conditions by reacting the solubilised wood with either acetyl chloride or benzoyl chloride. A phosphytilation reaction was also performed using 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphospholan. As a result, the functionalised wood developed an enhanced solubility in molecular solvents, thus enabling information about modifications of lignin, depolymerisation of cellulose and structure of lignin-carbohydrate complexes to be obtained by means of spectroscopic (2D-HSQC-NMR and 31P-NMR) and chromatographic (gel permeation chromatography) techniques. Py-GC-MS was used to investigate the degradation undergone by the lignocellulosic components on the basis of their pyrolysis products, without any pre-treatment of the samples. The application of all these combined techniques enabled a comprehensive characterisation of the whole cell wall of archaeological wood and the evaluation of its state of preservation. High depletion of carbohydrates and high extent of lignin oxidation were highlighted in the alum-treated objects, whereas a good preservation state was found for the untreated wood of the Oseberg ship. Graphical abstract ᅟ
Keywords: Waterlogged archaeological wood; Ionic liquids; NMR; GPC, Py(HMDS)-GC-MS
Analysis of Listeria using exogenous volatile organic compound metabolites and their detection by static headspace–multi-capillary column–gas chromatography–ion mobility spectrometry (SHS–MCC–GC–IMS) by Carl Taylor; Fraser Lough; Stephen P. Stanforth; Edward C. Schwalbe; Ian A. Fowlis; John R. Dean (4247-4256).
Listeria monocytogenes is a Gram-positive bacterium and an opportunistic food-borne pathogen which poses significant risk to the immune-compromised and pregnant due to the increased likelihood of acquiring infection and potential transmission of infection to the unborn child. Conventional methods of analysis suffer from either long turn-around times or lack the ability to discriminate between Listeria spp. reliably. This paper investigates an alternative method of detecting Listeria spp. using two novel enzyme substrates that liberate exogenous volatile organic compounds in the presence of α-mannosidase and d-alanyl aminopeptidase. The discriminating capabilities of this approach for identifying L. monocytogenes from other species of Listeria are investigated. The liberated volatile organic compounds (VOCs) are detected using an automated analytical technique based on static headspace–multi-capillary column–gas chromatography–ion mobility spectrometry (SHS–MCC–GC–IMS). The results obtained by SHS–MCC–GC–IMS are compared with those obtained by the more conventional analytical technique of headspace–solid phase microextraction–gas chromatography–mass spectrometry (HS–SPME–GC–MS). The results found that it was possible to differentiate between L. monocytogenes and L. ivanovii, based on their VOC response from α-mannosidase activity.
Keywords: Volatile organic compounds; Bacteria; Listeria spp.; Static headspace–multi-capillary column–gas chromatography–ion mobility spectrometry (SHS–MCC–GC–IMS); GC–MS
Design and development of amperometric biosensor for the detection of lead and mercury ions in water matrix—a permeability approach by Manju Bhargavi Gumpu; Uma Maheswari Krishnan; John Bosco Balaguru Rayappan (4257-4266).
Intake of water contaminated with lead (Pb2+) and mercury (Hg2+) ions leads to various toxic effects and health issues. In this context, an amperometric urease inhibition-based biosensor was developed to detect Pb2+ and Hg2+ ions in water matrix. The modified Pt/CeO2/urease electrode was fabricated by immobilizing CeO2 nanoparticles and urease using a semi-permeable adsorption layer of nafion. With urea as a substrate, urease catalytic activity was examined through cyclic voltammetry. Further, maximum amperometric inhibitive response of the modified Pt/CeO2/urease electrode was observed in the presence of Pb2+ and Hg2+ ions due to the urease inhibition at specific potentials of −0.03 and 0 V, respectively. The developed sensor exhibited a detection limit of 0.019 ± 0.001 μM with a sensitivity of 89.2 × 10−3 μA μM−1 for Pb2+ ions. A detection limit of 0.018 ± 0.003 with a sensitivity of 94.1 × 10−3 μA μM−1 was achieved in detecting Hg2+ ions. The developed biosensor showed a fast response time (<1 s) with a linear range of 0.5–2.2 and 0.02–0.8 μM for Pb2+ and Hg2+ ions, respectively. The modified electrode offered a good stability for 20 days with a good repeatability and reproducibility. The developed sensor was used to detect Pb2+ and Hg2+ ions contaminating Cauvery river water and the observed results were in good co-ordination with atomic absorption spectroscopic data.
Keywords: Amperometry; Urease; Enzyme inhibition; Metal ions; Lead and mercury
Novel fast analytical method for indirect determination of MCPD fatty acid esters in edible oils and fats based on simultaneous extraction and derivatization by Renata Jędrkiewicz; Agnieszka Głowacz-Różyńska; Justyna Gromadzka; Piotr Konieczka; Jacek Namieśnik (4267-4278).
A novel method for indirect determination of MCPD esters levels in lipid samples has been developed. The method is based on combination of extraction and derivatization in the same sample preparation step. It is achieved by the application of diethyl ether as extraction solvent for isolation of analytes released from esterified forms from the water phase and as dilution solvent for solid PBA – the derivatization agent. It is a noteworthy improvement of recommended indirect approaches available in the literature because such steps as sample clean-up, multiple liquid–liquid extractions, and preconcentration are excluded in the proposed solution. In this way, the developed procedure is shortened and simplified. Such an approach also minimizes the utilization of organic solvents; therefore, it is in accordance with the principles of “green analytical chemistry.” In spite of the fact that the step of sample clean-up is omitted, no deterioration in GC-MS system performance was observed. Equivalence testing of the developed procedure and AOCS cd 29b-13 official method (SGS) has been conducted. It was concluded that results obtained by both methods do not significantly differ statistically. The procedure has been applied to determination of MCPD esters concentrations in lipid fractions isolated by accelerated solvent extraction technique from such foodstuffs as bakery products, salty deep-fried snacks, and instant products. In all investigated samples, the level of bound MCPD was elevated. Additionally, for both procedures, the environmental impact (with the use of analytical Eco-scale) and uncertainty budget have been assessed and compared.
Keywords: Foods/beverages; Organic compounds/trace organic compounds; GC; Quality assurance/control; Simultaneous extraction and derivatization; MCPD esters
Optimization of an ultrasound-assisted derivatization for GC/MS analysis of oxygenated organic species in atmospheric aerosol by Maria Chiara Pietrogrande; Francesco Manarini; José Benito Quintana; Rosario Rodil; Eugenia Villaverde-de-Sáa; Marco Visentin (4279-4291).
A novel ultrasound-assisted derivatization followed by GC/MS analysis was developed for the quantification of oxygenated organic species in ambient aerosol. Derivatization parameters mostly influencing the analytical response were investigated, i.e., solvent type, reagent concentration, and reaction duration. Response surface methodology was used to design experiments and a quadratic model was utilized to predict the variables and establish the optimal conditions. The study was performed on standard solutions of 30 compounds representing the major classes of oxygenated compounds typically found in ambient aerosol, i.e., low molecular weight carboxylic acids, sugars, and phenols. In comparison with conventional methods, the optimized procedure uses mild reaction temperature (room temperature instead of 70 °C), reduces the amount of silyl reagent (24 vs. 40 μL), and shortens derivatization times (45 vs. 70 min), participating in the current trend of analytical chemistry towards clean, green methods that reduce costs and decrease pollution. Once optimized, the ultrasound procedure was validated by assessing for repeatability, linearity, detection limits, and derivative stability. For all oxygenated organic species, the proposed method showed a good reproducibility—as the relative standard deviations (RSDs%, n = 5) of intra-day analysis were ≤7% — a good linearity with the correlation coefficients of calibration curves R 2 ≥ 99.8, and low detection limits, ranging from 0.34 to 6.50 ng μL−1; thus it is suitable for its applicability in air quality monitoring. Finally, this method was successfully applied to determine 30 oxygenated organic species in three ambient PM2.5 samples collected at an urban site in Northern Italy in three different seasons. Graphical abstract Ultrasound-assisted derivatization is a green alternative method for GC/MS analysis of oxygenated organic species in atmospheric aerosol towards reduction of energy and reactive consumption.
Keywords: Ultrasound-assisted derivatization; GC/MS method; Experimental design and response surface methodology; Atmospheric aerosol; Oxygenated organic species
Towards the isolation and estimation of elemental carbon in atmospheric aerosols using supercritical fluid extraction and thermo-optical analysis by Hafiz Abdul Azeem; Johan Martinsson; Kristina Eriksson Stenström; Erik Swietlicki; Margareta Sandahl (4293-4300).
Air-starved combustion of biomass and fossil fuels releases aerosols, including airborne carbonaceous particles, causing negative climatic and health effects. Radiocarbon analysis of the elemental carbon (EC) fraction can help apportion sources of its emission, which is greatly constrained by the challenges in isolation of EC from organic compounds in atmospheric aerosols. The isolation of EC using thermo-optical analysis is however biased by the presence of interfering compounds that undergo pyrolysis during the analysis. EC is considered insoluble in all acidic, basic, and organic solvents. Based on the property of insolubility, a sample preparation method using supercritical CO2 and methanol as co-solvent was developed to remove interfering organic compounds. The efficiency of the method was studied by varying the density of supercritical carbon dioxide by means of temperature and pressure and by varying the methanol content. Supercritical CO2 with 10% methanol by volume at a temperature of 60 °C, a pressure of 350 bar and 20 min static mode extraction were found to be the most suitable conditions for the removal of 59 ± 3% organic carbon, including compounds responsible for pyrolysis with 78 ± 16% EC recovery. The results indicate that the method has potential for the estimation and isolation of EC from OC for subsequent analysis methods and source apportionment studies.
Keywords: Atmospheric aerosols; Elemental carbon; Pyrolytic organic carbon; Source apportionment; Supercritical carbon dioxide; Thermo-optical analysis