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Analytical and Bioanalytical Chemistry (v.404, #5)


Morpho-spectral imaging for investigation of disease progression by Cyril Petibois (pp. 1275-1276).
is Assistant Professor of Biochemistry at the University of Bordeaux, France, and is involved in the development of imaging methods for analysis of biosamples (CNRS UMR 5248 research unit; “Spectro-imaging of Biosystems” group). His research interest is to develop multimodal imaging methods for full characterization of biosamples, from synthetic models to individual cells and small animals, combining elemental, morphological, molecular, and chemical techniques. The laboratory is also engaged in the development of high-performance imaging methods using synchrotron radiation, notably using the IR and X-ray beamlines at major European and Asian synchrotron radiation facilities.

Imaging translocation and transformation of bioavailable selenium by Stanleya pinnata with X-ray microscopy by Wren Amos; Samuel Webb; Yijin Liu; Joy C. Andrews; Danika L. LeDuc (pp. 1277-1285).
Selenium hyperaccumulator Stanleya pinnata, Colorado ecotype, was supplied with water-soluble and biologically available selenate or selenite. Selenium distribution and tissue speciation were established using X-ray microscopy (micro-X-ray fluorescence and transmission X-ray microscopy) in two dimensions and three dimensions. The results indicate that S. pinnata tolerates, accumulates, and volatilizes significant concentrations of selenium when the inorganic form supplied is selenite and may possess novel metabolic capacity to differentiate, metabolize, and detoxify selenite concentrations surpassing field concentrations. The results also indicate that S. pinnata is a feasible candidate to detoxify selenium-polluted soil sites, especially locations with topsoil polluted with soluble and biologically available selenite.

Keywords: Selenium phytoremediation; Stanleya pinnata ; X-ray fluorescence; Transmission X-ray microscopy


X-ray microscopy and tomography detect the accumulation of bare and PEG-coated gold nanoparticles in normal and tumor mouse tissues by C-C. Chien; C-C. Cheng; H. H. Chen; Y. Hwu; Y. S. Chu; C. Petibois; A. Chen; Y-T. Ching; G. Margaritondo (pp. 1287-1296).
We demonstrate that, with appropriate staining, high-resolution X-ray microscopy can image complicated tissue structures—cerebellum and liver—and resolve large or small amounts of Au nanoparticles in these tissues. Specifically, images of tumor tissue reveal high concentrations of accumulated Au nanoparticles. PEG (poly(ethylene glycol)) coating is quite effective in enhancing this accumulation and significantly modifies the mechanism of uptake by reticuloendothelial system (RES) organs.

Keywords: High resolution X-ray microscopy; Nanoparticles; 3D tissue imaging


3D elemental sensitive imaging using transmission X-ray microscopy by Yijin Liu; Florian Meirer; Junyue Wang; Guillermo Requena; Phillip Williams; Johanna Nelson; Apurva Mehta; Joy C. Andrews; Piero Pianetta (pp. 1297-1301).
Determination of the heterogeneous distribution of metals in alloy/battery/catalyst and biological materials is critical to fully characterize and/or evaluate the functionality of the materials. Using synchrotron-based transmission x-ray microscopy (TXM), it is now feasible to perform nanoscale-resolution imaging over a wide X-ray energy range covering the absorption edges of many elements; combining elemental sensitive imaging with determination of sample morphology. We present an efficient and reliable methodology to perform 3D elemental sensitive imaging with excellent sample penetration (tens of microns) using hard X-ray TXM. A sample of an Al–Si piston alloy is used to demonstrate the capability of the proposed method.

Keywords: Transmission X-ray microscopy; Synchrotron radiation; 3D elemental mapping


Use of fractal zone plates for transmission X-ray microscopy by Xin Ge; Zhili Wang; Kun Gao; Dajiang Wang; Zhao Wu; Jian Chen; Zhiyun Pan; Kai Zhang; Youli Hong; Peiping Zhu; Ziyu Wu (pp. 1303-1309).
In this contribution we discuss the possibility of designing a modified transmission X-ray microscope by using fractal zone plates (Fzps) as diffractive optical elements. In the modified transmission X-ray microscope optical layout, we first introduced a fractal zone plate as the microscope objective. Indeed, a fractal zone plate cannot only be used as an image-forming component but also as a condenser element to achieve an extended depth of field. Numerical analysis reveals that fractal zone plates and conventional Fresnel zone plates have similar imaging capabilities under different coherent illumination. Using a fractal zone plate as a condenser we also simulated axial irradiance. Results confirm that fractal zone plates can improve focusing capability with an extended depth of field. Although preliminary, these simulations clearly reveal that fractal zone plates, when available, will be of great help in microscope layouts, in particular for foreseen high-resolution applications in the “water window” as strongly required in biological research.

Keywords: Transmission X-ray microscopy; Fractal zone plate; Coherence; Focusing properties


Use of synchrotron-radiation-based FTIR imaging for characterizing changes in cell contents by Seydou Yao; Michel Moenner; Anders Engdahl; Cyril Petibois (pp. 1311-1316).
FTIR imaging of individual cells is still limited by the low signal-to-noise ratio obtained from analysis of such weakly absorbing organic matter when using a Globar IR source. In this study, we used FTIR imaging with a synchrotron radiation source and a focal plane array detector to determine changes in the cellular contents of cryofixed cells after culture for 48 h on Si3N4 substrate. Several spectral differences were observed for cells deprived of glucose compared with control cells: a lower amide I-to-amide II ratio (P < 0.01); a different secondary structure profile of proteins (obtained from amide I spectral region curve fitting), with a significant increase in non-ordered structure components (P < 0.01); and a higher ν(C = C–H)/ν as(CH3) absorption ratio (P < 0.01), suggesting increased unsaturation of fatty acyl chains. Therefore, our study has shown that FTIR imaging with a synchrotron radiation source enables determination of several spectral changes of individual cells between two experimental conditions, which thus opens the way to cell biology studies with this vibrational spectroscopy technique.

Keywords: Bioanalytical methods; Spectroscopy/instrumentation; IR spectroscopy/Raman spectroscopy; Imaging; Synchrotron radiation


In vivo skin leptin modulation after 14 MeV neutron irradiation: a molecular and FT-IR spectroscopic study by M. Cestelli Guidi; C. Mirri; E. Fratini; V. Licursi; R. Negri; A. Marcelli; R. Amendola (pp. 1317-1326).
This paper discusses gene expression changes in the skin of mice treated by monoenergetic 14 MeV neutron irradiation and the possibility of monitoring the resultant lipid depletion (cross-validated by functional genomic analysis) as a marker of radiation exposure by high-resolution FT-IR (Fourier transform infrared) imaging spectroscopy. The irradiation was performed at the ENEA Frascati Neutron Generator (FNG), which is specifically dedicated to biological samples. FNG is a linear electrostatic accelerator that produces up to 1.0 × 1011 14-MeV neutrons per second via the D-T nuclear reaction. The functional genomic approach was applied to four animals for each experimental condition (unirradiated, 0.2 Gy irradiation, or 1 Gy irradiation) 6 hours or 24 hours after exposure. Coregulation of a subclass of keratin and keratin-associated protein genes that are physically clustered in the mouse genome and functionally related to skin and hair follicle proliferation and differentiation was observed. Most of these genes are transiently upregulated at 6 h after the delivery of the lower dose delivered, and drastically downregulated at 24 h after the delivery of the dose of 1 Gy. In contrast, the gene coding for the leptin protein was consistently upregulated upon irradiation with both doses. Leptin is a key protein that regulates lipid accumulation in tissues, and its absence provokes obesity. The tissue analysis was performed by monitoring the accumulation and the distribution of skin lipids using FT-IR imaging spectroscopy. The overall picture indicates the differential modulation of key genes during epidermis homeostasis that leads to the activation of a self-renewal process at low doses of irradiation.

Keywords: Skin; Leptin; Wound healing; Ionizing radiation; FT-IR imaging


High-speed X-ray microscopy by use of high-resolution zone plates and synchrotron radiation by Qiyue Hou; Zhili Wang; Kun Gao; Zhiyun Pan; Dajiang Wang; Xin Ge; Kai Zhang; Youli Hong; Peiping Zhu; Ziyu Wu (pp. 1327-1330).
X-ray microscopy based on synchrotron radiation has become a fundamental tool in biology and life sciences to visualize the morphology of a specimen. These studies have particular requirements in terms of radiation damage and the image exposure time, which directly determines the total acquisition speed. To monitor and improve these key parameters, we present a novel X-ray microscopy method using a high-resolution zone plate as the objective and the matching condenser. Numerical simulations based on the scalar wave field theory validate the feasibility of the method and also indicate the performance of X-ray microscopy is optimized most with sub-10-nm-resolution zone plates. The proposed method is compatible with conventional X-ray microscopy techniques, such as computed tomography, and will find wide applications in time-resolved and/or dose-sensitive studies such as living cell imaging.

Keywords: X-ray microscopy; High-resolution zone plate; Radiation dose; Exposure time; Synchrotron radiation


Studies on the metabolism of five model drugs by fungi colonizing cadavers using LC-ESI-MS/MS and GC-MS analysis by Jorge A. Martínez-Ramírez; Kerstin Voigt; Frank T. Peters (pp. 1339-1359).
It is well-known that cadavers may be colonized by microorganisms, but there is limited information if or to what extent these microbes are capable of metabolizing drugs or poisons, changing the concentrations and metabolic pattern of such compounds in postmortem samples. The aim of the present study was to develop a fungal biotransformation system as an in vitro model to investigate potential postmortem metabolism by fungi. Five model drugs (amitriptyline, metoprolol, mirtazapine, promethazine, and zolpidem) were each incubated with five model fungi known to colonize cadavers (Absidia repens, Aspergillus repens, Aspergillus terreus, Gliocladium viride, and Mortierella polycephala) and with Cunninghamella elegans (positive control). Incubations were performed in Sabouraud medium at 25 °C for 5 days. After centrifugation, a part of the supernatants was analyzed by liquid chromatography-tandem mass spectrometry with product ion scanning. Another part was analyzed by full scan gas chromatography-mass spectrometry after extraction and derivatization. All model drugs were metabolized by the control fungus resulting in two (metoprolol) to ten (amitriptyline) metabolites. Of the model fungi, only Abs. repens and M. polycephala metabolized the model drugs: amitriptyline was metabolized to six and five, metoprolol to two and two, mirtazapine to five and three, promethazine to six and nine, and zolpidem to three and four metabolites, respectively. The main metabolic reactions were demethylation, oxidation, and hydroxylation. The presented in vitro model is applicable to studying drug metabolism by fungi colonizing cadavers.

Keywords: Metabolism; Fungi; Cadavers; LC-ESI-MS/MS; GC-MS


Development of a five-plex flow cytometric immunoassay for the simultaneous detection of six coccidiostats in feed and eggs by Monique E. Bienenmann-Ploum; Anne-Catherine Huet; Katrina Campbell; Terence L. Fodey; Ursula Vincent; Willem Haasnoot; Philippe Delahaut; Christopher T. Elliott; Michel W. F. Nielen (pp. 1361-1373).
Coccidiostats are the only veterinary drugs still permitted to be used as feed additives to treat poultry for coccidiosis. To protect consumers, maximum levels for their presence in food and feed have been set by the European Union (EU). To monitor these coccidiostats, a rapid and inexpensive screening method would be a useful tool. The development of such a screening method, using a flow cytometry-based immunoassay, is described. The assay uses five sets of colour-coded paramagnetic microspheres for the detection of six selected priority coccidiostats. Different coccidiostats, with and without carrier proteins, were covalently coupled onto different bead sets and tested in combination with polyclonal antisera and with a fluorescent-labelled secondary antibody. The five optimal combinations were selected for this multiplex and a simple-to-use sample extraction method was applied for screening blank and spiked eggs and feed samples. A very good correlation (r ranging from 0.995 to 0.999) was obtained with the responses obtained in two different flow cytometers (Luminex 100 and FLEXMAP 3D). The sensitivities obtained were in accordance with the levels set by the EU as the measured limits of detection for narasin/salinomycin, lasalocid, diclazuril, nicarbazin (4,4′-dinitrocarbanilide) and monensin in eggs were 0.01, 0.1, 0.5, 53 and 0.1 μg/kg and in feed 0.1, 0.2, 0.3, 9 and 1.5 μg/kg, respectively. Figure

Keywords: Coccidiostats; Multiplex flow cytometric immunoassay; Colour-coded beads; Eggs; Feed


Development and validation of two multiresidue liquid chromatography tandem mass spectrometry methods based on a versatile extraction procedure for isolating non-steroidal anti-inflammatory drugs from bovine milk and muscle tissue by Alessandra Gentili; Fulvia Caretti; Simona Bellante; Lucia Mainero Rocca; Roberta Curini; Alessandro Venditti (pp. 1375-1388).
The main difficulties in analysing non-steroidal anti-inflammatory drugs (NSAIDs) in food and biological samples are due to the tight non-covalent interactions established with matrix proteins and the amount of occurring fatty material. The present paper describes an effective extraction procedure able to isolate fifteen NSAIDs (acetaminophen, salicylic acid, ibuprofen, diclofenac, flunixin and its metabolite 5-hydroxy-flunixin, nimesulide, phenylbutazone, meclofenamic acid, tolfenamic acid, meloxicam, carprofen, ketoprofen, naproxen and etodolac) from bovine milk and muscle tissue through two succeeding steps: (a) deproteinisation/extraction with organic solvent, essential to lower the medium dielectric constant and, therefore, to release the analytes from matrix; (b) SPE clean-up on OASIS cartridges. Lipids were easily removed during low-temperature centrifugations. The advantages of the developed procedure pertain to the efficient removal of the fat substances (very low matrix effect and high recovery yields) and its versatility, since it can be applied both to milk and muscle with few adjustments due to the diversity of the two matrices. Ion-pairing reversed-phase chromatography combined with the negative electrospray detection was able to achieve low detection capabilities (CCβs) for all analytes and, in particular, for diclofenac whose Maximum Residue Limit (MRL) in milk is 0.1 μg kg−1. The methods were validated according to the guidelines of the Commission Decision 2002/657/EC and then applied for a small monitoring study. A number of samples showed traces of salicylic acid (SA), but its occurrence was not ascribed to a misuse of drugs (aspirin, salicylic acid) since SA, accumulating in plants in response to a pathogen attack, may be introduced into the food chain. Figure Figurative representation of NSAIDs contamination in milk

Keywords: NSAIDs; LC-tandem MS; Bovine milk; Bovine muscle tissue


Direct and quantitative analysis of underivatized acylcarnitines in serum and whole blood using paper spray mass spectrometry by Qian Yang; Nicholas E. Manicke; He Wang; Christopher Petucci; R. Graham Cooks; Zheng Ouyang (pp. 1389-1397).
A simple protocol for rapid quantitation of acylcarnitines in serum and whole blood has been developed using paper spray mass spectrometry. Dried serum and whole blood containing a mixture of ten acylcarnitines at various concentrations were analyzed as spots from paper directly without any sample pretreatment, separation, or derivatization. The composition of the spray solvent was found to be a critical factor: for serum samples, spray solvent of methanol/water/formic acid (80:20:0.1) gave the best signal intensity while for blood samples which contain more matrix components, acetonitrile/water (90:10) was a much more suitable spray solvent. For the paper type and size used, 0.5 μL of sample provided an optimal signal for both serum and whole blood samples. For quantitative profiling, the limits of quantitation obtained from both serum and blood were much lower than the clinically validated cutoff values for diagnosis of fatty acid oxidation disorders in newborn screening. Linearity (R 2 > 0.95) and reproducibility (RSD ∼10 %) were achieved in the concentration ranges from 100 nM to 5 μM for the C2 acylcarnitine, and for other acylcarnitines, these values were from 10 to 500 nM. Acylcarnitine profiles offer an effective demonstration of the fact that paper spray mass spectrometry is an appropriate, simple, rapid method with high sensitivity and high reproducibility applicable to newborn screening tests. Figure Direct and quantitative analysis of underivatized acylcarnitines in serum and whole blood using paper spray mass spectrometry

Keywords: Paper spray; Ambient ionization; Mass spectrometry; Acylcarnitines; Newborn screening


Comparing the efficiencies of hydrazide labels in the study of protein carbonylation in human serum albumin by Zafer Ugur; Chelsea M. Coffey; Scott Gronert (pp. 1399-1411).
In this work, we establish a methodology for comparing the efficiencies of different hydrazide labels for detecting protein carbonyls. We have chosen acrolein-modified human serum albumin as a model. This system provides a convenient means of reproducibly generating carbonylated protein. Five hydrazide-based labels were tested. Three carry a biotin affinity tag, and the others are simple fatty acid hydrazides. For the biotin-based labels, the yield of the labeling reaction varies considerably, and the most commonly used label, biotin hydrazide, gives the lowest yield. The total tandem mass spectrometry (MS/MS) spectrum counts of modified peptides are similar for all of the biotin-based tags, indicating that factors beyond the labeling efficiency are important in determining the effectiveness of the label. In addition, there is a large variation in the number of spectra obtained for specific, modified peptides depending on the nature of the labeling group. This variation implies that the relative detectability of a particular modification site is highly dependent on the tagging reagent, and more importantly, titration schemes aimed at identifying the most reactive site based on its threshold concentration will be biased by the choice of tagging reagent. The fatty acid hydrazides are somewhat more effective than the biotin-based hydrazides in generating identifiable MS/MS spectra but offer no opportunity for enrichment. For the biotin-based tags, avidin affinity chromatography was used with the tryptic digests, and each tag led to similar enrichment levels. Figure Spectrum counts for HSA peptides modified by acrolein and labeled with different hydrazide tags

Keywords: Acrolein; Oxidative stress; Protein carbonylation; Mass spectrometry


Quantitative profiling of oxylipins through comprehensive LC-MS/MS analysis: application in cardiac surgery by Katrin Strassburg; Annemarie M. L. Huijbrechts; Kirsten A. Kortekaas; Jan H. Lindeman; Theresa L. Pedersen; Adrie Dane; Ruud Berger; Arjan Brenkman; Thomas Hankemeier; John van Duynhoven; Eric Kalkhoven; John W. Newman; Rob J. Vreeken (pp. 1413-1426).
Oxylipins, including eicosanoids, affect a broad range of biological processes, such as the initiation and resolution of inflammation. These compounds, also referred to as lipid mediators, are (non-) enzymatically generated by oxidation of polyunsaturated fatty acids such as arachidonic acid (AA). A plethora of lipid mediators exist which makes the development of generic analytical methods challenging. Here we developed a robust and sensitive targeted analysis platform for oxylipins and applied it in a biological setting, using high performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) operated in dynamic multiple reaction monitoring (dMRM). Besides the well-described AA metabolites, oxylipins derived from linoleic acid, dihomo-γ-linolenic acid, α-linolenic acid, eicosapentaenoic acid and docosahexaenoic acid were included. Our comprehensive platform allows the quantitative evaluation of approximately 100 oxylipins down to low nanomolar levels. Applicability of the analytical platform was demonstrated by analyzing plasma samples of patients undergoing cardiac surgery. Altered levels of some of the oxylipins, especially in certain monohydroxy fatty acids such as 12-HETE and 12-HEPE, were observed in samples collected before and 24 h after cardiac surgery. These findings indicate that this generic oxylipin profiling platform can be applied broadly to study these highly bioactive compounds in relation to human disease. Figure LC-MS/MS chromatogram of 104 oxylipins on a Triple Quadrupole MS system employing dynamic MRM in the Negative Ion Electrospray mode

Keywords: HPLC-MS/MS; dMRM; 12-HETE; 12-HEPE


Resolving the problem of chromatographic overlap by 3D cross correlation (3DCC) processing of LC, MS and NMR data for characterization of complex glycan mixtures by Henning N. Behnken; Meike Fellenberg; Miriam P. Koetzler; Raffael Jirmann; Tim Nagel; Bernd Meyer (pp. 1427-1437).
Chromatographic overlap is a common problem in the analysis of complex mixtures. As a result, it is not possible to identify the components because each resulting NMR or MS spectrum contains multiple components. We introduce three-dimensional cross correlation (3DCC) that dissects NMR spectra of a mixture into spectra of the individual components without actually separating them. Correlation of peaks from MS and NMR profiles along a common LC time domain yields 3DCC NMR spectra of pure components correlated with a mass and a retention time. The method requires an LC run followed by fractionation and recording of MS and NMR spectra. The method is applicable to mixtures of any classes of molecules. Here, we demonstrate its application to a mixture of complex glycans obtained from a glycoprotein. Fourteen glycans eluting within only 3 min showed heavy overlap in the chromatographic run. 3DCC allowed their direct characterization without separation. Some of these structures from the glycoprotein bovine fibrinogen had not previously been described. The 3DCC procedure has been implemented in standard software. Actually, 3DCC can be used for any combination of separation techniques, like LC or GC, combined with two characterization methods like UV, IR, Raman, NMR or MS. Figure LC runs of complex mixtures often result in overlap of several analytes and prohibit thereby characterization by NMR. The new 3DCC method allows extraction of pure NMR spectra directly from mixtures by correlating NMR and MS data from an LC run.

Keywords: Glycans; Cross correlation; Nuclear magnetic resonance (NMR); Mass spectrometry (MS); Deconvolution; Liquid chromatography (LC)


Vanadium bromoperoxidase-coupled fluorescent assay for flow cytometry sorting of glucose oxidase gene libraries in double emulsions by Radivoje Prodanovic; Raluca Ostafe; Milan Blanusa; Ulrich Schwaneberg (pp. 1439-1447).
A Vanadium bromoPeroxidase-coupled fluorescent assay (ViPer) for ultrahigh-throughput screening of glucose oxidase (GOx) gene libraries employing double emulsions and flow cytometry was developed. The assay is based on detection of the product of a GOx reaction, hydrogen peroxide, that is first converted to a hypobromide by vanadium bromoperoxidase in the presence of sodium bromide. The hypobromide is afterwards detected in a reaction with a fluorogenic probe, 3-carboxy-7-(4′-aminophenoxy)-coumarine, where fluorescent 3-carboxy-coumarine is released. The ViPer screening system is three times more sensitive than a horseradish peroxidase coupled detection system and more resistant to bleaching of fluorescence in excess of peroxide. Using the ViPer screening system a high epPCR gene library containing 100,000 different GOx variants was screened for active clones in less than 1 h by flow cytometry. A library containing 0.15 % of yeast cells expressing active enzyme variants and with an average GOx activity in the liquid culture of 0.47 U/mL, after one round of sorting, had 28.12 % of the yeast cells expressing the active GOx (an enrichment factor of 200) and 26.8 U/mL of the GOx activity in the liquid culture (an enrichment factor of 57). The developed screening system could be adapted and used in a directed evolution of GOx and other hydrogen peroxide-producing enzymes (oxidases) and glycosidases if coupled with a carbohydrate oxidase.

Keywords: In vitro compartmentalization; Directed evolution; Hydrogen peroxide; FACS


Comparative study of the three different fluorophore antibody conjugation strategies by Dilip Shrestha; Adrienn Bagosi; János Szöllősi; Attila Jenei (pp. 1449-1463).
The progression in bioconjugational chemistry has significantly contributed to the evolution and success of protein biology. Mainly, antibody chemistry has been a subject of intensive study owing to the expansion of research areas warranted by using various derivatives of conjugated antibodies. Three reactive moieties (amine, sulfhydryl and carbohydrate) in the antibodies are chiefly favored for the conjugational purpose. This feature is known for decades, nevertheless, amine based conjugation is still the most preferred strategy despite the appreciation the other two methods receive in conserving the antigen binding affinity (ABA). No single report has been published, according to our knowledge, where these three conjugation strategies were applied to the same fluorophore antibody systems. In this study, we evaluated conjugation yield, time demand and cost efficiency of these conjugation procedures. Our results showed that amine based conjugations was by far the best technique due to its simplicity, rapidity, ease of operation, higher conjugate yield, cheaper cost and potential for larger fluorophore/protein labeling ratio without having much effect in ABA. Furthermore, sulfhydryl labeling clearly excelled in terms of reduced non-specific binding and mild effect in ABA but was usually complicated by an asymmetric antibody reduction due to mercaptoethylamine while carbohydrate oxidation based strategy performed the worst during our experiment.

Keywords: Fluorophore antibody conjugation; Amine targeted; Sulfhydryl targeted; Carbohydrate targeted; Mercaptoethylamine; Sodium periodate


Surface-enhanced Raman scattering (SERS) revealing chemical variation during biofilm formation: from initial attachment to mature biofilm by Yuanqing Chao; Tong Zhang (pp. 1465-1475).
Surface-enhanced Raman scattering (SERS) has recently been proved to be a promising technique for characterizing the chemical composition of the biofilm matrix. In the present study, to fully understand the chemical variations during biofilm formation, SERS based on silver colloidal nanoparticles was applied to evaluate the chemical components in the matrix of biofilm at different growth phases, including initial attached bacteria, colonies, and mature biofilm. Meanwhile, atomic force microscopy was also applied to study the changes of biofilm morphology. Three model bacteria, including Escherichia coli, Pseudomonas putida, and Bacillus subtilis, were used to cultivate biofilms. The results showed that the content of carbohydrates, proteins, and nucleic acids in the biofilm matrix increased significantly along with the biofilm growth of the three bacteria judging from the intensities and appearance probabilities of related marker peaks in the SERS spectra. The content of lipids, however, only increased in the Gram-negative biofilms (E. coli and P. putida) rather than the Gram-positive biofilm (B. subtilis). Our findings strongly suggest the SERS has significant potential for studying chemical variations during biofilm formation. Figure Achieving surface-enhanced Raman scattering by coating silver nanoparticles on biofilm surface.

Keywords: SERS; Biofilm formation; Biofilm matrix; Raman microscopy; Atomic force microscopy


Preparation of imidazole-functionalized silica by surface-initiated atom transfer radical polymerization and its application for hydrophilic interaction chromatography by Lei Zhang; Xiaojun Dai; Fei Xu; Fuqiang Wang; Bolin Gong; Yinmao Wei (pp. 1477-1484).
A novel imidazole-functionalized stationary phase for hydrophilic interaction chromatography (HILIC) was prepared via surface-initiated atom transfer radical polymerization (SI-ATRP). 1-Vinylimidazole as a monomer was polymerized on the surface of initiator-immobilized silica by SI-ATRP using CuCl and 2,2′-bipyridyl as a catalyst. The graft chain length and polymer grafting density were controlled by varying the ratio of monomer to initiator. The resulting materials were characterized by elemental analysis and thermogravimetric analysis. Then, high-performance liquid chromatography separation of eight nucleobases/nucleosides was performed on the imidazole-functionalized chromatographic column in HILIC mode. The effects of mobile phase composition, buffer pH, and column temperature on the separation of nucleobases/nucleosides were investigated, and the retention mechanisms were studied. Chromatographic parameters were calculated, and the results showed that surface adsorption through hydrogen bonding and electrostatic interaction dominated the retention behavior of the solutes in HILIC mode. Lastly, the stationary phase was successfully used to determine the nucleobases and nucleosides from Cordyceps militaris.

Keywords: Imidazole-functionalized silica; Surface-initiated atom transfer radical polymerization; Hydrophilic interaction chromatography; Nucleobases; Nucleosides; Cordyceps militaris


High-throughput analysis of therapeutic and diagnostic monoclonal antibodies by multicapillary SDS gel electrophoresis in conjunction with covalent fluorescent labeling by Ákos Szekrényes; Udo Roth; Márta Kerékgyártó; Andrea Székely; István Kurucz; Karen Kowalewski; András Guttman (pp. 1485-1494).
Capillary gel electrophoresis (CGE) in the presence of sodium dodecyl sulfate (SDS) is a well-established and widely used protein analysis technique in the biotechnology industry, and increasingly becoming the method of choice that meets the requirements of the standards of International Conference of Harmonization (ICH). Automated single channel capillary electrophoresis systems are usually equipped with UV absorbance and/or laser-induced fluorescent (LIF) detection options offering general applicability and high detection sensitivity, respectively; however, with limited throughput. This shortcoming is addressed by the use of multicapillary gel electrophoresis (mCGE) systems with LED-induced fluorescent detection (LED-IF), also featuring automation and excellent detection sensitivity, thus widely applicable to rapid and large-scale analysis of biotherapeutics, especially monoclonal antibodies (mAb). The methodology we report in this paper is readily applicable for rapid purity assessment and subunit characterization of IgG molecules including detection of non-glycosylated heavy chains (NGHC) and separation of possible subunit variations such as truncated light chains (Pre-LC) or alternative splice variants. Covalent fluorophore derivatization and the mCGE analysis of the labeled IgG samples with multi-capillary gel electrophoresis are thoroughly described. Reducing and non-reducing conditions were both applied with and without peptide N-glycosidase F mediated deglycosylation.

Keywords: Biotherapeutics; Quality analysis; Multicapillary gel electrophoresis; Antibody purity; Fluorescent labeling


Determination of nitrotyrosine in Arabidopsis thaliana cell cultures with a mixed-mode solid-phase extraction cleanup followed by liquid chromatography time-of-flight mass spectrometry by Paula Berton; Juan C. Domínguez-Romero; Rodolfo G. Wuilloud; Beatriz Sánchez-Calvo; Mounira Chaki; Alfonso Carreras; Raquel Valderrama; Juan C. Begara-Morales; Francisco J. Corpas; Juan B. Barroso; Bienvenida Gilbert-López; Juan F. García-Reyes; Antonio Molina-Díaz (pp. 1495-1503).
In this work, a method for the determination of trace nitrotyrosine (NO2Tyr) and tyrosine (Tyr) in Arabidopsis thaliana cell cultures is proposed. Due to the complexity of the resulting extracts after protein precipitation and enzymatic digestion and the strong electrospray signal suppression displayed in the detection of both Tyr and NO2Tyr from raw A. thaliana cell culture extracts, a straightforward sample cleanup step was proposed. It was based on the use of mixed-mode solid-phase extraction (SPE) using MCX-type cartridges (Strata™-X-C), prior to identification and quantitation using fast liquid chromatography–electrospray time-of-flight mass spectrometry. Unambiguous confirmation of both amino acids was accomplished with accurate mass measurements (with errors lower than 2 ppm) of each protonated molecule along with a characteristic fragment ion for each species. Recovery studies were accomplished to evaluate the performance of the SPE sample preparation step obtaining average recoveries in the range 92–101 %. Limit of quantitation obtained for NO2Tyr in A. thaliana extracts was 3 nmol L−1. Finally, the proposed method was applied to evaluate stress conditions of the plant upon different concentrations of peroxynitrite, a protein-nitrating compound, which induces the nitration of Tyr at the nanomolar range. Detection and confirmation of the compounds demonstrated the usefulness of the proposed approach. Figure Determination of trace nitrotyrosine and tyrosine in Arabidopsis thaliana cell cultures by liquid chromatography time-of-flight mass spectrometry is achieved

Keywords: Nitrotyrosine; Arabidopsis thaliana ; Nitrosative stress; Liquid chromatography; Mass spectrometry; Solid-phase extraction


Removal of sulfonamide antibiotics upon conventional activated sludge and advanced membrane bioreactor treatment by María Jesús García Galán; M. Silvia Díaz-Cruz; Damià Barceló (pp. 1505-1515).
This work reports the removal efficiencies of nine sulfonamides (SAs) and one of their acetylated metabolites during conventional activated sludge (CAS) and membrane bioreactor (MBR) treatments. Two different types of membranes were studied, hollow-fiber membranes and flat-sheet membranes, in two separate pilot plants operating in parallel to a full-scale CAS treatment. A total of 48 water samples and 16 sewage sludge samples were analyzed by liquid chromatography–tandem mass spectrometry. We obtained 100 % elimination in the MBR effluents for three SAs (sulfadiazine, sulfadimethoxine, and sulfamethoxypyridazine) and the metabolite. For the rest of the SAs, the removal efficiencies during CAS and MBR treatments were similar and usually below 55 %. Sulfamethizole was the most recalcitrant SA, exhibiting negative removal efficiencies in all the treatments investigated. The concentrations of SAs in the different sewage sludge types were also calculated and ranged from 0.01 to 11 ng g-1. Furthermore, adsorption and biodegradation of SAs in activated sludge were investigated in two sets of batch reactors, which were spiked at high and low concentration (1,000 and 50 ng mL-1, respectively). All SAs followed a similar trend and, with the exception of sulfathiazole, were not fully eliminated after 25 days of treatment.

Keywords: Sulfonamides; Wastewater; Conventional wastewater treatment; Membrane bioreactor; Removal efficiencies


Sampling of organophosphorus pesticides at trace levels in the atmosphere using XAD-2 adsorbent and analysis by gas chromatography coupled with nitrogen–phosphorus and ion-trap mass spectrometry detectors by Mario Vincenzo Russo; Pasquale Avino; Giuseppe Cinelli; Ivan Notardonato (pp. 1517-1527).
This paper shows an analytical methodology based on solid-phase extraction by XAD-2 adsorbent and gas chromatography (GC) coupled with nitrogen–phosphorus (NPD) and ion-trap mass spectrometry detectors (ITMS) in negative chemical ionization (NCI) mode analyses for investigating organophosphorus pesticides (OPs) at trace levels (in nanograms per cubic meter) in the atmosphere: in particular, we set up a procedure for analyzing 38 OPs. For the analytical methodology linearity responses have been obtained in GC-NPD (r > 0.9982) and GC-NCI/ITMS (r > 0.9974) in a large linearity range (0.10–500 pg μL−1 in both cases) whereas the limits of detection range between 0.01 and 0.03 pg μL−1 in both the techniques with a relative standard deviation (RSD) below 9.0 in both cases. Particular attention has been devoted to investigate the effect of different solvents (n-hexane, benzene, chloroform, carbon disulfide, acetonitrile) on the OP recovery as well the breakthrough volumes have been evaluated (100 % recovery up to 4,286 L g−1). The study has also investigated the OP recoveries at different sampling flow rates (1.5 and 2.0 L min−1) for determining the optimal conditions for sample collection. Finally, the whole approach has been successfully applied to real samples collected in four different areas in the Molise region (Central Italy) during different seasons: the results show that parathion-ethyl, dimethoate, omethoate, and malathion are present in all periods at low levels (ranging between 70 and 10 ng m−3): their levels in such periods can be correlated with spraying as well atmospheric conditions favoring the dispersion/accumulation of these pollutants Figure Sampling system of organophosphorus pesticides in atmosphere and relative GC-NPD chromatogram

Keywords: Organophosphorus pesticides; Adsorbent; XAD 2; GC-NPD; GC-NCI/ITMS; Atmospheric pollution


Ionic liquids supported on magnetic nanoparticles as a sorbent preconcentration material for sulfonylurea herbicides prior to their determination by capillary liquid chromatography by Mohamed Bouri; Madalina Gurau; Rachid Salghi; Igor Cretescu; Mohammed Zougagh; Ángel Rios (pp. 1529-1538).
A magnetic material based on N-methylimidazolium ionic liquid and Fe3O4 magnetic nanoparticles incorporated in a silica matrix has been used to extract and preconcentrate sulfonylurea herbicides, such as thifensulfuron methyl (TSM), metsulfuron methyl (MSM), triasulfuron (TS), tribenuron methyl (TBM) and primisulfuron methyl (PSM) from polluted water samples, prior to their analysis by capillary liquid chromatography with a diode array detector (DAD). Under the optimum conditions, this method allows the determination of TSM, MSM, TS, TBM and PSM in a linear range between 5 and 100 ng mL−1, with relative standard deviation values lower than 5.3 % (n = 10), in all cases. Detection limits ranging between 1.13 and 2.95 ng mL−1 were achieved. The usefulness of the proposed method was demonstrated by the analysis of river water samples, obtaining recoveries higher than 91 %. Figure

Keywords: Magnetic nanoparticles; Ionic liquids; Sulfonylurea herbicides; Polluted water samples


Study on the effect of chain-length compatibility of mixed anionic–cationic surfactants on the cloud-point extraction of selected organophosphorus pesticides by Ketsarin Seebunrueng; Yanawath Santaladchaiyakit; Supalax Srijaranai (pp. 1539-1548).
The chain-length compatibility of mixed anionic–cationic surfactants was investigated for the extraction of organophosphorus pesticides (OPPs). Cationic surfactants with different chain lengths (n = 12 and 16) were mixed with sodium dodecyl sulfate (SDS; n = 12) for the mixed anionic–cationic surfactants-based extraction. Six OPPs were studied including azinphos-methyl, parathion-methyl, fenitrothion, diazinon, chlorpyrifos, and prothiophos. Reversed-phase high-performance liquid chromatography was used for the determination of the studied OPPs. The extraction was performed using mixtures of SDS and cationic surfactants including dodecyltrimethyl ammonium bromide or dodecyltrimethylammonium bromide (DTAB; n = 12) and cetyltrimethyl ammonium bromide or cetyltrimethyl ammonium bromide (CTAB; n = 16). The parameters affecting the extraction efficiencies of two extraction systems were studied and discussed. The optimum condition for SDS-DTAB was 15 mmol L−1 SDS and 1 mmol L−1 DTAB in the presence of 15 % (w/v) sodium chloride (NaCl). Meanwhile, the condition for SDS-CTAB was 10 mmol L−1 SDS and 1.0 mmol L−1 CTAB with 10 % (w/v) NaCl. Under the optimum conditions, the extraction efficiency of SDS-DTAB (66–85 %) was slightly higher than that of SDS-CTAB (61–82 %). In addition, the SDS-DTAB system also gave greater enrichment factor than SDS-CTAB for all the studied OPPs. This result may be due to the compatibility of chain length between SDS and DTAB. The extraction using SDS-DTAB was successfully applied to determine OPPs in fruit samples (i.e., pomelo, apple, and pineapple). No contamination by the studied OPPs in samples was observed. Good accuracy with recoveries ranging from 77 to 105 % was obtained. Low limits of detection were in the range of 0.003–0.01 mg kg−1 which are below the MRLs established by EU-MRLs for the OPPs residues in fruit samples. Fig The cloud point extraction using the equal chain length (n=12) of cationic and anionic surfactants (SDS−DTAB) provided more stable micellar aggregates than the SDS-CTAB (n=12, 16) resulting in higher extraction efficiency

Keywords: Mixed anionic–cationic surfactants cloud-point extraction; Sodium dodecyl sulfate; Dodecyltrimethylammonium bromide; Cetyltrimethyl ammonium bromide; Organophosphorus pesticide; High-performance liquid chromatography


Rapid determinations of saccharides in high-energy drinks by short-capillary electrophoresis with contactless conductivity detection by Blanka Vochyánová; František Opekar; Petr Tůma; Karel Štulík (pp. 1549-1554).
The methodology for separations of saccharides in standard electrophoretic systems has been transferred to the short-capillary electrophoresis format. The laboratory-designed apparatus used employs a quartz capillary with an internal diameter of 10 μm, a total length of 10 cm, and an effective length of 4 cm, in combination with contactless conductivity detection. It has been applied to separations of neutral mono- and disaccharides. The saccharides are separated in the anionic form, in solutions of alkali hydroxides, namely, KOH, NaOH, and LiOH. The separation of a model mixture of five saccharides (sucrose, lactose, glucose, fructose, and ribose) takes less than 1 min, the LOD equaling 15, 35, 19, 17, and 24 mg L−1 and the LOQ equaling 52, 117, 63, 53, and 79 mg L−1 for sucrose, lactose, glucose, fructose, and ribose, respectively. The technique developed has been used to determine sucrose, glucose and fructose in high-energy drinks. The separation is finished within less than 50 s; the saccharide contents determined are identical with the declared values within the reliability interval in most cases, the RSD value being mostly less than 2 %. In general, the separation system developed is very convenient for rapid analyses of large sets of similar samples, e.g., in product quality control or environmental monitoring. Figure Rapid determination of saccharides by CZE

Keywords: Capillary electrophoresis; Short capillary; Contactless conductivity detection; Saccharides; Energy drinks


Preparation of a magnetic molecularly imprinted polymer with pseudo template for rapid simultaneous determination of cyromazine and melamine in bio-matrix samples by Xianhua Wang; Qiuxue Fang; Shipeng Liu; Lei Chen (pp. 1555-1564).
A magnetic molecularly imprinted polymer (M-MIP) for cyromazine and melamine was prepared by simple suspension polymerization using a pseudo template, 2-(4,6-diamino-1,3,5-triazin-2-ylamino)ethanethiol disulfide. The M-MIP was characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, and vibrating sample magnetometry. Molecular recognition properties and binding capability to cyromazine and melamine were evaluated by adsorption testing, which showed the M-MIP had better affinity and selectivity than the magnetic non-imprinted polymer (M-NIP) for cyromazine and melamine. A method based on molecularly imprinted solid-phase extraction assisted by magnetic separation was developed for extraction of cyromazine and melamine from bio-matrix samples. Various conditions, for example desorption conditions, amount of M-MIP, extraction time, and sample pH were optimized. High-performance liquid chromatography with UV detection was used to determine cyromazine and melamine after extraction. The proposed method was successfully applied to determination of cyromazine and melamine in egg and milk samples. Recovery of standard spiked cyromazine and melamine from these samples was between 71.86 and 80.57 %, with intraday and interday relative standard deviation ranging from 3.45 to 6.39 % and from 3.95 to 7.84 %, respectively. The results indicate that the pseudo template M-MIP can be used for preconcentration, purification, and analysis of cyromazine and melamine in bio-matrix samples.

Keywords: Magnetic molecularly imprinted polymer; Solid phase extraction; Magnetic separation; Cyromazine; Melamine


Microwave-assisted extraction and determination of enrofloxacin and danofloxacin photo-transformation products in soil by Andrea Speltini; Michela Sturini; Federica Maraschi; Antonella Profumo; Angelo Albini (pp. 1565-1569).
Here we describe the extraction from soil of the major photo-transformation products (PTPs) of enrofloxacin (ENR) and danofloxacin (DAN), two fluoroquinolones (FQs) widely used in veterinary medicine and of growing environmental concern, because their PTPs have been shown to retain high antibacterial activity. The microwave-assisted extraction (MAE) technique developed previously for determination of FQs, and based on use of an alkaline aqueous solution of Mg2+ as a complexing agent for the analytes, was applied to agricultural soil samples fortified with different amounts of the PTPs and residues of the parent compounds (53–1000 ng g−1 for ENR, 24–148 ng g−1 for DAN). The PTPs, obtained by irradiation of thin layers of the two drugs, were, after extraction, separated and quantified by HPLC–FD. Good recovery (70–130 %) and precision (RSDs 1–6 % for repeatability and 9–22 % for reproducibility) were obtained by use of the overall analytical procedure. The method was applied for the first time to study the in-soil lifecycle of ENR and DAN PTPs, generated in the matrix by irradiation under natural sunlight, at environmentally significant concentrations. Results indicated that soil-adsorbed FQ PTPs are themselves liable to photodegradation and have lifetimes comparable with those of parent compounds.

Keywords: Fluoroquinolone photo-transformation products; Microwave-assisted extraction; Soil


Ascorbic acid for homogenous redox buffering in electrospray ionization–mass spectrometry by Sabine Plattner; Robert Erb; Jean-Pierre Chervet; Herbert Oberacher (pp. 1571-1579).
Electrospray ionization (ESI) involves the dispersion of a liquid containing analytes of interest into a fine aerosol by applying a high potential difference to the sample solution with respect to a counter electrode. Thus, from the electrochemical point of view, the ESI source represents a two-electrode controlled-current electrochemical flow cell. The electroactive compounds part of the solvent sprayed may be altered by occurring electrolysis (oxidation in positive ion mode and reduction in negative ion mode). These reactions can be troublesome in the context of unknown identification and quantification. In the search for a simple, inexpensive, and efficient way to suppress electrochemical oxidation in positive ESI, the usability of ascorbic acid, hydroquinone, and glutathione for homogenous redox buffering was tested. Performance of the antioxidants was assessed by analyzing pharmaceutical compounds covering a broad range of functional groups prone to oxidation. Different emitter setups were applied for continuous infusion, flow injection, and liquid chromatography/mass spectrometry experiments. Best performance was obtained with ascorbic acid. In comparison to hydroquinone and glutathione, ascorbic acid offered superior antioxidant activity, a relatively inert oxidation product, and hardly any negative effect on the ionization efficiency of analytes. Furthermore, ascorbic acid suppressed the formation of sodiated forms and was able to induce charge state reduction. Only in the very special case of analyzing a compound isobaric to ascorbic acid, interference with the low-abundant [ascorbic acid+H]+ signal may become a point of attention. Figure Ascorbic acid efficiently suppresses analyte oxidation and formation of sodiated forms in positive electrospray ionization

Keywords: Mass spectrometry; Electrospray ionization; Electrochemistry; Redox buffering


Speciation of lead in seawater and river water by using Saccharomyces cerevisiae immobilized in agarose gel as a binding agent in the diffusive gradients in thin films technique by Guilherme Favoreto Pescim; Gabriela Marrach; Monizze Vannuci-Silva; Laís Alves Souza; Amauri Antonio Menegário (pp. 1581-1588).
Saccharomyces cerevisiae immobilized in agarose gel is proposed as a binding agent for the diffusive gradients in thin films (DGT) technique for determination of Pb in river water and seawater. DGT samplers were assembled with the proposed binding agent (25-mm disk containing 20 %, m/v, S. cerevisiae and 3.0 %, m/v, agarose) and a diffusive layer of cellulose (3MM Chr chromatography paper of 25-mm diameter). The effects of some DGT parameters (e.g., immersion time, ionic strength, and pH) were evaluated. Elution of Pb from the binding agent was effectively done with 1.75 mol L−1 HNO3. The deployment curve (between 2 and 24 h) was characterized by a significant uptake of Pb (346 ng Pb h−1) and good linear regression (R 2 = 0.9757). The experimental results are in excellent agreement with the predicted theoretical curve for mass uptake. Consistent results were found for solutions with ionic strengths of 0.005 mol L−1 or greater and within a pH range of 4.5–8.5. Interferences from Cu (20:1), Mn (20:1), Fe (20:1), Zn (20:1), Ca (250:1), and Mg (250:1) in Pb retention were negligible. Determination of Pb in spiked river water samples (from the Corumbataí and Piracicaba rivers) performed using the proposed device was in agreement with total dissolved Pb, whereas measurements in seawater suggest that of the various species of Pb present in the samples, only cationic Pb species are adsorbed by the agarose–yeast gel disks. The in situ concentration of Pb obtained at two different sites of the Rio Claro stream (Corumbataí basin) were 1.13 ± 0.01 and 1.34 ± 0.04 μg L−1. For 72-h deployments, a detection limit of 0.75 μg L−1 was calculated. The combination of inductively coupled plasma optical emission spectroscopy and in situ deployments of DGT samplers during the 72-h period makes possible the determination of labile Pb in river water.

Keywords: Saccharomyces cerevisiae ; Diffusive gradients in thin films; Passive sampler; Speciation; Fractionation


Automated system for on-line determination of dimethylarsinic and inorganic arsenic by hydride generation–atomic fluorescence spectrometry by L. L. Chaparro; L. Ferrer; V. Cerdà; L. O. Leal (pp. 1589-1595).
A multisyringe flow-injection approach has been coupled to hydride generation–atomic fluorescence spectrometry (HG-AFS) with UV photo-oxidation for dimethylarsinic (DMA), inorganic As and total As determination, depending on the pre-treatment given to the sample (extraction or digestion). The implementation of a UV lamp allows on-line photo-oxidation of DMA and the following arsenic detection, whereas a bypass leads the flow directly to the HG-AFS system, performing inorganic arsenic determination. DMA concentration is calculated by the difference of total inorganic arsenic and measurement of the photo-oxidation step. The detection limits for DMA and inorganic arsenic were 0.09 and 0.47 μg L−1, respectively. The repeatability values accomplished were of 2.4 and 1.8 %, whereas the injection frequencies were 24 and 28 injections per hour for DMA and inorganic arsenic, respectively. This method was validated by means of a solid reference material BCR-627 (muscle of tuna) with good agreement with the certified values. Satisfactory results for DMA and inorganic arsenic determination were obtained in several water matrices. The proposed method offers several advantages, such as increasing the sampling frequency, low detection limits and decreasing reagents and sample consumption, which leads to lower waste generation.

Keywords: Dimethylarsinic; Inorganic arsenic; Multisyringe flow-injection analysis (MSFIA); Photo-oxidation; Atomic fluorescence; Hydride generation


Sol–gel-based molecularly imprinted xerogel for capillary microextraction by Habib Bagheri; Hamed Piri-Moghadam (pp. 1597-1602).
A novel molecularly imprinted xerogel (MIX) based on organically modified silica (ORMOSIL) was successfully prepared for on-line capillary microextraction (CME) coupled with high-performance liquid chromatography (HPLC). The sol–gel-based xerogel was prepared using only one precursor and exhibited extensive selectivity towards triazines along with significant thermal and chemical stability. Atrazine was selected as a model template molecule and 3-(trimethoxysilyl)propylmethacrylate (TMSPMA) as a precursor in which the propylmethacrylate moiety was responsible for van der Waals, dipole–dipole, and hydrogen-bond interactions with the template. This moiety plays a key role in creation of selective sites while methoxysilyl groups in TMSPMA acted as crosslinkers between the template and the propylmethacrylate moiety. Moreover, a non-imprinted xerogel (NIX) was also prepared in the absence of the template for evaluating the extraction efficiency of the prepared MIX. Then, the prepared imprinted and non-imprinted xerogels were used for extraction of three selected analytes of triazines class including atrazine, ametryn, and terbutryn, which have rather similar structures. The extraction efficiency of the prepared xerogel for atrazine, the template molecule, was found to be ten times greater than the efficiency achieved by the non-imprinted one. In the meantime, the extraction efficiency ratio of MIX to NIX for ametryn and terbutryn was also rather significant (eight times). Moreover, other compounds from different classes including dicamba, mecoprop, and estriol were also analyzed to evaluate the selectivity of the prepared MIX towards triazines. The ratio of enrichment factors (EF) of MIX to NIX for atrazine, ametryn, terbutryn, dicamba, mecoprop, and estriol were about 10, 8, 8, 2, 2, and 3, respectively. The linearity for the analytes was in the range of 5–700 μg L−1. Limit of detection was in the range of 1–5 μg L−1 and the RSD% values (n = 5) were all below 6.6 % at the 20 μg L−1 level. The developed method was also applied to real water samples and the relative recovery percentages obtained for the spiked water samples were from 92 to 104 %. The CME loop, containing the prepared MIX, exhibited a rather long life time due to its remarkable solvent and mechanical stability. Even after 100 runs, no decrease in the peak areas was observed. The developed method could easily provide the possibility of preparing a selective sorbent in a unique way with the lowest possible cost and time. Figure

Keywords: Sol–gel technology; Molecularly imprinted xerogel (MIX); Organically modified silica; Capillary microextraction; On-line approach; High-performance liquid chromatography–UV detection


Using Zn/Al layered double hydroxide as a novel solid-phase extraction adsorbent to extract polycyclic aromatic hydrocarbons at trace levels in water samples prior to the determination of gas chromatography–mass spectrometry by Yan-Long Liu; Jia-Bin Zhou; Ru-Song Zhao; Xiang-Feng Chen (pp. 1603-1610).
This paper demonstrates, for the first time, the great potential of using Zn/Al layered double hydroxide intercalated sodium dodecyl benzene sulfonate (Zn/Al-SDBS-LDH) as a solid-phase extraction (SPE) material in the extraction of persistent organic pollutants prior to the determination of gas chromatography–mass spectrometry in environmental water samples. Zn/Al-SDBS-LDH, a relatively inexpensive and simply prepared material, was synthesized and used as a SPE adsorbent to quantitatively determine the concentration of five polycyclic aromatic hydrocarbons (PAHs) in environmental water samples. Factors affecting extraction efficiency, such as, eluent type, eluent volume, flow rate of sample, sample volume, and amount of adsorbent, were investigated and optimized in detail. Experimental results indicate that there is an excellent linear relationship between peak area and the concentration of PAHs over the range of 5–500 ng L−1, and the precisions (relative standard deviation (RSD)) were 2.5–6.3 % under the optimum conditions. Based on the ratio of chromatographic signal-to-base line noise (S/N = 3), the limits of detection could reach 1.2–3.2 ng L−1. This novel method was successfully applied to the analysis of PAHs in environmental water samples. As such, we show here that the use of Zn/Al-SDBS-LDH as SPE adsorbent materials, coupled with gas chromatography–mass spectrometry, is an excellent improvement in the routine analysis of PAHs at trace levels in the environment.

Keywords: Zn/Al layered double hydroxide; Polycyclic aromatic hydrocarbon; Solid-phase extraction; Gas chromatography–mass spectrometry

Erratum to: Analytical methods for tracing plant hormones by Fuyou Du; Guihua Ruan; Huwei Liu (pp. 1615-1615).
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