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Analytica Chimica Acta (v.718, #)

Editorial Board (pp. iii).

A simple protocol for Matrix Assisted Laser Desorption Ionization- time of flight-mass spectrometry (MALDI-TOF-MS) analysis of lipids and proteins in single microsamples of paintings by Inez D. van der Werf; Cosima D. Calvano; Francesco Palmisano; Luigia Sabbatini (pp. 1-10).

.Display Omitted► BD extraction and MALDI for fast identification of binders in single microsamples. ► Simultaneous extraction of lipids and proteins from pigmented paint layers. ► Use of RapiGest to improve efficiency of protein digestion and purification step. ► Investigation of the effect of pigments on ageing of lipids and proteins. ► Application of the protocol to the study of a 15th century Italian panel painting.A simple protocol, based on Bligh–Dyer (BD) extraction followed by MALDI-TOF-MS analysis, for fast identification of paint binders in single microsamples is proposed. For the first time it is demonstrated that the BD method is effective for the simultaneous extraction of lipids and proteins from complex, and atypical matrices, such as pigmented paint layers. The protocol makes use of an alternative denaturing anionic detergent (RapiGest™) in order to improve efficiency of protein digestion and purification step. Detection of various lipid classes, such as triacylglycerols (TAGs) and phospholipids (PLs), and their oxidation by-products was accomplished, whereas proteins could be identified by peptide mass fingerprinting. The effect of pigments on ageing of lipids and proteins was also investigated.Finally, the proposed protocol was successfully applied to the study of a late-15th century Italian panel painting allowing the identification of various proteinaceous and lipid sections in organic binders, such as egg yolk, egg white, animal glue, casein, and drying oil.

Keywords: Bligh–Dyer; Conservation science; Paint binder; MALDI-TOF-MS; Proteomics; Lipidomics

On-line sample pre-concentration in microfluidic devices: A review by Braden C. Giordano; Dean S. Burgi; Sean J. Hart; Alex Terray (pp. 11-24).

Display Omitted► Online modes of pre-concentration on microfluidic devices are discussed. ► The implementation of on-chip electrophoretic stacking is presented. ► Non-electrophoretic modes, including solid-phase extraction, are explored in detail.On-line sample preconcentration is an essential tool in the development of microfluidic-based separation platforms. In order to become more competitive with traditional separation techniques, the community must continue to develop newer and more novel methods to improve detection limits, remove unwanted sample matrix components that disrupt separation performance, and enrich/purify analytes for other chip-based actions. Our goal in this review is to familiarize the reader with many of the options available for on-chip concentration enhancement with a focus on those manuscripts that, in our assessment, best describe the fundamental principles that govern those enhancements. Sections discussing both electrophoretic and nonelectrophoretic modes of preconcentration are included with a focus on device design and mechanisms of preconcentration. This review is not meant to be a comprehensive collection of every available example, but our hope is that by learning how on-line sample concentration techniques are being applied today, the reader will be inspired to apply these techniques to further enhance their own programs.

Keywords: Preconcentration; Microfluidics; Stacking; Extraction

Development and validation of a methodology for uranium radiochronometry reference material preparation by Zsolt Varga; Adrian Nicholl; Maria Wallenius; Klaus Mayer (pp. 25-31).

Display Omitted► We developed a novel methodology to prepare a uranium radiochronology reference material. ► The amount of decay products present in uranium is only the function of elapsed time. ► The reference material is a quality control tool in nuclear forensics and safeguards.The paper describes a methodology for a reference material preparation to be used for the determination of the production date (i.e. the time elapsed since the last chemical processing) of uranium materials based on the²³⁰Th/²³⁴U radiochronometer. The reference material was prepared from highly enriched uranium by a complete separation of thorium decay products, thus zeroing the initial daughter nuclide concentration at known time. The complete elimination of thorium from the starting material was verified by gamma spectrometric measurements and by addition of a²³²Th tracer to the material and its re-measurement in the final product after the separation. The validation of the methodology was carried out subsequently by comparing the ingrown daughter nuclide²³⁰Th and the measured²³⁰Th/²³⁴U ratio after recorded times following the last chemical separation with the calculated values obtained on the basis of their respective half-lives. The prepared reference material can be used as a quality control material for age determination of uranium in nuclear forensics and safeguards as well as for method validation.

Keywords: Age determination; Uranium; Inductively coupled plasma mass spectrometry; Nuclear safeguards; Nuclear forensics; Reference material

Identification of human protein complexes from local sub-graphs of protein–protein interaction network based on random forest with topological structure features by Zhan-Chao Li; Yan-Hua Lai; Li-Li Chen; Xuan Zhou; Zong Dai; Xiao-Yong Zou (pp. 32-41).

Display Omitted► Protein complexes are modeled as vertex-weighted graphs of interactions. ► Topology structure features are used to characterize protein complexes. ► Random forest is utilized to identify protein complexes from human protein interaction network. ► Some new protein complexes are identified and validated.In the post-genomic era, one of the most important and challenging tasks is to identify protein complexes and further elucidate its molecular mechanisms in specific biological processes. Previous computational approaches usually identify protein complexes from protein interaction network based on dense sub-graphs and incomplete priori information. Additionally, the computational approaches have little concern about the biological properties of proteins and there is no a common evaluation metric to evaluate the performance. So, it is necessary to construct novel method for identifying protein complexes and elucidating the function of protein complexes. In this study, a novel approach is proposed to identify protein complexes using random forest and topological structure. Each protein complex is represented by a graph of interactions, where descriptor of the protein primary structure is used to characterize biological properties of protein and vertex is weighted by the descriptor. The topological structure features are developed and used to characterize protein complexes. Random forest algorithm is utilized to build prediction model and identify protein complexes from local sub-graphs instead of dense sub-graphs. As a demonstration, the proposed approach is applied to protein interaction data in human, and the satisfied results are obtained with accuracy of 80.24%, sensitivity of 81.94%, specificity of 80.07%, and Matthew's correlation coefficient of 0.4087 in 10-fold cross-validation test. Some new protein complexes are identified, and analysis based on Gene Ontology shows that the complexes are likely to be true complexes and play important roles in the pathogenesis of some diseases. PCI-RFTS, a corresponding executable program for protein complexes identification, can be acquired freely on request from the authors.

Keywords: Protein complexes; Random forest; Protein–protein interaction network; Topological structures; Gene Ontology

Determination of oxytetracycline in milk samples by polymer inclusion membrane separation coupled to high performance liquid chromatography by Irma Pérez-Silva; José A. Rodríguez; Ma. Teresa Ramírez-Silva; Ma. Elena Páez-Hernández (pp. 42-46).

Display Omitted► Selective extraction and HPLC analysis of oxytetracycline (OTC) in milk samples. ► Preparation and characterization of a polymer inclusion membrane (PIM). ► Optimization of PIM–HPLC method using a Plackett–Burman experimental design. ► The OTC was isolated and the matrix interferences were eliminated. ► Limit of detection useful for OTC residues analysis in real milk samples (8ngmL⁻¹).The determination of oxytetracycline in milk samples using a polymer inclusion membrane concept with high performance liquid chromatography (HPLC) was studied. The membranes developed are composed by cellulose acetate as polymer base, Cyanex 923 as carrier and o-nitrophenyl octyl ether as plasticizer. In the optimal conditions, the method exhibits good linearity in the range 0.03–0.20mgL⁻¹ with a limit of detection and quantification of 8.2 and 27.3μgL⁻¹ respectively. The method was successfully applied to the analysis of milk samples with high selectivity.

Keywords: Cyanex; ^®; 923; Milk; Oxytetracycline; Plackett–Burman experimental design; Polymer inclusion membrane

Metabolic fingerprinting of high-fat plasma samples processed by centrifugation- and filtration-based protein precipitation delineates significant differences in metabolite information coverage by Thaer Barri; Jens Holmer-Jensen; Kjeld Hermansen; Lars O. Dragsted (pp. 47-57).

Display Omitted► We compared two PPP procedures for metabolite coverage from high-fat plasma samples. ► Fasted and postprandial high-fat plasma samples were compared after a protein-rich meal. ► fPPP procedure recovers more metabolites with varying polarity than cPPP procedure does. ► Markers of the postprandial plasma samples are aromatic and branched-chain amino acids.Metabolomics and metabolic fingerprinting are being extensively employed for improved understanding of biological changes induced by endogenous or exogenous factors. Blood serum or plasma samples are often employed for metabolomics studies. Plasma protein precipitation (PPP) is currently performed in most laboratories before LC–MS analysis. However, the impact of fat content in plasma samples on metabolite coverage has not previously been investigated. Here, we have studied whether PPP procedures influence coverage of plasma metabolites from high-fat plasma samples. An optimized UPLC-QTOF/MS metabolic fingerprinting approach and multivariate modeling (PCA and OPLS-DA) were utilized for finding characteristic metabolite changes induced by two PPP procedures; centrifugation and filtration. We used 12-h fasting samples and postprandial samples collected at 2h after a standardized high-fat protein-rich meal in obese non-diabetic subjects recruited in a dietary intervention. The two PPP procedures as well as external and internal standards (ISs) were used to track errors in response normalization and quantification. Remarkably and sometimes uniquely, the fPPP, but not the cPPP approach, recovered not only high molecular weight (HMW) lipophilic metabolites, but also small molecular weight (SMW) relatively polar metabolites. Characteristic SMW markers of postprandial samples were aromatic and branched-chain amino acids that were elevated ( p<0.001) as a consequence of the protein challenge. In contrast, some HMW lipophilic species, e.g. acylcarnitines, were moderately lower ( p<0.001) in postprandial samples. LysoPCs were largely unaffected. In conclusion, the fPPP procedure is recommended for processing high-fat plasma samples in metabolomics studies. While method improvements presented here were clear, use of several ISs revealed substantial challenges to untargeted metabolomics due to large and variable matrix effects.

Keywords: Metabolomics; Metabolic fingerprinting; Plasma protein precipitation; Centrifugation; Filtration; QTOF/MS

Highly efficient capillary polymerase chain reaction using an oscillation droplet microreactor by Dayu Liu; Guangtie Liang; Xiuxia Lei; Bin Chen; Wei Wang; Xiaomian Zhou (pp. 58-63).

An oscillation-flow approach using a droplet reactor was developed to fully explore the potential of continuous-flow PCR. By fully utilizing interfacial chemistry, a water-in-oil (w/o) droplet was automatically generated by allowing an oil–water plug to flow through a polytetrafluoroethylene (PTFE) capillary. Due to the movement of aqueous phase relative to the oil phase, the droplet moves further into the middle of the oil plug with increase in migration distance. The resulting droplet was transported spanning the two heating zones and was employed as the reactor of oscillating-flow PCR.Display Omitted► Droplet formation in a capillary. ► Transport the droplet using oscillation-flow. ► Oscillation droplet PCR. ► Improved reaction efficiency.The current work presents the development of a capillary-based oscillation droplet approach to maximize the potential of a continuous-flow polymerase chain reaction (PCR). Through the full utilization of interfacial chemistry, a water-in-oil (w/o) droplet was generated by allowing an oil–water plug to flow along a polytetrafluoroethylene (PTFE) capillary. The w/o droplet functioned as the reactor for oscillating-flow PCR to provide a stable reaction environment, accelerate reagent mixing, and eliminate surface adsorption. The capillary PCR approach proposed in the current research offers high amplification efficiency, fast reaction speed, and easy system control attributable to the oscillation droplet reactor. Experimental results show that the droplet-based micro-PCR assay requires lower reaction volume (2μL) and shorter reaction time (12min) compared with conventional PCR methods. Taking the amplification of the New Delhi metallo-beta-lactamase (NDM-1) gene as an example, the present work demonstrates that the oscillation droplet PCR assay is capable of achieving high efficiency up to 89.5% and a detection limit of 10 DNA copies. The miniature PCR protocol developed in the current work is fast, robust, and low-cost, thus exhibiting the potential for expansion into various practical applications.

Keywords: Miniature polymerase chain reaction; Oscillation-flow; Droplet; Polytetrafluoroethylene capillary

Parallel detection, quantification, and depth profiling of peptides with dynamic-secondary ion mass spectrometry (D-SIMS) ionized by C₆₀⁺–Ar⁺ co-sputtering by Chi-Jen Chang; Hsun-Yun Chang; Yun-Wen You; Hua-Yang Liao; Yu-Ting Kuo; Wei-Lun Kao; Guo-Ji Yen; Meng-Hung Tsai; Jing-Jong Shyue (pp. 64-69).

Display Omitted► Multiple peptides are detected and quantified at the same time without labeling. ► C₆₀⁺ ion is responsible for generating molecular-specific ions at high mass. ► The co-sputtering yielded more steady depth profile and more well defined interface. ► The fluence of auxiliary Ar⁺ does not affect the quantification curve. ► The damage from Ar⁺ is masked by high sputtering yield of C₆₀⁺.Time-of-flight secondary ion mass spectrometry (ToF-SIMS) using pulsed C₆₀⁺ primary ions is a promising technique for analyzing biological specimens with high surface sensitivities. With molecular secondary ions of high masses, multiple molecules can be identified simultaneously without prior separation or isotope labeling. Previous reports using the C₆₀⁺ primary ion have been based on static-SIMS, which makes depth profiling complicated. Therefore, a dynamic-SIMS technique is reported here. Mixed peptides in the cryoprotectant trehalose were used as a model for evaluating the parameters that lead to the parallel detection and quantification of biomaterials. Trehalose was mixed separately with different concentrations of peptides. The peptide secondary ion intensities (normalized with respect to those of trehalose) were directly proportional to their concentration in the matrix (0.01–2.5mol%). Quantification curves for each peptide were generated by plotting the percentage of peptides in trehalose versus the normalized SIMS intensities. Using these curves, the parallel detection, identification, and quantification of multiple peptides was achieved. Low energy Ar⁺ was used to co-sputter and ionize the peptide-doped trehalose sample to suppress the carbon deposition associated with C₆₀⁺ bombardment, which suppressed the ion intensities during the depth profiling. This co-sputtering technique yielded steadier molecular ion intensities than when using a single C₆₀⁺ beam. In other words, co-sputtering is suitable for the depth profiling of thick specimens. In addition, the smoother surface generated by co-sputtering yielded greater depth resolution than C₆₀⁺ sputtering. Furthermore, because C₆₀⁺ is responsible for generating the molecular ions, the dosage of the auxiliary Ar⁺ does not significantly affect the quantification curves.

Keywords: Secondary ion mass spectrometry; Cluster ion; Co-sputtering; Depth profile

A support for the identification of non-tryptic peptides based on low resolution tandem and sequential mass spectrometry data: The INSPIRE software by Ilario Losito; Fabio Mavelli; Annamaria Demarinis Loiotile; Francesco Palmisano (pp. 70-77).

. INSPIRE-based re-ranking of correct non-tryptic peptide sequences among those obtained from a search on the NCBInr database using the MS-Tag software (single taxonomy constrain); n.f.=correct sequence not found in the search output.Display Omitted► Non-tryptic peptide correct sequences may have low ranks in database search outputs. ► INSPIRE enables the re-ranking of correct sequences within the first ten places. ► INSPIRE makes MS³-based discrimination between concurrent sequences faster.A simple software, to be used as an aid in the identification of non-tryptic peptides based on low resolution (3D-ion trap) tandem (MS/MS) and sequential (MS³) mass spectrometry data, is presented.The program, named INSPIRE (Identification ofNon-tryptic peptideSequences based onProductI ons m/z ratios andRE lative abundances), provides alternative rankings for the several candidate sequences usually arising from protein database searches when non-tryptic peptides are involved and only low resolution MS/MS data are available. The rankings, based on parameters related to m/ z ratios and relative abundances of experimental product ions matching with predicted ones, can be exploited to reduce the number of candidates to be included in subsequent data processing based on MS³ measurements. The latter usually represents a mandatory step towards a reliable peptide identification when high resolution MS/MS data are not accessible.Sets of peptide sequences arising from MS/MS-based database searches for 63 previously identified non-tryptic peptides (all generated from milk proteins) were exploited to check the INSPIRE performance. It was found that, if retrieved among candidates after the database search, the correct sequence was always ranked among the first 10 ones when parameters calculated by INSPIRE were adopted for discrimination purposes. Under the same conditions the ranks provided by popular database search programs were significantly worse in a remarkable number of cases.

Keywords: Non-tryptic peptides; Peptide identification; Bioinformatics; Proteomics; Tandem and sequential mass spectrometry

Multidimensional Raman spectroscopic signature of sweat and its potential application to forensic body fluid identification by Vitali Sikirzhytski; Aliaksandra Sikirzhytskaya; Igor K. Lednev (pp. 78-83).

Display Omitted► Raman microspectroscopy was used for nondestructive identification of sweat traces for forensic purposes. ► Calculated multidimensional spectroscopic signature of sweat allowed eliminating the effect of heterogeneity of sweat. ► Any sweat sample can be represented as the combination of two fluorescent backgrounds and three Raman spectral components. ► Spectroscopic signature of sweat was fitted to all of the dry sweat samples with high goodness-of-fit statistical results.This proof-of-concept study demonstrated the potential of Raman microspectroscopy for nondestructive identification of traces of sweat for forensic purposes. Advanced statistical analysis of Raman spectra revealed that dry sweat was intrinsically heterogeneous, and its biochemical composition varies significantly with the donor. As a result, no single Raman spectrum could adequately represent sweat traces. Instead, a multidimensional spectroscopic signature of sweat was built that allowed for the presentation of any single experimental spectrum as a linear combination of two fluorescent backgrounds and three Raman spectral components dominated by the contribution from lactate, lactic acid, urea and single amino acids.

Keywords: Raman spectroscopy; Sweat; Principle components; Statistical analysis; Forensic science; Body fluid identification

Flow injection chemiluminescence sensor based on core–shell magnetic molecularly imprinted nanoparticles for determination of sulfadiazine by Fuguang Lu; Huaijiang Li; Min Sun; Lulu Fan; Huamin Qiu; Xiangjun Li; Chuannan Luo (pp. 84-91).

The preparation of core–shell magnetic molecularly imprinted nanoparticles for determination of sulfadiazine in flow injection chemiluminescence.Display Omitted► A sensitive and selectivity sensor for determination of sulfadiazine was developed. ► The magnetic molecularly imprinted polymers exhibited excellent adsorption property. ► The magnetic imprinted products were introduced as chemiluminescence element. ► The sensor displayed high selectivity, low detection limit and long-term stability etc.A novel flow injection chemiluminescence (FI-CL) sensor for determination of sulfadiazine (SDZ) using core–shell magnetic molecularly imprinted polymers (MMIPs) as recognition element is developed. Briefly, a hydrophilic MMIPs layer was produced at the surface of Fe₃O₄@SiO₂ magnetic nanoparticles (MNPs) via combination of molecular imprinting and reversible stimuli responsive hydrogel. And it provided the MMIPs with excellent adsorption capacity and rapid adsorption rate due to the imprinted sites mostly situated on the surface of MMIPs. Then the prepared SDZ-MMIPs were packed into flow cell to establish a novel FI-CL sensor. The sensor provided a wide linear range for SDZ of 4.0×10⁻⁷ to 1.0×10⁻⁴molL⁻¹ with a detection limit of 1.54×10⁻⁷molL⁻¹. And the relative standard deviation (RSD) for the determination of 1.0×10⁻⁶molL⁻¹ SDZ was 2.56% ( n=11). The proposed method was applied to determine SDZ in urine samples and satisfactory results were obtained.

Keywords: Sulfadiazine; Magnetic molecularly imprinted polymer; Adsorption; Chemiluminescence; Sensor

Normalization using a tagged-internal standard assay for analysis of antibody arrays and the evaluation of serological biomarkers for liver disease by Deok-Hoon Kong; Jae-Wan Jung; Keun Na; Seul-Ki Jeong; Young-Ki Paik; Se-Hui Jung; In-Bum Suh; Young-Myeong Kim; Kwon-Soo Ha (pp. 92-98).

Display Omitted► We analyzed six serum proteins from 79 human serum samples using antibody arrays. ► We evaluated five normalization methods for minimizing systemic experimental variation. ► Median-centered/IgM-ELISA normalization provided was found to be optimal. ► Using this normalization, we identified potential biomarkers for liver disease. ► Potential biomarkers were verified by Western blot.For minimizing systemic experimental variation in the analysis of antibody array data, we developed a novel median-centered/IgM-tagged-internal standard (TIS) assay normalization using median-centering and TIS assay-based determination of serum IgM concentrations. We evaluated five normalization methods by analyzing correlation coefficients and coefficients of variation for six serum proteins using human serum samples from normal controls ( n=25) and patients with liver cirrhosis ( n=25) or hepatocellular carcinoma (HCC; n=29). Median-centered normalization improved correlation coefficients, while IgM-based normalizations improved coefficients of variation. The TIS assay was more efficient, economical, and reproducible for determining IgM concentrations than enzyme-linked immunosorbent assay. Additionally, we normalized antibody array data for six serum proteins using the median-centered/IgM-TIS assay, and evaluated serum biomarkers through distribution analysis of normalized fluorescence intensities and receiver operating characteristic analyses for the diagnosis of liver cirrhosis and HCC. Apolipoprotein A-1 and a combination of alpha-fetoprotein and C-reactive protein were determined to be potential serological biomarkers for liver cirrhosis and HCC, respectively. Thus, median-centered/IgM-TIS assay normalization is a useful approach for analyzing antibody array data and evaluating serological biomarkers for the diagnosis of liver disease or cancers.

Keywords: Abbreviations; AFP; alpha-fetoprotein; ApoA-1; apolipoprotein A-1; AUC; area under the ROC curve; CA19-9; carbohydrate antigen 19-9; CRP; C-reactive protein; HCC; hepatocellular carcinoma; NHS; N-hydroxysuccinimide; ROC; Receiver operating characteristic; SAP; serum amyloid P; TIS; tagged-internal standard; VDBP; vitamin D-binding proteinHepatocellular carcinoma; Liver cirrhosis; IgM; Biomarker; Median-centered/IgM-TIS assay; Normalization

Multiplex dipstick immunoassay for semi-quantitative determination of Fusarium mycotoxins in cereals by Veronica M.T. Lattanzio; Noan Nivarlet; Vincenzo Lippolis; Stefania Della Gatta; Anne-Catherine Huet; Philippe Delahaut; Benoit Granier; Angelo Visconti (pp. 99-108).

.Display Omitted► We developed a rapid method based on a multiplex dipstick immunoassay. ► The assay allowed the determination of major Fusarium toxins in wheat, oats, maize. ► We obtained cut off levels close to EU regulatory levels.A multiplex dipstick immunoassay based method for the simultaneous determination of major Fusarium toxins, namely zearalenone, T-2 and HT-2 toxins, deoxynivalenol and fumonisins in wheat, oats and maize has been developed. The dipstick format was based on an indirect competitive approach. Four test lines (mycotoxin–BSA conjugates) and one control line were located on the strip membrane. Labelled antibodies were freeze-dried within the microwell. Two matrix-related sample preparation protocols have been developed for wheat/oats (not containing fumonisins) and maize (containing fumonisins) respectively. The use of a methanol/water mixture for sample preparation allowed recoveries in the range 73–109% for all mycotoxins in all tested cereals, with relative standard deviation less than 10%. The optimized immunoassay was able to detect target mycotoxins at cut off levels equal to 80% of EU maximum permitted levels, i.e. 280, 400, 1400 and 3200μgkg⁻¹, respectively, for zearalenone, T-2/HT-2 toxins, deoxynivalenol and fumonisins in maize, and 80, 400 and 1400μgkg⁻¹, respectively, for zearalenone, T-2/HT-2 toxins and deoxynivalenol in wheat and oats. Analysis of naturally contaminated samples resulted in a good agreement between multiplex dipstick and validated confirmatory LC–MS/MS. The percentage of false positive results was less than or equal to 13%, whereas no false negative results were obtained. Data on the presence/absence of 6 mycotoxins at levels close to EU regulatory levels were obtained within 30min. The proposed immunoassay protocol is rapid, inexpensive, easy-to-use and fit for purpose of rapid screening of mycotoxins in cereals.

Keywords: Fusarium; toxins; Lateral flow; Wheat; Oats; Maize

Surface imprinted thin polymer film systems with selective recognition for bovine serum albumin by David R. Kryscio; Nicholas A. Peppas (pp. 109-115).

Display Omitted► We develop a novel surface imprinting technique for the recognition of BSA. ► We address the main obstacles preventing success in the field. ► Reproducible recognition is demonstrated. ► Statistically significant selectivity is shown for the template versus competitors.Molecularly imprinted polymers are synthetic antibody mimics formed by the crosslinking of organic or inorganic polymers in the presence of an analyte which yields recognitive polymer networks with specific binding pockets for that biomolecule. Surface imprinted polymers were synthesized via a novel technique for the specific recognition of bovine serum albumin (BSA). Thin films of recognitive networks based on 2-(dimethylamino)ethyl methacrylate (DMAEMA) as the functional monomer and varying amounts of either N,N′-methylenebisacrylamide (MBA) or poly(ethylene glycol) (400) dimethacrylate (PEG400DMA) as the crosslinking agent were synthesized via UV free-radical polymerization and characterized. A clear and reproducible increase in recognition of the template BSA was demonstrated for these systems at 1.6–2.5 times more BSA recognized by the MIP sample relative to the control polymers. Additionally, these polymers exhibited selective recognition of the template relative to competing proteins with up to 2.9 times more BSA adsorbed than either glucose oxidase or bovine hemoglobin. These synthetic antibody mimics hold significant promise as the next generation of robust recognition elements in a wide range of bioassay and biosensor applications.

Keywords: Molecular imprinted polymers; Protein imprinting; Thin film; Bovine serum albumin

Determination of sodium, potassium, calcium and magnesium cations in biodiesel by ion chromatography by Lilia Basilio de Caland; Eva Lúcia Cardoso Silveira; Matthieu Tubino (pp. 116-120).

Display Omitted► Quantitation of sodium, potassium, magnesium and calcium cations in biodiesel. ► Aqueous acidic extraction. ► Extraction effectiveness tested. ► Simultaneous analysis. ► Comparison with official method using three different matrixes.This work reports an ion chromatographic (IC) method for the quantitative determination of inorganic cations (Na⁺, K⁺, Mg²⁺ and Ca²⁺) in biodiesel samples that were synthesized from different vegetable oils and fat. The proposed method uses water extraction, heating and ultrasound. The limits of detection (LOD) for each ion, in milligrams of the analyte per kilogram of biodiesel (mgkg⁻¹), were respectively: 0.11 (Na⁺); 0.42 (K⁺); 0.23 (Ca²⁺); and 0.36 (Mg²⁺). The accuracy of the method was studied through recovery tests. For comparison, two samples were also analyzed using an Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) procedure. The paired Student t test and the Snedecor F test showed that both methods offer equivalent results in terms of accuracy and precision. The operational simplicity, accuracy and precision of the proposed method suggest that it can be a good alternative for the determination of inorganic cations in biodiesel samples.

Keywords: Biodiesel; Inorganic cations; Ion chromatography; Analysis; Biofuel

Cationic cyclodextrins chemically-bonded chiral stationary phases for high-performance liquid chromatography by Ren-Qi Wang; Teng-Teng Ong; Weihua Tang; Siu-Choon Ng (pp. 121-129).

Covalently bonded cationic β-CD chiral stationary phases (CSPs) prepared by graft polymerization onto silica gel were successfully applied in high-performance liquid chromatography (HPLC).Display Omitted► Covalently bonded cationic CD CSPs prepared by graft polymerization of CD onto silica gel. ► Cationic CD CSPs were successfully applied in chiral HPLC. ► Imidazolium-based CSP afforded better enantioseparation than ammonium-based under NPLC. ► Cationic moiety of CSPs formed hydrogen bonding with analytes to enhance enantioseparation. ► Inclusion complexation and ionic interactions accentuated enantioseparations.Two covalently bonded cationic β-CD chiral stationary phases (CSPs) prepared by graft polymerization of 6^A-(3-vinylimidazolium)-6-deoxyperphenylcarbamate-β-cyclodextrin chloride or 6^A-(N,N-allylmethylammonium)-6-deoxyperphenylcarbamoyl-β-cyclodextrin chloride onto silica gel were successfully applied in high-performance liquid chromatography (HPLC). Their enantioseparation capability was examined with 12 racemic pharmaceuticals and 6 carboxylic acids. The results indicated that imidazolium-containing β-CD CSP afforded more favorable enantioseparations than that containing ammonium moiety under normal-phase HPLC. The cationic moiety on β-CD CSPs could form strong hydrogen bonding with analytes in normal-phase liquid chromatography (NPLC) to enhance the analytes’ retention and enantioseparations. In reversed-phase liquid chromatography (RPLC), the analytes exhibited their maximum retention when the pH of mobile phase was close to their p K_a value. Inclusion complexation with CD cavity and columbic/ionic interactions with cationic substituent on the CD rim would afford accentuated retention and enantioseparations of the analytes.

Keywords: β-cyclodextrin; Chiral stationary phase; High-performance liquid chromatography; Enantioseparation; Electrostatic force; Ionic liquid

Immobilization of chitosan in sol–gel phases for chiral open-tubular capillary electrochromatography by Jian-Lian Chen; Hong-Jie Syu (pp. 130-137).

Display Omitted► Sequence in synthetic steps determines the chitosan loading in the sol–gel phases. ► Chitosan moieties bearing carboxylic acid groups dominate the EOF. ► High loading of the chitosan chiral selector caused the high k″ and α values. ► Consider the hydrophobicity of the sol–gel phases in the chiral CEC separations. ► Some sol–gel phases were superior in resolution and time to the monolayered phase.Three different approaches for immobilizing cross-linked chitosan molecules (CS-s) in sol–gel phases to form chiral OT-CEC capillaries were comparatively investigated in this study. To synthesize column I, a bare capillary was first silanized with triethoxysilane (TEOS) and then reacted with the reaction product of 3-glycidyloxypropyltrimethoxysilane (GTS) and CS-s. Column II was prepared by the silanization of a bare capillary with a mixture of TEOS and GTS silanes followed by reaction with CS-s. To obtain column III, all the reagents, including TEOS, GTS, and CS-s were reacted together in a bare capillary. The SEM images showed that the column I phase consisted of two distinct layers, GTS and TEOS sol–gel films, while column II and III phases were homogeneous phases. By elemental analysis, the chitosan contents of the columns were found to decrease in the order column I>II>III, which corresponded to the order of the electroosmotic mobility values obtained from the measurements of the electroosmotic flow in the columns. The retention factor and the selectivity for the chiral separation of phenylglycine enantiomers in the optimized Tris running buffer (100mM, pH 7.5) also followed this decreasing order. Besides the strength of the interaction with the immobilized functional chitosan, the hydrophobicity of the column affected the resolution of enantiomeric samples. The hydrophilic alanine sample could only be resolved by column III, but the hydrophobic tryptophan and catechin enantiomers were better separated by columns I and II. A reverse-phase mechanism has been found in the separations. Furthermore, the resolution and analysis time of column I and II phases were superior to the phase simply bonded with molecular chitosan.

Keywords: Capillary electrochromatography; Chiral stationary phase; Chitosan; Open-tubular; Sol–gel

Computer-aided molecular modeling study of enantioseparation of iodiconazole and structurally related triadimenol analogues by capillary electrophoresis: Chiral recognition mechanism and mathematical model for predicting chiral separation by Wuhong Li; Guangguo Tan; Liang Zhao; Xiaofei Chen; Xinrong Zhang; Zhenyu Zhu; Yifeng Chai (pp. 138-147).

Display Omitted► Molecular modeling studies chiral recognition mechanism of iodiconazole with HP-γ-CD. ► The good separation obtained is due to the big binding energy difference. ► A new mathematical equation is established to predict chiral separation. ► Molecular modeling serves as a useful method for studying chiral separation.Chiral separation of iodiconazole, a new antifungal drug, and 12 new structurally related triadimenol analogues had been developed by capillary electrophoresis (CE) using hydroxypropyl-γ-cyclodextrin (HP-γ-CD) as the chiral selector. The effect of structural features of analytes on Δ t and R_s was studied under the optimum separation conditions. Using molecular docking technique and binding energy calculations, the inclusion process between HP-γ-CD and enantiomers was investigated and chiral recognition mechanisms were discussed. The results suggest that hydrogen bonding between fluorine at position 4 of the phenyl group beside the chiral carbon and the hydroxyl group on the HP-γ-CD rim and face to face π–π interactions between two phenyl rings highly contributed to the enantiorecognition process between HP-γ-CD and iodiconazole. The N-methyl group beside chiral carbon also played an important role in enantiomeric separation. Additionally, the big difference in binding energy (ΔΔ E) highly contributed to good separation in the presence of HP-γ-CD chiral selector, which may be a helpful initial guide for chiral selector selection and predicting the result of enantioseparation. Furthermore, the new mathematical equation established based on the results of molecular mechanics calculations exhibited good capability in predicting chiral separation of these triadimenol analogues using HP-γ-CD mediated CE.

Keywords: Molecular modeling; Enantioseparation; Hydroxypropyl-γ-cyclodextrin; Iodiconazole; Chiral recognition mechanism; Mathematical model

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Analytica Chimica Acta (v.718, #)