Analytica Chimica Acta (v.913, #C)

Today virgin and extra-virgin olive oil (VOO and EVOO) are food with a large number of analytical tests planned to ensure its quality and genuineness. Almost all official methods demand high use of reagents and manpower. Because of that, analytical development in this area is continuously evolving. Therefore, this review focuses on analytical methods for EVOO/VOO which use fast and smart approaches based on chemometric techniques in order to reduce time of analysis, reagent consumption, high cost equipment and manpower.Experimental approaches of chemometrics coupled with fast analytical techniques such as UV–Vis spectroscopy, fluorescence, vibrational spectroscopies (NIR, MIR and Raman fluorescence), NMR spectroscopy, and other more complex techniques like chromatography, calorimetry and electrochemical techniques applied to EVOO/VOO production and analysis have been discussed throughout this work. The advantages and drawbacks of this association have also been highlighted.Chemometrics has been evidenced as a powerful tool for the oil industry. In fact, it has been shown how chemometrics can be implemented all along the different steps of EVOO/VOO production: raw material input control, monitoring during process and quality control of final product.Display Omitted
Keywords: Olive oil; Chemometrics; Analytical techniques; Quality control; Authentication;

Applications of capillary electrophoresis with chemiluminescence detection in clinical, environmental and food analysis. A review by Francisco J. Lara; Diego Airado-Rodríguez; David Moreno-González; José F. Huertas-Pérez; Ana M. García-Campaña (22-40).
This paper reviews the latest developments and analytical applications of chemiluminescence detection coupled to capillary electrophoresis (CE-CL). Different sections considering the most common CL systems have been included, such as the tris(2,2ʹ-bipyridine)ruthenium(II) system, the luminol and acridinium derivative reactions, the peroxyoxalate CL or direct oxidations. Improvements in instrumental designs, new strategies for improving both resolution and sensitivity, and applications in different fields such as clinical, pharmaceutical, environmental and food analysis have been included. This review covers the literature from 2010 to 2015.Display Omitted
Keywords: Capillary electrophoresis; Chemiluminescence; Pharmaceutical analysis; Environmental analysis; Food analysis;

A tutorial review for employing enzymes for the construction of G-quadruplex-based sensing platforms by Dik-Lung Ma; Wanhe Wang; Zhifeng Mao; Chao Yang; Xiu-Ping Chen; Jin-Jian Lu; Quan-Bin Han; Chung-Hang Leung (41-54).
With rapid advances in the field of DNA chemistry, nucleic acids and DNA-modifying enzymes have recently emerged as versatile components for the construction of oligonucleotide-based sensors. Meanwhile, the G-quadruplex motif has been widely employed for the development of DNA-based assays due to its diverse structural variety. In this tutorial, we introduce the principles of G-quadruplex-based sensing and the use of DNA-modifying enzymes for sensor platform development. We also highlight recent studies of the application of DNA-modifying enzymes for the development of G-quadruplex-based luminescent detection platforms with a view towards how those enzymes play an important role in sensitivity enhancement.Display Omitted
Keywords: Oligonucleotide-based sensor; G-quadruplex; Enzyme; Sensor construction;

Optimization of a liquid chromatography ion mobility-mass spectrometry method for untargeted metabolomics using experimental design and multivariate data analysis by Abdellah Tebani; Isabelle Schmitz-Afonso; Douglas N. Rutledge; Bruno J. Gonzalez; Soumeya Bekri; Carlos Afonso (55-62).
High-resolution mass spectrometry coupled with pattern recognition techniques is an established tool to perform comprehensive metabolite profiling of biological datasets. This paves the way for new, powerful and innovative diagnostic approaches in the post-genomic era and molecular medicine. However, interpreting untargeted metabolomic data requires robust, reproducible and reliable analytical methods to translate results into biologically relevant and actionable knowledge. The analyses of biological samples were developed based on ultra-high performance liquid chromatography (UHPLC) coupled to ion mobility - mass spectrometry (IM-MS). A strategy for optimizing the analytical conditions for untargeted UHPLC-IM-MS methods is proposed using an experimental design approach. Optimization experiments were conducted through a screening process designed to identify the factors that have significant effects on the selected responses (total number of peaks and number of reliable peaks). For this purpose, full and fractional factorial designs were used while partial least squares regression was used for experimental design modeling and optimization of parameter values. The total number of peaks yielded the best predictive model and is used for optimization of parameters setting.Display Omitted
Keywords: Experimental design; Mass spectrometry; Ion mobility; Metabolomics; Chemometrics;

In the present study, a molecularly imprinted solid-phase microextraction fiber (MIP-SPMEf) was synthesized and applied for the selective removal and extraction of the antiviral drug, abacavir (ABA). Morphology and structure characterization of fibers were performed by scanning electron microscopy and Fourier transform infrared spectra, respectively. The effects on the adsorption behavior of the process parameters were studied and the equilibrium data were fitted by the Langmuir, Freundlich and Langmuir-Freundlich models. The maximum adsorption capability (Qmax) was determined by Langmuir- Freundlich model and was 149 mg/g for MIP-SPMEf. In the next step, SPME methodology followed by liquid desorption and liquid chromatography with mass spectrometry (LC/MS) has been developed and evaluated for the determination of the target compound in environmental and biological matrices (surface waters, wastewaters and urine). Parameters that could influence SPME efficiency were investigated. Then, optimization of stirring speed, extraction time and salt content was carried out by using a central composite design (CCD) and response surface methodology (RSM). A quadratic model between dependent and independent variables was built. Under the optimum conditions (extraction time 40 min, stirring rate 650 rpm and salt content 0.3% NaCl w/v) the validated method presented a high sensitivity and selectivity with LODs and LOQs in the range of 10.1–13.6 and 33.3–43.9 ng/L, respectively. The developed method was successfully applied to the analysis of ABA in real samples. The percentage extraction efficiency ranged from 88 to 99% revealing good accuracy and absence of matrix effects.Display Omitted
Keywords: Abacavir; Anti-retroviral drugs; Antiviral drugs; Central composite design; Molecularly imprinted polymers; Solid phase microextraction;

In the present work, an automated on-line electrochemically controlled in-tube solid-phase microextraction (EC-in-tube SPME) coupled with HPLC-UV was developed for the selective extraction and preconcentration of indomethacin as a model analyte in biological samples. Applying an electrical potential can improve the extraction efficiency and provide more convenient manipulation of different properties of the extraction system including selectivity, clean-up, rate, and efficiency. For more enhancement of the selectivity and applicability of this method, a novel molecularly imprinted polymer coated tube was prepared and applied for extraction of indomethacin. For this purpose, nanostructured copolymer coating consisting of polypyrrole doped with ethylene glycol dimethacrylate was prepared on the inner surface of a stainless-steel tube by electrochemical synthesis. The characteristics and application of the tubes were investigated. Electron microscopy provided a cross linked porous surface and the average thickness of the MIP coating was 45 μm. Compared with the non-imprinted polymer coated tubes, the special selectivity for indomethacin was discovered with the molecularly imprinted coated tube. Moreover, stable and reproducible responses were obtained without being considerably influenced by interferences commonly existing in biological samples. Under the optimal conditions, the limits of detection were in the range of 0.07–2.0 μg L−1 in different matrices. This method showed good linearity for indomethacin in the range of 0.1–200 μg L−1, with coefficients of determination better than 0.996. The inter- and intra-assay precisions (RSD%, n = 3) were respectively in the range of 3.5–8.4% and 2.3–7.6% at three concentration levels of 7, 70 and 150 μg L−1. The results showed that the proposed method can be successfully applied for selective analysis of indomethacin in biological samples.An automated on-line method for selective extraction and preconcentration of the indomethacin in biological samples was developed.Display Omitted
Keywords: Electrochemically controlled; In-tube solid phase microextraction; Indomethacin; Molecularly imprinted polymer; Polypyrrole;

High-throughput screening (HTS) is often required in enzyme inhibitor drugs screening. Mass spectrometry (MS) provides a powerful method for high-throughput screening enzyme inhibitors because its high speed, sensitivity and property of lable free. However, most of the MS methods need complicated sampling interface system. Overall throughput was limited by sample loading in these cases. In this study, we develop a simple interface which coupled droplet segmented system to a venturi easy ambient sonic-spray ionization mass spectrometer. It is fabricated by using a single capillary to act as both sampling probe and the emitter, which simplifies the construction, reduces the cost and shorten the sampling time. Samples sucked by venturi effect are segmented to nanoliter plugs by air, then the plugs can be detected by MS directly. This system eliminated the need for flow injection which was popular used in classic scheme. The new system is applied to screen angiotensin converting enzyme inhibitors. High-throughput was achieved in analyzing 96 samples at 1.6 s per sample. The plugs formation was at 0.5s per sample. Carry-over between samples was less than 5%, the peak height RSD was 2.92% (n = 15). Dose-response curves of 3 known inhibitors were also measured to validate its potential in drug discovery. The calculated IC50 agreed well with reported values.Display Omitted
Keywords: High-throughput screening; Angiotensin converting enzyme inhibitors; Venturi easy ambient sonic-spray ionization mass spectrometry; Sampling interface;

Uranium aqueous speciation in the vicinity of the former uranium mining sites using the diffusive gradients in thin films and ultrafiltration techniques by Jagoda Drozdzak; Martine Leermakers; Yue Gao; Marc Elskens; Vannapha Phrommavanh; Michael Descostes (94-103).
The performance of the Diffusive Gradients in Thin films (DGT) technique with Chelex®-100, Metsorb™ and Diphonix® as binding phases was evaluated in the vicinity of the former uranium mining sites of Chardon and L'Ecarpière (Loire-Atlantique department in western France). This is the first time that the DGT technique with three different binding agents was employed for the aqueous U determination in the context of uranium mining environments. The fractionation and speciation of uranium were investigated using a multi-methodological approach using filtration (0.45 μm, 0.2 μm), ultrafiltration (500 kDa, 100 kDa and 10 kDa) coupled to geochemical speciation modelling (PhreeQC) and the DGT technique. The ultrafiltration data showed that at each sampling point uranium was present mostly in the 10 kDa truly dissolved fraction and the geochemical modelling speciation calculations indicated that U speciation was markedly predominated by CaUO2(CO3)3 2−. In natural waters, no significant difference was observed in terms of U uptake between Chelex®-100 and Metsorb™, while similar or inferior U uptake was observed on Diphonix® resin. In turn, at mining influenced sampling spots, the U accumulation on DGT-Diphonix® was higher than on DGT-Chelex®-100 and DGT-Metsorb™, probably because their performance was disturbed by the extreme composition of the mining waters. The use of Diphonix® resin leads to a significant advance in the application and development of the DGT technique for determination of U in mining influenced environments. This investigation demonstrated that such multi-technique approach provides a better picture of U speciation and enables to assess more accurately the potentially bioavailable U pool.Display Omitted
Keywords: Uranium; Diffusive gradients in thin films; Ultrafiltration; Diphonix®; Former mining sites; Bioavailable fraction;

Protein-bound tyrosine oxidation, nitration and chlorination by-products assessed by ultraperformance liquid chromatography coupled to tandem mass spectrometry by Isabel Torres-Cuevas; Julia Kuligowski; María Cárcel; Consuelo Cháfer-Pericás; Miguel Asensi; Rønnaug Solberg; Elena Cubells; Antonio Nuñez; Ola Didrik Saugstad; Máximo Vento; Javier Escobar (104-110).
Free radicals cause alterations in cellular protein structure and function. Oxidized, nitrated, and chlorinated modifications of aromatic amino acids including phenylalanine and tyrosine are reliable biomarkers of oxidative stress and inflammation in clinical conditions.To develop, validate and apply a rapid method for the quantification of known hallmarks of tyrosine oxidation, nitration and chlorination in plasma and tissue proteins providing a snapshot of the oxidative stress and inflammatory status of the organism and of target organs respectively.The extraction and clean up procedure entailed protein precipitation, followed by protein re-suspension and enzymatic digestion with pronase. An Ultra Performance Liquid Chromatography–tandem Mass Spectrometry (UPLC-MS/MS) method was developed to quantify protein released ortho-tyrosine (o-Tyr), meta-tyrosine (m-Tyr), 3-nitrotyrosine (3NO2-Tyr) and 3-chlorotyrosine (3Cl-Tyr) as well as native phenylalanine (Phe) and tyrosine (p-Tyr) in plasma and tissue from a validated hypoxic newborn piglet experimental model.In plasma there was a significant increase in the 3NO2-Tyr/p-Tyr ratio. On the other hand m-Tyr/Phe and 3Cl-Tyr/p-Tyr ratios were significantly increased in liver of hypoxic compared with normoxic animals. Although no significant differences were found in brain tissue, a clear tendency to increased ratios was observed under hypoxic conditions.UPLC-MS/MS has proven suitable for the analysis of plasma and tissue samples from newborn piglets. The analysis of biomarkers of protein oxidation, nitration and chlorination will be applied in future studies aiming to provide a deeper insight into the mechanisms of oxidation-derived protein modification caused during neonatal asphyxia and resuscitation.Display Omitted
Keywords: Protein oxidation; Protein nitration; Phenylalanine; Tyrosine; Liquid chromatography; Mass spectrometry; Biomarkers; Plasma; Tissue;

A new, fully automated, rapid method, referred to as kernel principal component analysis residual diagnosis (KPCARD), is proposed for removing cosmic ray artifacts (CRAs) in Raman spectra, and in particular for large Raman imaging datasets. KPCARD identifies CRAs via a statistical analysis of the residuals obtained at each wavenumber in the spectra. The method utilizes the stochastic nature of CRAs; therefore, the most significant components in principal component analysis (PCA) of large numbers of Raman spectra should not contain any CRAs. The process worked by first implementing kernel PCA (kPCA) on all the Raman mapping data and second accurately estimating the inter- and intra-spectrum noise to generate two threshold values. CRA identification was then achieved by using the threshold values to evaluate the residuals for each spectrum and assess if a CRA was present.CRA correction was achieved by spectral replacement where, the nearest neighbor (NN) spectrum, most spectroscopically similar to the CRA contaminated spectrum and principal components (PCs) obtained by kPCA were both used to generate a robust, best curve fit to the CRA contaminated spectrum. This best fit spectrum then replaced the CRA contaminated spectrum in the dataset. KPCARD efficacy was demonstrated by using simulated data and real Raman spectra collected from solid-state materials. The results showed that KPCARD was fast (<1 min per 8400 spectra), accurate, precise, and suitable for the automated correction of very large (>1 million) Raman datasets.Display Omitted
Keywords: Cosmic ray artifacts; Raman spectroscopy; Correction; Kernel PCA; Quantitative;

Silver nanoparticles coated graphene electrochemical sensor for the ultrasensitive analysis of avian influenza virus H7 by Jiaoling Huang; Zhixun Xie; Zhiqin Xie; Sisi Luo; Liji Xie; Li Huang; Qing Fan; Yanfang Zhang; Sheng Wang; Tingting Zeng (121-127).
A new, highly sensitive electrochemical immunosensor with a sandwich-type immunoassay format was designed to quantify avian influenza virus H7 (AIV H7) by using silver nanoparticle-graphene (AgNPs-G) as trace labels in clinical immunoassays. The device consists of a gold electrode coated with gold nanoparticle-graphene nanocomposites (AuNPs-G), the gold nanoparticle surface of which can be further modified with H7-monoclonal antibodies (MAbs). The immunoassay was performed with H7-polyclonal antibodies (PAbs) that were attached to the AgNPs-G surface (PAb-AgNPs-G). This method of using PAb-AgNPs-G as detection antibodies shows high signal amplification and exhibits a dynamic working range of 1.6 × 10−3∼16 ng/mL, with a low detection limit of 1.6 pg/mL at a signal-to-noise ratio of 3σ. In summary, we showed that this novel immunosensor is highly specific and sensitive to AIV H7, and the established assay could potentially be applied to rapidly detect other pathogenic microorganisms.Display Omitted
Keywords: Graphene; Electrochemical immunosensor; Nanolabel; Sensitivity enhancement; Avian influenza virus H7;

Direct growth of MnOOH nanorod arrays on a carbon cloth for high-performance non-enzymatic hydrogen peroxide sensing by Weina Xu; Jianlin Liu; Mingjun Wang; Lin Chen; Xue Wang; Chenguo Hu (128-136).
Novel MnOOH nanorod arrays directly growing on a flexible carbon cloth substrate (MnOOH/CC) is first synthesized through a facile hydrothermal technique and utilized as an electrocatalyst for non-enzymatic detection of hydrogen peroxide. The as-prepared MnOOH nanorods are uniformly distributed on the carbon cloth with a 3D porous network structure, which provides a high specific surface area and numerous electroactive sites. The electrode based on the carbon cloth-supported MnOOH nanorod arrays exhibits a higher sensitivity (692.42 μA mM−1 cm−2) and a wider linear range (20 μm–9.67 mM) with a detection limit of 3.2 μM (S/N = 3) compared with the electrode based on the rigid graphite substrate supported the random distributed MnOOH nanorods. Further, the MnOOH/CC possesses an outstanding flexibility and can conveniently be assembled into the required shape for a specific use, thus the arc-shaped MnOOH/CC electrodes are fabricated whose electrocatalytic activity toward the hydrogen peroxide reduction remains nearly unchanged in comparison with the unbent state. Due to its excellent sensitivity, reproducibility, anti-interference and stability, the electrode based on the carbon cloth-supported MnOOH nanorod arrays is believed to be promising for applications in high efficiency flexible hydrogen peroxide sensing.Display Omitted
Keywords: Manganite; Carbon cloth; Nanorod array; Non-enzymatic sensor; Hydrogen peroxide;

Gold nanostar-enhanced surface plasmon resonance biosensor based on carboxyl-functionalized graphene oxide by Qiong Wu; Ying Sun; Pinyi Ma; Di Zhang; Shuo Li; Xinghua Wang; Daqian Song (137-144).
A new high-sensitivity surface plasmon resonance (SPR) biosensor based on biofunctional gold nanostars (AuNSs) and carboxyl-functionalized graphene oxide (cGO) sheets was described. Compared with spherical gold nanoparticles (AuNPs), the anisotropic structure of AuNSs, which concentrates the electric charge density on its sharp tips, could enhance the local electromagnetic field and the electronic coupling effect significantly. cGO was obtained by a diazonium reaction of graphene oxide (GO) with 4-aminobenzoic acid. Compared with GO, cGO could immobilize more antibodies due to the abundant carboxylic groups on its surface. Testing results show that there are fairly large improvements in the analytical performance of the SPR biosensor using cGO/AuNSs-antigen conjugate, and the detection limit of the proposed biosensor is 0.0375 μg mL−1, which is 32 times lower than that of graphene oxide-based biosensor.Display Omitted
Keywords: Carboxyl-functionalized graphene oxide; Gold nanostars; Surface plasmon resonance (SPR) biosensor; Pig IgG;

Metabolite profiling of licorice (Glycyrrhiza glabra) from different locations using comprehensive two-dimensional liquid chromatography coupled to diode array and tandem mass spectrometry detection by Lidia Montero; Elena Ibáñez; Mariateresa Russo; Rosa di Sanzo; Luca Rastrelli; Anna Lisa Piccinelli; Rita Celano; Alejandro Cifuentes; Miguel Herrero (145-159).
Profiling of the main metabolites from several licorice (Glycyrrhiza glabra) samples collected at different locations is carried out in this work by using comprehensive two-dimensional liquid chromatography (LC × LC) coupled to diode array (DAD) and mass spectrometry (MS) detectors. The optimized method was based on the application of a HILIC-based separation in the first dimension combined with fast RP-based second dimension separation. This set-up was shown to possess powerful separation capabilities allowing separating as much as 89 different metabolites in a single sample. Identification and grouping of metabolites according to their chemical class were achieved using the DAD, MS and MS/MS data. Triterpene saponins were the most abundant metabolites followed by glycosylated flavanones and chalcones, whereas glycyrrhizic acid, as expected, was confirmed as the main component in all the studied samples. LC × LC-DAD-MS/MS was able to resolve these complex licorice samples providing with specific metabolite profiles to the different licorice samples depending on their geographical origin. Namely, from 19 to 50 specific compounds were exclusively determined in the 2D-chromatograms from the different licorice samples depending on their geographical origin, which can be used as a typical pattern that could potentially be related to their geographical location and authentication.Display Omitted
Keywords: LC × LC; Licorice; Metabolite; Triterpene saponins; Phenolic compounds; Authentication;

Implementation of a data reduction and visualization method for use with high-speed gas chromatography and time-of-flight mass spectrometry (GC-TOFMS) is reported. The method, called the “2D m/z cluster method” facilitates analyte detection, deconvolution, and identification, by accurately measuring peak widths and retention times using a fast TOFMS sampling frequency (500 Hz). Characteristics and requirements for high speed GC are taken into consideration: fast separations with narrow peak widths and high peak capacity, rapid data collection rate, and effective peak deconvolution. Transitioning from standard GC (10–60+ minute separations) to fast GC (1–10 min separations) required consideration of how to properly analyze the data. This report validates use of the 2D m/z cluster method with newly developed GC technology that produces ultra-fast separations (∼1 min) with narrow analyte peak widths. Low thermal mass gas chromatography (LTM-GC) operated at a heating rate of 250 °C/min coupled to a LECO Pegasus III TOFMS analyzed a 115 component test mixture in 120 s with peak widths-at-base, w b (4σ), of 350 ms (average) to produce a separation with a high peak capacity, n c ∼ 340 (at unit resolution R s = 1). The 2D m/z cluster method is shown to separate overlapped analytes to a limiting R s ∼ 0.03, so the effective peak capacity was increased nearly 30-fold to n c ∼10,000 in the 120 s separation. The method, when coupled with LTM-GC-TOFMS, is demonstrated to provide unambiguous peak rank (i.e. the number of analytes per overlapped peak in the total ion current (TIC)), by visualizing locations of pure and chromatographically overlapped m/z. Hence, peak deconvolution and identification using MCR-ALS (multivariate curve resolution – alternating least squares) is demonstrated.Display Omitted
Keywords: Gas chromatography; Low thermal mass (LTM); Peak capacity; TOFMS; Chemometric data analysis;