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Analytical and Bioanalytical Chemistry (v.401, #5)

Aldo Roda (Ed.): Chemiluminescence and bioluminescence: past, present and future by Sapna K. Deo (pp. 1461-1462).

Perry G. Wang (Ed.): Monolithic chromatography and its modern applications by Frantisek Svec (pp. 1463-1464).

A toast to wine analysis by Isabelle Pianet (pp. 1465-1465).

is currently in charge of CESAMO, the analytical center of the Institut des Sciences Moléculaires. She has developed different NMR techniques in the field of 3D structural characterization as well as dynamic and diffusion measurements in collaboration with chemists in Bordeaux. Since the late 1990s, she has also developed a research theme on the astringency induced by procyanidins, tannins found in grapes and wine. Astringency, an important sensation in the mouth, results from a strong interaction occurring between tannins and salivary proteins. This research covers synthesis of procyanidins, their structural characterization and dynamic behavior, identification in grapes and wine, and the physicochemical characterization of their interactions with human salivary proteins.

Formation of pyranoanthocyanins in red wines: a new and diverse class of anthocyanin derivatives by Victor de Freitas; Nuno Mateus (pp. 1467-1477).

Pyranoanthocyanins constitute one of the most important classes of anthocyanin-derived pigments occurring naturally in red wine. Nonetheless, correct assignment of their structures and pathways of formation in red wine has been relatively recent—less than two decades. Study of these newly discovered pigments is progressively unfolding the chemical pathways that drive the evolution of red wine colour during ageing. The objective of this paper is to review current knowledge regarding the pathway of formation in red wine of a great variety of pyranoanthocyanin structures, namely carboxypyranoanthocyanins, methylpyranoanthocyanins, pyranoanthocyanin-flavanols, pyranoanthocyanin-phenols, portisins, oxovitisins, and pyranoanthocyanin dimers. The chromatic features of some of the compounds, for example their colour expression and acid–base equilibria in aqueous media, are also discussed.

Keywords: Anthocyanins; Pyranoanthocyanin; Vitisins; Portisins; Red wines; Wine pigments

Technical solutions for analysis of grape juice, must, and wine: the role of infrared spectroscopy and chemometrics by D. Cozzolino; W. Cynkar; N. Shah; P. Smith (pp. 1479-1488).

Information about constituents of grape juice, must, and wine can be used for management and decision support systems in order to improve, monitor, and adapt grape and wine production to new challenges. Numerous sensors that gather this information are either currently available or in development. Nevertheless there is still a need to adapt these sensors to special requirements, for example robustness, calibration and maintenance, operating costs, duration, sensitivity, and specificity to a particular application. The sensors commonly used by the wine industry are those that are based on mid-infrared (MIR), near-infrared (NIR), visible (VIS) and ultraviolet (UV) spectroscopy. This article reviews some recent technical solutions for analysis of juice, must and wine based on the combination of infrared spectroscopy and chemometrics.

Keywords: Vibrational spectroscopy; Wine; Must; Near-infrared; Mid-infrared; Authentication; Composition

New strategies to study the chemical nature of wine oligomeric procyanidins by Christelle Absalon; Sandy Fabre; Isabelle Tarascou; Eric Fouquet; Isabelle Pianet (pp. 1489-1499).

Tannins represent a key element in red wine flavors, so researchers have made a lot of effort to try to understand the role of their structure in wine taste in recent decades. We report some new routes to achieve a true structure–taste relationship for the major tannins found in wine, which are procyanidins in their monomeric or oligomeric state. All these routes use synthetic standards. New advances in their synthesis and their analyses using chromatographic methods, NMR spectroscopy, and mass spectrometry to obtain more precise information about their chemical structure, including their stereochemistry and their precise degree of polymerization and galloylation, are described. Figure Tannins, mainly procyanidins, represent a key element in red wine taste and flavors. They are especially involved in the sensation of astringency. Identifying them to achieve a true structure-taste Relationship remains a real challenge for researchers. This review reports on new routes to collect more and more information about the chemical nature of procyanidins present in wine.

Keywords: Procyanidins; Wine analysis; Synthesis; Chromatography; NMR; Mass spectrometry

Beyond the characterization of wine aroma compounds: looking for analytical approaches in trying to understand aroma perception during wine consumption by Carolina Muñoz-González; Juan J. Rodríguez-Bencomo; M. Victoria Moreno-Arribas; M. Ángeles Pozo-Bayón (pp. 1501-1516).

The volatile compounds present in wines are responsible for the quality of the wine aroma. The analysis of these compounds requires different analytical techniques depending on the type of compounds and their concentration. The importance at sensorial level of each compound should be evaluated by using olfactometric techniques and reconstitution and omission studies. In addition, wine aroma is influenced by other factors such as wine matrix, which could affect the compounds’ volatility, decreasing or increasing their concentration in the headspace above the wine. Moreover, when a wine is consumed, several oral physiological variables could affect aroma perception. The focus of this review is to outline the most recent advances in wine aroma analysis and the most innovative techniques in trying to elucidate the main factors that influence wine aroma perception during consumption.

Keywords: Wine aroma characterization; Isolation techniques, Aroma interactions; In vitro aroma analysis; In vivo aroma analysis; Wine consumption

Determination of stilbene derivatives in Burgundy red wines by ultra-high-pressure liquid chromatography by Lemia Boutegrabet; Agnes Fekete; Norbert Hertkorn; Yorgos Papastamoulis; Pierre Waffo-Téguo; Jean Michel Mérillon; Philippe Jeandet; Régis D. Gougeon; Philippe Schmitt-Kopplin (pp. 1517-1525).

The polyphenols, for example stilbenes and flavonoids, are an important family of compounds present in grapes and wines. Several studies have shown that stilbenes are antioxidants and cancer-preventing agents. For the first time, eight natural stilbenes (trans-resveratrol, trans-piceid, cis-piceid, trans-astringin, trans-piceatannol, (+)-trans-ε-viniferin, pallidol, and hopeaphenol), isolated and purified from Vitis vinifera, were simultaneously analysed by ultra-high-pressure liquid chromatography coupled with photodiode-array detection. Separation of the stilbenes by UHPLC was optimized with the assistance of “Quality-by-Design” commercial software. Four different reversed-phase columns packed with 1.5–1.7-μm particles were tested and compared for their retention behaviour and separation efficiency. On the basis of the performance characteristics determined, the VisionHT C18 HL column was selected for the stilbenes studied, because resolution of the critical pair was 1.5 with a peak width of 2–4 s. The optimized method resulted in highly repeatable retention times (RSD 0.03–0.07%), peak areas (RSD 3–6%), and linear ranges were between 0.005 and 50 mg L⁻¹ for most of the compounds. All stilbenes, except trans-astringin, trans-piceatannol, and pallidol were identified and quantified in Burgundy red wines at different concentrations after direct injection of the wines. Figure

Keywords: Stilbenes; Wine; UHPLC; Chromatographic columns; Quality-by-Design

Capillary electrophoresis methods for the determination of covalent polyphenol–protein complexes by John D. Trombley; Thomas N. Loegel; Neil D. Danielson; Ann E. Hagerman (pp. 1527-1533).

The bioactivities and bioavailability of plant polyphenols including proanthocyanidins and other catechin derivatives may be affected by covalent reaction between polyphenol and proteins. Both processing conditions and gastrointestinal conditions may promote formation of covalent complexes for polyphenol-rich foods and beverages such as wine. Little is known about covalent reactions between proteins and tannin, because suitable methods for quantitating covalent complexes have not been developed. We established capillary electrophoresis methods that can be used to distinguish free protein from covalently bound protein–polyphenol complexes and to monitor polyphenol oxidation products. The methods are developed using the model protein bovine serum albumin and the representative polyphenol (−)epigallocatechin gallate. By pairing capillaries with different diameters with appropriate alkaline borate buffers, we are able to optimize resolution of either the protein–polyphenol complexes or the polyphenol oxidation products. This analytical method, coupled with purification of the covalent complexes by diethylaminoethyl cellulose chromatography, should facilitate characterization of covalent complexes in polyphenol-rich foods and beverages such as wine.

Keywords: Tannin–protein interactions; Wine polyphenols; Serum albumin; Epigallocatechin gallate; Capillary electrophoresis

Identification, amounts, and kinetics of extraction of C-glucosidic ellagitannins during wine aging in oak barrels or in stainless steel tanks with oak chips by Michaël Jourdes; Julien Michel; Cédric Saucier; Stéphane Quideau; Pierre-Louis Teissedre (pp. 1535-1543).

The C-glucosidic ellagitannins are found in wine as a result of its aging in oak barrels or in stainless steel tanks with oak chips. Once dissolved in this slightly acidic solution, the C-glucosidic ellagitannins vescalagin can react with nucleophilic entities present in red wine, such as ethanol, catechin, and epicatechin, to generate condensed hybrid products such as the β-1-O-ethylvescalagin and the flavano-ellagitannins (acutissimin A/B and epiacutissimin A/B), respectively. During this study, we first monitored the extraction kinetic and the evolution of the eight major oak-derived C-glucosidic ellagitannins in red wines aged in oak barrels or in stainless steel tank with oak chips. Their extraction rates appeared to be faster during red wine aging in stainless steel tanks with oak chips. However, their overall concentrations in wines were found higher in the wine aged in barrels. The formation rates of the vescalagin-coupled derivatives were also estimated for the first time under both red wine aging conditions (i.e., oak barrels or stainless steel tanks with oak chips). As observed for the oak-native C-glucosidic ellagitannins, the concentrations of these vescalagin derivatives were higher in the red wine aged in oak barrels than in stainless steel tanks with oak chips. Despite these differences, their relative composition was similar under both red wine aging conditions. Finally, the impact of the oak chips size and toasting level on the C-glucosidic ellagitannins concentration in wine was also investigated.

Keywords: C-glucosidic ellagitannins; Flavano-ellagitannins; Oak barrel-oak chips; Wine

Quantification of chitinase and thaumatin-like proteins in grape juices and wines by D. Le Bourse; A. Conreux; S. Villaume; P. Lameiras; J.-M. Nuzillard; P. Jeandet (pp. 1545-1553).

Chitinases and thaumatin-like proteins are important grape proteins as they have a great influence on wine quality. The quantification of these proteins in grape juices and wines, along with their purification, is therefore crucial to study their intrinsic characteristics and the exact role they play in wines. The main isoforms of these two proteins from Chardonnay grape juice were thus purified by liquid chromatography. Two fast protein liquid chromatography (FLPC) steps allowed the fractionation and purification of the juice proteins, using cation exchange and hydrophobic interaction media. A further high-performance liquid chromatography (HPLC) step was used to achieve higher purity levels. Fraction assessment was achieved by mass spectrometry. Fraction purity was determined by HPLC to detect the presence of protein contaminants, and by nuclear magnetic resonance (NMR) spectroscopy to detect the presence of organic contaminants. Once pure fractions of lyophilized chitinase and thaumatin-like protein were obtained, ultra-HPLC (UHPLC) and enzyme-linked immunosorbent assay (ELISA) calibration curves were constructed. The quantification of these proteins in different grape juice and wine samples was thus achieved for the first time with both techniques through comparison with the purified protein calibration curve. UHPLC and ELISA showed very consistent results (less than 16% deviation for both proteins) and either could be considered to provide an accurate and reliable quantification of proteins in the oenology field.

Keywords: Wine; Chromatography; Protein; ELISA; Quantification; Purification

Intrinsic ratios of glucose, fructose, glycerol and ethanol ¹³C/¹²C isotopic ratio determined by HPLC-co-IRMS: toward determining constants for wine authentication by François Guyon; Laetitia Gaillard; Marie-Hélène Salagoïty; Bernard Médina (pp. 1555-1562).

High-performance liquid chromatography linked to isotope ratio mass spectrometry (HPLC-co-IRMS) via a Liquiface© interface has been used to simultaneously determine ¹³C isotope ratios of glucose (G), fructose (F), glycerol (Gly) and ethanol (Eth) in sweet and semi-sweet wines. The data has been used the study of wine authenticity. For this purpose, 20 authentic wines from various French production areas and various vintages have been analyzed after dilution in pure water from 20 to 200 times according to sugar content. If the ¹³C isotope ratios vary according to the production area and the vintage, it appears that internal ratios of ¹³C isotope ratios ( $$ {R_{{{}^{{13}}{ ext{C}}}}} $$ ) of the four compounds studied can be considered as a constant. Thus, ratios of isotope ratios are found to be 1.00 ± 0.04 and 1.02 ± 0.08 for $$ {R_{{{}^{{13}}{{ ext{C}}_{{{ ext{G/F}}}}}}}} $$ and $$ {R_{{{}^{{13}}{{ ext{C}}_{{{ ext{Gly/Eth}}}}}}}} $$ , respectively. Moreover, $$ {R_{{{}^{{13}}{{ ext{C}}_{{{ ext{Eth/Sugar}}}}}}}} $$ is found to be 1.15 ± 0.10 and 1.16 ± 0.08 for $$ {R_{{{}^{{13}}{{ ext{C}}_{{{ ext{Gly/Sugar}}}}}}}} $$ . Additions of glucose, fructose and glycerol to a reference wine show a variation of the $$ {R_{{{}^{{13}}{ ext{C}}}}} $$ value for a single product addition as low as 2.5 g/L⁻¹. Eighteen commercial wines and 17 concentrated musts have been analyzed. Three wine samples are suspicious as the $$ {R_{{{}^{{13}}{ ext{C}}}}} $$ values are out of range indicating a sweetening treatment. Moreover, concentrated must analysis shows that ¹³C isotope ratio can be also used directly to determine the authenticity of the matrix. Figure HPLC-co-IRMS chromatogram of a diluted sweet wine.

Keywords: HPLC-co-IRMS; Isotope ratio; Sugar; Glycerol; Ethanol; Constant; Sweet wines; Concentrated musts; Control

Characterization of oxidized tannins: comparison of depolymerization methods, asymmetric flow field-flow fractionation and small-angle X-ray scattering by Aude Vernhet; Stéphane Dubascoux; Bernard Cabane; Hélène Fulcrand; Eric Dubreucq; Céline Poncet-Legrand (pp. 1563-1573).

Condensed tannins are a major class of plant polyphenols. They play an important part in the colour and taste of foods and beverages. Due to their chemical reactivity, tannins are not stable once extracted from plants. A number of chemical reactions can take place, leading to structural changes of the native structures to give so-called derived tannins and pigments. This paper compares results obtained on native and oxidized tannins with different techniques: depolymerization followed by high-performance liquid chromatography analysis, small-angle X-ray scattering (SAXS) and asymmetric flow field-flow fractionation (AF4). Upon oxidation, new macromolecules were formed. Thioglycolysis experiments showed no evidence of molecular weight increase, but thioglycolysis yields drastically decreased. When oxidation was performed at high concentration (e.g., 10 g L⁻¹), the weight average degree of polymerization determined from SAXS increased, whereas it remained stable when oxidation was done at low concentration (0.1 g L⁻¹), indicating that the reaction was intramolecular, yet the conformations were different. Differences in terms of solubility were observed; ethanol being a better solvent than water. We also separated soluble and non-water-soluble species of a much oxidized fraction. Thioglycolysis showed no big differences between the two fractions, whereas SAXS and AF4 showed that insoluble macromolecules have a weight average molecular weight ten times higher than the soluble ones. Figure Comparison of UV and MALLS fractograms obtained with water-soluble and -insoluble fractions of oxidized tannins in EtOH. Water-insoluble fractions exhibit a broader size distribution and has a weight average molecular weight about ten times larger than the -soluble one

Keywords: Tannins; Oxidation; Molecular weight determination; Small-angle X-ray scattering; AF4-MALLS; Depolymerization

Determination of the geographical origin of Brazilian wines by isotope and mineral analysis by S. V. Dutra; L. Adami; A. R. Marcon; G. J. Carnieli; C. A. Roani; F. R. Spinelli; S. Leonardelli; C. Ducatti; M. Z. Moreira; R. Vanderlinde (pp. 1575-1580).

In the present research, we studied wines from three different south Brazilian winemaking regions with the purpose of differentiating them by geographical origin of the grapes. Brazil's wide territory and climate diversity allow grape cultivation and winemaking in many regions of different and unique characteristics. The wine grape cultivation for winemaking concentrates in the South Region, mainly in the Serra Gaúcha, the mountain area of the state of Rio Grande do Sul, which is responsible for 90% of the domestic wine production. However, in recent years, two new production regions have developed: the Campanha, the plains to the south and the Serra do Sudeste, the hills to the southeast of the state. Analysis of isotopic ratios of ¹⁸O/¹⁶O of wine water, ¹³C/¹²C of ethanol, and of minerals were used to characterize wines from different regions. The isotope analysis of δ¹⁸O of wine water and minerals Mg and Rb were the most efficient to differentiate the regions. By using isotope and mineral analysis, and discrimination analysis, it was possible to classify the wines from south Brazil.

Keywords: Wine; Stable isotopes; Minerals; Geographical origin

A flow-injection mass spectrometry fingerprinting method for authentication and quality assessment of Scutellaria lateriflora-based dietary supplements by Jianghao Sun; Pei Chen (pp. 1581-1588).

Scutellaria lateriflora, commonly known as skullcap, is used as an ingredient in numerous herbal products. However, it has been occasionally adulterated/contaminated with Teucrium canadense and/or Teucrium chamaedrys, commonly known as germander, due to the morphological similarities between the two genera. The latter contains hepatotoxic diterpenes. Despite the potential hepatotoxicity introduced by germander contamination, analytical methodologies for the authentication and quality assessment of S. lateriflora-based dietary supplements have not been reported. In this study, a flow-injection/mass spectrometry fingerprinting method in combination with principal component analysis was used to survey S. lateriflora-based dietary supplements sold in the USA.

Keywords: Scutellaria ; Teucrium ; MS; Fingerprinting; PCA

Screening a fragment cocktail library using ultrafiltration by Sayaka Shibata; Zhongsheng Zhang; Konstantin V. Korotkov; Jaclyn Delarosa; Alberto Napuli; Angela M. Kelley; Natasha Mueller; Jennifer Ross; Frank H. Zucker; Frederick S. Buckner; Ethan A. Merritt; Christophe L. M. J. Verlinde; Wesley C. Van Voorhis; Wim G. J. Hol; Erkang Fan (pp. 1589-1595).

Ultrafiltration provides a generic method to discover ligands for protein drug targets with millimolar to micromolar K _d, the typical range of fragment-based drug discovery. This method was tailored to a 96-well format, and cocktails of fragment-sized molecules, with molecular masses between 150 and 300 Da, were screened against medical structural genomics target proteins. The validity of the method was confirmed through competitive binding assays in the presence of ligands known to bind the target proteins.

Keywords: Ultrafiltration; Screening; Fragment-based drug discovery; Compound library

MALDI-ToF mass spectrometry–multivariate data analysis as a tool for classification of reactivation and non-culturable states of bacteria by Boris Kuehl; Silke-Mareike Marten; Yvonne Bischoff; Gerald Brenner-Weiß; Ursula Obst (pp. 1597-1604).

Some bacterial life states are only difficult to describe and to detect because they are on the border of active metabolism. A prominent example is the so-called viable but non-culturable state, which is mainly characterized by the inability of bacteria to grow on synthetic media. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-ToF/MS) in combination with multivariate data analysis represents a powerful tool for mass-spectrometric pattern recognition of biological samples. This method is already used for differentiation of bacterial strains. In this study we present a rapid readout method based on MALDI-ToF/MS in combination with principal component analysis to classify the bacterial non-culturable state using Enterococcus faecalis as a model organism. By applying this technique to samples of different physiological states, distinct clusters were calculated and all mass spectra were classified correctly into groups of similar type concerning their physiological state.

Keywords: Matrix-assisted laser desorption ionization time-of-flight mass spectrometry; Viable but non-culturable; Multivariate data analysis; Cluster analysis; Principal component analysis

Surface characterization and efficiency of a matrix-free and flat carboxylated gold sensor chip for surface plasmon resonance (SPR) by L. Roussille; G. Brotons; L. Ballut; G. Louarn; D. Ausserré; S. Ricard-Blum (pp. 1605-1621).

We report the preparation and characterization of a matrix-free carboxylated surface plasmon resonance (SPR) sensor chip with high sensing efficiency by functionalizing a bare gold thin film with a self-assembled monolayer of 16-mercaptohexadecanoic acid (SAM–MHDA chip). The self assembled monolayer surface coverage of the gold layer was carefully evaluated and the SAM was characterized by infrared reflection absorption spectroscopy, X-ray photoemission spectroscopy, atomic force microscopy, X-ray reflectivity-diffraction, and SPR experiments with bovine serum albumin. We compared the SPR signal obtained on this chip made of a dense monolayer of carboxylic acid groups with commercially available carboxylated sensor chips built on the same gold substrate, a matrix-free C1 chip, and a CM5 chip with a ~100 nm dextran hydrogel matrix (GE Healthcare). Two well-studied interaction types were tested, the binding of a biotinylated antibody (immunoglobulin G) to streptavidin and an antigen–antibody interaction. For both interactions, the well characterized densely functionalized SAM–MHDA chip gave a high signal-to-noise ratio and showed a gain in the availability of immobilized ligands for their partners injected in buffer flow. It thus compared favourably with commercially available sensor chips. Fig. 1 The surface plasmon resonance (SPR) sensor chip efficiencies of three different carboxylated chips, from the comparison of the number of captured analyte molecules divided by the number of immobilized ligand molecules (A/L ratio).

Keywords: Self-assembled monolayer; gold surface; surface characterization; biosensor; protein–protein interaction; surface plasmon resonance

Determination of the binding sites for oxaliplatin on insulin using mass spectrometry-based approaches by Charlotte Møller; Richard R. Sprenger; Stefan Stürup; Peter Højrup (pp. 1623-1633).

Using insulin as a model protein for binding of oxaliplatin to proteins, various mass spectrometric approaches and techniques were compared. Several different platinum adducts were observed, e.g. addition of one or two diaminocyclohexane platinum(II) (Pt(dach)) molecules. By top-down analysis and fragmentation of the intact insulin–oxaliplatin adduct using nano-electrospray ionisation quadrupole time-of-flight mass spectrometry (nESI-Q-ToF-MS), the major binding site was assigned to histidine5 on the insulin B chain. In order to simplify the interpretation of the mass spectrum, the disulphide bridges were reduced. This led to the additional identification of cysteine6 on the A chain as a binding site along with histidine5 on the B chain. Digestion of insulin–oxaliplatin with endoproteinase Glu-C (GluC) followed by reduction led to the formation of five peptides with Pt(dach) attached. Identification of several of the binding sites was obtained using matrix-assisted laser desorption/ionization (MALDI)-ToF-ToF-MS and liquid chromatography-nESI-Q-ToF-MS. Upon comparing the top-down and bottom-up approaches, the suitability of the bottom-up approach for determining binding sites was questioned, as the release and possible re-association of Pt(dach) were demonstrated upon enzymatic digestion. The associated advantages and disadvantages of ESI and MALDI were also pointed out. Figure Determination of binding sites for oxaliplatin on insulin. Both top-down and bottom-up approaches are used as well as MALDI an nESI. The different approaches adn techniques are compared.

Keywords: Binding sites; Bottom-up; Insulin; Mass spectrometry; Oxaliplatin; Top-down

Raman detection of localized transferrin-coated gold nanoparticles inside a single cell by Jin-Ho Park; Jin Park; Uuriintuya Dembereldorj; Keunchang Cho; Kangtaek Lee; Sung Ik Yang; So Yeong Lee; Sang-Woo Joo (pp. 1635-1643).

We investigated the cellular uptake behavior of non-fluorescent metal nanoparticles (NPs) by use of surface-enhanced Raman scattering (SERS) combined with dark-field microscopy (DFM). The uptake of Au NPs inside a single cell could also be identified by DFM first and then confirmed by z-depth-dependent SERS at micrometer resolution. Guided by DFM for the location of Au NPs, an intracellular distribution assay was possible using Raman dyes with unique vibrational marker bands in order to identify the three-dimensional location inside the single cell by obtaining specific spectral features. Au NPs modified by 4-mercaptobenzoic acid (MBA) bearing its –COOH surface functional group were used to conjugate transferrin (Tf) protein using the 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride (EDC) reaction. The protein conjugation reaction on Au surfaces was examined by means of color change, absorption spectroscopy, and SERS. Our results demonstrate that DFM techniques combined with SERS may have great potential for monitoring biological processes with protein conjugation at the single-cell level. Figure z-Depth-dependent Raman detection of localized transferrin-coated gold nanoparticles inside a single cell

Keywords: Dark-field microscopy; Surface-enhanced Raman scattering; Gold nanoparticles; Single-cell monitoring; Protein conjugation; Intracellular location

CMOS image sensor for detection of interferon gamma protein interaction as a point-of-care approach by Mohana Marimuthu; Karthikeyan Kandasamy; Chang Geun Ahn; Gun Yong Sung; Min-Gon Kim; Sanghyo Kim (pp. 1645-1653).

Complementary metal oxide semiconductor (CMOS)-based image sensors have received increased attention owing to the possibility of incorporating them into portable diagnostic devices. The present research examined the efficiency and sensitivity of a CMOS image sensor for the detection of antigen–antibody interactions involving interferon gamma protein without the aid of expensive instruments. The highest detection sensitivity of about 1 fg/ml primary antibody was achieved simply by a transmission mechanism. When photons are prevented from hitting the sensor surface, a reduction in digital output occurs in which the number of photons hitting the sensor surface is approximately proportional to the digital number. Nanoscale variation in substrate thickness after protein binding can be detected with high sensitivity by the CMOS image sensor. Therefore, this technique can be easily applied to smartphones or any clinical diagnostic devices for the detection of several biological entities, with high impact on the development of point-of-care applications.

Keywords: CMOS sensors; Immunoassays; Indium nanoparticles; Interferon gamma; Photon

Distinct hepatic lipid profile of hypertriglyceridemic mice determined by easy ambient sonic-spray ionization mass spectrometry by Luciane C. Alberici; Helena C. F. Oliveira; Rodrigo R. Catharino; Anibal E. Vercesi; Marcos N. Eberlin; Rosana M. Alberici (pp. 1655-1663).

Easy ambient sonic-spray ionization mass spectrometry (EASI-MS) was used to interrogate the hepatic lipid profiles of hypertriglyceridemic and control normotriglyceridemic mice. The analyses of ex vivo complex lipid mixtures were made directly with EASI-MS without accompanying separation steps. Intense ions for phosphatidylcholines and triacylglycerols were observed in the positive ion mode whereas the spectra in the negative ion mode provided profiles of phosphatidylethanolamines and phosphatidylinositol. EASI-MS was coupled to high-performance thin-layer chromatography for analysis of free fatty acids. Fourier transform–ion cyclotron resonance–mass spectrometry was also employed to confirm the identity of the detected lipids. We demonstrated higher incorporation of oleic acid in phosphatidylcholine and triacylglycerol composition, higher relative abundance of arachidonic acid containing phosphatidylinositol, and overall distinct free fatty acid profile in the livers of genetic hypertriglyceridemic mice. We propose that these alterations in liver lipid composition are related to the higher tissue and body metabolic rates described in these hypertriglyceridemic mice.

Keywords: Hypertriglyceridemia; Mice liver; Ambient ionization; Mass spectrometry; Lipids

Separation of long DNA fragments by inversion field capillary electrophoresis by Zhenqing Li; Xiaoming Dou; Yi Ni; Yoshinori Yamaguchi (pp. 1665-1671).

This study reports improved pulsed field capillary electrophoresis (PFCE) for separation of large DNA ladders. Important analytical conditions, including gel polymer concentration, ratio of forward to backward pulse duration, and separation potential, were investigated for their effects on the separation performance of DNA ranging in size from 0.1 to 10.0 kilo base pairs (kbp). Results show that DNA fragments from 0.1 to 8.0 kbp can be resolved with high resolution, simultaneously, in a short time. The ratio of forward to backward pulse duration affects the separation performance for DNA fragments greater than 1.5 kbp, and 3 or 4 is the optimum value of the ratio for separation of DNA up to 10 kbp. Furthermore, the separations that were obtained with 74–19,329 bp λ-DNA restriction fragments clearly demonstrate a dramatic improvement in the separation time and resolution over the conventionally used square-wave PFCE. The inversion field capillary electrophoresis reported here may help enable future DNA analysis studies to be performed quickly and effectively. Figure Electropherogram of the DNA (0.1-10.0 kbp) fragments in 0.3% HEC (1300K) by (A) CE: 1500V; (B) CE: 900V; (C) IFCE.

Keywords: Capillary electrophoresis; Electrophoresis; DNA separation; HEC; Pulsed field capillary electrophoresis; Inversion field capillary electrophoresis

Comparison of the performance characteristics of two tubular contactless conductivity detectors with different dimensions and application in conjunction with HPLC by Jonas Josef Peter Mark; Pavel Coufal; Frantisek Opekar; Frank-Michael Matysik (pp. 1673-1680).

Two tubular capacitively coupled contactless conductivity detection (C⁴D) cells with different geometric dimensions were evaluated with regard to their main analytical characteristics under non-separation and separation conditions in conjunction with liquid chromatography. A comparison of the performance of the tubular cells to a previously tested thin-layer detection cell was drawn. Additionally, using a theoretical model the experimental results were compared with sets of calculated values and partially enabled to model the complex behavior of C⁴D detection in combination with high-performance liquid chromatography (HPLC). While cell 1 is characterized by a geometric cell volume of 0.6 μL, a wall thickness of 675 μm, and an inner diameter of 125 μm, the respective values for cell 2 are 2.3 μL, 200 μm, and 250 μm. The main analytical parameters were evaluated using a potassium chloride (KCl) solution. The limits of detection were 0.4 μM KCl (5.7 × 10⁻⁶ S m⁻¹) for cell 1 and 0.2 μM KCl (3.2 × 10⁻⁶ S m⁻¹) for cell 2, which compares well to the previously found 0.2 μM for the thin-layer cell. A pair of linear ranges was found for both cells in a concentration interval ranging from 1 × 10⁻⁶ to 1 × 10⁻⁴ M (corresponding to 1.5 × 10⁻⁵ to 1.5 × 10⁻³ S m⁻¹) KCl, respectively. Furthermore, the detector cells were applied to the HPLC separation of a model compound system consisting of benzoic acid, lactic acid, octanesulphonic acid, and sodium capronate. Separation of the compounds was achieved with a Biospher PSI 100 C18 column using 60% aqueous acetonitrile mobile phase. Calibration curves for the examined model system were well correlated (r² > 0.997), and it was found that under separation conditions the arrangement with the lower cell volume (cell 1) yields higher sensitivity and respectively lower limits of detection for all model compounds. Compared with the thin-layer cell, the tubular cells show better overall performance in regard to the determined analytical characteristics.

Keywords: Contactless conductivity detection; Flow analysis; Electrochemical detection; Detection cell geometry; Liquid chromatography

Simultaneous detection and quantification of parecoxib and valdecoxib in canine plasma by HPLC with spectrofluorimetric detection: development and validation of a new methodology by G. Saccomanni; M. Giorgi; S. Del Carlo; C. Manera; A. Saba; M. Macchia (pp. 1681-1688).

Parecoxib is the injectable prodrug of valdecoxib, a cicloxygenase-2 selective drug, currently used in human medicine. Recent studies have suggested both its excellent clinical effectiveness and wide safety profile. The aim of the present study was to develop and validate a new high-performance liquid chromatography (HPLC) with spectrofluorimetric detection method to quantify parecoxib and valdecoxib in canine plasma. Several parameters both in the extraction and the detection method were evaluated. The applicability of the method was determined by administering parecoxib to one dog: the protocol provided the expected pharmacokinetic results. The final mobile phase was acetonitrile: AcONH₄ (10 mM; pH 5.0) 55:45, v/v, with a flow rate of 0.4 mL min⁻¹, and excitation and emission wavelengths of 265 and 375 nm, respectively. The analytical column was a reverse-phase C18 ODS2 3-μm particle size. Protein precipitation in acidic medium followed by two successive liquid–liquid steps was carried out. The best extraction solvent was cyclohexane:Et₂O (3:2, v/v) that gave recoveries ranging from 81.1% to 89.1% and from 94.8% to 103.6% for parecoxib and valdecoxib, respectively. The limits of quantification were 25 and 10 ng mL⁻¹ for parecoxib and valdecoxib, respectively. The chromatographic runs were specific with no interfering peaks at the retention times of the analytes, as confirmed by HPLC–mass spectrometry experiments. The other validation parameters were in agreement with the European Medicines Evaluation Agency and International Conference on Harmonisation guidelines. In conclusion, this method (extraction, separation and applied techniques) is simple and effective. This is the first time that use of a HPLC with spectrofluorimetric detection technique to simultaneously detect parecoxib and valdecoxib in plasma has been reported. This technique may have applications for pharmacokinetic studies. Figure 1 In vivo metabolism of the prodrug parecoxib in the active ingredient valdecoxib

Keywords: Parecoxib; Valdecoxib; Plasma; HPLC; Fluorescence; Cox-2 inhibitor

Solid-phase microfibers based on polyethylene glycol modified single-walled carbon nanotubes for the determination of chlorinated organic carriers in textiles by Wei-Ya Zhang; Yin Sun; Cheng-Ming Wang; Cai-Ying Wu (pp. 1689-1697).

Based on polyethylene glycol modified single-walled carbon nanotubes, a novel sol–gel fiber coating was prepared and applied to the headspace microextraction of chlorinated organic carriers (COCs) in textiles by gas chromatography-electron capture detection. The preparation of polyethylene glycol modified single-walled carbon nanotubes and the sol–gel fiber coating process was stated and confirmed by infrared spectra, Raman spectroscopy, and scanning electron microscopy. Several parameters affecting headspace microextraction, including extraction temperature, extraction time, salting-out effect, and desorption time, were optimized by detecting 11 COCs in simulative sweat samples. Compared with the commercial solid-phase microextraction fibers, the sol–gel polyethylene glycol modified single-walled carbon nanotubes fiber showed higher extraction efficiency, better thermal stability, and longer life span. The method detection limits for COCs were in the range from 0.02 to 7.5 ng L⁻¹ (S/N = 3). The linearity of the developed method varied from 0.001 to 50 μg L⁻¹ for all analytes, with coefficients of correlation greater than 0.974. The developed method was successfully applied to the analysis of trace COCs in textiles, the recoveries of the analytes indicated that the developed method was considerably useful for the determination of COCs in ecological textile samples. Figure

Keywords: Headspace solid-phase microextraction; Polyethylene glycol modified single-walled carbon nanotubes; Chlorinated organic carriers; Textile

Application of ethyl chloroformate derivatization for solid-phase microextraction–gas chromatography–mass spectrometric determination of bisphenol-A in water and milk samples by Mohana Krishna Reddy Mudiam; Rajeev Jain; Virendra K. Dua; Amit Kumar Singh; V. P. Sharma; R. C. Murthy (pp. 1699-1705).

A simple and rapid analytical method based on in-matrix ethyl chloroformate (ECF) derivatization has been developed for the quantitative determination of bisphenol-A (BPA) in milk and water samples. The samples containing BPA were derivatised with ECF in the presence of pyridine for 20 s at room temperature, and the non-polar derivative thus formed was extracted using polydimethylsiloxane solid-phase microextraction (SPME) fibres with thicknesses of 100 μm followed by analysis using gas chromatography–mass spectrometry. Three alkyl chloroformates (methyl, ethyl and isobutyl chloroformate) were tested for optimum derivatisation yields, and ECF has been found to be optimum for the derivatisation of BPA. Several parameters such as amount of ECF, pyridine and reaction time as well as SPME parameters were studied and optimised in the present work. The limit of detection for BPA in milk and water samples was found to be 0.1 and 0.01 μg L⁻¹, respectively, with a signal-to-noise ratio of 3:1. The limit of quantitation for BPA in milk and water was found to be 0.38 and 0.052 μg L⁻¹, respectively, with a signal-to-noise ratio of 10:1. In conclusion, the method developed was found to be rapid, reliable and cost-effective in comparison to silylation and highly suitable for the routine analysis of BPA by various food and environmental laboratories. Figure Schematic diagram for the analysis of bisphenol-A using SPME/GC-MS after ECF derivatization in water and milk samples

Keywords: Bisphenol-A; GC–MS; Ethyl chloroformate; SPME; Water; Milk

Catanionic surfactant ambient cloud point extraction and high-performance liquid chromatography for simultaneous analysis of organophosphorus pesticide residues in water and fruit juice samples by Ketsarin Seebunrueng; Yanawath Santaladchaiyakit; Phimpha Soisungnoen; Supalax Srijaranai (pp. 1707-1716).

A mixed anionic–cationic surfactant cloud point extraction (CPE) has been developed using sodium dodecyl sulfate (SDS) and tetrabutylammonium bromide (TBABr) for the extraction and preconcentration of organophosphorus pesticides (OPPs) at ambient temperature before analysis by high-performance liquid chromatography. The studied OPPs were azinphos-methyl, parathion-methyl, fenitrothion, diazinon, chlorpyrifos, and prothiophos. The optimum conditions of the mixed anionic–cationic CPE were 50 mmol L⁻¹ SDS, 100 mmol L⁻¹ TBABr, and 10% (w/v) NaCl. The extracted OPPs were successfully separated within 11 min using the conditions of a Waters Symmetry C8 column, a flow rate of 0.8 mL min⁻¹, a gradient elution of methanol and water, and detection at 210 nm. Linearity was found over the range 0.05–5 μg mL⁻¹, with the correlation coefficients higher than 0.996. The enrichment factor of the target analytes was in the range 6–11, which corresponds to their limits of detection from 1 to 30 ng mL⁻¹. High precisions (intra-day and inter-day) were obtained with relative standard deviation <1.5% (t _R) and 10% (peak area). Accuracies (% recovery) of the different spiked OPP concentrations were 82.7–109.1% (water samples) and 80.3–113.3% (fruit juice samples). No contamination by the OPPs was observed in any studied samples.

Keywords: Mixed anionic–cationic surfactant cloud point extraction; Organophosphorus pesticide; High-performance liquid chromatography; Water; Fruit juice

Erratum to: Quantification of chitinase and thaumatin-like proteins in grape juices and wines by D. Le Bourse; A. Conreux; S. Villaume; P. Lameiras; J.-M. Nuzillard; P. Jeandet (pp. 1717-1717).

Erratum to: Determination of the geographical origin of Brazilian wines by isotope and mineral analysis by S. V. Dutra; L. Adami; A. R. Marcon; G. J. Carnieli; C. A. Roani; F. R. Spinelli; S. Leonardelli; C. Ducatti; M. Z. Moreira; R. Vanderlinde (pp. 1719-1719).

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Analytical and Bioanalytical Chemistry (v.401, #5)