World Congress on Biosensors 2014

World Congress on Biosensors 2014
Biosensors 2014

Thursday 29 March 2012

Just Published: Journal of Chromatography A


A new issue of this journal has just been published. To see abstracts of the papers it contains (with links through to the full papers) click here:
Selected papers from the latest issue:

Low-density solvent based ultrasound-assisted emulsification microextraction and on-column derivatization combined with gas chromatography–mass spectrometry for the determination of carbamate pesticides in environmental water samples

29 March 2012, 09:38:25
Publication year: 2012
Source:Journal of Chromatography A, Volume 1235
Liang Guo, Hian Kee Lee
A fast and efficient method for the determination of trace level of carbamate pesticides using a lower-density-than-water solvent for ultrasound-assisted emulsification microextraction coupled to on-column derivatization and analysis by GC–MS has been developed and studied. In this approach, a soft plastic Pasteur pipette was employed as a convenient extraction device. Fifty microliters of extraction solvent, of lower density than water, was injected into the sample solution held in the pipette. The latter was immediately immersed in an ultrasound water bath to form an emulsion. After 2min extraction, the emulsion was fractionated into two layers by centrifugation. The upper layer (organic extract) could be collected conveniently by squeezing the bulb of the pipette, now held upside down, to move it into the narrow stem of the device, facilitating its retrieval for analysis. The extract was then combined with trimethylphenylammonium hydroxide and directly injected into a gas chromatography–mass spectrometry (GC–MS) system for on-column derivatization and analysis. The on-column derivatization provided an added convenience (since a separate step was not necessary). Parameters affecting the derivatization and extraction were investigated. Under the most favorable conditions, the method demonstrated high extraction efficiency with low limits of detection of between 0.01 and 0.1μg/L, good linearity in the range of 0.05–50μg/L, to 0.5–100μg/L, and good repeatability (RSD below 9.2%, n =5). The proposed method was evaluated by determining carbamate pesticides in river water samples.

Smart polymer mediated purification and recovery of active proteins from inclusion bodies

29 March 2012, 09:38:25
Publication year: 2012
Source:Journal of Chromatography A, Volume 1235
Saurabh Gautam, Priyanka Dubey, Pranveer Singh, S. Kesavardhana, Raghavan Varadarajan, Munishwar N. Gupta
Obtaining correctly folded proteins from inclusion bodies of recombinant proteins expressed in bacterial hosts requires solubilization with denaturants and a refolding step. Aggregation competes with the second step. Refolding of eight different proteins was carried out by precipitation with smart polymers. These proteins have different molecular weights, different number of disulfide bridges and some of these are known to be highly prone to aggregation. A high throughput refolding screen based upon fluorescence emission maximum around 340nm (for correctly folded proteins) was developed to identify the suitable smart polymer. The proteins could be dissociated and recovered after the refolding step. The refolding could be scaled up and high refolding yields in the range of 8mgL−1 (for CD4D12, the first two domains of human CD4) to 58mgL−1 (for malETrx, thioredoxin fused with signal peptide of maltose binding protein) were obtained. Dynamic light scattering (DLS) showed that polymer if chosen correctly acted as a pseudochaperonin and bound to the proteins. It also showed that the time for maximum binding was about 50min which coincided with the time required for incubation (with the polymer) before precipitation for maximum recovery of folded proteins. The refolded proteins were characterized by fluorescence emission spectra, circular dichroism (CD) spectroscopy, melting temperature (T m), and surface hydrophobicity measurement by ANS (8-anilino1-naphthalene sulfonic acid) fluorescence. Biological activity assay for thioredoxin and fluorescence based assay in case of maltose binding protein (MBP) were also carried out to confirm correct refolding.

One step solvent bar microextraction and derivatization followed by gas chromatography–mass spectrometry for the determination of pharmaceutically active compounds in drain water samples

29 March 2012, 09:38:25
Publication year: 2012
Source:Journal of Chromatography A, Volume 1235
Liang Guo, Hian Kee Lee
For the first time, a simple and novel one-step combined solvent bar microextraction with derivatization with GC–MS analysis, was developed for the determination of pharmaceutically active compounds (PhACs) in water samples. In the procedure, the derivatization reagent was added in the extraction solvent (solvent bar), so that the analytes could be extracted from the aqueous sample and simultaneously derivatized in the solvent bar to enhance their volatility and improve chromatographic performance. After extraction, the derivatized analytes in the extract were directly injected into a GC–MS system for analysis. Six PhACs including naproxen, ibuprofen, ketoprofen, propranolol, diclofenac, and alprenolol were used here to develop and evaluate the method. The parameters affecting the derivatization and extraction efficiency including derivatization time and temperature, the proportion of derivatization reagent, the type of organic solvent, extraction time, extraction temperature, pH of sample solution, effect of ionic strength, and sample agitation speed, were investigated in detail. Under the most favorable conditions, the method provided good limits of detection ranging from 0.006 to 0.022μg/L, linearity (from 0.1–50 to 0.2–50μg/L, depending on analytes) and repeatability of extractions (RSDs below 9.5%, n =5). The proposed method was compared to hollow fiber protected liquid-phase microextraction and solid-phase microextraction, and showed higher extraction efficiency and/or shorter extraction time. The proposed method was applied to the determination of six PhACs in drain water, and was demonstrated to be simple, fast and efficient.

Application of step-wise gradient high-performance counter-current chromatography for rapid preparative separation and purification of diterpene components from Pseudolarix kaempferi Gordon

29 March 2012, 09:38:25
Publication year: 2012
Source:Journal of Chromatography A, Volume 1235
Shichao He, Shucai Li, Jianhong Yang, Haoyu Ye, Shijie Zhong, Hang Song, Yongkui Zhang, Cheng Peng, Aihua Peng, Lijuan Chen
In general, simultaneously separation and purification of components with a broad polarity range from traditional Chinese medicine (TCM) is a challenge by an ordinary high-speed counter-current chromatography (HSCCC) method. In this paper, we describes a rapid and efficient separation method of combining three-step gradient elution and two-step flow-rate gradient elution using high-performance counter-current chromatography (HPCCC) to separate 8 diterpene compounds simultaneously within 80min in a single run from the alcohol extract of Pseudolarix kaempferi Gordon. This separation process produced 166mg pseudolaric acid B O-β-d-glucopyranoside (PABGly), 152mg pseudolaric acid C (PAC), 8mg deacetylpseudolaric acid A (deacetylPAA), 5mg pseudolaric acid A O-β-d-glucopyranoside (PAAGly), 484mg pseudolaric acid B (PAB), 33mg pseudolaric acid B methyl ester (PAB methyl ester), 10mg pseudolaric acid A (PAA) and 18mg pseudolaric acid H (PAH) from 1.0g crude sample with purities of 98.6%, 99.6%, 92.3%, 92.2%, 99.2%, 99.4%, 98.3%, 91.0%, respectively. Our study indicates that the suitable combination of step-wise gradient elution and flow-rate gradient elution using HPCCC is an effective strategy to separate complex components from natural products.

Pareto-optimality study into the comparison of the separation potential of comprehensive two-dimensional liquid chromatography in the column and spatial modes

29 March 2012, 09:38:25
Publication year: 2012
Source:Journal of Chromatography A, Volume 1235
Dominique J.D. Vanhoutte, Gabriel Vivó-Truyols, Peter J. Schoenmakers
The expected performance of spatial (“flat-bed”) two-dimensional liquid chromatography ( x LC× x LC) has been calculated using the Pareto-optimality strategy. This approach allowed different objectives (total peak capacity, total analysis time, and total dilution) to be considered simultaneously and to establish optimal parameters (pressure drop, particle size, bed length, and initial spot size). The performance of spatial two-dimensional chromatographic systems was compared with that of conventional on-line, real-time two-dimensional column-liquid-chromatography systems ( t LC× t LC). The potential gain in peak capacity and/or analysis time of the spatial configuration was confirmed. By restricting the spatial parameters to realistic chromatographic conditions (limiting the stress, as counterbalance for the pressure drop through the sorbent bed, to 2500kg) it was found that x LC× x LC is attractive for very fast analysis of complex samples, rather than for extremely efficient separations. For example, a peak capacity of 780 may be achieved in only 2.7min using a 100×100mm sorbent bed of a quality currently encountered thin-layer chromatography. Furthermore, if beds can be packed as efficiently as contemporary columns, the predicted peak capacity increases to around 1000, corresponding to a peak-production rate of about 6.3peaks/s. Possibilities to boost the performance of x LC× x LC further are briefly discussed. Unless we can overcome the severe stress requirements of high-performance x LC× x LC, conventional t LC× t LC may be more amenable to very complex separations, thanks to the very high peak capacities. However, t LC× t LC separations will require long analysis times (e.g. 10,000 peaks in 37h, corresponding to 0.075peaks/s at a pressure drop of 40MPa). The best trade-off between total peak capacity, total analysis time, and total dilution under restricted (realistic) conditions was obtained using high pressures, small chromatographic beds, small particles, and relatively large sample spots.

A comparison of overload behaviour for some sub 2μm totally porous and sub 3μm shell particle columns with ionised solutes

29 March 2012, 09:38:25
Publication year: 2012
Source:Journal of Chromatography A, Volume 1235
Morgane M. Fallas, Stephan M.C. Buckenmaier, David V. McCalley
The overloading performance of some 2.7μm shell and sub 2μm totally porous columns, including one pair manufactured from similar materials with similar bonding chemistries, was compared using strongly acidic and basic probe compounds. In general, the capacity of shell particles was not greatly reduced, despite containing a smaller porous volume. Nevertheless, at low pH, both types of column were overloaded by only small concentrations of ionised solute. Considerable improvement could be gained by increasing the buffer concentration, although sensitivity in mass spectrometric detection may be compromised. The capacity of columns of different internal diameter may not be directly compared merely by scaling the injection volumes, as it is possible that the sample is not homogeneously distributed across the column radius, especially in larger diameter columns, where the sample may travel preferentially through a central core of the packing. A totally porous charged surface hybrid phase gave much improved loading properties of the basic probe in low ionic strength mobile phases such as formic acid, often used in mass spectrometry. However, its relative advantage over conventional phases was reduced as the mobile phase ionic strength was increased. Furthermore, acidic compounds may give tailing on this phase. At pH 7, all columns tested showed evidence of interaction with ionised silanols; peak shapes improved as the buffer concentration was increased. Column efficiency first increased and then decreased as solute concentration was increased at constant buffer concentration, which can be attributed to the decreasing proportion of solute molecules retained by the ion exchange process.

Study of the retention behavior in zwitterionic hydrophilic interaction chromatography of isomeric hydroxy- and aminobenzoic acids

29 March 2012, 09:38:25
Publication year: 2012
Source:Journal of Chromatography A, Volume 1235
Giorgia Greco, Sylvia Grosse, Thomas Letzel
The retention behavior of fifteen isomeric hydroxy- and aminobenzoic acids in zwitterionic hydrophilic interaction chromatography was studied using a sulfobetaine phase (ZIC-HILIC). By an inspection of their molecular structures, the retention was related to the number, the position and hydrogen bond properties of the functional groups. The effect of the chromatographic conditions was analyzed in order to investigate the retention mechanism of the stationary phase. The increased retention observed for negative charged compounds when the mobile phase pH decreased was ascribed to a diminishing of the electrostatic repulsion with the underivatized silanol groups. Also the salt buffer concentration in the mobile was proved to have a great influence in the modulation of the electrostatic interactions. However, the retention behavior of the benzoic acids was not described by conventional ion-exchange models. Subsequently, a systematical analysis of partition, adsorption, and hydrophilic chromatographic models was presented. The results from the fittings indicated that partition processes govern mainly the ZIC-HILIC separation, but also adsorption processes via hydrogen bonds occurred for hydrogen donor analytes. Finally, the influence of the chromatographic conditions on the water enriched layer in which partition takes place has been evaluated by the elution behavior of toluene.

Multi-wavelength high-performance liquid chromatographic fingerprints and chemometrics to predict the antioxidant activity of Turnera diffusa as part of its quality control

29 March 2012, 09:38:25
Publication year: 2012
Source:Journal of Chromatography A, Volume 1235
J. Ricardo Lucio-Gutiérrez, Aurora Garza-Juárez, J. Coello, S. Maspoch, M.L. Salazar-Cavazos, Ricardo Salazar-Aranda, Noemi Waksman de Torres
The determination of the antioxidant activity of Turnera diffusa using partial least squares regression (PLSR) on chromatographic data is presented. The chromatograms were recorded with a diode array detector and, for each sample, an enhanced fingerprint was constructed by compiling into a single data vector the chromatograms at four wavelengths (216, 238, 254 and 345nm). The wavelengths were selected from a contour plot, in order to obtain the greater number of peaks at each of the wavelengths. A further pretreatment of the data that included baseline correction, scaling and correlation optimized warping was performed. Optimal values of the parameters used in the warping were found by means of simplex optimization. A PLSR model with four latent variables (LV) explained 52.5% of X variance and 98.4% of Y, with a root mean square error for cross validation of 6.02. To evaluate its reliability, it was applied to an external prediction set, retrieving a relative standard error for prediction of 7.8%. The study of the most important variables for the regression indicated the chromatographic peaks related to antioxidant activity at the used wavelengths.

Thermodynamic study of molecularly imprinted polymer used as the stationary phase in high performance liquid chromatography

29 March 2012, 09:38:25
Publication year: 2012
Source:Journal of Chromatography A, Volume 1235
Natalia Denderz, Jozef Lehotay, Jozef Čižmárik, Zuzana Cibulková, Peter Šimon
Molecularly imprinted polymer (MIP) and non-imprinted polymer (NIP) on the base of methacrylic acid prepared by a bulk polymerization were used as stationary phases for the HPLC analysis. The thermodynamic processes were carried out to investigate the temperature effects during sorption processes of potential local anaesthetics – morpholinoethyl esters of alkoxy-substituted phenylcarbamic acid (MEsP), local anaesthetic – diperodon, flavonoid – quercetin in methanol, acetonitrile and toluene (porogen) as mobile phases. Mobile phases and corresponding solvents were selected according to the solubility of each analyte. The template was chosen from the set of homologous of MEsP – 2-(morpholin-4-yl)ethyl (2-methoxyphenyl)carbamate. Values of retention factors were measured over the temperature range of 20–60°C. There were determined van’t Hoff curves – dependences between logarithms of the retention factors (ln k) and the inverse value of the temperature (1/T). Observed graphs were linear directly indicating that there were no changes of interaction mechanisms in the studied range of temperature. Selectivities (evaluated by the separation factors, α) and sorption selectivities (evaluated by the imprinting factors, IFs) of the MIP and the NIP toward template, related and not-related structures with the template were evaluated chromatographically. The highest separation factors and the imprinting factors (IF=4.73±0.35 for the template) were observed in methanol, not in porogen. Only in the case of quercetin the highest IF was observed in ACN (1.88±0.13). Contrary to expectations, the driving force for the affinity of the target molecules for both of polymers was enthalpic term (with an average of 54%, 82% and 84% contribution of enthalpic term for MeOH, ACN and toluene, respectively on the MIP and 53%, 57% and 65% for MeOH, ACN and toluene, respectively on the NIP). The MIP and NIP were also characterized by attenuated total reflectance analysis Fourier transform infrared spectroscopy (ATR-FTIR) and thermogravimetric analysis (TGA).

A simple and rapid extraction method for sensitive determination of perfluoroalkyl substances in blood serum suitable for exposure evaluation

29 March 2012, 09:38:25
Publication year: 2012
Source:Journal of Chromatography A, Volume 1235
Noelia Luque, Ana Ballesteros-Gómez, Stefan van Leeuwen, Soledad Rubio
In this work, we propose a microextraction method based on a new supramolecular solvent (SUPRAS) made up of reverse aggregates of hexanoic acid, combined with liquid chromatography/triple quadrupole mass spectrometry (LC/QQQ MS–MS) for the determination of the perfluoroalkyl substances (PFASs) in blood serum. A SUPRAS is a nano-structured liquid made up of surfactant aggregates synthesized through a self-assembly process. The method involved the acidification of 765μL of blood serum (600μmol of hydrochloric acid per mL of serum) followed by the addition of hexanoic acid (97μL) and tetrahydrofuran (THF) (600μL), conditions under which the supramolecular solvent (∼360μL) formed in situ after vortex-shaking and centrifugation. Parameters affecting extraction efficiency and concentration factors were studied. The overall sample treatment took only 20min and several samples (20–30) can be simultaneously analyzed using conventional lab equipments, making additional investments unnecessary. Recoveries for the internal standards in samples ranged from 75 to 89% with relative standard deviations between 1 and 15%. Calibration was based on the use of internal standards. The method was very sensitive with detection limits ranging from 2 to 20pgmL−1 for PFASs. The approach developed was successfully applied to the determination of PFASs in different blood serum samples. The concentration of PFASs found in samples of animal origin ranged between 17 and 197.3pgmL−1 and between 84 and 5168pgmL−1 in samples of human origin. Both the analytical and operational features of this method make it suitable for the evaluation of exposure to PFASs.

Advanced ultra high pressure liquid chromatography–tandem mass spectrometric methods for the screening of red wine anthocyanins and derived pigments

29 March 2012, 09:38:25
Publication year: 2012
Source:Journal of Chromatography A, Volume 1235
Philippus Alberts, Maria A. Stander, André de Villiers
Anthocyanins are responsible for the colour of red grapes and wine. In addition to their contribution to the sensory properties of wine, these compounds are also of interest due to their beneficial biological properties. Wine anthocyanins exhibit a large structural diversity due to variations in glycosylation and acylation patterns, which is further exacerbated by the diverse reactions involving grape-derived anthocyanins during wine ageing. Chromatographic as well as mass spectrometric resolution of wine anthocyanins is often precluded due to the complexity of these compounds. In this paper we report a rapid, high-efficiency ultra high pressure liquid chromatography (UHPLC) procedure with tandem mass spectrometric (MS/MS) detection for the in-depth screening of wine pigments. Selective detection of wine anthocyanins and derived pigments was achieved utilizing MS/MS in neutral loss scanning mode to observe the loss of dehydrated sugar moieties. This facilitated tentative compound identification based on molar mass information as well as the structured elution order of these compounds. In a second experiment, product ion spectra were recorded to allow identification of the anthocyanidin base using characteristic fragmentation patterns. The proposed methodology therefore involves two analyses for the sensitive and accurate identification of anthocyanins and their derived products in red wines. Mass spectra of wine anthocyanins under high energy collision induced dissociation (CID) conditions are reported, some for the first time. Significantly, chemical alteration of anthocyanins during wine ageing results in an off-set of the predominant fragments for each anthocyanidin base, whilst maintaining similar relative intensities. This allows unambiguous assignment of the derived products of anthocyanidin-glycosides. Using this approach, a total of 121 anthocyanins and derived compounds were identified in wines based on their relative reversed phase elution order as well as mass spectral information.

Determination of N-methyl-1,3-propanediamine in bovine muscle by liquid chromatography with triple quadrupole and ion trap tandem mass spectrometry detection

29 March 2012, 09:38:25
Publication year: 2012
Source:Journal of Chromatography A, Volume 1235
Clare Ho, Wai-On Lee, Yiu-Tung Wong
Morantel, pyrantel and their drug-related metabolites in food of animal-origin are regulated as sum of residues which may be hydrolysed to N-methyl-1,3-propanediamine (NMPA). In this study, an isotope dilution liquid chromatography tandem mass spectrometry (LC–MS/MS) method with pentafluoropropionic acid anhydride (PFPA) derivatization was developed for the determination of NMPA in bovine muscle. A stable isotope labeled internal standard N-methyl-d3-3,3′-d2-propane-1,3-diamine (NMPA-d5) was synthesized as internal standard. NMPA was derivatized with PFPA to form an N,N′-bis (pentafluoroacyl) derivative (NMPA-PFPA) and analyzed by liquid chromatography triple quadrupole mass spectrometry (LC-QqQ-MS/MS) and liquid chromatography ion trap mass spectrometry (LC-IT-MS/MS) using negative ion electrospray ionization (ESI). Chromatographic behavior of several perfluorocarboxylic acid anhydride derivatives of NMPA and other structurally related diamines on C-18 and perfluorophenyl (PFP) columns was studied. Conversion of the parent drugs to NMPA under various hydrolysis conditions was evaluated. In addition, comparison of the matrix effect and linearity with isotopically labeled internal standard (I.S.) and analogous I.S. were performed and investigated. The method was validated using fortified bovine muscle samples. The apparent recovery (obtained after correction with an isotopically labeled I.S.) was between 89% and 97% and repeatability was less than 10%. The lowest LOD and LOQ (0.42 and 1.39μg/kg, respectively) were obtained with LC-QqQ-MS/MS.

Evaluation of a generic multi-analyte method for detection of >100 representative compounds correlated to emergency events in 19 food types by ultrahigh-pressure liquid chromatography–tandem mass spectrometry

29 March 2012, 09:38:25
Publication year: 2012
Source:Journal of Chromatography A, Volume 1235
Anders Herrmann, Johan Rosén, Daniel Jansson, Karl-Erik Hellenäs
A generic extraction procedure combined with triple quadrupole mass spectrometric detection was evaluated for multi-residue analysis in 19 different foods. Measurable peaks could be obtained at relevant concentrations for 108 out of a total of 127 targeted compounds representing a wide range of physicochemical properties and compound classes related to emergency situations. Recoveries were determined for all 19 foods spiked with the 108 compounds. Seventy-five percent of the compounds had extraction recoveries of 70% or higher, with no compound below 46%. Suppression or enhancement effects on the MS response of the compounds dissolved in the extracts were low, as more than 80% of them had matrix effects between −35% and +20% and no compound was below −44% compared to matrix-free standard. In a validation, all compounds could be quantified at 200μg/kg and 400μg/kg food sample and 81% of the compounds at 40μg/kg. It is concluded that the method is useful for the detection of various types of organic chemical toxicants at levels generally well below concentration thresholds for severe acute intoxication.

Simultaneous determination of jasmonic acid epimers as phytohormones by chiral liquid chromatography–quadrupole time-of-flight mass spectrometry and their epimerization study

29 March 2012, 09:38:25
Publication year: 2012
Source:Journal of Chromatography A, Volume 1235
Yehua Han, Zhigui Zhou, Hongliang Wu, Honggang Nie, Rong Lei, Yu Bai, Huwei Liu
Jasmonic acid (JA) is an essential plant hormone involved in plant development and defense system. There are four stereoisomeric forms of JA and they act quite differently in vivo. In this work, a normal phase liquid chromatography–quadrupole time-of-flight mass spectrometry (NPLC–QTOF-MS) method using cellulose tris (4-methylbenzoate) coated silica gel as the chiral stationary phase was first established for the simultaneous discrimination and direct analysis of all the four JA stereoisomers without need of derivatization. A non-endogenous JA stereoisomer was introduced as the internal standard to ensure the reliability of the developed method. Satisfactory results were obtained in terms of sensitivity (limit of detection, 0.5ngmL−1 or 2.4fmol), linearity (R 2 =0.9996) and repeatability (run-to-run RSD of migration time and peak area, 0.37% and 5.9%, respectively, n =6). Endogenous rise of two natural JA stereoisomers was detected in tobacco leaves and their variations in response to mechanical wounding were monitored. In addition, the configurational stability of JA stereoisomers was investigated using the stereoisomerically pure forms which were not commercially available but easily obtained by our semi-preparative chiral LC method. Experimental evidence indicated that both of the two naturally existing JA stereoisomers were putative signals for wounding response, and the epimerization between them was not a spontaneous process simply promoted by the thermodynamical instability as expected before.

Derivatization and liquid chromatography–UV–tandem mass spectrometric analysis of perfluorinated carboxylic acids

29 March 2012, 09:38:25
Publication year: 2012
Source:Journal of Chromatography A, Volume 1235
Jinxue Qiu, Chunmei Wu, Yingyu Fang, Cui Yang, Xiuhua Li, Xiangfan Piao, Donghao Li
The presence of perfluorocarboxylates (PFCAs) in the environment is of increasing concern due to their possible toxicity to humans and bioaccumulation in organisms. PFCAs are frequently found in river water, sediment and organisms and sometimes even in groundwater. In order to quantitatively determine these PFCAs, a fast derivatization coupled with a liquid chromatography–ultraviolet detector–electrospray ionization-tandem mass spectrometry (LC–UV–ESI-MS/MS) method was developed. The PFCAs were quantitatively converted to their corresponding phenacyl esters using p-bromophenacyl bromide as the derivatization reagent. Under optimized reaction conditions, the conversion yield of the PFCAs ranged from 86 to 92% with low %RSD. The typical derivatization product (p-bromophenacyl bromide perfluorooctanoate) was characterized by 1H NMR, 13C NMR, FT-IR and mass spectrometry. UPLC with a BEH C18 column and CAN/H2O (8/2, v/v) as a mobile phase were used to separate the derivatives. The analytes were completely eluted within 6min and multidimensional detection using UV at 260nm and ESI–MRM in the negative ion mode were carried out. Bromide isotopic characteristic fragment ions appeared in the first Q1 scans, and four daughter ions of the MRMs at m/z [M−H−222], [M−H−250], [M−H−278] and [M−H−316] were used for quantification and confirmation. The mass spectral information ensured accurate identification of the analytes even when the sample matrices were complex. The method successfully eliminated the PFCAs background problems originating from polymeric parts in liquid chromatographic systems. The LODs of the method were lower than 5ngmL−1, and the relative standard deviation (RSD%) values ranged from 5.2 to 9.8%. The method was successfully applied for the quantification of PFCAs in river water contaminated by industrial wastewater, and this indicated that the method was useful in the determination of PFCAs in environmental samples.

Atmospheric pressure gas chromatography coupled to quadrupole-time of flight mass spectrometry as a powerful tool for identification of non intentionally added substances in acrylic adhesives used in food packaging materials

29 March 2012, 09:38:25
Publication year: 2012
Source:Journal of Chromatography A, Volume 1235
E. Canellas, P. Vera, C. Domeño, P. Alfaro, C. Nerín
Acrylic adhesives are used to manufacture multilayer laminates that are used in food packaging to form the geometric shape of the package as well as to stick labels on the packages. Once applied on the packaging adhesives can supply potential migrants that could endanger the packaged food. Adhesives are complex matrices where intentionally and non intentionally added substances are present, but the identification of the migrants is required by law. In this study atmospheric pressure gas chromatography coupled to a quadrupole hyphenated to a time of flight mass spectrometer (APGC–MS/Q-TOF) has been explored for identification of unknowns coming from three different acrylic adhesives. The results are compared to those obtained by conventional GC–MS-Q (quadrupole). Sixteen compounds were identified by GC–MS/Q and five of them were confirmed by APGC–MS/Q-TOF as their molecular ions were found. Moreover, additional three new compounds were identified and their structure was elucidated working with the spectra obtained by APGC–MS/Q-TOF. This finding was very relevant as these compounds were biocides suspected to be allergenic and cytotoxic in humans. Migration studies were carried out using Tenax as solid food simulant and the results showed that the three acrylic adhesives tested in this work were safe for being used in food packaging materials since the migration of compounds previously identified was below the limit established in the current legislation.

Source identification of petroleum hydrocarbons in soil and sediments from Iguaçu River Watershed, Paraná, Brazil using the CHEMSIC method (CHEMometric analysis of Selected Ion Chromatograms)

29 March 2012, 09:38:25
Publication year: 2012
Source:Journal of Chromatography A, Volume 1235
Fabiana D.C. Gallotta, Jan H. Christensen
A chemometric method based on principal component analysis (PCA) of pre-processed and combined sections of selected ion chromatograms (SICs) is used to characterise the hydrocarbon profiles in soil and sediment from Araucária, Guajuvira, General Lúcio and Balsa Nova Municipalities (Iguaçu River Watershed, Paraná, Brazil) and to indicate the main sources of hydrocarbon pollution. The study includes 38 SICs of polycyclic aromatic compounds (PACs) and four of petroleum biomarkers in two separate analyses. The most contaminated samples are inside the Presidente Getúlio Vargas Refinery area. These samples represent a petrogenic pattern and different weathering degrees. Samples from outside the refinery area are either less or not contaminated, or contain mixtures of diagenetic, pyrogenic and petrogenic inputs where different proportions predominate. The locations farthest away from industrial activity (Balsa Nova) contains the lowest levels of PAC contamination. There are no evidences to conclude positive matches between the samples from outside the refinery area and the Cusiana spilled oil.

Determination of descriptors for fragrance compounds by gas chromatography and liquid–liquid partition

29 March 2012, 09:38:25
Publication year: 2012
Source:Journal of Chromatography A, Volume 1235
Thushara Karunasekara, Colin F. Poole
Retention factors on a minimum of eight stationary phases at various temperatures by gas–liquid chromatography and liquid–liquid partition coefficients for five totally organic biphasic systems were combined to estimate descriptors for 28 fragrance compounds with an emphasis on compounds that are known or potential allergens. The descriptors facilitated the estimation of several properties of biological and environmental interest (sensory irritation threshold, odor detection threshold, nasal pungency threshold, skin permeability from water, skin–water partition coefficients, octanol–water partition coefficients, absorption by air particles, adsorption by diesel soot particles, air–water partition coefficients, and adsorption by film water). The descriptors are suitable for use in the solvation parameter model and facilitate the estimation of a wide range of physicochemical, chromatographic, biological, and environmental properties using existing models.

Rapid analysis of organochlorine and pyrethroid pesticides in tea samples by directly suspended droplet microextraction using a gas chromatography–electron capture detector

29 March 2012, 09:38:25
Publication year: 2012
Source:Journal of Chromatography A, Volume 1235
Dan Liu, Shungeng Min
A simple and efficient directly suspended droplet microextraction (DSDME) has been developed to extract and pre-concentrate organochlorine and pyrethrin pesticides from tea samples prior to analysis by a gas chromatography–electron capture detector (GC–ECD). The optimal experimental conditions of DSDME were: 100μL isooctane exposed for 15min to 5mL of the tea aqueous sample stirred at 1100rpm. For most of the target analytes, the optimal pretreatment of DSDME processes led to no significant interference of tea matrices. The approach was applied to the determination of organochlorine and pyrethroid pesticides in tea samples, with a linearity range of 0.0005–2μg/mL. The relative recoveries of all the pesticides ranged between 80.0% and 120.8% with relative standard deviations (RSDs) in the range of 0.8–19.9% (n =5). The limits of detections (LODs) ranged between 0.04 and 1μg/L for all the target pesticides.

Taylor dispersion analysis with two detection points on a commercial capillary electrophoresis apparatus

29 March 2012, 09:38:25
Publication year: 2012
Source:Journal of Chromatography A, Volume 1235
Joseph Chamieh, Farid Oukacine, Hervé Cottet
This work describes a simple technical modification for doing Taylor dispersion analysis with two UV detection points on a commercial capillary electrophoresis apparatus. So far, double UV detection was only possible using specific detectors that are external to the capillary electrophoresis apparatus. In this work, the detection interface of the capillary electrophoresis apparatus was easily modified to allow the introduction and the superposition of two capillary windows in the same interface (at the same detection point). This modification made possible the double detection of the sample zone in Taylor dispersion analysis using a loop. The peak dispersion using the modified interface was similar to that obtained on a non-modified UV interface. Diffusion coefficients (and the corresponding hydrodynamic radii) of small molecule and proteins were determined in good agreement with values of the literature and with RSD lower than 5%. 

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