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Analytica Chimica Acta (v.690, #1)

Editorial Board (pp. iii).

N-Alkylpyridinium isotope quaternization for matrix-assisted laser desorption/ionization Fourier transform mass spectrometric analysis of cholesterol and fatty alcohols in human hair by Hang Wang; Haoyang Wang; Li Zhang; Jing Zhang; Yinlong Guo (pp. 1-9).

Isotope-coded reagents have been developed for labeling of amino acids, phenols and fatty acids, but not for alcohols. In this work, a simple reaction based on direct N-alkylpyridinium isotope quaternization (NAPIQ) was developed for mild derivatization of cholesterol and fatty alcohols. Different from the conventional quaternary reagents with cations on themselves, two simple and charge-neutral reagents: pyridine and d₅-pyridine directly attached N-cationic tag onto the target compounds in the presence of trifluoromethanesulfonic anhydride (Tf₂O) without tedious sample preparation. The derivatization completed in 5min and achieved charge labeling of the target compounds, which significantly improved the detection limits of analytes by 10³-folds in further analysis by matrix-assisted laser desorption/ionization Fourier transform mass spectrometry (MALDI–FTMS). The use of commercially available d₀/ d₅-pyridine pairs facilitated isotope-coded chemical derivatization and avoided the use of isotope-labeled internal standards; the excess pyridine did not affect the signals of analytes. Utility of the NAPIQ method was examined in the identification of cholesterol and fatty alcohols in small amount of human hair sample (<0.5mg). The fluctuation of total cholesterol in human body was profiled during time by quantitatively comparing the different segments of a single strand of hair. This study combines the direct pyridinium quaternization with MALDI–FTMS, which offers a perspective and an alternative tool for the identification and quantification of substances in biological matrix by comparing d₀/ d₅ pairs, especially when isotope-labeled internal standards are unavailable.

Keywords: Isotope-coded reagent; Pyridinium quaternization; Alcoholic group; Chemical derivatization; Mass spectrometry

Nanoparticle-based electrochemical detection in conventional and miniaturized systems and their bioanalytical applications: A review by Weena Siangproh; Wijitar Dungchai; Poomrat Rattanarat; Orawon Chailapakul (pp. 10-25).

With recent advances in nanotechnology making more easily available the novel chemical and physical properties of metal nanoparticles (NPs), these have become extremely suitable for creating new sensing assays. Many kinds of NPs, including metal, metal-oxide, semiconductor and even composite-metal NPs, have been used for constructing electrochemical sensors. This article reviews the progress of NP-based electrochemical detection in recent applications, especially in bioanalysis, and summarizes the main functions of NPs in conventional and miniaturized systems. All references cited here generally show one or more of the following characteristics: a low detection limit, good signal amplification and simultaneous-detection capabilities.

Keywords: Metal nanoparticles; Electrochemical Sensors; Miniaturized Systems; Immunosensors; Biosensors

Protein profiling for cancer biomarker discovery using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and infrared imaging: A review by R. Bakry; M. Rainer; C.W. Huck; G.K. Bonn (pp. 26-34).

Cancer biomarker refers to a substance or process that is indicative of the presence of cancer in the body. A biomarker might be either a molecule secreted by a tumor or it can be a specific response of the body to the presence of cancer. Cancer biomarker-based diagnostics have applications for establishing disease predisposition, early detection, cancer staging, therapy selection, identifying whether or not a cancer is metastatic, therapy monitoring, assessing prognosis, and advances in the adjuvant setting. Full adoption of cancer biomarkers in the clinic has to date been slow, and only a limited number of cancer biomarker products are currently in routine use.Among proteomic technologies, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS) is a technique that has allowed rapid progress in cancer biology. Different further developed methods including e.g. SELDI (surface-enhanced laser desorption/ionization) and MELDI (material-enhanced laser desorption/ionization) are simple and high-throughput techniques that analyze with high sensitivity and specificity intact proteins expressed in complex biological mixtures, such as serum, urine, and tissues. The combination of mass spectrometry (MS) with infrared (IR) spectroscopic imaging is an attempt to combine different technologies in systems analytics. Both MALDI-TOF and infrared tissue imaging enable studying proteins distribution in tissue samples with a resolution down to 50 and 5μm, respectively.In this review, we summarize recent applications and the synergistic combination of these new technologies to proteomic profiling for cancer biomarker discovery.

Keywords: Biomarker; Cancer; Infrared spectroscopy; Mass spectrometry; Protein profiling

Multi-variable retention modelling in reversed-phase high-performance liquid chromatography based on the solvation method: A comparison between curvilinear and artificial neural network regression by Angelo Antonio D’Archivio; Maria Anna Maggi; Fabrizio Ruggieri (pp. 35-46).

The linear solvation energy relationships (LSERs) have been widely used in the last decades for description and prediction of retention in reversed-phase high-performance liquid chromatography (RP-HPLC). LSERs are usually applied to model the effect of solute structure on the RP-HPLC retention at a fixed separation condition. Some authors by combining LSER with known empirical relationships relating retention with mobile phase composition of binary eluents ( ϕ) have proposed a predictive model able to simultaneously relate RP-HPLC retention to both solute LSER descriptors and mobile phase composition. The resulting relationship can be established for a given column/organic modifier combination by curvilinear regression aimed at defining 18 model coefficients. In this study, we compare predictive performance of such approach and that of artificial neural network (ANN) regression in which the five solute LSER descriptors and ϕ are directly considered as the network inputs. To this purpose we analyse literature retention data of 31 molecules of different types collected on five reversed-phase columns either in water–acetonitrile and water–methanol mobile phase, the organic modifier content ranging between 20 and 70% (v/v). For each column/organic modifier combination both a curvilinear and an ANN-based model is built using data referred to 25 solutes, while the alternative models are later tested on the remaining six solutes excluded from calibration. Further, we compare capability of curvilinear and ANN regression after including into the respective models also variability related with the stationary phase, represented by the average retention of calibration solutes extrapolated at pure water as the mobile phase. The results of this investigation demonstrate that regardless of the kind of column and organic modifier ANN regression, as compared with curvilinear modelling, provides lower prediction errors and these are more uniformly distributed over the investigated retention range.

Keywords: Retention prediction; Artificial neural network; Reversed-phase high-performance liquid chromatography; Mobile phase; Solvatochromic descriptors

Optimised determinations of water in ethanol by encoded photometric near-infrared spectroscopy: A special case of sequential standard addition calibration by Richard J.C. Brown; Adam C. Keates; Andrew S. Brown (pp. 47-52).

A special limiting case of sequential standard addition calibration (S-SAC) has been applied to measurement of the water content of ethanol using encoded photometric near infrared spectroscopy. The method has shown good comparability with certified reference materials and to measurements made by Karl Fischer titration. The technique is quick and easy to use and should have application in high throughput and process measurement, for instance in biofuels analysis at port-of-entry or in bio-refineries. The characteristics of this limiting case of S-SAC have been fully described, and the corrections required to the value obtained by extrapolation to avoid bias have been calculated. The precision of the S-SAC procedure has been studied, and proposals have been made to optimise this with respect to the analytical precision. The technique should be applicable for the measurement of water in ethanol mass fractions of up to 0.1gg⁻¹ with an expanded uncertainty of less than 2% (relative).

Keywords: Water–ethanol mixtures; Near-infrared spectroscopy; Process analysis; Sequential standard addition calibration; Biofuels

Prediction of P2Y₁₂ antagonists using a novel genetic algorithm-support vector machine coupled approach by Ming Hao; Yan Li; Yonghua Wang; Shuwei Zhang (pp. 53-63).

Presently, a genetic algorithm (GA)-support vector machine (SVM) coupled approach is proposed for optimizing the 2D molecular descriptor subset generated for series of P2Y₁₂ (members of the G-protein-coupled receptor family) antagonists, with the statistical performance and efficiency of the model being simultaneously enhanced by SVM kernel-based nonlinear projection. As we know, this is the first QSAR study for prediction of P2Y₁₂ inhibition activity based on an unusually large dataset of 364 P2Y₁₂ antagonists with diversity of structures. In addition, three other widely used approaches, i.e., partial least squares (PLS), random forest (RF), and Gaussian process (GP) routines combined with GA (namely, GA–PLS, GA–RF, GA–GP, respectively) are also employed and compared with the GA–SVM method in terms of several rigorous evaluation criteria. The obtained results indicate that the GA–SVM model is a powerful tool for prediction of P2Y₁₂ antagonists, producing a conventional correlation coefficient R² of 0.976 andRcv2 (cross-validation) of 0.829 for the training set as well asRpred2 of 0.811 for the test set, which significantly outperforms the other three methods with the average R²=0.894,Rcv2=0.741,Rpred2=0.693. The proposed model with excellent prediction capacity from both the internal to external quality should be helpful for screening and optimization of potential P2Y₁₂ antagonists prior to chemical synthesis in drug development.

Keywords: P2Y; ₁₂; Genetic algorithm; Support vector machine; Descriptor selection

Maintaining the predictive abilities of multivariate calibration models by spectral space transformation by Wen Du; Zeng-Ping Chen; Li-Jing Zhong; Shu-Xia Wang; Ru-Qin Yu; Alison Nordon; David Littlejohn; Megan Holden (pp. 64-70).

In quantitative on-line/in-line monitoring of chemical and bio-chemical processes using spectroscopic instruments, multivariate calibration models are indispensable for the extraction of chemical information from complex spectroscopic measurements. The development of reliable multivariate calibration models is generally time-consuming and costly. Therefore, once a reliable multivariate calibration model is established, it is expected to be used for an extended period. However, any change in the instrumental response or variations in the measurement conditions can render a multivariate calibration model invalid. In this contribution, a new method, spectral space transformation (SST), has been developed to maintain the predictive abilities of multivariate calibration models when the spectrometer or measurement conditions are altered. SST tries to eliminate the spectral differences induced by the changes in instruments or measurement conditions through the transformation between two spectral spaces spanned by the corresponding spectra of a subset of standardization samples measured on two instruments or under two sets of experimental conditions. The performance of the method has been tested on two data sets comprising NIR and MIR spectra. The experimental results show that SST can achieve satisfactory analyte predictions from spectroscopic measurements subject to spectrometer/probe alteration, when only a few standardization samples are used. Compared with the existing popular methods designed for the same purpose, i.e. global PLS, univariate slope and bias correction (SBC) and piecewise direct standardization (PDS), SST has the advantages of implementation simplicity, wider applicability and better performance in terms of predictive accuracy.

Keywords: Calibration model maintenance; Spectral space transformation; Spectral standardization; Spectroscopic instruments; Process analytical technology

Towards an automated, standardized protocol for determination of equilibrium potential of ion-selective electrodes by Amy V. Mueller; Harold F. Hemond (pp. 71-78).

An automated real-time method for determination of ISE steady state value and response time is developed, following most recent IUPAC recommendations. Specifically, detection of the ‘steady state’ is related to (1) the time derivative of the emf as it reaches a limiting value (Δ E/Δ t_limit, e.g., 0.1–1.0mVmin⁻¹) and (2) the duration of time for which the absolute value of the time derivative remains less than this limiting value (stability window, denoted win_st). A suite of representative ISEs, including glass, solid state, and polymer-based electrodes, is examined to determine sensitivity of results to parameterization choice. Measurements taken over a wide range of concentration values and in un-processed samples (i.e., without use of ionic strength adjustment) provide insight into behavior of ISEs in applications where analyte concentrations span a wide range and/or sample pre-processing may not be an option, e.g., use of sensors for in situ environmental sampling. Results show that declared steady state emf is strongly sensitive to variations in Δ E/Δ t_limit but relatively unaffected by changes in the stability window when win_st ≥30s. Linearity of calibration curves produced, quantified by root mean squared error (RMSE) against a linear fit, improves as Δ E/Δ t_limit decreases, however the percentage of measurements which reach a declared steady state within the prescribed sample window (∼6.5min) falls with corresponding decreases in the Δ E/Δ t_limit parameter. Response time, defined as the time required to reach declared steady emf, is also a strong function of parameterization. Dependence of response times on sample composition and/or ISE membrane composition and type are also discussed; results for ISEs in samples comprised exclusively of interfering ions are included. In general, limiting emf derivatives of {0.25–0.4mVmin⁻¹} and stability windows of {30–40s} achieve both good analytical accuracy and compliance with potentially short sampling window requirements. Methodology based on use of these parameters can improve sampling speed and accuracy as well as promote inter-comparison of data and ISE characterizations among research teams.

Keywords: Ion selective electrodes; Equilibration detection; Automation

Multivariate optimization of the determination of zinc in diesel oil employing a novel extraction strategy based on emulsion breaking by Ricardo J. Cassella; Daniel M. Brum; Claudio F. Lima; Luiz Fernando S. Caldas; Carlos Eduardo R. de Paula (pp. 79-85).

This paper describes the extraction/pre-concentration of Zn from diesel oil and its determination by Flame Atomic Absorption Spectrometry (FAAS), proposed as a novel approach for these kinds of analyses and the multivariate optimization of the proposed procedure. The extraction of Zn is based on the emulsification of an aqueous solution containing Triton X-114 and HNO₃ with diesel oil samples followed by breaking of the emulsion by heating. The aqueous phase obtained after the emulsion breaking was collected and used for Zn quantification by FAAS. The methodology was optimized using a Doehlert design and the system variables were the concentrations of surfactant and HNO₃ in the solution employed in the emulsification and the temperature used in the emulsion breaking. The ratio between absorbance and the time required to break the emulsions was taken as response. Two sets of experiments, using different emulsifier agents, were run: the first one using Triton X-100 and the second one using Triton X-114. At optimized conditions, the emulsions were prepared by mixing 10mL of diesel oil with 2mL of a solution containing 5% w/v of Triton X-114 and 15% v/v of HNO₃ and broken by heating at 80°C. The proposed analytical procedure was applied in the analysis of six real samples of diesel oil and a recovery test was carried out by spiking the samples with known amounts of Zn (25 and 50μgL⁻¹), added as organometallic oiled standard. Recovery percentages achieved in this test were between 92 and 109%.

Keywords: Diesel oil; Flame atomic absorption spectrometry; Zinc; Extraction induced by emulsion breaking

A novel solid-phase microextraction method based on polymer monolith frit combining with high-performance liquid chromatography for determination of aldehydes in biological samples by Hui Xu; Shuyu Wang; Ganbing Zhang; Shiqiang Huang; Dandan Song; Yanping Zhou; Guangdou Long (pp. 86-93).

In this work, a polypropylene frit with porous network structure (20μm pole size) was first utilized as the mould of polymer monolithic material, poly(methacrylic acid-co-ethylene glycol dimethacrylate) (MAA-co-EDMA) monolith was synthesized within channels and macropores of the frit. A simple and sensitive solid-phase microextraction method based on polymer monolith frit coupled with high-performance liquid chromatography (HPLC) was established and applied to analysis of hexanal and heptanal in biological samples (human urine and serum). In the method, small molecule metabolites (aldehydes) in biological samples derivatized with 2,4-dinitrophenylhydrazine (DNPH), and the formed hydrazones were extracted simultaneously on the monolithic frit and thereafter ultrasound-assisted desorbed with acetonitrile as elution solvent. The experimental parameters with regard to polymerization, derivatization and extraction were investigated. Under the optimal conditions, the linearity was in the range of 0.02–5.0μmolL⁻¹ ( r=0.9994) for both hexanal and heptanal and the limits of detection ( S/ N=3) were 0.81nmolL⁻¹ for hexanal and 0.76nmolL⁻¹ for heptanal. The relative standard deviations (RSDs, n=5) were less than 6.5% for the same monolithic frit and less than 8.9% for the different monolithic frits. Satisfactory recoveries ranging from 70.71% to 88.73% were obtained for the urine samples. The method possesses many advantages including simple setup, fast analysis, low cost, sufficient sensitivity, good biological compatibility and less organic solvent consumption. The proposed method is a useful assistant tool in the clinical early diagnosis of lung disease by monitoring aldehyde biomarker candidates in complex biological samples.

Keywords: Abbreviations; HPLC; high-performance liquid chromatography; MAA-co-EDMA; methacrylic acid-co-ethylene glycol dimethacrylate; DNPH; 2,4-dinitrophenylhydrazine; PFBHA; O-2,3,4,5,6-(pentaﬂuorobenzyl) hydroxylamine hydrochloride; GC–MS; gas chromatography–mass spectrometry; SPME; solid-phase microextraction; PMME; polymer monolith microextraction; EDMA; ethylene glycol dimethacrylate; MAA; methacrylic acid; HMPA; 2-hydroxy-2-methyl-phenyl-1-acetone; SEM; scanning electron microscopySolid-phase microextraction (SPME); Polymer monolithic frit; Aldehydes; Biological matrix; High-performance liquid chromatography

Microchip extraction of catecholamines using a boronic acid functional affinity monolith by Cafer Cakal; Jerome P. Ferrance; James P. Landers; Perihan Caglar (pp. 94-100).

A novel solid phase extraction microchip with a boronic acid functional affinity monolithic disc was developed in this work. Vinyl phenylboronic acid–ethylene glycol dimethacrylate co-polymer monoliths, which have pore sizes up to 20μm, were investigated for extraction of catecholamines using adsorption and desorption studies in a batch system. Desorption yields of greater than 90% were achieved for catecholamines at pH 3 and below. Monolithic discs were then formed in chambers in borofloat glass microfluidic chips using in situ UV polymerization. Adsorption on the monolithic discs was performed via electrokinetic flow, with catecholamines determined via laser-induced native fluorescence (LINF) detection following electrokinetic elution. Microchips containing the boronic acid functional polymer discs worked well for extraction of catecholamines, providing greater than 100 fold concentration enrichment. This study demonstrated that a solid phase extraction microchip, containing an easily prepared monolith disc, will be useful for boronate affinity extraction of cis-diol containing compounds.

Keywords: Boronic acid functional affinity monolith; Catecholamines; Microchip SPE; Pre-concentration

Automatic flow methodology for kinetic and inhibition studies of reactions with poorly water-soluble substrates in ionic liquid systems by André R.T.S. Araujo; M. Lúcia M.F.S. Saraiva; José L.F.C. Lima (pp. 101-107).

In the present work an automatic generic tool, based on sequential injection analysis (SIA) for kinetic and inhibition studies of reactions with poorly water-soluble compounds in ionic liquid (IL)-containing systems, is described.The oxidation of the poorly water-soluble phenolic compound, caffeic acid, catalyzed by the mushroom tyrosinase, in different 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄])/buffer mixtures as reaction media, was investigated. This determination was based on measuring depletion rate of the substrate caffeic acid at its maximum wavelength ( λ_max 311nm).The influence of several parameters such as substrate and enzyme concentration, temperature, pH, delay times and measurement periods on the sensitivity and performance of the SIA system were studied and the optimum reaction conditions subsequently selected.The obtained results showed that tyrosinase was active in oxidising caffeic acid in this water-miscible IL and the presence of an impaired tyrosinase activity with increase in [bmim][BF₄] concentration as an increase in the apparent Michaelis–Menten constant (KMapp) was observed while the maximum reaction rate (Vmaxapp) remained fairly constant. The results were compared to those obtained when the assay was performed in water/methanol mixtures under the same conditions to substantiate [bmim][BF₄] as an alternative to conventional organic solvents.Additionally, it was shown that tyrosinase is effectively inhibited by the substrate analogues tested ( trans-cinnamic acid and 3,4-dihydroxybenzoic acid) in the IL-containing aqueous system used.

Keywords: Ionic liquid; Sequential injection analysis; Kinetic; Inhibition; Tyrosinase

Novel optical trace oxygen sensors based on platinum(II) and palladium(II) complexes with 5,10,15,20- meso-tetrakis-(2,3,4,5,6-pentafluorphenyl)-porphyrin covalently immobilized on silica-gel particles by Sergey M. Borisov; Philipp Lehner; Ingo Klimant (pp. 108-115).

New optical sensors for trace amounts of oxygen are based on platinum(II) and palladium(II) complexes of 5,10,15,20- meso-tetrakis-(2,3,4,5,6-pentafluorphenyl)-porphyrin covalently attached to the surface of amino-modified silica-gel particles. The dye-doped silica-gel particles are dispersed in silicone rubber. The Stern–Volmer plots show linear response and are virtually identical for either luminescence intensity and decay time. Other features include high photostability and rapid response times (∼150ms in gas phase). The sensors based on the palladium(II) complex show significantly higher sensitivity ( K_SV about 67kPa⁻¹ at 25°C) with the dynamic range from 0.02 to 100Pa. The sensitivity of the platinum(II) complexes is significantly lower ( K_SV=3.7–4.2kPa⁻¹, dynamic range 0.3–1000Pa). The sensors can be suitable for application in breweries, water boilers and for marine research (monitoring of oxygen minimum zones).

Keywords: Oxygen sensor; Palladium; Platinum; Porphyrin; Phosphorescence; Silica-gel

Effect of coating electrolytes on two-tailed surfactant bilayer coatings in capillary electrophoresis by Makedonka D. Gulcev; Charles A. Lucy (pp. 116-121).

Surfactants such as dioctadecyldimethylammonium bromide (DODAB) form semi-permanent coatings that effectively prevent adsorption of cationic proteins onto the fused silica capillary in capillary electrophoresis (CE). The bilayer coating is generated by flushing the capillary with a 0.1mM surfactant solution. However, formation of the bilayer is strongly dependent on the coating electrolyte. The effect of counter-ions, electrolyte concentrations and buffer co-ions were monitored based on: the separation of basic model proteins; the adsorption kinetics of DODA⁺ onto fused silica; and dynamic light scattering (DLS) to determine vesicle size. Low concentrations (≤10.0mM) and/or weakly associating buffers such as phosphate (pH 3.0), acetate (pH 4.0) and chloride should be used for DODAB coating solutions. Dissolving the surfactant in strongly associating electrolyte, such as phosphate at pH 7.0, results in poor coating of the capillary surface. Effective cationic bilayer coatings are formed if the buffer conditions favor formation of vesicles with diameters<300nm. Monitoring turbidity at 400nm provides a convenient means of verifying vesicle diameter variation of <5nm; that is, that the coating solution is effective.

Keywords: Capillary electrophoresis; Basic model proteins; Coatings; Two-tailed surfactants

Ethyl propiolate as a post-column derivatization reagent for thiols: Development of a green liquid chromatographic method for the determination of glutathione in vegetables by Constantinos K. Zacharis; Paraskevas D. Tzanavaras; Anastasia Zotou (pp. 122-128).

The present study reports the development, validation and application of a new green liquid chromatographic method for the determination of glutathione (GSH) in vegetable samples. In this work we introduce—for the first time—ethyl propiolate (EP) as an advantageous post-column derivatization reagent for thiolic compounds. GSH ( t_R=6.60min) and N-acetylcysteine (NAC, internal standard) ( t_R=11.80min) were separated efficiently from matrix endogenous compounds by using a 100% aqueous mobile phase (0.1%, v/v CH₃COOH in 1mmolL⁻¹ EDTA, Q_V=0.5mLmin⁻¹) and a Prevail^® reversed phase column that offers the advantage of stable packing material in aqueous mobile phases. The parameters of the post-column reaction (pH, amount concentration of the reagent, flow rates, length of the reaction coil and temperature) were studied. The linear determination range for GSH was 1–200μmolL⁻¹ and the LOD was 0.1μmolL⁻¹ (S/N=3). Total endogenous GSH was determined in broccoli, potato, asparagus and Brussels sprouts using the standards addition approach. The accuracy was evaluated by both recovery experiments ( R=91–110%) and comparison to an o-phthalaldehyde/glycine corroborative post-column derivatization fluorimetric method.

Keywords: Glutathione; Post-column derivatization; Vegetables; Ethyl propiolate; Liquid chromatography

Development of an ultra-high performance liquid chromatography analytical methodology for the profiling of olive ( Olea europaea L.) pulp proteins by Clara Esteve; Carmen Del Río; M. Luisa Marina; M. Concepción García (pp. 129-134).

Ultra-high performance liquid chromatography (UHPLC) constitutes an interesting proposal to speed protein separations but it is almost not explored. In this work UHPLC is proposed, for the first time, to separate olive pulp proteins. An important difficulty in the analysis of proteins is related to their extraction. The difficulty in the extraction of proteins from the olive pulp is derived from its high content in lipids and phenolic compounds. Eight different methods for the extraction of pulp proteins were designed and evaluated. The optimized extraction procedure consisted of a cleaning step to remove interfering compounds, followed by the extraction of proteins with a Tris–HCl buffer containing sodium dodecyl sulphate (SDS) and dithiothreitol (DTT), precipitation of proteins with acetone, and solubilization in the Tris–HCl buffer. This methodology yielded the most successful isolation of pulp proteins and enabled the optimization of a UHPLC methodology for their separation. The method was applied to the profiling of olive pulp proteins from different olive cultivars observing in all cases a protein that had never been described before.

Keywords: Proteins; Olive; Pulp; UHPLC; Extraction

Erratum to “Absolute quantification method and validation of airborne snow crab allergen tropomyosin using tandem mass spectrometry” [Anal. Chim. Acta 681 (2010) 49–55] by Anas M. Abdel Rahman; Andreas L. Lopata; Edward W. Randell; Robert J. Helleur (pp. 135-135).

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Analytica Chimica Acta (v.690, #1)