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Analytica Chimica Acta (v.673, #2)

Editorial Board (pp. i).

Interferences in the analysis of nanomolar concentrations of nitrate and phosphate in oceanic waters by Matthew D. Patey; Eric P. Achterberg; Micha J.A. Rijkenberg; Peter J. Statham; Matthew Mowlem (pp. 109-116).

This paper reports on investigations into interferences with the measurements of nanomolar nitrate+nitrite and soluble reactive phosphate (SRP) in oceanic surface seawater using a segmented continuous flow autoanalyser (SCFA) interfaced with a liquid-waveguide capillary flow-cell (LWCC). The interferences of silicate and arsenate with the analysis of SRP, the effect of sample filtration on the measurement of nanomolar nitrate+nitrite and SRP concentrations, and the stability of samples during storage are described.The investigation into the effect of arsenate (concentrations up to 100nM) on phosphate analysis (concentrations up to 50nM) indicated that the arsenate interference scaled linearly with phosphate concentrations, resulting in an overestimation of SRP concentrations of 4.6±1.4% for an assumed arsenate concentration of 20nM. The effect of added Si(OH)₄ was to increase SRP signals by up to 36±19nM (at 100μM Si(OH)₄). However, at silicate concentrations below 1.5μM, which are typically observed in oligotrophic surface ocean waters, the effect of silicate on the phosphate analysis was much smaller (≤0.78±0.15nM change in SRP). Since arsenate and silicate interferences vary between analytical approaches used for nanomolar SRP analysis, it is important that the interferences are systematically assessed in any newly developed analytical system.Filtration of surface seawater samples resulted in a decrease in concentration of 1.7–2.7nM (±0.5nM) SRP, and a small decrease in nitrate concentrations which was within the precision of the method (±0.6nM). A stability study indicated that storage of very low concentration nutrient samples in the dark at 4°C for less than 24h resulted in no statistically significant changes in nutrient concentrations. Freezing unfiltered surface seawater samples from an oligotrophic ocean region resulted in a small but significant increase in the SRP concentration from 12.0±1.3nM ( n=3) to 14.7±0.6nM ( n=3) (Student's t-test; p=0.021). The corresponding change in nitrate concentration was not significant (Student's t-test; p>0.05).

Keywords: Nanomolar nutrients; Ocean waters; Interferences; Filtration; Sample storage

Recent developments in cyanide detection: A review by Jian Ma; Purnendu K. Dasgupta (pp. 117-125).

The extreme toxicity of cyanide and environmental concerns from its continued industrial use continue to generate interest in facile and sensitive methods for cyanide detection. In recent years, there is also additional recognition of HCN toxicity from smoke inhalation and potential use of cyanide as a weapon of terrorism. This review summarizes the literature since 2005 on cyanide measurement in different matrices ranging from drinking water and wastewater, to cigarette smoke and exhaled breath to biological fluids like blood, urine and saliva. The dramatic increase in the number of publications on cyanide measurement is indicative of the great interest in this field not only from analytical chemists, but also researchers from diverse environmental, medical, forensic and clinical arena. The recent methods cover both established and emerging analytical disciplines and include naked eye visual detection, spectrophotometry/colorimetry, capillary electrophoresis with optical absorbance detection, fluorometry, chemiluminescence, near-infrared cavity ring down spectroscopy, atomic absorption spectrometry, electrochemical methods (potentiometry/amperometry/ion chromatography–pulsed amperometry), mass spectrometry (selected ion flow tube mass spectrometry, electrospray ionization mass spectrometry, gas chromatography–mass spectrometry), gas chromatography (nitrogen phosphorus detector, electron capture detector) and quartz crystal mass monitors.

Keywords: Keyword; Cyanide

Nanosilver-doped DNA polyion complex membrane for electrochemical immunoassay of carcinoembryonic antigen using nanogold-labeled secondary antibodies by Wei Wu; Ping Yi; Ping He; Tao Jing; Kelong Liao; Kang Yang; Haidong Wang (pp. 126-132).

A simple and sensitive electrochemical immunoassay protocol was developed for the detection of carcinoembryonic antigen (CEA) using nanosilver-doped DNA polyion complex membrane (PIC) as sensing interface. To construct such an immunosensor, double-stranded DNA was initially assembled onto the surface of thionine/Nafion-modified screen-printed carbon electrode to adsorb silver ions with positive charges, then silver ions were reduced to nanosilver particles with the aid of NaBH₄, and then anti-CEA antibodies were immobilized on the nanosilver surface. Gold nanoparticles conjugated with horseradish peroxidase-labeled anti-CEA were employed as signal antibodies for the detection of CEA with a sandwich-type assay format. Under optimal conditions, the immunosensor exhibited a dynamic range of 0.03–32ngmL⁻¹ with a low detection limit of 10pgmL⁻¹ CEA. Intra- and inter-assay imprecision (CVs) were <9.5% and 6.5%, respectively. The response could remain 90.1% of the original current at 30th day. 50 real samples were evaluated using the immunosensor and the enzyme-linked immunosorbent assay, respectively, and received in accordance with those two methods.

Keywords: Carcinoembryonic antigen; Electrochemical immunosensor; Polyion complex membrane; Silver nanoparticles

Biosensor for multiplex detection of two DNA target sequences using enzyme-functionalized Au nanoparticles as signal amplification by Xue-Mei Li; Pei-Yu Fu; Jin-Ming Liu; Shu-Sheng Zhang (pp. 133-138).

Multiplex electrochemical detection of two DNA target sequences in one sample using enzyme-functionalized Au nanoparticles (AuNPs) as catalytic labels for was proposed. This DNA sensor was fabricated using a “sandwich” detection strategy, involving two kinds of capture probes DNA immobilized on glassy carbon electrode (GCE), and hybridization with target DNA sequences, which further hybridized with the reporter DNA loaded on the AuNPs. The AuNP contained two kinds of DNA sequences, one was complementary to the target DNA, while the other was noncomplementary to the target. The noncomplementary sequences were linked with horseradish peroxidase (HRP) and alkaline phosphatase (ALP), respectively. Enhanced detection sensitivity was obtained where the AuNPs carriers increased the amount of enzyme molecules per hybridization. Electrochemical signals were generated from the enzymatic products produced from the substrates catalyzed by HRP and ALP. Under optimal conditions, a 33-mer sequence could be quantified over the ranges from 1.5×10⁻¹³ to 5.0×10⁻¹²M with a detection limit of 1.0×10⁻¹³M using HRP–AuNP as labels, and a 33-mer sequence could be quantified over the ranges from 4.5×10⁻¹¹M to 1.0×10⁻⁹M with a detection limit of 1.2×10⁻¹¹M using ALP–AuNP as labels.

Keywords: Electrochemical biosensor; Signal amplification; Enzyme; Au nanoparticles

Gallium(III) selective sensors based on 2-amino-3-(α-N-phenylmethyl-2′-amino-1′,4′-naphthoquinonyl)-1,4 naphthoquinones in poly (vinyl chloride) by Vinod K. Gupta; A.J. Hamdan; Manoj K. Pal (pp. 139-144).

Synthesis and application of 2-amino-3-(α-N-phenylmethyl-2′-amino-1′,4′-naphthoquinonyl)-1,4 naphthoquinone (S) as a neutral ionophore for the determination of gallium(III) in PVC-based membrane sensors has been described. The sensor based on membrane composition (w/w, mg%); 5.0 (S):30.0 (PVC):5.0 (KTpClPB):60.0 ( o-NPOE) is the best and showed a working range of 2.3×10⁻⁷ to 1.0×10⁻²M with detection limit of 1.2×10⁻⁷M. It can tolerate non-aqueous media up to 15% with a slope of 19.7mVdecade⁻¹ of activity. The sensor has been used to assess the Ga(III) concentration in different natural samples (peach and tomato leaves, coal-fly-ash and river sediments). It can be used for 2.5 months without any distortion in results, after which, leaching of ionophore was observed from the membrane phase. The proposed sensor has shown a good dynamic response time of 11s.

Keywords: Gallium(III); Poly (vinyl chloride); Ion-selective electrode; 2-Amino-3-(α-N-phenylmethyl-2′-amino-1′,4′-naphthoquinonyl)-1,4 naphthoquinone (; S; )

Electrochemical sensor for parabens based on molecular imprinting polymers with dual-templates by Yang Wang; Yuhua Cao; Cheng Fang; Qianqian Gong (pp. 145-150).

A selective, sensitive, rapid and reliable method based on molecularly imprinted polymers (MIPs) with dual templates to determine total content of parabens in cosmetics was developed. With methylparaben (MP) and propylparaben (PP) as dual-templates, methacrylic acid (MAA) as a functional monomer and tripropylene glycol diacrylate (TPGDA) as a cross-linker, MIPs film on a glassy carbon electrode was constructed as paraben sensor. At oxidation potential of 0.94V ( vs. SCE), the peak currents on the MIPs sensor were proportional to the concentration of parabens with square wave voltammetry. As the ratio of MP to PP in the MIPs was 1:1.25, the regression equations for four parabens were almost the same. The linear range was 20–100μM for MP and EP, 5–100μM for PP, and 5–80μM for BP, with detection limit of 0.4μM for MP and EP, 0.2μM for the others. The total content of parabens could be calculated according to the average of these four regress equations. At least 10 times of structural analogs, such as p-hydroxybenzoic acid, p-aminobenzoic acid and phenol would not interfere with the determination of parabens. Nonanalogous coexistences such as vitamin C had no response on the sensor at all. Rapid response of the MIPs sensor was obtained within 1min. MIPs sensor had been used to determine total content of parabens in cosmetic samples with recoveries between 98.7% and 101.8%. It reveals that the MIPs sensor with multi-templates has a potential to determine the total content of a group of homologous compounds.

Keywords: Dual-templates; Molecularly imprinted polymers; Parabens; Square wave voltammetry

Characterization of taste-active fractions in red wine combining HPLC fractionation, sensory analysis and ultra performance liquid chromatography coupled with mass spectrometry detection by María-Pilar Sáenz-Navajas; Vicente Ferreira; Marta Dizy; Purificación Fernández-Zurbano (pp. 151-159).

Five Tempranillo wines exhibiting marked differences in taste and/or astringency were selected for the study. In each wine the non-volatile extract was obtained by freeze-drying and further liquid extraction in order to eliminate remaining volatile compounds. This extract was fractionated by semipreparative C18-reverse phase-high performance liquid chromatography (C18-RP-HPLC) into nine fractions which were freeze-dried, reconstituted with water and sensory assessed for taste attributes and astringency by a specifically trained sensory panel. Results have shown that wine bitterness and astringency cannot be easily related to the bitter and astringent character of the HPLC fractions, what can be due to the existence of perceptual and physicochemical interactions. While the bitter character of the bitterest fractions may be attributed to some flavonols (myricetin, quercetin and their glycosides) the development of a sensitive UPLC–MS method to quantify astringent compounds present in wines has made it possible to demonstrate that proanthocyanidins monomers, dimers, trimers and tetramers, both galloylated or non-galloylated are not relevant compounds for the perceived astringency of the fractions, while cis-aconitic acid, and secondarily vainillic, and syringic acids and ethyl syringate, are the most important molecules driving astringency in two of the fractions (F5 and F6). The identity of the chemicals responsible for the astringency of the third fraction could be assigned to some proanthocyanidins (higher than the tetramer) capable to precipitate with ovalbumin.

Keywords: Sensory analysis; Taste; Astringency; Bitterness; Flavanols; Flavonols; Aconitic acid

A label-free differential proteomic analysis of mouse bronchoalveolar lavage fluid exposed to ultrafine carbon black by Kuo-Hsun Chiu; Wen-Lian William Lee; Chih-Ching Chang; San-Cher Chen; Yu-Chen Chang; Mei-Ning Ho; Jing-Fang Hsu; Pao-Chi Liao (pp. 160-166).

Ultrafine carbon black (ufCB) is a potential hazard to the lung. It causes changes in protein expression and it increases alveolar–capillary permeability in the lung. Label-free quantitative proteomic methods allow a sensitive and accurate analytical method for identifying and quantifying proteins in a protein mixture without chemically modifying the proteins. We used a label-free quantitative proteomic approach that combined and aligned LC–MS and LC–MS/MS spectra to analyze mouse bronchoalveolar lavage fluid (BALF) protein changes associated with exposure to ufCB. We developed a simple normalization method for quantification without spiking the internal standard. The intensities of unchanged peptides were used as normalization factors based on a statistical method to avoid the influence of peptides changed because of ufCB. LC–MS/MS spectra and then database searching were used to identify proteins. The relative abundances of the aligned peptides of identified proteins were determined using LC–MS spectra. We identified 132 proteins, of which 77 are reported for the first time. In addition, the expression of 15 inflammatory proteins and surfactant-associated proteins was regulated (i.e., 7 upregulated and 8 downregulated) compared with the controls. Several proteins not previously reported provide complementary information on the proteins present in mouse BALF, and they are potential biomarkers for the understanding of mechanisms involved in ufCB-induced lung disorders hypothesize that using the label-free quantitative proteomic approach introduced here is well suited for more rigorous, large-scale quantitative analysis of biological samples. We hypothesize that this label-free quantitative proteomic approach will be suited for a large-scale quantitative analysis of biological samples.

Keywords: Abbreviations; BALF; bronchoalveolar lavage fluid; CB; carbon black; ufCB; ultrafine carbon black; DeltaCn; difference in correlation score; Xcorr; cross-correlation; LA; large surfactant aggregates; SA; small surfactant aggregates; SP-D; surfactant-associated protein D; TNF-α; tumor necrosis factor-alphaBronchoalveolar lavage fluid (BALF); Label-free proteomics; Ultrafine carbon black (ufCB); Nanoparticle

NMR spectroscopy evaluation of direct relationship between soils and molecular composition of red wines from Aglianico grapes by Pierluigi Mazzei; Nicola Francesca; Giancarlo Moschetti; Alessandro Piccolo (pp. 167-172).

¹H NMR spectroscopy was employed to investigate the molecular quality of Aglianico red wines from the Campania region of Italy. The wines were obtained from three different Aglianico vineyards characterized by different microclimatic and pedological properties. In order to reach an objective evaluation of “terroir” influence on wine quality, grapes were subjected to the same winemaking procedures. The careful subtraction of water and ethanol signals from NMR spectra allowed to statistically recognize the metabolites to be employed in multivariate statistical methods: Principal Component Analysis (PCA), Discriminant Analysis (DA) and Hierarchical Clustering Analysis (HCA). The three wines were differentiated from each other by six metabolites: α-hydroxyisobutyrate, lactic acid, succinic acid, glycerol, α-fructose and β-d-glucuronic acid. All multivariate analyses confirmed that the differentiation among the wines were related to micro-climate, and carbonate, clay, and organic matter content of soils. Additionally, the wine discrimination ability of NMR spectroscopy combined with chemometric methods, was proved when commercial Aglianico wines, deriving from different soils, were shown to be statistically different from the studied wines. Our findings indicate that multivariate statistical elaboration of NMR spectra of wines is a fast and accurate method to evaluate the molecular quality of wines, underlining the objective relation with terroir.

Keywords: Nuclear Magnetic Resonance; Aglianico red wines; Multivariate statistical analysis; Terroir

Rapid detection of nivalenol and deoxynivalenol in wheat using surface plasmon resonance immunoassay by Tomoyuki Kadota; Yoko Takezawa; Satoshi Hirano; Osamu Tajima; Chris M. Maragos; Takashi Nakajima; Toshitsugu Tanaka; Yoichi Kamata; Yoshiko Sugita-Konishi (pp. 173-178).

A surface plasmon resonance (SPR) immunoassay using a monoclonal antibody was developed to measure nivalenol (NIV) and deoxynivalenol (DON) contamination in wheat. A highly sensitive and stable DON-immobilized sensor chip was prepared, and an SPR detection procedure was developed. The competitive inhibition assay used a monoclonal antibody that cross-reacts with NIV and DON. The half maximal inhibitory concentration (IC₅₀) values of the SPR assay were 28.8 and 14.9ngmL⁻¹ for NIV and DON, respectively. The combined responses of NIV and DON in wheat were obtained using a simultaneous detection assay in a one-step cleanup procedure. NIV and DON were separated using a commercial DON-specific immunoaffinity column (IAC) and their responses were obtained using an independent detection assay. Spiked tests using these toxins revealed that recoveries were in the range 91.5–107% with good relative standard deviations (RSDs) (0.40–4.1%) and that detection limits were 0.1 and 0.05mgkg⁻¹ for NIV and DON, respectively. The independent detection using IAC showed detection limits of 0.2 and 0.1mgkg⁻¹ for NIV and DON, respectively. SPR analysis results were correlated with those obtained using a conventional LC/MS/MS method for wheat co-contaminated with NIV and DON. These results suggested that the developed SPR assay is a practical method to rapidly screen the NIV and DON co-contamination of wheat and one of a very few immunoassays to detect NIV directly.

Keywords: Mycotoxin; Surface plasmon resonance; Immunoassay

Optical DNA detection based on gold nanorods aggregation by Zhanfang Ma; Le Tian; Tingting Wang; Chungang Wang (pp. 179-184).

Sequence-specific DNA detection is important in various biomedical applications such as gene expression profiling, disease diagnosis and treatment, drug discovery and forensic analysis. Herein, the localized surface plasmon resonance properties of unmodified gold nanorods (GNRs) in 1mM cetyltrimethyl-ammonium bromide solution were used for sensing DNA sequences, with good simplicity and sensitivity. The intensity of typical plasmon resonance absorption bands of the GNRs decreased with increasing cDNA concentration. The detection of a 30-mer single-stranded oligonucleotide as a model reached a detection limit of about 0.1pM. This study will be significant for as-prepared GNRs for future application in biological systems.

Keywords: Gold nanorods; Localized surface plasmon resonance; DNA detection; Optical sensor

Determination of inorganic arsenic species in natural waters—Benefits of separation and preconcentration on ion exchange and hybrid resins by Nureddin Ben Issa; Vladana N. Rajaković-Ognjanović; Branislava M. Jovanović; Ljubinka V. Rajaković (pp. 185-193).

A simple method for the separation and determination of inorganic arsenic (iAs) species in natural and drinking water was developed. Procedures for sample preparation, separation of As(III) and As(V) species and preconcentration of the total iAs on fixed bed columns were defined. Two resins, a strong base anion exchange (SBAE) resin and a hybrid (HY) resin were utilized. The inductively-coupled plasma-mass spectrometry method was applied as the analytical method for the determination of the arsenic concentration in water. The governing factors for the ion exchange/sorption of arsenic on resins in a batch and a fixed bed flow system were analyzed and compared. Acidity of the water, which plays an important role in the control of the ionic or molecular forms of arsenic species, was beneficial for the separation; by adjusting the pH values to less than 8.00, the SBAE resin separated As(V) from As(III) in water by retaining As(V) and allowing As(III) to pass through. The sorption activity of the hydrated iron oxide particles integrated into the HY resin was beneficial for bonding of all iAs species over a wide range of pH values from 5.00 to 11.00. The resin capacities were calculated according to the breakthrough points in a fixed bed flow system. At pH 7.50, the SBAE resin bound more than 370μgg⁻¹ of As(V) while the HY resin bound more than 4150μgg⁻¹ of As(III) and more than 3500μgg⁻¹ of As(V). The high capacities and selectivity of the resins were considered as advantageous for the development and application of two procedures, one for the separation and determination of As(III) (with SBAE) and the other for the preconcentration and determination of the total arsenic (with HY resin). Methods were established through basic analytical procedures (with external standards, certified reference materials and the standard addition method) and by the parallel analysis of some samples using the atomic absorption spectrometry-hydride generation technique. The analytical properties of both procedures were similar: the limit of detection was 0.24μgL⁻¹, the limit of quantification was 0.80μgL⁻¹ and the relative standard deviations for samples with a content of arsenic from 10.00 to 300.0μgL⁻¹ ranged from 1.1 to 5.8%. The interference effects of anions commonly found in water and some organic species which can be present in water were found to be negligible. Verification with certified reference materials proved that the experimental concentrations found for model solutions and real samples were in agreement with the certified values.

Keywords: Arsenic; Speciation; Separation; Preconcentration; Ion exchange; Hybrid resin

Novel, selective sample stacking microemulsion electrokinetic capillary chromatography induced by reverse migrating pseudostationary phase for the determination of the new ultra-short acting hypnotic “HIE-124” in mice serum by Mohamed Hefnawy; Mohammed Al-Omar; Saeed Julkhuf; Sabry Attia; Ehab Abourashed; Hussein El-Subbagh (pp. 194-199).

Microemulsion electrokinetic capillary chromatography (MEEKC) with sample stacking induced by reverse migrating pseudostationary phase (SRMP) technique in a suppressed electro-osmotic flow (EOF) strategy was investigated for analysing the new ultra-short hypnotic HIE-124 in mice serum. The proposed method utilized fused-silica capillary with a total length of 50cm (effective length 40cm), applied voltages for stacking and separation were 5.0kV for 4.30min and subsequently 25kV, respectively, with a sample injection of 0.5psi for 90s. All the runs were carried out at 25°C and detected at 213nm. The optimum microemulsion background electrolyte (BGE) solution consisted of 0.8% (v/v) ethyl acetate, 6.6% (v/v) butan-2-ol, 1.0% (v/v) acetonitrile, 2.0% (w/v) sodium dodecyl sulfate (SDS), and 89.6mL with 25mM phosphate buffer pH 8. When this preconcentration technique was used, the sample stacking and the separation processes took place successively with changing the voltage with an intermediate polarity switching step. The proposed method was validated carefully with respect to high specificity of the method, good linearity ( r=0.9994), fair wide linear concentration range (66–1500ngmL⁻¹), limit of detection and quantitation were 21.6 and 65.5ngmL⁻¹, respectively. The mean relative standard deviation (RSD) of the results of intra- and inter-day precision and accuracy were less than 6.0%, and overall recovery higher than 95% of HIE-124 in mice serum. The developed method could be used for the trace analyses of HIE-124 in serum and was finally used for the pharmacokinetic study investigation of HIE-124 in mice serum.

Keywords: HIE-124; Microemulsion electrokinetic capillary electrophoresis; Reverse migrating pseudostationary phase; Pharmacokinetics; Serum

Development of a fast capillary electrophoresis method to determine inorganic cations in biodiesel samples by Marcel Piovezan; Ana Carolina O. Costa; Alessandra Vincenzi Jager; Marcone Augusto Leal de Oliveira; Gustavo Amadeu Micke (pp. 200-205).

The aim of this study was to develop a fast capillary electrophoresis method for the determination of inorganic cations (Na⁺, K⁺, Ca²⁺, Mg²⁺) in biodiesel samples, using barium (Ba²⁺) as the internal standard. The running electrolyte was optimized through effective mobility curves in order to select the co-ion and Peakmaster software was used to determine electromigration dispersion and buffer capacity. The optimum background electrolyte was composed of 10mmolL⁻¹ imidazole and 40mmolL⁻¹ of acetic acid. Separation was conducted in a fused-silica capillary (32cm total length and 23.5cm effective length, 50μm I.D.), with indirect UV detection at 214nm. The migration time was only 36s. In order to obtain the optimized conditions for extraction, a fractional factorial experimental design was used. The variables investigated were biodiesel mass, pH, extractant volume, agitation and sonication time. The optimum conditions were: biodiesel mass of 200mg, extractant volume of 200μL and agitation of 20min. The method is characterized by good linearity in the concentration range of 0.5–20mgkg⁻¹ ( r>0.999), limit of detection was equal to 0.3mgkg⁻¹, inter-day precision was equal to 1.88% and recovery in the range of 88.0–120%. The developed method was successfully applied to the determination of cations in biodiesel samples.

Keywords: Capillary electrophoresis; Biodiesel; Inorganic cations; Fractional factorial design

Determination of melamine and related triazine by-products ammeline, ammelide, and cyanuric acid by micellar electrokinetic chromatography by Yi-Fen Hsu; Kuan-Ting Chen; Yu-Wei Liu; Shih-Huan Hsieh; Hsi-Ya Huang (pp. 206-211).

In this study, micellar electrokinetic chromatographic (MEKC) methods were developed for the detection of traces of melamine and its related by-products (ammeline, ammelide, and cyanuric acid). Two on-line sample concentration steps namely reversed electrode polarity stacking mode (REPSM) and cation-selective injection (CSI) were used for improving the detection sensitivity. For REPSM, a borate–NaOH buffer (pH 10, 35mM) composed of 60mM SDS and 10% (v/v) methanol, was used as carrier electrolyte, and samples were prepared in an aqueous solution of 10mM NaOH. In CSI, a phosphate buffer (pH 2, 50mM) containing 41mM SDS was used as the carrier electrolyte, and samples were prepared with an aqueous solution of 10mM NaOH and a phosphate buffer (pH 2.0, 25mM) in a volume ratio of 1:9. The results indicated that REPSM enhanced all analyte signals except for melamine, which could be concentrated only by the CSI. The detection limit was reduced from 1.7mgL⁻¹ to 2.8μgL⁻¹ for melamine by the optimal CSI step, and from 0.23–1.2mgL⁻¹ to 2.4–5.0μgL⁻¹ for the other three analytes by the optimal REPSM step. Tableware made of melamine and samples of flour were used as test samples, and the results indicated that the proposed MEKC methods can successfully determine contaminations from melamine. The study also indicated that when the plastic made of melamine was exposed only once to an acidic solution (acetic or phosphoric acid) at 80°C for 30min, melamine continuously leached out from the test sample even without any further treatment with an acidic solution.

Keywords: Melamine; Melamine derivatives; Melamine plastic materials; Food; Micellar electrokinetic chromatography

Erratum to “Combination of an e-nose, an e-tongue and an e-eye for the characterisation of olive oils with different degree of bitterness” [Anal. Chim. Acta 663 (2010) 91–97] by C. Apetrei; I.M. Apetrei; S. Villanueva; J.A. de Saja; F. Gutierrez-Rosales; M.L. Rodriguez-Mendez (pp. 212-212).

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Analytica Chimica Acta (v.673, #2)