Check out our New Publishers' Select for Free Articles

Analytica Chimica Acta (v.617, #1-2)

Editorial Board (pp. iii).

Contents (pp. vii-ix).

Preface by Jana Hajslova; Michel W.F. Nielen (pp. 1-2).

Coacervative extraction of Ochratoxin A in wines prior to liquid chromatography/fluorescence determination by Sergio García-Fonseca; Ana Ballesteros-Gómez; Soledad Rubio; Dolores Pérez-Bendito (pp. 3-10).

Coacervates made up of reverse micelles of decanoic acid were assessed as a new strategy for the simplification of wine sample treatment in the determination of Ochratoxin A (OTA). Simultaneous extraction/concentration of this contaminant was based on both hydrophobic and hydrogen bond OTA:coacervate interactions. Parameters affecting extraction efficiency and concentration factors were studied. Concentrations of decanoic acid and tetrahydrofuran (THF) were the most influential parameters, being 0.5% of acid and 5% of THF the selected ones. The procedure was very robust, so that the extractions were not influenced by the pH and the nature or concentration of matrix components. OTA recoveries from different types of wines (white, rosé and red) ranged between 85 and 100% and the actual concentration factors varied from 105 to 125 for sample volumes of 15mL. The detection limits for OTA, after liquid chromatography/fluorimetry (LC/FL) analysis of the coacervate (20μL), were 4.5ngL⁻¹ in white and rosé wines and 15ngL⁻¹ in red wines, values which were far below the threshold limit established for OTA by EU directives (2.0μgL⁻¹). No clean-up of the extracts was required for any of the samples analysed. The overall sample treatment took about 15–20min and several samples could be simultaneously treated using conventional lab equipment. The precision of the method, expressed as relative standard deviation, was about 5%. The approach developed was successfully applied to the determination of OTA in different wine samples from the South of Spain. The concentrations found ranged between 0.015 and 0.091μgL⁻¹.

Keywords: Ochratoxin A; Wine; Coacervate; Reverse micelles; Mycotoxins

Characterization of Polish rape and honeydew honey according to their mineral contents using ICP-MS and F-AAS/AES by Maria Madejczyk; Danuta Baralkiewicz (pp. 11-17).

In this work twelve elements (Al, B, Ca, Cr, Cu, Fe, K, Mg, Mn, Na, Ni and Zn) were determined in 30 honey samples from various locations within Poland and in two different types of honey- rape and honeydew. Trace elements (Al, B, Cr, Mn and Ni) were determined by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), however, major elements (Ca, K, Mg, Na) and Cu, Fe, Zn were determined by Flame Atomic Absorption Spectrometry (F-AAS).Cluster analysis of honey data revealed that the origin of honey samples correlated with their chemical composition. It was shown that rape honey includes lower amounts of manganese than honeydew honeys. Also honeydew honey includes much higher concentrations of Al, Cu, K, Fe and Ni in comparison with rape honey. Moreover honeydew honey was found to have a higher mineral content, which reflects sources from which the honey is composed. Trace element analysis showed that the differences in the values found in honey samples could be used as evidence of the quality of honey samples.

Keywords: Polish honey; Trace elements; Mineral content; Inductively Coupled Plasma-Mass Spectrometry; Flame Atomic Absorption Spectrometry, Flame Atomic Emission Spectrometry

Carbonyl value in monitoring of the quality of used frying oils by Reza Farhoosh; Seyed Mohammad Reza Moosavi (pp. 18-21).

In this study, a set of frying oil samples of different compositional properties but passed qualitative and quantitative standards, which were of various vegetable oil sources (individually or as blends), were obtained from seven of big oil factories in Iran. Before starting the frying process, all the frying oils had carbonyl values (CV) higher than 2μmolg⁻¹. The CV of most frying oils linearly increased until the end of the frying process, whereas for some of them, the CV increased and reached a maximum and then decreased to some extent. However, in a set of frying oil samples on average, the CV linearly increased as the frying time increased. There was a linear relationship between the CV and total polar compounds (TPC) throughout the frying process with a high determination coefficient ( R²=0.9747). The values found for carbonyl compounds of the frying oils during frying process ranged from 7.76±0.00 to 123.45±3.70μmolg⁻¹. Assuming that the limit of acceptance for TPC is 24%, this was roughly corresponded to 43.50μmolg⁻¹ for CV.

Keywords: Carbonyl value; Peroxide value; Total polar compounds; Used frying oil

Determination of quercetin and its glucosides in onion by electrochemical methods by D. Zielińska; L. Nagels; M.K. Piskuła (pp. 22-31).

Quercetin (Q), quercetin-3,4′-di O-β-glucoside (Q3,4′G), quercetin-3- O-β-glucoside (Q3G) and quercetin-4′- O-β-glucoside (Q4′G) were determined in onion bulbs ( Allium cepa) by HPLC with amperometric detection after analysis of the hydrodynamic voltammograms of flavonoid standards within the potential range of 50–1000mV and by cyclic voltammetry (CV) method. The hydrodynamic voltammetric profiles of flavonoids showed that the peak current of Q, Q3G, Q4′G and Q3,4′G increased rapidly when the applied potential exceeded +450mV ( vs. SCE). High sensitivity and low background current were observed at the applied potential of +950mV ( vs. SCE). The lower limits of detection (LOD) were determined at signal-to-noise ratio of 3 and showed the following values: 8.05×10⁻⁸M (Q), 1.08×10⁻⁷M (Q3G), 1.22×10⁻⁷M (Q4′G) and 2.6×10⁻⁷M (Q3,4′G). The data provided by HPLC-UV-MS confirmed the presence of Q, Q3G, Q4′G and Q3,4′G in 80% methanol extracts of lyophilised onion bulbs. The CV method was applied for the qualitative assessment of onion flavonoids followed by the determination of anodic peak potential ( E_a) of the standards. The qualitative analysis of onion flavonoids was based on the anodic peak current ( I_a) of the extracts after external standards addition. The recorded cyclic voltammograms of the above flavonoid standards showed that all four compounds had well-defined oxidation waves with peak potentials of 310, 390, 482 and 800mV ( vs. Ag/AgCl) for Q, Q3G, Q4′G and Q3,4′G in 50mM acetate–acetic buffer (pH 5.5) in 80% methanol, respectively. The study proved applicability of the CV method for identifying Q, Q3G, Q4′G and Q3,4′G in onion.

Keywords: Quercetin; Quercetin glucosides; Liquid chromatography; Amperometric detection; Cyclic voltammetry

Natural occurrence of ochratoxin A in dried figs by Funda Karbancıoğlu-Güler; Dilek Heperkan (pp. 32-36).

Ochratoxin A (OTA) contamination in dried figs was investigated using high performance liquid chromatography (HPLC) with fluorescence detection after extraction with methanol and orthophosphoric acid and clean up by an immunoaffinity column. The limit of detection for OTA was 0.12μgkg⁻¹. One hundred and fifteen samples were taken during the drying stage from 7 different districts in the Aegean Region in 2003 and 2004. Fifty-five (47.2%) of the 115 samples were found to contain detectable levels of ochratoxin A, ranging from 0.12 to 15.31μgkg⁻¹. However, the OTA level for a majority of the samples was low, with only 4 samples containing OTA exceeding 1μgkg⁻¹. The calculated overall median for the OTA level was below the limit of detection and the overall mean was estimated as 0.52μgkg⁻¹. Frequency of ochratoxin A contamination in dried figs harvested in 2003 and 2004 are 47 and 50%, respectively. Highest contamination ratio was determined in dried figs from Erbeyli (60%), followed by Selcuk (56%), and Ortaklar (50%).

Keywords: Ochratoxin A; Dried figs; High performance liquid chromatography; Mycotoxin

Development of a solid-phase microextraction gas chromatography with microelectron-capture detection method for a multiresidue analysis of pesticides in bovine milk by Maria Fernandez-Alvarez; Maria Llompart; J. Pablo Lamas; Marta Lores; Carmen Garcia-Jares; Rafael Cela; Thierry Dagnac (pp. 37-50).

A simple and rapid method based on solid-phase microextraction (SPME) technique followed by gas chromatography with microelectron-capture detection (GC-μECD) was developed for the simultaneous determination of more than 30 pesticides (pyrethroids and organochlorinated among others) in milk. To our knowledge, this is the first application of SPME for the determination of pyrethroid pesticides in milk. Negative matrix effects due to the complexity and lipophility of the studied matrix were reduced by diluting the sample with distilled water. A 2^5–1 fractional factorial design was performed to assess the influence of several factors (type of fiber coating, sampling mode, stirring, extraction temperature, and addition of sodium chloride) on the SPME procedure and to determine the optimal extraction conditions. After optimization of all the significant variables and interactions, the recommended procedure was established as follows: DSPME (using a polydimethylsiloxane (PDMS)/divinylbenzene (DVB) coating) of 1mL of milk sample diluted with Milli-Q water (1:10 dilution ratio), at 100°C, under stirring for 30min. The proposed method showed good linearity and high sensitivity, with limits of detection (LOD) at the sub-ngmL⁻¹ level. Within a day and among days precisions were also evaluated (R.S.D.<15%). One of the most important attainments of this work was the use of external calibration with milk-matched standards to quantify the levels of the target analytes. The method was tested with liquid and powdered milk samples with different fat contents covering the whole commercial range. The efficiency of the extraction process was studied at several analyte concentration levels obtaining high recoveries (>80% in most cases) for different types of full-fat milks. The optimized procedure was validated with powdered milk certified reference material, which was quantified using external calibration and standard addition protocols. Finally, the DSPME-GC-μECD methodology was applied to the analysis of milk samples collected in farms of dairy cattle from NW Spain.

Keywords: Solid-phase microextraction; Milk; Pyrethroids; Pesticides; Chlorinated pesticides; Factorial design

Decanoic acid reverse micelle-based coacervates for the microextraction of bisphenol A from canned vegetables and fruits by Amalia García-Prieto; Loreto Lunar; Soledad Rubio; Dolores Pérez-Bendito (pp. 51-58).

Decanoic acid reverse micelle-based coacervates were proposed for the extraction of bisphenol A (BPA) from canned vegetables and fruits prior to its determination by liquid chromatography and fluorescence detection at λ_exc=276nm and λ_em=306nm. The procedure involved the extraction of minute quantities (300–700mg) of homogenized food sample with an aqueous solution containing 10% of THF and 0.5% of decanoic acid, conditions under which the coacervate (around 340μL) formed in situ and instantaneously. The overall sample treatment, which included extraction and centrifugation, took about 25–30min, and several samples could be simultaneously treated using conventional lab equipment. No clean-up or solvent evaporation were required. Extraction efficiencies mainly depended on the decanoic acid and THF concentration in the aqueous solution and were not affected by the pH or the temperature in the ranges studied (1–4 and 20–60°C, respectively). Recoveries in samples ranged between about 81 and 96%. The precision of the method, expressed as relative standard deviation, was about 3% and the quantitation limit was around 9ngg⁻¹, which was far below the current specific migration limit (SML) set for BPA by the EU Commission (600ngg⁻¹). The method was successfully applied to the determination of BPA in the solid content of canned fruit salad, peaches in syrup, mango slices, red peppers, sweetcorn, green beans and peas. BPA was present at concentrations in the range from 7.8 to 24.4ngg⁻¹in canned fruits and from 55 to 103ngg⁻¹in canned vegetables.

Keywords: Bisphenol A; Canned vegetables and fruits; Coacervate; Reverse micelles; High performance liquid chromatography (HPLC); Fluorescence detection

Method for analysis dried vine fruits contaminated with ochratoxin A by Andrea C. Galvis-Sánchez; Antonio S. Barros; Ivonne Delgadillo (pp. 59-63).

The EU maximum limit of 10μgkg⁻¹ of OTA for dried vine fruits has been established since 2002 (European Commission, 2005). The presented work explore the capability of using Fourier infrared spectroscopy attenuated total reflection (FTIR-ATR) for the detection of ochratoxin A (OTA) in dried vine fruits in a range of concentration between 2 and 50μgkg⁻¹ OTA. The method developed included a sample pretreatment using a C18 cartridge which was efficient for the isolation of the mycotoxin. The PLS1 analysis of the spectrum of sultanas spiked with different OTA concentrations showed a good correlation between the spectral data and reference concentration for OTA ( R²=0.85).

Keywords: FTIR-ATR; Clean-up procedure; Sample preparation; Mycotoxin; Ochratoxin A

Development of a rapid and sensitive method for the simultaneous determination of 1,2-dibromoethane, 1,4-dichlorobenzene and naphthalene residues in honey using HS-SPME coupled with GC–MS by K. Tsimeli; T.M. Triantis; D. Dimotikali; A. Hiskia (pp. 64-71).

A new method for the simultaneous determination of 1,4-dichlorobenzene ( p-DCB), naphthalene and 1,2-dibromoethane (1,2-DBE) residues in honey has been developed. Analysis is carried out using gas chromatography–mass spectrometry (GC/MS) in selected ion monitoring mode (SIM), after extraction and preconcentration of target analytes by headspace solid-phase microextraction (HS-SPME), with a 100μm film thickness polydimethylsiloxane (PDMS) fiber.Several parameters affecting the extension of the adsorption process (i.e., addition of salt, extraction time, extraction temperature) were studied. The optimal conditions for the determination of these analytes were established.The proposed HS-SPME method showed good sensitivity, without carryover between the samples. Linearity was studied from 5 to 2500μgkg⁻¹ for p-DCB, 0.5 to 500μgkg⁻¹ for naphthalene and 5 to 500μgkg⁻¹ honey for 1,2-DBE with correlation coefficients ( r²) ranging from 0.9901 to 0.9999. Precision was assessed and both intra and inter-day R.S.D.s (%) were below 6.3%. The detection limits were found to be 1, 0.1 and 2μgkg⁻¹ honey for p-DCB, naphthalene and 1,2-DBE, respectively. The percentage recoveries that were evaluated with the proposed HS-SPME method and the standard addition calibration technique gave values among 72.8 and 104.3% for measurements in samples spiked with one target analyte or mixtures of the three.This method has been applied for the analysis of unknown honey samples. The results showed an excellent applicability of the proposed method for the determination of the target compounds in honey samples.

Keywords: Headspace solid-phase microextraction; 1,4-Dichlorobenzene; Naphthalene and 1,2-dibromoethane; Honey; Residues

Headspace solid-phase microextraction–gas chromatographic–time-of-flight mass spectrometric methodology for geographical origin verification of coffee by Sanja Risticevic; Eduardo Carasek; Janusz Pawliszyn (pp. 72-84).

Increasing consumer awareness of food safety issues requires the development of highly sophisticated techniques for the authentication of food commodities. The food products targeted for falsification are either products of high commercial value or those produced in large quantities. For this reason, the present investigation is directed towards the characterization of coffee samples according to the geographical origin. The conducted research involves the development of a rapid headspace solid-phase microextraction (HS-SPME)–gas chromatography–time-of-flight mass spectrometry (GC–TOFMS) method that is utilized for the verification of geographical origin traceability of coffee samples. As opposed to the utilization of traditional univariate optimization methods, the current study employs the application of multivariate experimental designs to the optimization of extraction-influencing parameters. Hence, the two-level full factorial first-order design aided in the identification of two influential variables: extraction time and sample temperature. The optimum set of conditions for the two variables was 12min and 55°C, respectively, as directed by utilization of Doehlert matrix and response surface methodology. The high-throughput automated SPME procedure was completed by implementing a single divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) 50/30μm metal fiber with excellent durability properties ensuring the completion of overall sequence of coffee samples. The utilization of high-speed TOFMS instrument ensured the completion of one GC–MS run of a complex coffee sample in 7.9min and the complete list of benefits provided by ChromaTOF software including fully automated background subtraction, baseline correction, peak find and mass spectral deconvolution algorithms was exploited during the data evaluation procedure. The combination of the retention index (RI) system using C₈–C₄₀ alkanes and the mass spectral library search was utilized for the confirmation of analyte identity in the reference authentic Brazilian coffee sample. The semi-quantitative results were then submitted to statistical evaluation, namely principal component analysis (PCA) for the establishment of geographical origin discriminations.

Keywords: Solid-phase microextraction; Gas chromatography–time-of-flight mass spectrometry; Multivariate experimental design; Coffee aroma; Principal component analysis; Geographical origin

Comparative LC–MS/MS profiling of free and protein-bound early and advanced glycation-induced lysine modifications in dairy products by Jörg Hegele; Timo Buetler; Thierry Delatour (pp. 85-96).

Free and protein-bound forms of early and advanced glycation-induced lysine (Lys) modifications were quantified in dairy products by LC–MS/MS using a stable isotope dilution assay. The glycation profiles for N^ɛ-fructoselysine (FL), N^ɛ-carboxymethyllysine (CML) and pyrraline (Pyr) were monitored in raw and processed cow milk to investigate whether free glycation products could serve as fast and simple markers to assess the extent of protein glycation in dairy products. In all milk samples, the fraction of free glycation adducts was predominantly composed of advanced modifications, e.g. 8.34±3.81nmol CML per μmol of free Lys (Lys_free) and 81.5±87.8nmol Pyrμmol⁻¹Lys_free⁻¹ vs. 3.72±1.29nmol FLμmol⁻¹Lys_free⁻¹. In contrast, the protein-bound early glycation product FL considerably outweighed the content of CML and Pyr in milk proteins of raw and processed cow milk, whereas severely heat treated milk products, e.g. condensed milk, contained a higher amount of protein-bound advanced glycation adducts. Typical values recorded for milk samples processed under mild conditions were 0.47±0.08nmol FLμmol⁻¹ of protein-bound Lys (Lys_p-b), 0.04±0.03nmolCML μmol⁻¹Lys_p-b⁻¹ and 0.06±0.02nmolPyrμmol⁻¹Lys_p-b⁻¹. It was particularly noticeable, however, that mild heat treatment of raw milk, i.e. pasteurization and UHT treatment, did not significantly increase the amount of both free and protein-bound Lys modifications. In conclusion, the profiles of free and protein-bound glycation-induced Lys modifications were found to be different and a screening of free glycation adducts does, therefore, not allow for a conclusion about the protein glycation status of dairy products.

Keywords: Glycation; Mass spectrometry; N; ^ɛ; -Carboxymethyllysine; N; ^ɛ; -Fructoselysine; Pyrraline; Dairy products

Rapid analysis of fungal cultures and dried figs for secondary metabolites by LC/TOF-MS by Hamide.Z. Şenyuva; John Gilbert; Şebnem Öztürkoğlu (pp. 97-106).

A liquid chromatography–time-of-flight mass spectrometry (LC/TOF-MS) method has been developed for profiling fungal metabolites. The performance of the procedure in terms of mass accuracy, selectivity (specificity) and repeatability was established by spiking aflatoxins, ochratoxins, trichothecenes and other metabolites into blank growth media. After extracting, and carrying out LC/TOF-MS analysis, the standards were correctly identified by searching a specially constructed database of 465 secondary metabolites. To demonstrate the viability of this approach 11 toxigenic and four non-toxigenic fungi from reference collections were grown on various media, for 7–14 days. The method was also applied to two toxigenic fungi, A. flavus (200–138) and A. parasiticus (2999–465) grown on gamma radiation sterilised dried figs, for 7–14 days. The fungal hyphae plus a portion of growth media or portions of dried figs were solvent extracted and analysed by LC/TOF-MS using a rapid resolution microbore LC column. Data processing based on cluster analysis, showed that electrospray ionization (ESI)–TOF-MS could be used to unequivocally identify metabolites in crude extracts. Using the elemental metabolite database, it was demonstrated that from culture collection isolates, anticipated metabolites. The speed and simplicity of the method has meant that levels of these metabolites could be monitored daily in sterilised figs. Over a 14-day period, levels of aflatoxins and kojic acid maximised at 5–6 days, whilst levels of 5-methoxysterigmatocystin remained relatively constant. In addition to the known metabolites expected to be produced by these fungi, roquefortine A, fumagillin, fumigaclavine B, malformins (peptides), aspergillic acid, nigragillin, terrein, terrestric acid and penicillic acid were also identified.

Keywords: Liquid chromatography–time-of-flight mass spectrometry; Aflatoxin B; ₁; Ochratoxin; Fungal cultures; Database

Effect of the use of recent commercial fungicides [under good and critical agricultural practices] on the aroma composition of Monastrell red wines by José Oliva; Amaya Zalacain; Paula Payá; María Rosario Salinas; Alberto Barba (pp. 107-118).

In the paper, the effect of several fungicide residues (famoxadone, fenhexamid, fluquinconazole, kresoxim-methyl, quinoxyfen and trifloxystrobin) has been studied in relation to the aroma composition of Monastrell red wines in terms of each compound concentration and OAV (Odour Activity Value) values. Two fungicide treatments were carried out with authorized formulates following the manufacturer doses. The first one was carried out under good agricultural practices (GAP), obeying the preharvest interval, and the second one under critical agricultural practices (CAP), applying at the day of harvesting. The wines obtained in the thirteen trials (one control, six with treated grapes obeying the preharvest interval and six treated at the day of harvesting or at most unfavourable conditions) were analysed by stir bar sorptive extraction and gas chromatography–mass spectrometry (SBSE–GC–MS). The method proposed showed good linearity over the concentration range tested, with correlation coefficients higher than 0.9 for all the analytes. The reproducibility and repeatability of the method was estimated between 1.0 and 18.52%. The detection and quantification limits of all analytes were lower than the concentration found in these Monastrell wines. The identified wine volatile compounds have been grouped according to: ethyl esters, acetates, C₆ compounds, terpenoids, acids and ethyl acetate, 3-methyl-1-butanol, 2-phenylethanol and benzaldehyde, as individual level. As results, it was observed that all fungicide treatments significantly affect the wine aroma composition. Each group of compounds has been associated to sensorial descriptor series (fatty, floral, fruity, herbaceous, solvent, rose and vinous), resulting that the best sensory valuated wines were the ones treated with fluquinconazole and fenhexamid under GAP.

Keywords: Critical agricultural practices; Fungicides; Good agricultural practices; Stir bar sorptive extraction; Wine aroma composition

Analysis of carbonyl compounds via headspace solid-phase microextraction with on-fiber derivatization and gas chromatographic–ion trap tandem mass spectrometric determination of their O-(2,3,4,5,6-pentafluorobenzyl)oxime derivatives by Hans-Georg Schmarr; Theodoros Potouridis; Sebastian Ganß; Wei Sang; Benedikt Köpp; Ursula Bokuz; Ulrich Fischer (pp. 119-131).

An improved method for the analysis of carbonyls is described utilizing a headspace solid-phase microextraction (HS-SPME) step and on-fiber derivatization with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) hydrochloride. Thermal desorption of the oxime derivatives formed on the fiber is followed by gas chromatographic separation coupled to an ion trap tandem mass spectrometer (GC–ITMS). Selecting specific fragment ions within the electron ionization (EI⁺) mass spectra of these oxime derivatives as precursor ions for MS–MS fragmentation provides a suitable method for the target analysis of individual carbonyl classes, such as alkanals, ( E)-2-alkenals, ( E, E)-2,4-alkadienals, and others. Retention indices on polar as well as on apolar stationary phases along with EI⁺ mass spectra patterns are presented for a large set of oxime derivatives, giving valuable information needed for unambiguous assignment of substances in complex sample matrices. The fast sample preparation and derivatization step via HS-SPME can be automated and is applicable to a variety of biological samples and foodstuffs, allowing rapid and sensitive screening analyses of important aldehydic biomarkers and aroma active compounds.

Keywords: Carbonyls; Aldehydes; O; -(2,3,4,5,6-Pentafluorobenzyl)hydroxylamine hydrochloride; Oximes; HS-SPME-GC-MS-MS; Ion trap mass spectrometry; Retention indices; Electron ionization mass spectra

A packaging contaminant: Isopropylthioxanthone (ITX) in dairy products by C. Benetti; R. Angeletti; G. Binato; A. Biancardi; G. Biancotto (pp. 132-138).

A fast, simple and very selective liquid chromatography–mass spectrometry (LC–MS) method for the detection of isopropylthioxanthone (ITX) in dairy products has been developed and validated. After addition of an ITX- d₃ as internal standard and a simple extraction from the sample with acetonitrile, the extract was centrifuged and directly injected into the LC–MS system. Chromatographic separation was achieved by means of a Gemini C18 column (100mm×2.0mm i.d. 5μm) using a gradient of aqueous 20mM ammonium formiate at pH 4.5 and methanol as the mobile phase, at a flow rate of 0.25mLmin⁻¹. The method was validated according to the guidelines laid down by the Commission Decision 2002/657/EC using the parent ion [M+H]⁺ ( m/ z 255) as quantification ion, and the fragment ion ( m/ z 213) obtained by in-source collision-induced dissociation (IS-CID) as confirmation ion. Absolute and relative recoveries rates were verified at 5, 10, 15μgkg⁻¹ in yoghurt samples and at 5μgkg⁻¹ in milk and pudding: mean absolute recoveries were 77% in yoghurt, 50% in pudding and 67% in milk; relative recoveries (after internal standard correction) were always >97% in each matrix. The detection limit (CCα) and the detection capability (CCβ) of method were 6.2 and 7.2μgkg⁻¹, respectively.

Keywords: Isopropylthioxanthone (ITX); Dairy products; Method validation; HPLC–MS

Fatty acid composition and volatile compounds of caviar from farmed white sturgeon ( Acipenser transmontanus) by Fabio Caprino; Vittorio Maria Moretti; Federica Bellagamba; Giovanni Mario Turchini; Maria Letizia Busetto; Ivan Giani; Maria Antonietta Paleari; Mario Pazzaglia (pp. 139-147).

The present study was conducted to characterize caviar obtained from farmed white sturgeons ( Acipenser transmontanus) subjected to different dietary treatments. Twenty caviar samples from fish fed two experimental diets containing different dietary lipid sources have been analysed for chemical composition, fatty acids and flavour volatile compounds. Fatty acid make up of caviar was only minimally influenced by dietary fatty acid composition. Irrespective of dietary treatments, palmitic acid (16:0) and oleic acid (OA, 18:1 n-9) were the most abundant fatty acid followed by docosahexaenoic acid (DHA, 22:6 n-3) and eicopentaenoic (EPA, 20:5 n-3).Thirty-three volatile compounds were isolated using simultaneous distillation–extraction (SDE) and identified by GC–MS. The largest group of volatiles were represented by aldehydes with 20 compounds, representing the 60% of the total volatiles. n-Alkanals, 2-alkenals and 2,4-alkadienals are largely the main responsible for a wide range of flavours in caviar from farmed white surgeon.

Keywords: Caviar; SDE; Volatiles; Fatty acids; Aroma

Stable carbon, nitrogen, and oxygen isotope analysis as a potential tool for verifying geographical origin of beef by Rumiko Nakashita; Yaeko Suzuki; Fumikazu Akamatsu; Yoshiko Iizumi; Takashi Korenaga; Yoshito Chikaraishi (pp. 148-152).

Stable isotope analysis of organic elements such as carbon and nitrogen has been employed as a powerful tool for provenance determination of food materials, because isotopic compositions of the materials reflect many factors in natural environment. In this study, we examined carbon, nitrogen, and oxygen isotope signatures of beef from Australia, Japan, and USA, in order to confirm the method as a potential tool for verifying geographical origin of beef commercially distributed in Japan. Defatted dry matter of beef from USA was characterized by higher carbon isotopic composition (−13.6‰ to −11.1‰) than that from Japan (−19.6‰ to −17.0‰) and Australia (−23.6‰ to −18.7‰). That from Australia was characterized by higher oxygen isotopic composition (+15.0‰ to +19.4‰) than that from Japan (+7.3‰ to +13.6‰) and USA (+9.5‰ to +11.7‰). The oxygen isotopic composition in Japanese beef showed a positive correlation with the isotopic composition of cattle drinking water, the difference in which is clearly latitude dependent. These results suggest that a comparison of carbon, nitrogen, and oxygen isotopic compositions is applicable as a potential tool to discriminate the provenance of beef not only between different countries (i.e. Australia, Japan, and USA) but also among different regions within Japan.

Keywords: Beef; Geographical origin; δ; ¹³; C; δ; ¹⁵; N; δ; ¹⁸; O

Structure–activity relationships for the fluorescence of ochratoxin A: Insight for detection of ochratoxin A metabolites by Christine Frenette; Robert J. Paugh; Mariana Tozlovanu; Maud Juzio; Annie Pfohl-Leszkowicz; Richard. A. Manderville (pp. 153-161).

Ochratoxin A (OTA) is a mycotoxin produced by Aspergillus and Penicillium that is widely found as a contaminant of food products. The toxin is a renal carcinogen in male rats, the cause of mycotoxicoses in pigs and has been associated with chronic human kidney diseases. Bioactivation has been implicated in OTA-mediated toxicity, although inconsistent results have been reported, due, in part, to the difficulty in detecting OTA metabolites in vivo. Liquid chromatography (LC) coupled with fluorescence detection (FLD) is the most widely used analytical detection method for OTA. Under acidic conditions the toxin generates blue fluorescence (465nm) that is due to an excited state intramolecular proton transfer (ESIPT) process that generates an emissive keto tautomer. Disruption of this ESIPT process quenches fluorescence intensity and causes a blue shift in emission maxima. The aim of the present study was to determine the impact of the C5-chlorine atom, the lactone moiety and the amide bond on OTA fluorescence and derive optical parameters for OTA metabolites that have been detected in vitro. Our results highlight the limitations of LC/FLD for OTA metabolites that do not undergo ESIPT. For emissive derivatives, our absorption and emission data improves the sensitivity of LC/FLD (3–4-fold increase in the limit of detection (LOD)) for OTA analogues bearing a C5–OH group, such as the hydroquinone (OTHQ) metabolite and the glutathione conjugate of OTA (OTA–GSH). This increased sensitivity may facilitate the detection of OTA metabolites bearing a C5–OH group in biological fluids and enhance our understanding of OTA-mediated toxicity.

Keywords: Ochratoxin A; Fluorescence; Limit of detection; Metabolite

The quality of our drinking water: Aluminium determination with an acoustic wave sensor by Marta I.S. Veríssimo; M. Teresa S.R. Gomes (pp. 162-166).

A new methodology based on an inexpensive aluminium acoustic wave sensor is presented. Although the aluminium sensor has already been reported, and the composition of the selective membrane is known, the low detection limits required for the analysis of drinking water, demanded the inclusion of a preconcentration stage, as well as an optimization of the sensor. The necessary coating amount was established, as well as the best preconcentration protocol, in terms of oxidation of organic matter and aluminium elution from the Chelex-100.The methodology developed with the acoustic wave sensor allowed aluminium quantitation above 0.07mgL⁻¹. Several water samples from Portugal were analysed using the acoustic wave sensor, as well as by UV–vis spectrophotometry.Results obtained with both methodologies were not statistically different ( α=0.05), both in terms of accuracy and precision. This new methodology proved to be adequate for aluminium quantitation in drinking water and showed to be faster and less reagent consuming than the UV spectrophotometric methodology.

Keywords: Bulk acoustic wave sensor; Aluminium; Drinking water

Feasibility of using a surface plasmon resonance-based biosensor to detect and quantify yessotoxin by Eva S. Fonfría; Natalia Vilariño; Mercedes R. Vieytes; Takeshi Yasumoto; Luis M. Botana (pp. 167-170).

Yessotoxin (YTX) is a disulfated polyether toxin produced by marine dinoflagellates. Although there is no clear evidence that YTX is toxic to humans, it is a major cause of false positives in DSP toxin detection by mouse bioassay. We developed a new detection and quantification method for yessotoxin using a BiaCore X Surface plasmon resonance (SPR)-based biosensor. The assay is based in the interaction of YTX with phosphodiesterase enzymes (PDE), one of its cellular targets. The injection of several YTX concentrations (3–12μM) over immobilized PDE I, showed a dose dependent binding signal, which K_obs (observed rate constant) allowed us to obtain a calibration curve with a linear fit. The detection of yessotoxin using SPR-based biosensor allows the quantification of the toxin with an automated and repetitive method at concentrations in the range of the 1mgkg⁻¹ European regulatory limit.

Keywords: Abbreviations; SPR; surface plasmon resonance; DSP; diarrhetic shellfish poisoning; YTX; yessotoxin; PDE; phosphodiesterase; DMSO; dimethyl sulfoxide; PBS; phosphate-buffered saline; HBS-EP; hepes buffered saline; NHS; N; -hydroxysuccimide; EDC; ethyl-; N; -(dimethylaminopropyl)carbodiimide; HPLC; high pressure liquid chromatography; LC–MS; liquid chromatography–mass spectrometrySurface plasmon resonance; Phycotoxin; Yessotoxin; DSP; Phosphodiesterase; Biosensor; Shellfish; Analytical method

Detecting spoiled fruit in the house of the future by Daniel L.A. Fernandes; João A.B.P. Oliveira; M. Teresa S.R. Gomes (pp. 171-176).

An electronic nose based on acoustic wave sensors has been developed to detect spoilt fruit. Different varieties of fruits, edible and rotten, were analysed. Starting from six sensors, the minimum number of sensors capable of discriminating between spoiled and unspoiled fruit was found. The discrimination capability of the sensor array was studied separately for each fruit variety, as well as for the whole set. Mathematical models were built to classify the fruits within a fruit variety, in an objective and clear way. The models were able to distinguish between edible and rotten fruits with 100% success for New Hall oranges, Golden apples, Kiwis and William pears, and with 97.2% of success for the Starking apples. Without forming fruit variety subsets, discrimination between edible and rotten fruit was achieved with 95% success.

Keywords: Electronic nose; Acoustic wave sensor; Fruit; Spoilage

Biosensor immunoassay for the screening of dioxin-like polychlorinated biphenyls in retail fish by Tomoaki Tsutsumi; Noriko Miyoshi; Kumiko Sasaki; Tamio Maitani (pp. 177-183).

Dioxin-like polychlorinated biphenyls (DL-PCBs) often make up the majority of the toxic equivalent (TEQ) contribution of dioxins found in fish samples. For the purpose of making risk assessments, it is therefore important to develop screening methods for determining TEQ concentrations of DL-PCBs in retail fish. We have developed a rapid biosensor immunoassay (BIA) for DL-PCBs that uses a surface plasmon resonance sensor (Biacore 3000). The BIA is highly specific for 2,3′,4,4′,5-pentachlorobiphenyl (PCB 118) that is generally the most abundant DL-PCB isomer found in fish. The fish extracts were first cleaned up on a multilayer silica gel column followed by an alumina column, then subjected to the assay. The quantitative limit of the assay was 1ng PCB 118 per gram of tested sample. Dilution and recovery tests using purified fish extracts suggested that the matrix effect was minimized in the assay by diluting the analyzed samples. The assay results for retail fish samples ( n=7) agreed well with those obtained by an enzyme-linked immunoassay (ELISA) using the same monoclonal antibody: ELISA has been already validated for determining DL-PCBs in fish samples, so BIA performs well in this analysis. Finally, BIA results for the TEQ concentrations of DL-PCBs in retail fish samples ( n=10) correlated well with those obtained by high-resolution gas chromatography coupled to high-resolution mass spectrometry ( r=0.89). Our method is therefore useful for screening retail fish to determine the TEQ concentrations of DL-PCBs.

Keywords: Dioxin-like PCBs; Dioxins; Biosensor immunoassay; Biacore; Fish; Screening

Analysis of thyreostatic drugs in thyroid samples by Ultra-Performance Liquid Chromatography tandem mass spectrometry detection by S. Abuín; F. Centrich; A. Rúbies; R. Companyó; M.D. Prat (pp. 184-191).

A method based on ultra-performance liquid chromatography–electrospray ionisation–tandem mass spectrometry for the determination of six thyreostatic drugs in thyroid tissue has been optimised and validated in accordance with the Decision 2002/657/EC. Samples are extracted with methanol and the extracts cleaned-up on silica cartridges. The recoveries range from 40% for 6-phenyl-2-thiouracil to 79% for 2-thiouracil. Quantification is carried out with blank tissue samples spiked with the analytes in the range 25–500μgkg⁻¹. 5,6-Dimethyl-2-thiouracil is used as internal standard. CCα and CCβ are in the ranges 4.3–16.1μgkg⁻¹ and 8.7–20.7μgkg⁻¹, respectively. Accuracy, expressed as percentage of error, is lower than 6% and relative standard deviation in reproducibility conditions falls between 5.6 and 10.3%. Nowadays, the proposed method is routinely implemented in the laboratory of the Agència de Salut Pública de Barcelona and allows processing of up to 20 samples per day.

Keywords: Thyreostatic drugs; Thyroid samples; Ultra-Performance Liquid Chromatography; Liquid chromatography tandem mass spectrometry detection

Determination of α-amylase inhibitor activity of phaseolamin from kidney bean ( Phaseolus vulgaris) in dietary supplements by HPAEC-PAD by Maurizio Mosca; Concetta Boniglia; Brunella Carratù; Stefania Giammarioli; Valentina Nera; Elisabetta Sanzini (pp. 192-195).

Some dietary supplements, so-called ‘starch-blockers’, used to control overweight, are based on the protein concentrate of the kidney bean, known to contain high levels of the α-amylase inhibitor phaseolamin, which may hinder the digestion of complex carbohydrates, thereby promoting or supporting weight loss.Currently, methods to determine the levels of α-amylase inhibitor are based on the measurement of α-amylase activity using colorimetric methods that cannot be applied to dietary supplements because they are complex mixtures of different ingredients that may interfere with the measurement. The aim of this study was to develop an alternative method to determine the level of phaseolamin in dietary supplements, using high-performance anion-exchange chromatography coupled with pulsed amperometric detection (HPAEC-PAD) to measure the amount of maltose resulting from the action of the enzyme porcine α-amylase on soluble starch in the presence and absence of the inhibitor.The assay described proved sensitive and accurate for use with both dietary supplements and raw materials.

Keywords: Phaseolamin; High-performance anion-exchange chromatography coupled with pulsed amperometric detection determination; Dietary supplements

On-line stacking techniques for the nonaqueous capillary electrophoretic determination of acrylamide in processed food by Filiz Tezcan; F. Bedia Erim (pp. 196-199).

In the present study, field amplified sample stacking (FASS) techniques in the nonaqueous capillary electrophoresis method (NACE) were introduced for the on-line concentration of the acrylamide to improve acrylamide detection at 210nm by diode-array detection. Acetonitrile (ACN) as a nonaqueous solvent permits acrylamide to be protonated through the change of its acid–base chemistry, allowing capillary electrophoretic separation of this compound. Choosing 30mmolL⁻¹ HClO₄, 20mmolL⁻¹ NaClO₄, 218mmolL⁻¹ CH₃COOH in ACN as the separation electrolyte and employing sample stacking methods, the LOD value of acrylamide was decreased to 2.6ngmL⁻¹ with electrokinetic injection and 4.4ngmL⁻¹ with hydrodynamic injection. Optimized stacking conditions were applied to the determination of acrylamide in several foodstuffs. The method is simple, rapid, inexpensive, and widely applicable for the determination of acrylamide in food samples.

Keywords: Acrylamide; Nonaqueous capillary electrophoresis; Sample stacking; Food

Quantification of appetite suppressing steroid glycosides from Hoodia gordonii in dried plant material, purified extracts and food products using HPLC-UV and HPLC–MS methods by Hans-Gerd Janssen; Chris Swindells; Philip Gunning; Weijun Wang; Christian Grün; Krishna Mahabir; Vinesh J. Maharaj; Peter J. Apps (pp. 200-207).

High-performance liquid chromatography (HPLC)-UV and HPLC–Mass Spectrometry (MS) methods were developed for the quantitative analysis of the family of Hoodia gordonii steroid glycosides with appetite suppressing properties in dried plant material, in purified and enriched extracts and in various prototype food-products fortified with H. gordonii extracts.For solid materials, e.g. dried plants or for non-fatty foods, extraction of the steroid glycosides is performed using methanol. For products where the steroid glycosides are present in an oil matrix, direct injection of the oil after dilution in tetrahydrofuran is applied. The HPLC separation is performed on an octyl-modified reversed-phase column in the gradient mode with UV detection at λ=220nm. Quantification is performed against an external calibration line prepared using either one of the pure steroid glycosides or geranyl-tiglate. Short- and long-term repeatabilities of the methods are better than 3 and 6%, respectively. Recoveries are better than 85%, even in the analysis of the least abundant steroid glycosides in a complex yoghurt drink. Linearity is better than 3–4 orders of magnitude and the detection limits are below approximately 2μgg⁻¹ for the individual steroid glycosides in dried plant material and food products. HPLC–MS is used to confirm that the steroid glycosides contain the characteristic steroid core, the carbohydrate chain and the tigloyl group.

Keywords: Hoodia; Hoodia gordonii; Steroid glycosides; Quantitative analysis; Foods; High-performance liquid chromatography-ultraviolet; High-performance liquid chromatography–mass spectrometry

United Nations Environment Programme Capacity Building Pilot Project—Training and interlaboratory study on persistent organic pollutant analysis under the Stockholm Convention by J. de Boer; H. Leslie; S.P.J. van Leeuwen; J.-W. Wegener; B. van Bavel; G. Lindström; N. Lahoutifard; H. Fiedler (pp. 208-215).

Within the framework of a United Nations Environment Programme (UNEP) Capacity Building Project for training of laboratory staff in developing countries on persistent organic pollutant (POP) analysis, an interlaboratory study was organised following an initial evaluation of the performance of laboratories (reality check) and a series of training sessions. The target compounds were polychlorinated biphenyls (PCB) and organochlorine pesticides (OCP). Seven laboratories from five countries (Ecuador, Uruguay, Kenya, Moldova, and Fiji) participated. Most of the laboratories had no experience in determining PCBs. Although chromatograms improved considerably after the training and installation of new gas chromatographic (GC) columns at participating laboratories, the level of performance in the interlaboratory study was essentially on par with the moderate performance level achieved by European POP laboratories in the 1980s. Only some individual results were within ±20% of the target values. The relative standard deviations (R.S.D.s) in POP concentrations determined by laboratories in a sediment sample were >200% in a number of cases. The results for a certified herring sample were better with at least some R.S.D. values below 50% and most below 100%. Clean up was as one of the main sources of error. After inspection it was ascertained that training of laboratory staff and investments in simple consumables such as glassware and GC columns would help to improve the quality of the analysis more than major investments in expensive instrumentation. Creating an effective network of POP laboratories at different continents together with a series of interlaboratory studies and workshops is suggested to improve the measurements of POPs in these countries.

Keywords: Stockholm Convention; Persistent organic pollutants; Interlaboratory study; Training

Optimization of solid phase extraction clean up and validation of quantitative determination of corticosteroids in urine by liquid chromatography–tandem mass spectrometry by Jens Hinge Andersen; Lene Gram Hansen; Mikael Pedersen (pp. 216-224).

A solid phase extraction (SPE) method for extraction and clean up of 9 synthetic corticosteroids was optimized for quantification by reversed-phase high-performance liquid chromatography/negative electrospray ionisation mass spectrometry. Clean up was accomplished using a mixed mode polymeric strong anion exchange SPE column. The final method was validated according to EU regulations for determination of residues of veterinarian drugs in products of animal origin.Initial results showed a large difference in ion suppression between samples of porcine and bovine urine. The aim of optimisation was to design a procedure that minimised this difference while using a single SPE procedure and a fast HPLC method that enabled sufficient separation of the epimers beta- and dexamethason.To include conjugated corticosteroids in the analysis, the sample was hydrolysed with Helix Pomatia β-glucuronidase/aryl sulfatase. For the final method, which included fluocinolone acetonid, triamcinolone acetonid, beclomethasone, flumethasone, dexamethasone, betamethasone, 6α-methylprednisolone, prednisone and prednisolone, a quantification based on spiked samples carried through the entire analytical procedure was used. For quantification of triamcinolone acetonid an internal standard (triamcinolon acetonid-D6) was used.Relative average recoveries from 96 to 103% were found, except for beclomethason (113%). Absolute average recoveries were 81–99%. Quantification limits (decision limits, CCα) were demonstrated to be not higher than 1μgL⁻¹ (3μgL⁻¹ for prednisone and prednisolone). The internal reproducibility, determined by triplicates from spiking at three different levels in six analytical series was 7–19% (at 2–4μgL⁻¹) except for prednisone and prednisolone (26–27% at 3–6μgL⁻¹).

Keywords: Corticosteroids; Liquid chromatography–tandem mass spectrometry; Validation; Urine; Ion-suppression

Determination of vitamin E and carotenoid pigments by high performance liquid chromatography in shell of Chionoecetes opilio by María Vilasoa-Martínez; Carina Calaza-Ramos; Julia López-Hernández; María Asunción Lage-Yusty; Perfecto Paseiro Losada; Ana Rodríguez-Bernaldo de Quirós (pp. 225-229).

This study reports the optimization of a method for the determination of vitamin E and carotenoids in shells of Chionoecetes opilio samples by online HPLC coupled with UV–vis and fluorescence detectors. The carotenoids were determined with diode-array detector ( λ 450nm) and vitamin E with fluorescence detection ( λ_ex 288, λ_em 331nm).Two extractions methods were compared, saponification followed by an extraction step and a simple extraction with acetone. The last one was selected because allows to determine all compounds.Linearity, precisions and recoveries achieved for all compounds were satisfactory.Mean concentrations (mg per 100g dry weight) were; 23.3 for vitamin E, 9.49 for astaxanthin and 0.2mg for β-carotene.

Keywords: Carotenoids; Vitamin E; Crab shell; High performance liquid chromatography

Fast screening and quantitation of microcystins in microalgae dietary supplement products and water by liquid chromatography coupled to time of flight mass spectrometry by Didier Ortelli; Patrick Edder; Emmanuelle Cognard; Philippe Jan (pp. 230-237).

Cyanobacteria, commonly called “blue-green algae”, may accumulate in surface water supplies as “blooms” and may concentrate on the surface as blue-green “scums”. Some species of cyanobacteria produce toxins and are of relevance to water supplies and to microalgae dietary supplements. To ensure the safety of drinking water and blue-green algae products, analyses are the only way to determine the presence or absence of toxins. This paper shows the use of ultra performance liquid chromatography (UPLC) coupled to orthogonal acceleration time of flight (TOF) mass spectrometry for the detection and quantitation of microcystins. The method presented is very sensitive, simple, fast, robust and did not require fastidious clean-up step. Limits of detection of 0.1μgL⁻¹ in water and 0.1–0.2μgg⁻¹ in microalgae samples were achieved. Method performances were satisfactory and appropriate for monitoring of water and dietary supplements. The method was applied in routine to samples taken from Swiss market or buy on internet website. Among 19 samples, six showed the presence of microcystins LR and LA at harmful levels.

Keywords: Microcystins; Cyanobacteria; Liquid chromatography; Ultra performance liquid chromatography; Time of flight; Mass spectrometry; Blue-green algae; Spirulina; Dietary food supplements

Bioassay directed identification of natural aryl hydrocarbon-receptor agonists in marmalade by Karin van Ede; An Li; Elsa Antunes-Fernandes; Patrick Mulder; Ad Peijnenburg; Ron Hoogenboom (pp. 238-245).

Citrus fruit and citrus fruit products, like grapefruit, lemon and marmalade were shown to contain aryl hydrocarbon receptor (AhR) agonists, as detected with the DR CALUX^® bioassay. This is of interest regarding the role of the Ah-receptor pathway in the adverse effects of dioxins, PCBs and other aromatic hydrocarbons. So far it is unclear which compounds in citrus fruit are responsible for the AhR-mediated activity and whether regular exposure to these compounds can cause effects comparable to, e.g. dioxins.The present study aimed at developing a method for identifying unknown Ah-receptor agonists in citrus products based on bioassay directed analysis, using marmalade as a first target. Following extraction with hexane and purification on an aluminium oxide-column, the extract was fractionated by HPLC using a C-18 semi-preparative column. Fractions were extracted, solvent-exchanged into dimethylsulfoxide and subsequently tested with DR CALUX^®. Extracts were shown to contain primarily coumarins, furocoumarins (FCs) and polymethoxyflavones (PMFs). Identification of fractions most active in the bioassay via LC/MS revealed that bergapten (an FC) is the most important Ah-receptor agonist in marmalade. The approach and method developed resulted in the successful identification of the bioactive component. However, potential pitfalls of the procedure will be discussed.

Keywords: Bioassay directed identification; Aryl hydrocarbon-receptor; Furocoumarin; Bergapten; DR CALUX; ^®

Sections

Personal tools

Analytica Chimica Acta (v.617, #1-2)

Sections

Personal tools

Local resources

Analytica Chimica Acta (v.617, #1-2)