Check out our New Publishers' Select for Free Articles

Analytica Chimica Acta (v.634, #2)

Editorial Board (pp. i).

Novel approaches for selenium speciation in foodstuffs and biological specimens: A review by Zoyne Pedrero; Yolanda Madrid (pp. 135-152).

Selenium is an essential element for human health. It has been recognized as an antioxidant and chemopreventive agent in cancer. Selenium is known to develop its biological activity via selenocysteine residue in the catalytically active centre of selenoproteins. The main source of selenium in human beings is the diet. However, in several regions of the world the content of selenium in diet has been estimated insufficient for a correct expression of the proteins. The beneficial effects of selenium on human health are strongly dependent on its chemical form and concentration. This review critically evaluated the state-of-the art of selenium speciation in biological matrices mainly focused in nutritional and food products. Besides the number of publications related to selenium speciation, isolation and accurate characterization and quantification of selenium species is still a challenge. Hyphenated techniques based on coupling chromatography separation with inductively coupled plasma spectrometry (ICP-MS) and its combination with molecular mass spectrometry (ESI-MS, ESI-MS–MS and MALDI-TOF) and isotopic dilution allow identification, quantification and structural characterization of selenium species. Particular attention is paid in the development of Se-enriched food and nutritional products and how the application of the techniques mentioned above is mandatory to get reliable results on selenium metabolisms in these particular matrices.

Keywords: Abbreviations; AAS; atomic absorption spectroscopy; APCI; atmospheric pressure chemical ionization; CE; capillary electrophoresis; ESSADI; estimated safe and adequate daily dietary intake; GC; gas chromatography; CRM; certified reference material; ESI; electrospray ionization; GMetSeCys; γ-glutamyl selenomethylselenocysteine; HPLC; high performance liquid chromatography; ICP-MS; inductively coupled plasma spectrometry; IDA; isotope dilution analysis; IE; ion exchange; LA; laser ablation; LC; liquid chromatography; MALDI; matrix-assisted laser desorption ionization time-of flight; MeSeMet; methylselenomethionine; MetSeCys; selenomethylselenocysteine; PAGE; polyacrylamide gel electrophoresis; PrSeCys; Se-propylselenocysteine; PSD; post-source decay; RP; reversed phase; RDA; recommended dietary allowance; SEC; size exclusion chromatography; SeCM; seleno-cystamine; SeCys; selenocysteine; SeCys; ₂; selenocystine; SeEt; selenoethionine; SeHoCys; ₂; Se-homocysteine; SeMet; selenomethionine; SeUr; selenourea; TMSe; trimethylselenoniumSelenium; Speciation; Food and nutritional products; Sample treatment; Hyphenated technique; Mass spectrometry

Determination of trace amounts of sodium and lithium in zirconium dioxide (ZrO₂) using liquid electrode plasma optical emission spectrometry by Michiko Banno; Eiichi Tamiya; Yuzuru Takamura (pp. 153-157).

This paper describes a quantitative measurement of trace elements (Na, Li) in high purity zirconium dioxide powder using liquid electrode plasma optical emission spectrometry (LEP-OES). Conventionally, for such type of measurements, inductively coupled plasma optical emission spectrometry (ICP-OES) is frequently employed. The detection limits of elements in zirconium by ICP-OES are degraded due to the spectra interference between the trace elements and zirconium of the matrix, because zirconium is a line rich element in spectra obtained by ICP-OES. LEP-OES is an elemental analysis method developed by the authors. The measurement principle is simple, as follows. Sample solution is put into a narrow channel on a small cuvette and voltage pulse is applied from both ends of the channel. At the center of the channel which is made narrower, the voltage and current are concentrated there, and plasma is generated. From the emission of the plasma, the quantitative analysis of the elements in the solution is achieved. The LEP-OES has the property that the emission of zirconium is relatively weak, so that highly sensitive measurement of trace elements in zirconium matrix can be conducted without interference. Sample solution is prepared by dissolving high purity zirconium dioxide powder and trace amounts of Na or Li with sulfuric acid. The voltage dependence and the pulse width dependence of optical emission spectra are also investigated. With increase of the voltage or the pulse width, the ratio of emission intensities of Na to those of hydrogen increases. This suggests that the ratio of sensitivity of two elements is variable, that means the element selectivity is controllable to some extent by the measurement conditions in LEP-OES. In the case of Na and H, the ratio can be controlled from 7.4 to 21.6%. Finally, the detection limits (3S.D.) of the trace elements, Na and Li, in 4000μgg⁻¹ zirconium dioxide aqueous solution are found to be 0.02 and 0.133μgg⁻¹, respectively. These values correspond to 5μgg⁻¹ for Na, 33.25μgg⁻¹ for Li in original high purity zirconium dioxide powder. The correlation coefficient of calibration curve was 0.995 for Na, 0.985 for Li. Those are comparable to the literature values of detection limits using ICP-OES.

Keywords: Liquid electrode plasma optical emission spectrometry; Zirconium dioxide; Trace element detection; Without interference

Spectral quality assessment and application for gel-based matrix-assisted laser desorption ionization-time of flight tandem mass spectrometer by Dong Yun; Haojie Lu; Pengyuan Yang; Fuchu He (pp. 158-165).

Gel-based matrix-assisted laser desorption ionization-time of flight tandem mass spectrometer (MALDI TOF/TOF MS) is one of the dominant methods of current proteomics, utilizing both peptide mass fingerprinting (PMF) and peptide fragment fingerprinting (PFF) for protein identification on a spot-to-spot basis. However, the unique impact of the quality of the corresponding mass spectrometry spectra remains largely unreported, and has motivated the development and use of an automatic spectra-assessment method. In this study, a multi-variant regression approach has been utilized to assess spectral quality for both PMF and PFF spectra obtained from MALDI TOF/TOF MS. The assessment index has been applied to investigations of MASCOT search results. Systematic examination of two large-scale sets of human liver tissue data has proved that spectral quality was a key factor in significant matching. Based on large-scale investigations on individual PMF search, individual PFF search and their combination, respectively, the filtering of bad quality spectra or spots proves to be an efficient way to improve search efficiency of all search modes in MASCOT. Meanwhile, a validation method based on score differences between normal and decoy (reverse or random) database searches is proposed to precisely define the positive matches. Further analysis showed that spectral quality assessment was also efficient in representing the quality of 2-DE gel spots and promoted the discovery of potential post-translation modifications.

Keywords: Abbreviations; CRRDB; components retaining random sequence database; ELDP; excess of limit-digested peptides; HLPP; Human Liver Proteome Project; IPI; international protein index database; LS; least square; MALDI-TOF/TOF MS; matrix-assisted laser desorption ionization-time of flight tandem mass spectrometer; MDLC; multi-dimension liquid chromatography; MS; mass spectrometer; PFF; peptide fragment fingerprinting; SQscore; spectral quality score; RDB; reverse database; ROC; receiver operating characteristicSpectral quality assessment; Database search; Matrix-assisted laser desorption ionization-time of flight tandem mass spectrometer; Quality control

Determination of α-linolenic acid and linoleic acid in edible oils using near-infrared spectroscopy improved by wavelet transform and uninformative variable elimination by Di Wu; Xiaojing Chen; Pinyan Shi; Sihan Wang; Fengqin Feng; Yong He (pp. 166-171).

This paper proposes an analytical method for simultaneous near-infrared (NIR) spectrometric determination of α-linolenic and linoleic acid in eight types of edible vegetable oils and their blending. For this purpose, a combination of spectral wavelength selection by wavelet transform (WT) and elimination of uninformative variables (UVE) was proposed to obtain simple partial least square (PLS) models based on a small subset of wavelengths. WT was firstly utilized to compress full NIR spectra which contain 1413 redundant variables, and 42 wavelet approximate coefficients were obtained. UVE was then carried out to further select the informative variables. Finally, 27 and 19 wavelet approximate coefficients were selected by UVE for α-linolenic and linoleic acid, respectively. The selected variables were used as inputs of PLS model. Due to original spectra were compressed, and irrelevant variables were eliminated, more parsimonious and efficient model based on WT-UVE was obtained compared with the conventional PLS model with full spectra data. The coefficient of determination ( r²) and root mean square error prediction set (RMSEP) for prediction set were 0.9345 and 0.0123 for α-linolenic acid prediction by WT-UVE-PLS model. The r² and RMSEP were 0.9054, 0.0437 for linoleic acid prediction. The good performance showed a potential application using WT-UVE to select NIR effective variables. WT-UVE can both speed up the calculation and improve the predicted results. The results indicated that it was feasible to fast determine α-linolenic acid and linoleic acid content in edible oils using NIR spectroscopy.

Keywords: Near-infrared spectroscopy; α-Linolenic acid and linoleic acid; Edible oils; Wavelet transform (WT); Uninformative variable elimination (UVE)

Prediction of sensory properties of Brazilian Arabica roasted coffees by headspace solid phase microextraction-gas chromatography and partial least squares by J.S. Ribeiro; F. Augusto; T.J.G. Salva; R.A. Thomaziello; M.M.C. Ferreira (pp. 172-179).

Volatile compounds in fifty-eight Arabica roasted coffee samples from Brazil were analyzed by SPME-GC-FID and SPME-GC-MS, and the results were compared with those from sensory evaluation. The main purpose was to investigate the relationships between the volatile compounds from roasted coffees and certain sensory attributes, including body, flavor, cleanliness and overall quality. Calibration models for each sensory attribute based on chromatographic profiles were developed by using partial least squares (PLS) regression. Discrimination of samples with different overall qualities was done by using partial least squares-discriminant analysis (PLS-DA). The alignment of chromatograms was performed by the correlation optimized warping (COW) algorithm. Selection of peaks for each regression model was performed by applying the ordered predictors selection (OPS) algorithm in order to take into account only significant compounds. The results provided by the calibration models are promising and demonstrate the feasibility of using this methodology in on-line or routine applications to predict the sensory quality of unknown Brazilian Arabica coffee samples.According to the PLS-DA on chromatographic profiles of different quality samples, compounds 3-methypropanal, 2-methylfuran, furfural, furfuryl formate, 5-methyl-2-furancarboxyaldehyde, 4-ethylguaiacol, 3-methylthiophene, 2-furanmethanol acetate, 2-ethyl-3,6-dimethylpyrazine, 1-(2-furanyl)-2-butanone and three others not identified compounds can be considered as possible markers for the coffee beverage overall quality.

Keywords: Processed coffee; Solid phase microextraction; Correlation optimized warping; Principal component analysis and partial least squares

Spectrophotometric determination of acidity and tautomeric constants and hydrogen bonding strength for a new Schiff base using hard modeling and multivariate curve resolution alternative least squares methods by Abbas Afkhami; Farzad Khajavi; Hamid Khanmohammadi (pp. 180-185).

The equilibria of a new Schiff base derived from 3,6-bis((aminoethyl)thio)pyridazine were studied spectrophotometrically with the aid of factor-analytical methods. Hard modeling program was used for determination of the acidity constants of the Schiff base in dimethylformamide (DMF)/water mixture (30:70 v/v). In this method acidity constant equations act as hard models and the score vectors obtained by decomposing of absorbance data matrix will be linear combinations of equilibrium concentrations of species that exist in the absorption matrix. Two rank annihilation factor analysis (TRAFA) was used as a standard method to investigate the accuracy of the method. The tautomerization constant, K_t, of the Schiff base solution in various DMF/water mixtures has also been determined using spectral variations of the Schiff base solutions in various volume ratios of water with the aid of evolving factor analysis (EFA) and multivariate curve resolution alternative least squares (MCR-ALS) methods. In addition the intramolecular hydrogen bonding strength and its related thermodynamic parameters have been determined using MCR-ALS and spectral variation of the Schiff base solutions in different temperatures.

Keywords: Schiff base; Tautomeric constants; Acidic constants; Hydrogen bond; Hard modeling method

In situ solvent formation microextraction based on ionic liquids: A novel sample preparation technique for determination of inorganic species in saline solutions by Majid Baghdadi; Farzaneh Shemirani (pp. 186-191).

In this research, a novel microextraction technique based on ionic liquids (ILs) termed in situ solvent formation microextraction (ISFME) is developed. In this method, small amount of sodium hexafluorophosphate (NaPF₆, as an ion-pairing agent) was added to the sample solution containing very small amount of 1-hexyl-3-methylimidazolium tetrafluoroborate ([Hmim][BF₄], as hydrophilic IL). A cloudy solution was formed as a result of formation of fine droplets of 1-hexyl-3-methylimidazolium hexafluorophosphate [Hmim][PF₆]. After centrifuging, the fine droplets of the extractant phase settled to the bottom of the conical-bottom glass centrifuge tube.ISFME is a simple and rapid method for extraction and preconcentration of metal ions from water samples and can be applied for the sample solutions containing very high concentrations of salt. Furthermore, this technique is much safer in comparison with the organic solvent extraction.Reliability of the introduced methodology was evaluated by analyzing water reference material. ISFME was successfully applied to determining mercury (II) in several real water samples. Michler thioketone (TMK) was chosen as a complexing agent. Analysis was carried out using spectrophotometric detection method. Type and amount of IL, temperature and the other parameters were optimized. Under the optimum conditions, the limit of detection (LOD) was 0.7ngmL⁻¹ and the relative standard deviation (R.S.D.) was 1.94% for 40ngmL⁻¹ mercury.

Keywords: In situ solvent formation microextraction; Ionic liquid; Sample preparation; Mercury; Real water samples; Spectrophotometry

Speciation analysis of inorganic arsenic in natural water by carbon nanofibers separation and inductively coupled plasma mass spectrometry determination by Shizhong Chen; Xilin Zhan; Dengbo Lu; Cheng Liu; Li Zhu (pp. 192-196).

In this paper, carbon nanofibers (CNFs) as a novel solid phase extraction sorbent were developed for speciation preconcentration and separation of inorganic arsenic species As(III) and As(V) prior to determination by inductively coupled plasma mass spectrometry (ICP-MS). It was found that during all the steps of the separation, As(III) was selectively sorbed on the microcolumn packed with CNFs within a pH range of 1.0–3.0 in the presence of ammonium pyrroinedithiocarbamate (APDC), while As(V) was passed through the microcolumn without the retention. Various experimental parameters affecting the separation and determination of As(III) and As(V) have been investigated in detail. Under the optimized conditions, the detection limits of this method for As(III) were 0.0045ngmL⁻¹ with an enrichment factor of 33 and 0.24ngmL⁻¹ for As(V), and the relative standard deviations for As(III) and As(V) were 2.6% and 1.9% ( n=9, c=1.0ngmL⁻¹), respectively. In order to verify the accuracy of the method, a certified reference of water sample was analyzed, and the results obtained were in good agreement with the certified values. The proposed method was applied for the analysis of inorganic arsenic species in groundwater and lake water with the recovery of 92–106%.

Keywords: Carbon nanofibers; Arsenic; Solid phase extraction; Speciation; Inductively coupled plasma mass spectrometry

Accelerated solvent-based extraction and enrichment of selected plasticisers and 4-nonylphenol, and extraction of tin from organotin sources in sediments, sludges and leachate soils by Antoinette M. Reid; Concepta A. Brougham; Andrew M. Fogarty; James J. Roche (pp. 197-204).

Enrichment techniques have become an important feature in the trace analysis of oestrogen mimicking chemicals in the environment. Recent developments such as accelerated solvent extraction (ASE) have improved extraction recoveries in a wide variety of solid matrices including sediments, sludges and leachate soils. Such samples taken from the Irish Midlands Shannon Catchment region during the winter of 2004/5 and suspected to contain certain xenooestrogens or hormonally active agents were extracted using this technique, which was then coupled with high performance liquid chromatography (HPLC) for quantification purposes. ASE was thus employed to both isolate and pre-concentrate targeted analytes using the minimum amount of solvent hence making extractions more conservational. Two simple, yet extremely sensitive liquid chromatographic methods were developed based on UV detection; one for phthalates and one for alkylphenols, with recoveries reaching up to 92.0%. Acid digestion was used for the extraction of the tin and organotin compounds with analysis by polarography. In river sediment, levels of up to 24.4mgkg⁻¹ phthalate, 1.14mgkg⁻¹ 4-nonylphenol and 118mgkg⁻¹ tin were found. In leachate sediments, values up to 49.8mgkg⁻¹ phthalate, 1.57mgkg⁻¹ 4-nonylphenol, and 36.0mgkg⁻¹ tin were determined. In sludge, values up to 174mgkg⁻¹ phthalate and 22.8mgkg⁻¹ 4-nonylphenol were quantified. The highest value of tin (118mgkg⁻¹) was found present in an area of high leisure craft activity. Typical sediment levels of tin at other river locations ranged between 1.20 and 37.5mgkg⁻¹.

Keywords: Accelerated solvent extraction; Phthalates; 4-Nonylphenol; Tin; Sediments; Xenooestrogens

Microwave-assisted double insert vapour-phase digestion of organic samples by Keijo Eilola; Paavo Perämäki (pp. 205-208).

A microwave-assisted double insert multimode vapour-phase digestion method was developed for the digestion of organic samples. The experimental set-up was based on a third generation-type teflon microwave vessel, equipped with an automatic pressure regulating type vessel cover. A borosilicate glass holder insert, containing a smaller quartz sample insert, was fitted inside the vessel. Sulphuric acid was added to the holder insert as a microwave absorbing and temperature transferring liquid, which transferred heat to the sample insert (into which the sample was weighed) and charred the sample material. Oxidation of the sample material was carried out simultaneously with charring using nitric acid vapour, which was generated by the 1:1 (v/v) sulphuric acid–nitric acid mixture located in the bottom of the microwave vessel. This set-up generated high digestion efficiency, without any of the interferences normally associated with direct sulphuric acid usage. The method was used for determining the concentrations of Cd, Cr, Cu, Mn, Mo, Zn and Fe in certified organic reference materials using ICP-OES instrumentation. The certified organic reference materials were NRCC DOLT-2 dogfish liver, NIST-SRM 1577b bovine liver and IRMM VDA cadmium in polyethylene No. 001 and No. 004. The results were in good agreement with the certified values, forepart from Cd. For Cd the results were lower than the certified values due to volatilization losses. Sample materials that could not be digested by an earlier procedure were completely digested during a single-step, 30min digestion. The tested sample materials included certified reference materials, 3-nitrobenzoic acid (3-NBA) and pike ( Esox lucius) muscle. The residual carbon concentrations in the digestion solutions were below the detection limit of the TOC instrument. This type of digestion method is described here for the first time in the literature.

Keywords: Vapour-phase; Digestion; Microwave; Inductively coupled plasma optical emission spectrometer; Double insert

An interior needle electropolymerized pyrrole-based coating for headspace solid-phase dynamic extraction by Habib Bagheri; Esmaeil Babanezhad; Faezeh Khalilian (pp. 209-214).

A headspace solid-phase dynamic extraction (HS-SPDE) technique was developed by the use of polypyrrole (PPy) sorbent, electropolymerized inside the surface of a needle, as a possible alternative to solid-phase microextraction (SPME). Thermal desorption was subsequently, employed to transfer the extracted analytes into the injection port of a gas chromatography–mass spectrometry (GC–MS). The PPy sorbent including polypyrrole-dodecyl sulfate (PPy-DS) was deposited on the interior surface of a stainless steel needle from the corresponding aqueous electrolyte by applying a constant deposition potential. The homogeneity and the porous surface structure of the coating were examined using the scanning electron microscopy (SEM).The developed method was applied to the trace level extraction of some polycyclic aromatic hydrocarbons (PAHs) from aqueous sample. In order to enhance the extraction efficiency and increase the partition coefficient of analytes, the stainless steel needle was cooled at 5°C, while the sample solution was kept at 80°C. Optimization of influential experimental conditions including the voltage of power supply, the time of PPy electrodeposition, the extraction temperature, the ionic strength and the extraction time were also investigated. The detection limits of the method under optimized conditions were in the range of 0.002–0.01ngmL⁻¹. The relative standard deviations (R.S.D.) at a concentration level of 0.1ngmL⁻¹ were obtained between 7.54 and 11.4% ( n=6). The calibration curves of PAHs showed linearity in the range of 0.01–10ngmL⁻¹. The proposed method was successfully applied to the extraction of some selected PAHs from real-life water samples and the relative recoveries were higher than 90% for all the analytes.

Keywords: Headspace solid-phase dynamic extraction; Inside needle capillary adsorption trap; Polypyrrole; Polycyclic aromatic hydrocarbons; Gas chromatography–mass spectrometry; Water analysis

On-line coupling of solid-phase extraction to liquid chromatography–tandem mass spectrometry for the determination of macrolide antibiotics in environmental water by Jie Ding; Nanqi Ren; Ligang Chen; Lan Ding (pp. 215-221).

An automated on-line solid-phase extraction–liquid chromatography–tandem mass spectrometry (SPE–LC–MS/MS) system was developed for the determination of macrolide antibiotics including erythromycin (ETM), roxithromycin (RTM), tylosin (TLS) and tilmicosin (TMC) in environmental water samples. A Capcell Pak MF Ph-1 column packed with restricted access material (RAM) was used as SPE column for the concentration of the analytes and clean-up of the sample. One milliliter water sample was injected into the conditioned SPE column and the matrix was washed out with 3mL high purity water. By rotation of the switching valve, macrolides (MLs) were eluted in the back-flush mode and transferred to the analytical column by the chromatographic mobile phase. The matrix effect was evaluated by the directly injection LC–MS and on-line SPE–LC–MS methods. The limits of detection (LODs) and limits of quantification (LOQs) obtained are in the range of 2–6 and 7–20ngL⁻¹, respectively, which means that the proposed method is suitable for trace analysis of MLs at low level concentration. The intra- and inter-day precisions are in the range of 2.9–7.2% and 3.3–8.9%, respectively. In the three fortified levels (20, 200 and 2000ngL⁻¹), recoveries of MLs ranging from 86.5% to 98.3% are obtained.

Keywords: Macrolide antibiotics; Environmental water; Solid-phase extraction; Liquid chromatography–tandem mass spectrometry; On-line analysis

Evaluation of tris(4,7-diphenyl-1,10-phenanthrolinedisulfonate)ruthenium(II) as a chemiluminescence reagent by Geoffrey P. McDermott; Elizabeth M. Zammit; Elspeth K. Bowen; Michaela M. Cooke; Jacqui L. Adcock; Xavier A. Conlan; Frederick M. Pfeffer; Neil W. Barnett; Gail A. Dyson; Paul S. Francis (pp. 222-227).

Previous studies have suggested that tris(4,7-diphenyl-1,10-phenanthrolinedisulfonate)ruthenium(II) (Ru(BPS)₃⁴⁻) has great potential as a chemiluminescence reagent in acidic aqueous solution. We have evaluated four different samples of this reagent (two commercially available and two synthesised in our laboratory) in comparison with tris(2,2′-bipyridine)ruthenium(II) (Ru(bipy)₃²⁺) and tris(1,10-phenanthroline)ruthenium(II) (Ru(phen)₃²⁺), using a range of structurally diverse analytes. In general, Ru(BPS)₃⁴⁻ produced more intense chemiluminescence, but the oxidised Ru(BPS)₃³⁻ species is less stable in aqueous solution than Ru(bipy)₃³⁺ and produced a greater blank signal than Ru(bipy)₃³⁺ or Ru(phen)₃³⁺, which had a detrimental effect on sensitivity. Although the complex is often depicted with the sulfonate groups of the BPS ligand in the para position on the phenyl rings, NMR characterisation revealed that the commercially available BPS material used in this study was predominantly the meta isomer.

Keywords: Chemiluminescence detection; Ruthenium complexes; Ru(BPS); ₃; ⁴⁻; RuBPS; Flow injection analysis

An ultra-clean technique for accurately analysing Pb isotopes and heavy metals at high spatial resolution in ice cores with sub-pgg⁻¹ Pb concentrations by Laurie J. Burn; Kevin J.R. Rosman; Jean-Pierre Candelone; Paul Vallelonga; Graeme R. Burton; Andrew M. Smith; Vin I. Morgan; Carlo Barbante; Sungmin Hong; Claude F. Boutron (pp. 228-236).

Measurements of Pb isotope ratios in ice containing sub-pgg⁻¹ concentrations are easily compromised by contamination, particularly where limited sample is available. Improved techniques are essential if Antarctic ice cores are to be analysed with sufficient spatial resolution to reveal seasonal variations due to climate. This was achieved here by using stainless steel chisels and saws and strict protocols in an ultra-clean cold room to decontaminate and section ice cores. Artificial ice cores, prepared from high purity water were used to develop and refine the procedures and quantify blanks. Ba and In, two other important elements present at pgg⁻¹ and fgg⁻¹ concentrations in Polar ice, were also measured. The final blank amounted to 0.2±0.2pg of Pb with²⁰⁶Pb/²⁰⁷Pb and²⁰⁸Pb/²⁰⁷Pb ratios of 1.16±0.12 and 2.35±0.16, respectively, 1.5±0.4pg of Ba and 0.6±2.0fg of In, most of which probably originates from abrasion of the steel saws by the ice. The procedure was demonstrated on a Holocene Antarctic ice core section and was shown to contribute blanks of only ∼5%, ∼14% and ∼0.8% to monthly resolved samples with respective Pb, Ba and In concentrations of 0.12pgg⁻¹, 0.3pgg⁻¹ and 2.3fgg⁻¹. Uncertainties in the Pb isotopic ratio measurements were degraded by only ∼0.2%.

Keywords: Ice cores; Antarctica; Mass spectrometry; Lead isotopes; Barium; Indium

Development of a certified reference material for the content of nitroimidazole parent drugs and hydroxy metabolites in pork meat by R. Zeleny; H. Schimmel; F. Ulberth; H. Emons (pp. 237-242).

Nitroimidazoles have been applied in the past to poultry and pigs to treat protozoan diseases and to combat bacterial infections, but due to adverse health effects their use in food-producing animals has meanwhile been banned in the EU. The request for a certified reference material in a representative matrix was stipulated by the responsible Community Reference Laboratory and is underpinned by the need to improve the accuracy and comparability of measurement data and to establish metrological traceability of analytical results. The Institute for Reference Materials and Measurements (IRMM) has responded to this demand by developing and producing a new certified matrix reference material, ERM-BB124. This incurred lyophilised pork meat material was certified according to ISO guides 34 and 35 for the mass fractions of six nitroimidazole compounds. Processing of the frozen muscle tissue to the final material was accomplished by application of cutting, freeze-drying, mixing and milling techniques. Homogeneity and stability measurements were performed using liquid chromatography tandem mass spectrometry. The relative standard uncertainty due to possible heterogeneity showed to be below 1.8% for all analytes. Potential degradation during transport and storage was assessed by isochronous stability studies. No significant instability was detected at a storage temperature of −20°C for a shelf-life of 2 years. The certified mass fraction values were assigned upon evaluation of the data acquired in an international laboratory inter-comparison involving 12 expert laboratories using different sample preparation procedures, but exclusively LC–MS/MS methods. Relative standard uncertainty contributions for the characterisation (between-lab variation of mean values) were found to be between 1.6 and 4.8%. Certified values for five analytes were in the range of 0.7 to 6.2μgkg⁻¹, with expanded relative uncertainties ranging between 7 and 14%. Dimetridazole could be certified as “<0.25μgkg⁻¹ with a probability of 95%”. All values are traceable to the International System of Units (SI). The material is intended to be used for method validation purposes (including trueness estimation) and for method performance assessment.

Keywords: Certified reference material; Nitroimidazoles; Pork meat; Liquid chromatography-tandem mass spectrometry; Inter-comparison

Langmuir–Blodgett film based on MEH-PPV for cholesterol biosensor by Zimple Matharu; Sunil K. Arya; S.P. Singh; Vinay Gupta; B.D. Malhotra (pp. 243-249).

Cholesterol oxidase (ChOx) has been immobilized onto conducting poly[2-methoxy,5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV)/stearic acid (SA) Langmuir–Blodgett film transferred onto octadecanethiol (ODT) modified gold plate. The ChOx/MEH-PPV/SA LB film bioelectrode exhibits has been characterized by FT-IR, contact angle, and atomic force microscopy. The response of the ChOx/MEH-PPV/SA LB film bioelectrode carried out using differential pulse voltammetry (DPV) studies reveal linearity from 1.29 to 12.91mM of cholesterol concentration and response time as 30s. This ChOx/MEH-PPV/SA bioelectrode exhibits values of correlation coefficient as 0.9939, standard deviation as 0.0029μA and limit of detection as 1.66mM. UV–visible spectrophotometer studies reveal that 5.2×10⁻³U of ChOx are actively working per cm² area of ChOx/MEH-PPV/SA LB film bioelectrode and this bioelectrode is thermally stable upto 55°C with reusability of about 60 times.

Keywords: Langmuir–Blodgett film; poly[2-methoxy,5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene]; Cholesterol oxidase; Differential pulse voltammetry; Ultraviolet–visible

Specific detection of oxytetracycline using DNA aptamer-immobilized interdigitated array electrode chip by Yeon Seok Kim; Javed H. Niazi; Man Bock Gu (pp. 250-254).

An electrochemical sensing system for oxytetracycline (OTC) detection was developed using ssDNA aptamer immobilized on gold interdigitated array (IDA) electrode chip. A highly specific ssDNA aptamer that bind to OTC with high affinity was employed to discriminate other tetracyclines (TCs), such as doxycycline (DOX) and tetracycline (TET). The immobilized thiol-modified aptamer on gold electrode chip served as a biorecognition element for the target molecules and the electrochemical signals generated from interactions between the aptamers and the target molecules was evaluated by cyclic voltammetry (CV) and square wave voltammetry (SWV). The current decrease due to the interference of bound OTC, DOX or TET was analyzed with the electron flow produced by a redox reaction between ferro- and ferricyanide. The specificity of developed EC-biosensor for OTC was highly distinguishable from the structurally similar antibiotics (DOX and TET). The dynamic range was determined to be 1–100nM of OTC concentration in semi-logarithmic coordinates.

Keywords: Aptamer; Electrochemical detection; Oxytetracycline; Interdigitated array electrode

A capacitive immunosensor for detection of cholera toxin by Mahmoud Labib; Martin Hedström; Magdy Amin; Bo Mattiasson (pp. 255-261).

Contamination of food with biological toxins as well as their potential use as weapons of mass destruction has created an urge for rapid and cost effective analytical techniques capable of detecting trace amounts of these toxins. This paper describes the development of a sensitive method for detection of cholera toxin (CT) using a flow-injection capacitive immunosensor based on self-assembled monolayers. The sensing surface consists of monoclonal antibodies against the B subunit of CT (anti-CT), immobilized on a gold transducer. Experimental results show that the immunosensor responded linearly to CT concentrations in the range from 1.0×10⁻¹³ to 1.0×10⁻¹⁰M under optimized conditions. The limit of detection (LOD) was 1.0×10⁻¹⁴M. Two more analytical methods were employed for detection of CT using the same antibody namely, sandwich ELISA and surface plasmon resonance (SPR)-based immunosensor. The former had an LOD of 1.2×10⁻¹²M and a working range from 3.7×10⁻¹¹ to 2.9×10⁻¹⁰M whereas, the later had an LOD of 1.0×10⁻¹¹M and a linearity ranging from 1.0×10⁻⁹ to 1.0×10⁻⁶M. These results demonstrate that the developed capacitive immunosensor system has a higher sensitivity than the other two techniques. The binding affinity of CT to the immobilized anti-CT was determined using the SPR-based immunosensor and an association constant ( K_A) of 1.4×10⁹M⁻¹ was estimated.

Keywords: Cholera toxin; Capacitive immunosensor; Surface plasmon resonance; Enzyme-linked immunosorbent assays

A novel ratiometric fluorescent Fe³⁺ sensor based on a phenanthroimidazole chromophore by Weiying Lin; Lingliang Long; Lin Yuan; Zengmei Cao; Jianbo Feng (pp. 262-266).

Phenanthroimidazole derivative1 has been developed as a rare example of ratiometric fluorescent sensors for Fe³⁺. Interestingly, upon treatment with Fe³⁺, the sensor displayed a ratiometric fluorescent response with an enhancement of the ratios of emission intensities at 440 and 500nm from 0.36 to 3.24. The detection range of the sensor for Fe³⁺ is in the 1.0×10⁻⁵–1.5×10⁻⁴M concentration range and the detection limit is 5.26×10⁻⁶M. In addition, the sensor showed good selectivity to Fe³⁺ with the selectivity coefficients(KFe3+=SFe3+/S0) of Fe³⁺ over other metal ions tested in the range of 5–68.

Keywords: Fluorescent sensors; Fluorescence; Iron; Ratiometric; Phenanthroimidazole

New rapid methods for determination of total LAS in sewage sludge by high performance liquid chromatography (HPLC) and capillary electrophoresis (CE) by M. Villar; M. Callejón; J.C. Jiménez; E. Alonso; A. Guiraúm (pp. 267-271).

Linear alkylbenzene sulfonates (LAS) are the most common synthetic anionic surfactant used in domestic and industrial detergents, with a global production of 2.4×10⁶tyear⁻¹. After use and disposal, LAS may enter the environment by one of the several routes, including by direct discharge to surface water or discharge to water from sewage treatment plants. Sewage treatment plants break down LAS only partly: some of them remain in effluent and other fraction is adsorbed in sewage solid.New and rapid methods for determination of total LAS from sewage sludge based on microwave assisted extraction and HPLC–FL and CE–DAD determination are proposed. The extraction of total LAS is carried out by using microwaves energy, an extraction time of 10min and 5mL of methanol. For HPLC–FL determination, mobile phase acetonitrile–water was used, comprising 60% (v/v) from 0 to 1min and a flow rate of 1mLmin⁻¹ programmed to 100% acetonitrile between 1 and 2min and a flow rate of 2mLmin⁻¹. The final composition was maintained for a further 5min. The determination of total LAS by CE–DAD was performed in a phosphate buffer (10mM, pH 9). The separation voltage was 25kV and the temperature of the capillary was 30°C. Injections were performed in the pressure mode and the injection time was set at 12s. The determination of total LAS is carried out in less than 5min. The methods did not require clean-up or preconcentration steps. Detection limit for total LAS in the sludge was 3.03mgkg⁻¹ using HPLC–FL and 21.0mgkg⁻¹ using CE–DAD, and recoveries were >85% using both determination methods. Concentrations of total LAS obtained using both methods were compared with the sum of concentrations of homologues LAS C-10, LAS C-11, LAS C-12 and LAS C-13 obtained using microwaves assisted extraction and HPLC–FL and CE–DAD determination.

Keywords: Sewage sludge; Linear alkylbenzene sulfonates; Liquid chromatography; Capillary electrophoresis

Authentication and quantitative analysis on the chemical profile of Xanthium fruit (Cang-Er-Zi) by high-performance liquid chromatography-diode-array detection tandem mass spectrometry method by Ting Han; Qiao-Yan Zhang; Hong Zhang; Jun Wen; Yang Wang; Bao-Kang Huang; Khalid Rahman; Han-Chen Zheng; Lu-Ping Qin (pp. 272-278).

A high-performance liquid chromatographic method using diode-array detection and electrospray ionization tandem mass spectrometry (HPLC-DAD–ESI-MS/MS) was developed for the qualitative and quantitative analysis on Xanthium fruit, a commonly used traditional Chinese medicine. In this study, 7 characteristic components, 1-O-caffeoylquinic acid, 4-O-caffeoylquinic acid, chlorogenic acid, 1,5-O-di-caffeoylquinic acid, 1,3-O-di-caffeoylquinic acid, 4,5-O-di-caffeoylquinic acid and 1,3,5-O-tri-caffeoylquinic acid were identified and quantified by a validated HPLC-DAD method, and a fingerprint comprised of 12 markers was established under the same operating conditions. Furthermore, HPLC–ESI-MS/MS method was successfully used to deduce the structure of three main constituents. On the basis of the established chromatographic profiles, 30 populations of cocklebur samples including 3 related species and 1 unknown species were divided into 3 chemotypes, indicated that place of origin significantly influences the kinds and content of components in cocklebur, and hence affects their quality. The simultaneous determination of 7 caffeoylquinic acids in the 30 samples showed a great variety in the amounts of caffeoylquinic acids present. The study indicated that some species such as Xanthium mongolicum of the genus Xanthium might be suitable for development as new alternative sources of caffeoylquinic acids to supplement the officially listed Xanthium species, and the abundant constituents such as chlorogenic acid perhaps should be recorded in some authorized publications and applied to the quality control or quality evaluation for Xanthium in China. The entire analytical procedure is reproducible and suitable for the authentication and quantification of Xanthium fruits.

Keywords: Xanthium; spp.; Cang-Er-Zi; Caffeoylquinic acid; High-performance liquid chromatographic; Electrospray ionization tandem mass spectrometry

Spectrum–effect relationships between ultra performance liquid chromatography fingerprints and anti-bacterial activities of Rhizoma coptidis by Wei-Jun Kong; Yan-Ling Zhao; Xiao-He Xiao; Jia-Bo Wang; Han-Bing Li; Zu-Lun Li; Cheng Jin; Yi Liu (pp. 279-285).

The fingerprints of Rhizoma coptidis from various sources were established by ultra performance liquid chromatography (UPLC) and the anti-bacterial activities of R. coptidis on Escherichia coli ( E. coli) growth was studied by microcalarimetry. The UPLC fingerprints were evaluated using similarity analysis (SA) and hierarchical clustering analysis (HCA). Some quantitative parameters obtained from the thermo-genic curves of E. coli growth affected by R. coptidis were analyzed using principal component analysis (PCA). The spectrum–effect relationships between UPLC fingerprints and anti-bacterial activities were investigated using canonical correlation analysis (CCA). The results showed that close correlation existed between the spectrum–effect relationships. Berberine, jateorrhizine and palmatine in the UPLC fingerprints might be the main anti-bacterial components. The anti-bacterial activities of R. coptidis were related with the main active constituents, along with the production place and the harvesting time of this herb, the latitude and longitude of the place. This work provides a general model of the combination of UPLC and microcalorimetry to study the spectrum–effect relationships of R. coptidis, which can be used to discover principle components of it on bioactivity.

Keywords: Rhizoma coptidis; Ultra performance liquid chromatography fingerprints; Microcalorimetry; Anti-bacterial activities; Spectrum–effect relationships

Sections

Personal tools

Analytica Chimica Acta (v.634, #2)

Sections

Personal tools

Local resources

Analytica Chimica Acta (v.634, #2)