Skip to content. Skip to navigation
Sections
Personal tools
You are here: Home
Featured Journal
Navigation
Site Search
 
Search only the current folder (and sub-folders)
Log in


Forgot your password?
New user?
Check out our New Publishers' Select for Free Articles
Journal Search

Analytical and Bioanalytical Chemistry (v.385, #1)

The mechanics of getting tenure by Apryll M. Stalcup (pp. 1-5).
Goldberg Variations Challenge by Juris Meija (pp. 6-7).
Solution to DNA Sequencing Challenge by Juris Meija (pp. 8-9).
Shawn Doonan: Nucleic acids by Jörg D. Hoheisel (pp. 10-11).
Atmospheric Analytical Chemistry by Thorsten Hoffmann (pp. 16-17).

Detection and quantification of levoglucosan in atmospheric aerosols: a review by Gal Schkolnik; Yinon Rudich (pp. 26-33).
Levoglucosan is a tracer for biomass burning sources in atmospheric aerosol particles. Therefore, much effort has been recently put into developing methods for its quantification. This review describes and compares both established and emerging analytical methods for levoglucosan quantification in ambient aerosol samples, with the special needs of the environmental analytical chemist in mind.

Keywords: Levoglucosan; Aerosols; Source apportionment; Bioanalytical methods


Capillary-HPLC-ESI-MS/MS method for the determination of acidic products from the oxidation of monoterpenes in atmospheric aerosol samples by Jörg Warnke; Rolf Bandur; Thorsten Hoffmann (pp. 34-45).
A method is presented for the determination of acidic products from terpene oxidation in filter samples of the atmospheric particle phase. Oxidation products of monoterpenes are believed to add a large fraction to the secondary organic aerosol (SOA) in the troposphere. Those products with structures containing one or more carboxylic acid groups have especially low vapour pressures and therefore they are believed to contribute substantially to the particle phase. Although many experiments were performed in simulation chambers to study the SOA generation by oxidation of terpenes, concentration measurements of products in the atmospheric particle phase are still rare. This is especially true for oxidation products of terpenes other than α- and β-pinene. Therefore, we developed a method for the quantification of acidic products from terpene oxidation in atmospheric aerosol samples. After passing a PM 2.5 (PM = particulate matter) pre-separator to remove coarse particles, fine atmospheric particles were collected onto quartz fibre filters. A backup filter was placed behind the first filter to estimate possible sampling artifacts. The filters were extracted in an ultrasonic bath using methanol. After enrichment and re-dissolving in water the samples were analysed using a capillary-HPLC-ESI(−)-MSn set-up. The ion trap mass spectrometer could be used to gain structural information about the analytes and to enhance the selectivity of the measurements by using its MS/MS capability. A variety of products from different terpenes could be identified and quantified in samples of the ambient atmosphere using reference data from chamber experiments. Due to strong matrix effects quantification of samples from the real atmosphere had to be done by the standard addition method.

Keywords: Terpenes; Secondary organic aerosol; Sampling artifacts; Quantification; Carboxylic acids; Liquid chromatography–mass spectrometry


Life in the sabkha: Raman spectroscopy of halotrophic extremophiles of relevance to planetary exploration by Howell G. M. Edwards; Mahmood A. Mohsin; Fadhil N. Sadooni; Nik F. Nik Hassan; Tasnim Munshi (pp. 46-56).
The Raman spectroscopic biosignatures of halotrophic cyanobacterial extremophiles from sabkha evaporitic saltpans are reported for the first time and ideas about the possible survival strategies in operation have been forthcoming. The biochemicals produced by the cyanobacteria which colonise the interfaces between large plates of clear selenitic gypsum, halite, and dolomitized calcium carbonates in the centre of the salt pans are identifiably different from those which are produced by benthic cyanobacterial mats colonising the surface of the salt pan edges in the intertidal zone. The prediction that similar geological formations would have been present on early Mars and which could now be underlying the highly peroxidised regolith on the surface of the planet has been confirmed by recent satellite observations from Mars orbit and by localised traverses by robotic surface rovers. The successful adoption of miniaturised Raman spectroscopic instrumentation as part of a scientific package for detection of extant life or biomolecular traces of extinct life on proposed future Mars missions will depend critically on interpretation of data from terrestrial Mars analogues such as sabkhas, of which the current study is an example.

Keywords: Raman spectroscopy; Sabkha; Evaporites; Halotrophs; Extremophiles; Cyanobacteria


Determination of a wide range of volatile and semivolatile organic compounds in snow by use of solid-phase micro-extraction (SPME) by Gregor Kos; Parisa A. Ariya (pp. 57-66).
Quantification and transformation of organic compounds are pivotal in understanding atmospheric processes, because such compounds contribute to the oxidative capacity of the atmosphere and drive climate change. It has recently been recognized that chemical reactions in snow play a role in the production or destruction of photolabile volatile organic compounds (VOC). We present an environmentally friendly method for determination of VOC and semi-VOC in snow collected at three sites—remote, urban, and (sub-)arctic. A solid-phase micro-extraction (SPME) procedure was developed and (semi-)VOC were identified by gas chromatography with mass spectrometric detection (GC–MS). A broad spectrum of (semi-)VOC was found in snow samples, including aldehydes, and aromatic and halogenated compounds. Quantification was performed for 12 aromatic and/or oxygenated compounds frequently observed in snow by use of neat standard solutions. The concentrations detected were between 0.12 (styrene and ethylbenzene) and 316 μg L−1 (toluene) and limits of detection varied between 0.11 (styrene) and 1.93 μg L−1 (benzaldehyde). These results indicate that the SPME technique presented is a broad but selective, versatile, solvent-free, ecological, economical, and facile method of analysis for (semi-)VOC in natural snow samples.

Keywords: Snow; Volatile organic compounds (VOC); Atmospheric chemistry; SPME; GC–MS


Determination of selenium in sediment by isotope-dilution inductively coupled plasma mass spectrometry with an octapole reaction cell by Kazumi Inagaki; Akiko Takatsu; Atsuko Nakama; Sakae Eyama; Takashi Yarita; Kensaku Okamoto; Koichi Chiba (pp. 67-75).
A method is described for determination of selenium in sediment by isotope-dilution inductively coupled plasma mass spectrometry with an octapole reaction cell (ID–ICP–ORCMS). Sediment samples were digested with HNO3, HClO4, and HF, and the digestion included an elaborate evaporation process to remove bromine from the digested solution. Simple strong cation-exchange disk filtration was used to remove rare earth elements (REE) from the digested solution, because REE2+ seriously interfere with Se isotopes (i.e. 156Gd2+ with 78Se+, 160Gd2+ with 80Se+). Addition of acetic acid to the filtrate was examined to improve the sensitivity of ICP–ORCMS measurement of Se+ by means of a carbon-enhancement effect. The interfering $$Ar_{2}^{ + }$$ for selenium isotopes were almost eliminated by use of H2 as reaction gas. Interference from BrH+ formed in the reaction cell was negligible because the Br was removed in the evaporation process. Approximately 99.5% of REE were removed by cation-exchange disk filtration yet more than 99% of Se remained in the filtrate solution. The intensity for Se+ was enhanced approximately fourfold by addition of 5% (v/v) of acetic acid whereas that for $$Ar^{ + }_{2}$$ was barely enhanced. Measured 80Se/78Se ratios in unspiked digested solutions of the sample were in good agreement with that for an Se standard solution. The analytical results for Se in the certified reference materials MESS-3 and PACS-1 were in good agreement with their certified values, with small uncertainties.

Keywords: Selenium; Sediment; Isotope dilution; ICPMS; Cation-exchange disk filtration


Determination of dissolved iron(III) in estuarine and coastal waters by adsorptive stripping chronopotentiometry (SCP) by Ricardo D. Riso; Matthieu Waeles; Benoît Pernet-Coudrier; Pierre Le Corre (pp. 76-82).
An adsorptive stripping chronopotentiometric (SCP) method has been developed for quantification of dissolved iron in estuarine and coastal waters. After UV-digestion of filtered samples the Fe(III) ions in non-deoxygenated samples were complexed with solochrom violet RS (SVRS). The complexes were then accumulated by adsorption on the surface of a mercury-film electrode. The stripping step was performed by applying a constant current of −17 μA. Sensitivity and detection limit were 15 ms nmol−1 L (270 ms μg−1 L) and 1.5 nmol L−1 (84 ng L−1), respectively, for 60-s electrolysis time. Compared with the only other chronopotentiometric method available for measurement of iron in natural waters, our procedure is fifty times more sensitive in a quarter of the electrolysis time. It therefore enables detection of the concentrations currently found in estuarine and coastal waters. The method was successfully used to study the behaviour and seasonal variations of dissolved iron in the Penzé estuary, NW France.

Keywords: Dissolved iron; Stripping chronopotentiometry; Estuarine waters; Coastal waters


Modified superheated water extraction of pesticides from spiked sediment and soil by O. Chienthavorn; P. Su-in (pp. 83-89).
In this study a laboratory-made superheated water system was applied in order to extract some pesticides from sand, sediment and soil samples. Extraction efficiencies were investigated at different time intervals with regard to temperature, type and amount of organic modifier. Pesticides were removed from the aqueous extract using dichloromethane as a trapping solvent. The optimal extraction temperature from sand specimens for malathion, heptachlor, aldrin, dieldrin, butachlor, metalaxyl and propiconazole was found to be 160 °C, while those for chlordane and thiobencarb were 120 °C and 180 °C, respectively. The static extraction time for heptachlor, aldrin, dieldrin, butachlor and metalaxyl was found to be 15 min, whereas for malathion and thiobencarb it was 5 min, and for chlordane and propiconazole it was 10 and 20 min, respectively. Recoveries for the extractions of the pesticides from sand under optimized extraction conditions ranged between 96 and 101%. Those obtained from sediment under such conditions were unsatisfactory, and were consequently improved by adding an organic modifier to the superheated water, and sodium chloride to the extract during liquid-liquid extraction. These procedures were optimized further for the parameters described and recoveries exceeded 91%, with the exception of butachlor. The extraction technique was also applied to soil samples at a reduced water flow rate of 0.5 mL min−1, yielding recoveries of 82–105%, and 76% for dieldrin. The reproducibilities, expressed as relative standard deviations (RSDs), ranged between 2 and 13%.

Keywords: Superheated water; Extraction; Pesticide; Soil; Sediment


Silver(I)-selective electrode based on [Bz2Oxo4(18)dieneS4] tetrathia macrocyclic carrier by Ashok Kumar Singh; Puja Saxena (pp. 90-95).
A polystyrene-based membrane of 7,8:16,17-dibenzo-6,9,15,18-tetraoxo-1,5,10,14-tetrathiacyclooctadeca-7,16-diene [Bz2Oxo4(18)dieneS4] was fabricated using sodium tetraphenylborate (NaTPB) and dioctyl phthalate (DOP) as anion excluder and plasticizing agent. The best performance was obtained from the membrane with the composition ionophore [Bz2Oxo4(18)dieneS4]:polystyrene:DOP:NaTPB, 5:100:150:10 (w/w). The response of the electrode was linear over a wide range of concentration, 1.26×10–6–1.00×10–1 mol L−1 for silver ion with a Nernstian slope of 58.4±0.1 mV per decade and a detection limit of 1.0×10−6 mol L−1. The electrode was found to be chemically inert and of adequate stability with a response time of 10 s and could be used for a period of 3 months without change of potential. It worked satisfactorily in mixtures containing up to 35% (v/v) non-aqueous content. The proposed membrane sensor had good selectivity for Ag+ over a wide variety of metal ions in the pH range 2.2–8.5. It was successfully used as an indicator electrode in potentiometric titration of silver ion. The electrode was also useful for determination of Ag+ in waste from photographic films.

Keywords: Ag+-selective electrode; Tetrathia macrocycle; Polystyrene matrix; Potentiometry


Isocratic separation of ginsenosides by high-performance liquid chromatography on a diol column at subambient temperatures by Da-Wei Lou; Yoshihiro Saito; Paweł K. Zarzycki; Mitsuhiro Ogawa; Kiyokatsu Jinno (pp. 96-104).
An improved high-performance liquid chromatographic method for separation of a number of ginsenosides has been developed. The influence of temperature (from 0 to 25°C) on the retention and separation of the ginsenosides was studied by applying a binary mobile phase (acetonitrile/water, 82:18 v/v) and a diol column (LiChrospher 100 Diol). The column temperature is one of the more important parameters for the retention and separation of the components investigated. Selected thermodynamic parameters, including changes of enthalpy (ΔH°) and entropy (ΔS°), were estimated from linear van’t Hoff plots, and possible retention mechanisms were discussed. Moreover, the best separation conditions were selected based on optimization criteria including maximum retention time (t R max), minimum resolution (R s min), and relative resolution product (r). Temperature regions close to 14°C offered the highest selectivity and almost equal distribution of the ginsenosides peaks across the chromatogram. Under such isocratic conditions, excellent separation of chromatographic standards and selected ginseng samples was achieved in less than 16 min.

Keywords: Column liquid chromatography; Subambient temperatures; van’t Hoff plot; Diol column; Ginsenosides


Rapid determination of reduced and oxidized glutathione levels using a new thiol-masking reagent and the enzymatic recycling method: application to the rat liver and bile samples by Imam H. Shaik; Reza Mehvar (pp. 105-113).
A microtiter plate assay for quantitation of reduced (GSH) and oxidized (GSSG) glutathione in the rat liver tissue and bile is described. The assay is based on the established enzymatic recycling method and a new thiol-masking reagent, 1-methyl-4-vinyl-pyridinium trifluoromethane sulfonate (M4VP). Samples were first processed by homogenization with (liver) or addition of (bile) sulfosalicylic acid. The total glutathione and GSSG were then determined before and after rapid (≤2 min) and efficient (100%) masking of the GSH content of the samples with M4VP followed by the enzymatic recycling assay. The percentages of error and coefficient of variation of the assay were within the accepted guidelines, indicating the accuracy and precision of the assay in the range of 6.25–100 pmol GSH per microplate well and 2.17–140 pmol GSSG per well, with lower limit of quantitation of 6.25 and 2.17 pmol per well for GSH and GSSG, respectively. Furthermore, the recoveries of added GSH or GSSG from the liver and bile samples were accurate and precise. The assay was applied to measurement of GSH, GSSG, and GSH:GSSG ratio in the liver and serially collected bile samples in sham-operated and ischemic rat livers, demonstrating a depletion of glutathione and a decrease in the GSH:GSSG ratio as a result of ischemia. The developed assay is rapid, sensitive, accurate, and precise and is suitable for studies of the redox status of liver under physiologic and pathophysiologic conditions.

Keywords: Glutathione; Liver; Bile; Rat; Enzyme recycling reaction; Ischemia


High-throughput bioanalysis with simultaneous acquisition of metabolic route data using ultra performance liquid chromatography coupled with time-of-flight mass spectrometry by Desmond O’Connor; Russell Mortishire-Smith (pp. 114-121).
The capability of ultra performance liquid chromatography coupled with time-of-flight mass spectrometry (UPLC/TOFMS) in the high-throughput quantitative analysis of a drug candidate in plasma has been investigated. Data obtained were compared with results from conventional analysis by high-performance liquid chromatography with tandem mass spectrometric detection on a triple quadrupole instrument (HPLC/MS/MS). The accuracies and precisions of the two approaches were comparable. The UPLC/TOFMS system displayed excellent robustness over the course of 276 injections of protein-precipitated plasma samples. With the instrumentation used, the limits of detection and quantification were approximately five-fold higher with UPLC/TOFMS than for HPLC/MS/MS. Nevertheless, the UPLC/TOFMS system proved adequate to quantify plasma concentrations of a drug molecule administered orally to rats at a pharmacologically relevant dose of 4 mg/kg. As well as providing quantitative data on the test compound, it was also possible to extract data for eight different metabolites, including several isomeric species (three +O and three +2O) from the UPLC/TOFMS data sets, using an analytical method with a 2.5-minute run time. Selectivity for the test compound and its metabolites was derived from the accurate mass capabilities of the TOF instrument, and no MS method development was required.

Keywords: TOFMS; Metabolic routes; Bioanalysis


Isolating the whole complex of target proteins of FK506 using affinity resins from novel solid phases by Teruki Takahashi; Takaaki Shiyama; Tomoko Mori; Ken Hosoya; Akito Tanaka (pp. 122-127).
The development of novel solid phases enabled us to create affinity resins that could be used to isolate the whole complex of target proteins responsible for the immunosuppressive effects of FK506 from rat brain lysate, whereas the affinity resins from commercially available matrices could not achieve this isolation. The results illustrate the enhanced effectiveness of the affinity resin made from this novel material at identifying the target protein of the bioactive compound compared to resins made from the well-known materials Affigel or Toyopearl. This effectiveness arises because the novel material is hydrophilic enough to reduce nonspecific binding proteins and because it has a higher density of ligands that capture the nonubiquitous target protein.

Keywords: Affinity resins; Poly(methacrylate); FK506; Calcineurin; Calmodulin


Chemiluminescence determination of metformin based on hydroxyl radical reaction and molecularly imprinted polymer on-line enrichment by Chao He; Zhujun Zhang; Deyong He; Yan Xiong (pp. 128-133).
A novel and simple chemiluminescence (CL) method has been developed and validated for determination of metformin. This method is based on hydroxyl radical chemiluminescence—the hydroxyl radical generated by reaction of Cu(II) and hydrogen peroxide oxidizes rhodamine B (RhB) to produce weak CL which can be enhanced by metformin. At the same time, metformin molecularly imprinted polymer (MIP) was synthesized. After enrichment based on the selectivity of metformin-MIP, the CL method was successfully applied to the determination of metformin in human serum. The linear range was from 1.0×10−8 to 1.0×10−6 g mL−1 and the detection limit was 4×10−9 g mL−1. The relative standard deviation at 2.0×10−7 g mL−1 by use of MIP was 3.67% (n=7).

Keywords: Flow injection; Chemiluminescence; Hydroxyl radical; Metformin; Molecularly imprinted polymer


New accessory for studies of isotopic 1H/2H exchange and biomolecular interactions using transmission infrared spectroscopy by Arantxa Rodríguez-Casado; Marina Molina; Pedro Carmona (pp. 134-138).
We present here a new accessory for IR transmission measurements of 1H/2H exchange, as an ancillary tool for monitoring structural features of biomolecules in aqueous solution. This new accessory results from the combination of two dialysis membranes and a conventional liquid cell having two cylinders containing 2H2O buffer. When compared with conventional transmission measurements, carried out either after dissolving lyophilized biomolecules in 2H2O or after dialyzing the aqueous solution considered against 2H2O buffer, this accessory shows the following advantages: (1) controlled measurements over the initial steps of this isotopic exchange and absence of molecular aggregation, and (2) smaller sample amounts. This new Fourier transform IR cell can also be used to analyze ligand–biomolecule and drug–cell interactions.

Keywords: Fourier transform IR spectroscopy; 1H/2H Isotopic exchange; Biomolecules


Fluorescence enhancement of the protein–curcumin–sodium dodecyl benzene sulfonate system and protein determination by Feng Wang; Jinghe Yang; Xia Wu; Fei Wang; Shufang Liu (pp. 139-145).
Protein can greatly enhance the fluorescence of curcumin (CU) in the presence of sodium dodecyl benzene sulfonate (SDBS). Experiments indicate that under the optimum conditions, the enhanced intensity of fluorescence is proportional to the concentration of proteins in the range of 0.0050–20.0 μg mL−1 for bovine serum albumin (BSA), 0.080–20.0 μg mL−1 for human serum albumin (HSA), and 0.040–28.0 μg mL−1 for egg albumin (EA). Their detection limits (S/N=3) are 1.4 ng mL−1, 20 ng mL−1, and 16 ng mL−1, respectively. The method has been satisfactorily used for the determination of proteins in actual samples. In comparison with most of fluorimetric methods, this method is quick and simple, has high sensitivity and good stability. The interaction mechanism is also studied.

Keywords: Fluorescence enhancement; Protein; Curcumin; SDBS; Fluorimetry


New insights from X-ray photoelectron spectroscopy into the chemistry of covalent enzyme immobilization, with glutamate dehydrogenase (GDH) on silicon dioxide as an example by Luigia Longo; Giuseppe Vasapollo; Maria Rachele Guascito; Cosimino Malitesta (pp. 146-152).
A three-step process for immobilization of glutamate dehydrogenase (GDH) on the surface of silicon dioxide has been studied by X-ray photoelectron spectroscopy (XPS). The enzyme layer was deposited on the silicon dioxide surface after first exposing the surface to 3-aminopropyltriethoxysilane (3-APTS) and reacting the silylated surface with glutaraldehyde (GA). Fine XPS analysis, performed after each step of the chemical procedure, revealed unknown details of the step-by-step construction of the enzyme layer under different experimental conditions.

Keywords: X-ray photoelectron spectroscopy; Glutamate dehydrogenase; Enzyme covalent immobilization; Silicon dioxide


Investigating the post-chemiluminescence behavior of phenothiazine medications in the luminol–potassium ferricyanide system: molecular imprinting–post-chemiluminescence method for the determination of chlorpromazine hydrochloride by Weifen Niu; Na Feng; Fei Nie; Jiuru Lu (pp. 153-160).
A new post-chemiluminescence (PCL) phenomenon was observed when phenothiazine medications were injected into the reaction mixture after the chemiluminescence (CL) reaction of luminol and potassium ferricyanide had finished. A possible reaction mechanism was proposed based on studies of the kinetic characteristics of the CL, CL spectra, fluorescence spectra, and on other experiments. The feasibility of determining various phenothiazine medications by utilizing these PCL reactions was examined. A molecular imprinting–post-chemiluminescence (MI-PCL) method was established for the determination of chlorpromazine hydrochloride using a chlorpromazine hydrochloride-imprinted polymer (MIP) as the recognition material. The method displayed high selectivity and high sensitivity. The linear range of the method was 1.0×10−8∼1.0×10−6, with a linear correlation coefficient of 0.9985. The detection limit was 3×10−9 g/ml chlorpromazine hydrochloride, and the relative standard deviation for a 1.0×10−7 g/ml chlorpromazine hydrochloride solution was 4.0% (n=11). The method has been applied to the determination of chlorpromazine hydrochloride in urine and animal drinking water with satisfactory results.

Keywords: Post-chemiluminescence (PCL); Molecular imprinted polymer (MIP); Phenothiazine medications; Chlorpromazine hydrochloride


Adsorptive stripping voltammetric determination of netilmicin in the presence of formaldehyde by Nan Sun; Weimin Mo; Baoxiang Hu; Zhenlu Shen (pp. 161-167).
A linear sweep adsorptive stripping voltammetric method for the determination of netilmicin in the presence of formaldehyde has been proposed for the first time. In the presence of 3.0×10−3 g ml−1 formaldehyde, netilmicin exhibits a sensitive cathodic peak at −1.30 V (vs. the saturated calomel electrode, SCE) in a medium of Britton–Robinson buffer (pH 8.7) with a scan rate of 100 mV s−1 after a preconcentration period of 120 s at −1.10 V (vs. SCE). The peak current showed a linear dependence on the netilmicin concentration over the range 4.2×10−9–1.0×10−7 g ml−1. The achieved limits of detection and quantitation were 1.0×10−10 and 3.3×10−10 g ml−1 netilmicin, respectively. It was deduced from the experiments that the amine–aldehyde condensation product formed between netilmicin and formaldehyde is mainly responsible for the appearance of the peak. The electrochemical behavior of netilmicin in the presence of formaldehyde has been studied. The method was applied to the direct determination of netilmicin in injectable formulations and spiked human urine and serum samples.

Keywords: Linear sweep adsorptive stripping voltammetry; Netilmicin; Formaldehyde


Certification of a new selenized yeast reference material (SELM-1) for methionine, selenomethinone and total selenium content and its use in an intercomparison exercise for quantifying these analytes by Zoltán Mester; Scott Willie; Lu Yang; Ralph Sturgeon; Joseph A. Caruso; María Luisa Fernández; Peter Fodor; Robert J. Goldschmidt; Heidi Goenaga-Infante; Ryszard Lobinski; Paulette Maxwell; Shona McSheehy; Aleksandra Polatajko; Baki B. M. Sadi; Alfredo Sanz-Medel; Christine Scriver; Joanna Szpunar; Raimund Wahlen; Wayne Wolf (pp. 168-180).
A new selenized yeast reference material (SELM-1) produced by the Institute for National Measurement Standards, National Research Council of Canada (INMS, NRC) certified for total selenium (2,059±64 mg kg−1), methionine (Met, 5,758±277 mg kg−1) and selenomethionine (SeMet, 3,431±157 mg kg−1) content is described. The ±value represents an expanded uncertainty with a coverage factor of 2. SeMet and Met amount contents were established following a methanesulfonic acid digestion of the yeast using GC-MS and LC-MS quantitation. Isotope dilution (ID) calibration was used for both compounds, using 13C-labelled SeMet and Met. Total Se was determined after complete microwave acid digestion based on ID ICP-MS using a 82Se spike or ICP-OES spectrometry using external calibration. An international intercomparison exercise was piloted by NRC to assess the state-of-the-art of measurement of selenomethione in SELM-1. Determination of total Se and methionine was also attempted. Seven laboratories submitted results (2 National Metrology Institutes (NMIs) and 5 university/government laboratories). For SeMet, ten independent mean values were generated. Various acid digestion and enzymatic procedures followed by LC ICP-MS, LC AFS or GC-MS quantitation were used. Four values were based on species-specific ID calibration, one on non-species-specific ID with the remainder using standard addition (SA) or external calibration (EC). For total selenium, laboratories employed various acid digestion procedures followed by ICP-MS, AFS or GC-MS quantitation. Four laboratories employed ID calibration, the remaining used SA or EC. A total of seven independent results were submitted. Results for methionine were reported by only three laboratories, all of which used various acid digestion protocols combined with determination by GC-MS and LC UV. The majority of participants submitted values within the certified range for SeMet and total Se, whereas the intercomparison was judged unsuccessful for Met because only two external laboratories provided values, both of which were outside the certified range.

Keywords: Selenomethionine; Yeast; Reference material; Speciation; Intercomparison


Detection of residual bacitracin A, colistin A, and colistin B in milk and animal tissues by liquid chromatography tandem mass spectrometry by Eric Chun-hong Wan; Clare Ho; Della Wai-mei Sin; Yiu-chung Wong (pp. 181-188).
Liquid chromatography coupled with electrospray ionization tandem mass spectrometry (LC-MS/MS) was applied to the determination of residual bacitracin A, colistin A, and colistin B in milk and animal tissue samples. Prior to instrumental analysis, samples were subjected to acid extraction followed by solid-phase cleanup using Strata-X cartridges. Mass spectral acquisitions were performed under selective multiple reaction monitoring (MRM) mode at m/z 199 and 670 from triply charged precursors of bacitracin A (m/z 475); m/z 385 and 379 from triply charged precursors of colistin A (m/z 391); and m/z 380 and 374 from triply charged precursors of colistin B (m/z 386). Method precision was evaluated from spike recovery of samples fortified at concentrations corresponding to 2/5 of the maximum residue limits (MRLs) for each of the analytes under study. Intra-day and inter-day variations were found to range from 90.9 to 104% with relative standard deviation (RSD) <6.5%, and from 90.1 to 106% with RSD <9.1%, respectively. Limits of quantification (LOQs) were defined as the spiking concentrations at 2/5 MRL, and limits of detection (LODs) were 10–47 μg kg−1 for bacitracin A, 1–16 μg kg−1 for colistin A, and 6–14 μg kg−1 for colistin B in milk and animal tissues. The presented method has good precision and high sensitivity and was applied as a fast screening protocol and a quantitative tool for monitoring of the concerned polypeptides in foods as part of a surveillance program.

Keywords: Bacitracin colistin milk; Animal tissues; LC-MS/MS


Study of the bioavailability of selenium in cows’ milk after a supplementation of cow feed with different forms of selenium by Óscar Muñiz-Naveiro; Raquel Domínguez-González; Adela Bermejo-Barrera; Pilar Bermejo-Barrera; José A. Cocho; José M. Fraga (pp. 189-196).
The purpose of the work described in this paper was to develop an easy and quick in-vitro method for comparing the bioavailability of selenium in cows’ milk after different cow feed. The study focuses on bioavailability differences resulting from the use of different selenium species (organic selenium as selenised yeast and sodium selenite) for supplementation of forage. A procedure for determination of selenium in cows’ milk and dialysates, by hydride-generation atomic-fluorescence spectrometry (HG-AFS) after microwave-assisted acid digestion, was optimised. The results show it is possible to obtain cows’ milk enriched with selenium at different concentration without altering the original composition of the milk. The bioavailability was statistically greater for cows’ milk obtained after supplementation of forage with organic selenium at levels of 0.4 and 0.5 μg Se g−1 than for that obtained after supplementation with inorganic and organic selenium at levels of 0.2 and 0.3 μg Se g−1.

Keywords: Selenium; Cows’ milk; In-vitro digestion; Selenium bioavailability; Hydride-generation atomic-fluorescence spectrometry


An automatic flow injection analysis procedure for photometric determination of ethanol in red wine without using a chromogenic reagent by Sivanildo S. Borges; Rejane M. Frizzarin; Boaventura F. Reis (pp. 197-202).
An automatic reagentless photometric procedure for the determination of ethanol in red wine is described. The procedure was based on a falling drop system that was implemented by employing a flow injection analysis manifold. The detection system comprised an infrared LED and a phototransistor. The experimental arrangement was designed to ensure that the wine drop grew between these devices, thus causing a decrease in the intensity of the radiation beam coming from the LED. Since ethanol content affected the size of the wine drop this feature was exploited to develop an analytical procedure for the photometric determination of ethanol in red wine without using a chromogenic reagent. In an attempt to prove the usefulness of the proposed procedure, a set of red wines were analysed. No significant difference between our results and those obtained with a reference method was observed at the 95% confidence level. Other advantages of our method were a linear response ranging from 0.17 up to 5.14 mol L−1 (1.0 up to 30.0%) ethanol (R=0.999); a limit of detection of 0.05 mol L−1 (0.3%) ethanol; a relative standard deviation of 2.5% (n=10) using typical wine sample containing 2.14 mol L−1 (12.5%) ethanol; and a sampling rate of 50 determinations per hour.

Keywords: Photometric ethanol determination; Flow injection analysis; Falling drop system; LED-based photometer; Red wine


Effect of interferents present in the internal solution or in the conducting polymer transducer on the responses of ion-selective electrodes by Agata Michalska; Marcin Ocypa; Krzysztof Maksymiuk (pp. 203-207).
The effect of interferents present on the opposite side of the Pb2+-selective membrane has been studied for both internal solution and all-solid-state sensors with a conducting polymer (CP) transducer. For interferents with moderate selectivity coefficients (sodium cations) present in the internal solution or in the CP transducer phase, super-Nernstian responses were obtained. For sensors containing strongly discriminated interferents (lithium ions), however, responses typical of conventional electrodes are observed, despite the low activity of primary ions on the opposite side of the membrane. This effect is attributed to hindered incorporation of interfering ions into the membrane, which also impairs the long term stability of the potential. Because of the relatively small absolute amounts of interferents in the transducer of all-solid-state sensors, their exchange for primary ions occurs quickly. Thus, transformation of the sensor to one with a micromolar detection limit and high potential stability is observed.

Keywords: Ion-selective electrodes; All-solid-state potentiometric sensor; Selectivity; Stability
Featured Book
Web Search
Powered by Plone CMS, the Open Source Content Management System

This site conforms to the following standards: