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Analytical and Bioanalytical Chemistry (v.385, #5)
W. Mächtle and L. Börger (Eds.) Analytical Ultracentrifugation of Polymers and Nanoparticles
by Helmut Cölfen (pp. 795-796).
A new time-resolved fluorometric microarray detection system using core–shell-type fluorescent nanosphere and its application to allergen microarray by Takeshi Matsuya; Kazuhiko Otake; Shigeru Tashiro; Nobuhiro Hoshino; Motomi Katada; Tsuneo Okuyama (pp. 797-806).
We have developed a new time-resolved fluorometric (TRF) microarray detection system consisting of fluorescent NH2 nanosphere, TRF microarray detector and gamma-irradiated polystyrene chip. Using the TRF microarray detector, we detected 500 particles of the fluorescent nanosphere in one channel. Cross-talk fluorescence from the adjacent channels was little observed in the TRF microarray detector (<0.0004 %). The TRF microarray detection system was further applied for serum allergen-specific immunoglobulin E (IgE) multi-analyses. As a labeled tag antibody, an anti-human IgE Fab’ fragment-conjugated fluorescent nanosphere (Fab’ nanosphere) was prepared as described previously. As a chip surface appropriate for allergen immobilization, the polystyrene chip surface was modified by gamma irradiation. The immunoassay reactivity using the gamma-irradiated polystyrene chip was approximately 2.5-times improved compared with that of the non-treated polystyrene chip. Non-specific adsorption of the Fab’ nanosphere onto the gamma-irradiated polystyrene chip surface was very low level (<0.0009 %). In only 20 μl of serum, six allergen-specific IgEs could be simultaneously determined in one reaction well in fewer than 90 min. Good correlation curves were obtained between the microarray immunoassay and the CAP RAST fluoro-enzyme immunoassay (CAP/RAST FEIA) method (r>0.961). Reproducibility (CVs) of the microarray immunoassay was 8.6 % to 19.0 % (n=5).
Keywords: Fluorescent nanosphere; Microarray; Time-resolved fluorescence; Allergy-specific IgE
ClcR-based biosensing system in the detection of cis-dihydroxylated (chloro-)biphenyls by Jessika Feliciano; Shifen Xu; Xiyuan Guan; Hans-Joachim Lehmler; Leonidas G. Bachas; Sylvia Daunert (pp. 807-813).
Polychlorinated biphenyls (PCBs) are a group of organic pollutants that are persistent when released into the environment. Among the metabolites of PCBs, dihydroxylated PCBs are also considered as toxic compounds. Various studies have shown that dihydroxylated PCBs affect the reproductive, immune, nervous, and endocrine systems. Detection of these chemicals in environmental and biological samples could provide first-hand information about their levels and lead to a better understanding of their role in toxicity. To that end, we developed a sensing system for the detection of dihydroxylated PCBs based on the clc operon. The Pseudomonas putida clc operon encodes a catabolic pathway for degradation of chlorocatechols, which are major metabolites of a large number of chlorinated compounds. In P. putida, the expression of these genes is regulated by a protein encoded by the gene clcR located upstream from the clcABD genes. We demonstrate here for the first time that dihydroxy PCBs can also induce the clc operon. Our sensing system employs P. putida bacteria harboring a plasmid in which the reporter gene, lacZ, is under the control of the regulatory protein ClcR. Consequently, when exposed to dihydroxy PCBs, the bacteria express β-galactosidase in an amount related to the concentration of the corresponding dihydroxy PCB. Various dihydroxylated PCBs, differing in the number and position of chlorines and in the position of hydroxyls, were tested for their ability to induce expression of β-galactosidase. Detection limits as low as 1×10−6 mol L−1 were obtained for various dihydroxylated PCBs.
Keywords: PCB; Whole-cell biosensor; Clc operon; β-galactosidase; Reporter gene
Pretreatment and one-shot separating analysis of whole catecholamine metabolites in plasma by using LC/MS by Tomomi Hasegawa; Kastuya Wada; Eiso Hiyama; Tsutomu Masujima (pp. 814-820).
Catecholamines are biogenic amines that play an important role in the nervous system. Some catecholamines have been used as tumor makers of phenochromocytoma, paraganglioma and neuroblastoma. The analysis of total catecholamine metabolites should be useful for one-shot screening of multiple aspects of diseases; however, it is difficult to do this, because the catecholamine metabolites are divided into three groups: five amines, one amino acid and three carbonic acids. Catecholamines and small molecules were separated from plasma proteins by an internal-surface reversed-phase column (protein-coated octadeyclsilica column) and were analyzed by liquid chromatography (LC)/mass spectrometry (MS) using electrospray ionization time-of-flight MS. Using a reversed-phase column and hydrophilic mobile phases, we succeeded in the separation of nine catecholamines, all of which had similar structures. These nine substances were eluted in the following order: norepinephrine, epinephrine, normetanephrine, dopamine, metanephrine, 3,4-dihydroxyphenylalanine, vanillomandelic acid, 3,4-dihydroxyphenylacetic acid and homovanillic acid. The reproducibility of this method was acceptable. The highest coefficient of variation was 7.4%. In addition, various types of compounds were separated from and detected in plasma proteins by applying LC/MS. The plasma direct injection method, which uses an internal-surface reversed-phase column and an ion-pair reagent, allowed us to separate small molecules from plasma proteins. MS detected some compounds that high-performance LC could not succeed in separating and detecting with UV detection. We think that the method can be applied to find new markers in neuroblastoma, by comparing the plasma of patients with that of normal infants. The method can be also used to help in making a diagnosis of other diseases and finding their new makers.
Keywords: Neuroblastoma; Catecholamine; Internal-surface reversed-phase column; Liquid chromatography/mass spectrometry
Mass spectrometric identification and characterization of antimony complexes with ribose-containing biomolecules and an RNA oligomer by Helle Rüsz Hansen; Spiros A. Pergantis (pp. 821-833).
Mass spectrometric techniques have been used to study the interaction of inorganic Sb(V) with biomolecules containing a ribose or deoxyribose moiety. Electrospray (ES) mass spectra of reaction mixtures containing inorganic Sb(V) and one of several biomolecules (adenosine, cytidine, guanosine, uridine, adenosine-5′-monophosphate, adenosine-3′,5′-cyclic monophosphate, ribose, or 2′-deoxyadenosine) afforded high-mass antimony-containing ions corresponding to Sb(V)–biomolecule complexes of stoichiometry 1:1, 1:2, or 1:3. The complexes were characterized by collision-induced dissociation (CID) tandem mass spectrometry (MS) using ion-trap multistage MS. The CID results revealed that Sb(V) binds to the ribose or deoxyribose moiety. Structures are proposed for the Sb–biomolecule complexes. Analysis of the reaction mixtures by reversed-phase chromatography coupled on-line to either inductively coupled plasma (ICP) MS or ES–MS showed that in solution Sb(V) forms complexes with all the analyzed biomolecules with vicinal cis hydroxyl groups. Evidence (from size-exclusion chromatography ICP–MS and direct infusion ES–MS) of complexation of Sb(V) with an RNA oligomer, but not with a DNA oligomer, supports the suggestion that the presence of vicinal cis hydroxyl groups is critical for complexation to occur. This is the first direct evidence of complexation of Sb(V) with RNA. Results obtained by studying the effect of changing reaction conditions, i.e. pH, reaction time, and Sb/biomolecule molar ratio, on the extent of Sb–biomolecule formation suggest the reaction may be of physiological importance. Selected reaction monitoring (SRM) and precursor-ion-scanning tandem MS were investigated to determine their potential to detect trace levels of the Sb–biomolecule complexes in biological samples. Application of SRM MS–MS in combination with high-performance liquid chromatography enabled successful detection of an Sb–adenosine complex that had been spiked into a complex biological matrix (liver homogenate).
Keywords: Antimony; RNA; Ribonucleoside; Chromatography; Electrospray; ICP–MS
31P NMR study on the autophosphorylation of insulin receptors in the plasma membrane by Yili Ge; Hong Peng; Kaixun Huang (pp. 834-839).
A nonradioactive 31P nuclear magnetic resonance (NMR) spectroscopy protocol has been developed and used to investigate in vitro autophosphorylation of insulin receptors. Optimum experimental conditions have been explored, and the effects of Mn2+ and phosphocreatine (PCr) on the determination of the phosphorylation reaction have been assayed. The method was used to monitor the time courses of the phosphorylation reaction in solution. The results from this NMR study were in agreement with observations of insulin receptor phosphorylation made by using Western blotting.
Keywords: Autophosphorylation; Insulin Receptor; ATP; 31P NMR; PCr (phosphocreatine)
Capillary isoelectric focusing of microorganisms in the pH range 2–5 in a dynamically modified FS capillary with UV detection by Marie Horká; Filip Růžička; Veronika Holá; Karel Šlais (pp. 840-846).
The isoelectric points of many microbial cells lie within the pH range spanning from 1.5 to 4.5. In this work, we suggest a CIEF method for the separation of cells according to their isoelectric points in the pH range of 2–5. It includes the segmental injection of the sample pulse composed of the segment of the selected simple ampholytes, the segment of the bioanalytes and the segment of carrier ampholytes into fused silica capillaries dynamically modified by poly(ethylene glycole). This polymer dissolved in the catholyte, in the anolyte and in the injected sample pulse was used for a prevention of the bioanalyte adsorption on the capillary surface and for the reduction of the electroosmotic flow. Between each focusing run, the capillaries were washed with the mixture of acetone/ethanol to achieve the reproducible and efficient CIEF. In order to trace of pH gradients, low-molecular-mass pI markers were used. The mixed cultures of microorganisms, Escherichia coli CCM 3954, Candida albicans CCM 8180, Candida parapsilosis, Candida krusei, Candida glabrata, Candida tropicalis, CCM 8223, Proteus vulgaris, Klebsiela pneumoniae, Staphylococcus aureus CCM 3953, Streptococcus agalactiae CCM 6187, Enterococcus faecalis CCM 4224 and Staphylococcus epidermidis CCM 4418, were focused and separated by the CIEF method suggested here. This CIEF method enables the separation and detection of the microbes from the mixed cultures within several minutes. The minimum detectable number of microbial cells was less than 103.
Keywords: CIEF, pH range 2–5; Spacers; pI markers; Microorganisms; UV detection
Method for homogeneous spotting of antibodies on membranes: application to the sensitive detection of ochratoxin A by Debjani Saha; Debopam Acharya; Tarun K. Dhar (pp. 847-854).
Membrane-based dot immunoassays are now widely used in almost every branch of biology and medicine. However, the quality of the immobilized antigen or antibody spots on the membranes was found to be highly operator-dependent and spotting by conventional methods often leads to heterogeneous spot morphologies and deposition inconsistencies. To circumvent these problems, a spotting method has been developed which is based on focussed absorption of an applied antibody solution through an aqueous network of capillary channels formed between the membrane and a wetted absorbent body. The method does not require any equipment for creating vacuum and according to assay requirements highly homogeneous spots of uniform size, in the range of 0.8- to 9-mm diameter, can be obtained by varying the volume of the applied antibody solution. Spot intensities were sufficiently high even at high antibody dilutions. Immobilization of anti-ochratoxin A (anti-OA) antibody by this method gave 2-fold increased sensitivity in a competitive assay of the toxin compared to conventional spotting methods. The calculated CV of the colour intensity for spots of different sizes (0.8 to 9 mm) was between 4.5 and 1%. Application of this spotting technique has been demonstrated for detection of OA in wine and coffee samples with the elimination of matrix interferences in the same immunoassay system. This was achieved by selective removal of nonspecific interfering substances from the sample extract during the assay. The detection limit of OA in wine (1 μg L−1) and coffee (2.5 μg kg−1) obtained by the present new method is superior to values reported recently. Thus, the present new method will be highly useful for improved performance of membrane-based immunoassays in almost every branch of biology and medicine.
Keywords: Membrane immunoassay; Homogeneous spotting; Uniform morphology; Cleanup; Ochratoxin
Analysis of urine for cysteine, cysteinylglycine, and homocysteine by high-performance liquid chromatography by K. Kuśmierek; R. Głowacki; E. Bald (pp. 855-860).
A new analytical method is proposed for simultaneous determination, by liquid chromatography, of the three main urinary thiols–cysteine, cysteinylglycine, and homocysteine. To measure the total amount of these thiols urine is reduced with sodium borohydride, to convert disulfides to thiols which are then derivatized with 2-chloro-1-methylquinolinium tetrafluoroborate. Separation and quantitation of the 2-S-quinolinium thiol derivatives formed were achieved by high-performance liquid chromatography with detection at 355 nm. Validation showed the method enabled reliable simultaneous determination of these aminothiols in urine. The calibration graphs for each analyte, obtained by use of normal urine spiked with increasing amounts of cysteine, cysteinylglycine, and homocysteine, were linear (R 2≥0.997) over the range covering most practical situations. The recovery of the assay was 98–100% and sensitivity was 0.12–0.25 μmol L−1. The method was applied to 91 different samples of normal urine to establish reference values for the aminothiols, normalized on creatinine.
Keywords: Cysteine; Cysteinylglycine; Homocysteine; Urine; HPLC
Highly sensitive spectrofluorimetric determination of trace amounts of lecithin by Weiwei Bian; Chongqiu Jiang (pp. 861-865).
A new spectrofluorimetric method was developed for the determination of trace amounts of lecithin using the ciprofloxacin (CIP)–terbium (Tb3+) ion complex as a fluorescent probe. In a buffer solution at pH=5.60, lecithin can remarkably reduce the fluorescence intensity of the CIP–Tb3+ complex at λ=545 nm. The reduced fluorescence intensity of the Tb3+ ion is proportional to the concentration of lecithin. Optimum conditions for the determination of lecithin were also investigated. The linear range and detection limit for the determination of lecithin were 1.0×10−6–3.0×10−5 mol L−1 and 3.44×10−7 mol L−1, respectively. This method is simple, practical, and relatively free of interference from coexisting substances. Furthermore, it has been successfully applied to assess lecithin in serum samples.
Keywords: Lecithin; Ciprofloxacin; Spectrofluorimetry; Terbium
Feasibility of preparing and analyzing gas standards containing heavy hydrocarbons (C10–C16) by George C. Rhoderick (pp. 866-874).
State and federal agencies are beginning to monitor ambient air for compounds related to diesel exhaust. The National Institute of Standards and Technology (NIST) was asked to develop standards containing heavy (C10–C16) alkanes which could then be used in air monitoring and exhaust studies. Several primary gravimetric standards, containing heavy (C10–C16) alkanes in nitrogen, were developed and analyzed by gas chromatography (GC) with flame-ionization detection (FID). The results of this research indicate that accurate gas standards containing these hydrocarbons can be prepared. However, the analytical results show that the temperature of the transfer system from the gas cylinder to the GC column (including the gas-sample valve) must be heated in order to prevent adsorption of these compounds within the analytical system. The results indicate that even at elevated temperatures these compounds are being absorbed within the system. The results show that quantitative results cannot be obtained by using one compound such as hexane, as an internal standard to determine the concentration of other hydrocarbons. Quantitative and accurate results are best obtained if standards for each hydrocarbon of interest are used to determine concentrations of unknowns for the respective hydrocarbon.
Keywords: Heavy hydrocarbons; Diesel exhaust; Primary gas standards; Gravimetric gas standards; Analysis; Gas chromatography
SPE-HPLC purification of endocrine-disrupting compounds from human serum for assessment of xenoestrogenic activity by Philip Sebastian Hjelmborg; Mandana Ghisari; Eva Cecilie Bonefeld-Jorgensen (pp. 875-887).
Assessment of xenoestrogenic activity in human serum samples requires the removal of endogenous sex hormones to assure that the activity measured originates from xenobiotic compounds only. Serum samples representing high, medium and lower accumulation of persistent organic pollutants (POPs) were extracted using solid-phase extraction (SPE) followed by normal-phase high-performance liquid chromatography (NP-HPLC) for separation of POPs from endogenous hormones. The recovery of polychlorinated biphenyl (PCB) congeners in spiked serum samples was up to 86 %, making the extraction method suitable for the study. MVLN cells, stably transfected with an estrogen receptor (ER) luciferase reporter vector (estrogen response element chemically activated luciferase expression, ERE-CALUX), were exposed to the reconstituted SPE-HPLC extracts for determination of the integrated estrogenic activity. The effects of PCBs were analyzed by direct in vitro exposure of PCBs (nos. 138, 153, 180) and by ex vivo analysis of SPE-HPLC extracts from serum spiked with the PCBs. Similar effects on ER transactivation were observed for the direct in vitro and the ex vivo analysis experiments. The ER transactivation responses determined for actual serum samples were in the linear range of the dose-response curve. 17β-Estradiol titrations showed that the xenoestrogenic effects were mediated via ER. Moreover, our SPE-HPLC-ERE-CALUX assay was demonstrated to elicit high interlaboratory correlation. In the present study the combination of SPE-HPLC purification and the ex vivo estrogenic responses measured by ERE-CALUX was validated and considered to be a valuable tool to assess the combined ER effect of lipophilic serum POPs where additive/synergistic and agonistic/antagonistic effects are integrated giving an overall estimate of exposure and bioactivity.
Keywords: Solid-phase extraction–high-performance liquid chromatography; Estrogen response element chemically activated luciferase expression; MVLN; Endocrine disruption; Xenoestrogens
Powerful preconcentration method for capillary electrophoresis and its application to analysis of ultratrace amounts of polycyclic aromatic hydrocarbons by Yoshitaka Takagai; Ryoutaro Akiyama; Shukuro Igarashi (pp. 888-894).
For environmental analyses, a high-performance and powerful preconcentration system exceeding 1×107-fold was developed that was composed of a blue cotton method (solid extraction method)/homogeneous liquid–liquid extraction method/on-line concentration method for capillary electrophoresis (CE). This system was named the “triplex concentration system” and it was achieved by finding a new phase-separation phenomenon (homogeneous liquid–liquid extraction) from a water-miscible organic solvent. Parts per trillion levels of polycyclic aromatic hydrocarbons (PAHs) were used as model analytical targets in this study. With the proposed method, 20-L levels of environmental water could be preconcentrated up to 1×107-fold within a maximum of 1 h. The parts per trillion levels of PAHs were easily determined even using UV/CE, which has a serious sensitivity problem, and the detection limit of benzo[a]pyrene was 3.60 ppt. This system was also used as a practical monitoring method for the Miyata River (in Japan).
Keywords: Powerful preconcentration; Capillary electrophoresis; Polycyclic aromatic hydrocarbons; Homogeneous liquid–liquid extraction; Triplex
UV/Vis spectra and solubility of some naphthoquinones, and the extraction behavior of plumbagin from Plumbago scandens roots in supercritical CO2 by S. V. Rodrigues; L. M. Viana; W. Baumann (pp. 895-900).
The solubility of 1,4-naphthoquinone, plumbagin, lawsone, and juglone in supercritical carbon dioxide was determined spectroscopically at 40°C, and in the pressure range 8–18 MPa. Their solubilities at 12 MPa were between 0.3 and 10 g L−1. Plumbagin from Plumbago scandens L. roots was extracted at 40°C and 20 MPa. The extracted plumbagin mass fraction was up to 0.2% in fresh roots but down to about 0.006% in aged roots. n-Hexane and chloroform extraction of such aged roots indicates that the older and dryer the roots are, the stronger they bind plumbagin. Reversed-phase HPLC indicated a relatively pure plumbagin extract with supercritical carbon dioxide.
Keywords: 1,4-Naphthoquinone; Plumbagin; Juglone; Lawsone; Supercritical CO2
Microwave-assisted solvent extraction and gas chromatography ion trap mass spectrometry procedure for the determination of persistent organochlorine pesticides (POPs) in marine sediment by Nieves Carro; Isabel García; María Ignacio; Ana Mouteira (pp. 901-909).
Microwave-assisted solvent extraction of persistent organochlorine pesticides (POPs) in marine sediment was developed and optimized by means of two-level factorial designs. Six variables (microwave power, extraction time and temperature, amount of sample, solvent volume, and sample moisture) were considered as factors in the optimization process. The results show that the amount of sample to be extracted and solvent volume are statistically significant for the overall recovery of the studied pesticides, although compromise conditions have to be established with the object of avoiding overpressure in closed vessels. After extraction, a clean up step including the use of a silica cartridge was performed prior to chromatographic determination in order to remove interferences. The optimized procedure was compared to conventional Soxhlet extraction. The MS-MS ion preparation mode was applied to improve the sensitivity and selectivity of the chromatographic technique.
Keywords: Microwave-assisted solvent extraction; Persistent organochlorine pesticides; Marine sediment; Gas chromatography mass spectrometry
Quantitative NMR spectroscopy of complex technical mixtures using a virtual reference: chemical equilibria and reaction kinetics of formaldehyde–water–1,3,5-trioxane by Michael Maiwald; Thomas Grützner; Eckhard Ströfer; Hans Hasse (pp. 910-917).
Quantitative 1H NMR spectroscopy was used to study chemical equilibria and reaction kinetics of both the formation and decomposition of 1,3,5-trioxane in aqueous formaldehyde solutions. The reaction was homogeneously catalyzed with up to 0.10 g g−1 sulfuric acid at temperatures between 360 and 383 K so that most of the experiments had to be carried out pressurized. The studied mixtures were complex due to the formation of methylene glycol and poly(oxymethylene) glycols in aqueous formaldehyde and the presence of considerable amounts of ionized species. Most common internal standards are decomposed by the hot sulfuric acid and external standards were not applicable using the flow NMR probe or pressurizable NMR sample tubes. Therefore, for the quantification of the small trioxane signals, a novel procedure was applied, in which electronically generated NMR signals were used as highly stable Virtual References (VR). The NMR decoupler channel with wave-form generator was used as the source of the reference signal, which was irradiated into the probe using the lock coil. Details on the experimental procedure are presented. It is shown that the presented method yields reliable quantitative reaction data for the complex studied mixtures.
Keywords: NMR spectroscopy; Quantitative spectroscopy; Virtual reference; 1,3,5-trioxane; Formaldehyde
Ultrasound-assisted extraction of pesticides from olive branches: a multifactorial approach to method development by A. Peña; F. Ruano; M. D. Mingorance (pp. 918-925).
A rapid and simple method has been developed for the analysis in olive branches of two insecticides currently used in olive pest control, dimethoate and α-cypermethrin. The effects of analytical conditions on pesticide recovery and the optimal extraction conditions were evaluated by means of a factorial design. The use of this chemometric tool in analytical method development allows the identification of the principal and interaction effects of the extraction conditions on the recovery of pesticides. It also gives information about the location of pesticide maximum recovery with minimal experimental investment. Extraction was carried out with an ultrasonic bath and the experimental conditions studied included the volume of extractant, the time of extraction, the number of extraction steps and the sample weight. The sample was further cleaned up using a Florisil solid-phase extraction cartridge. For the overall extraction procedure, recoveries of 99 % for α-cypermethrin and 90 % for dimethoate from the spiked samples were found for 1 g of sample extracted three times with 35 mL hexane, sonicating for 2 min in each step. The complete process including ultrasonic extraction and filtration will not require more than 15–20 min, in contrast with several hours for conventional liquid–solid extraction techniques. The proposed method allows a high sample throughput, as commonly required in monitoring studies.
Keywords: Dimethoate; α-Cypermethrin; Olive tree; Ultrasonic extraction; Experimental designs
A novel thiocyanate-selective electrode based on a zinc–phthalocyanine complex by Wen-Ju Xu; Ya-Qin Chai; Ruo Yuan; Su-Li Liu (pp. 926-930).
A novel thiocyanate (SCN−)-selective PVC membrane electrode based on a zinc-phthalocyanine (ZnPc) complex as neutral carrier is described. The membrane electrode containing ZnPc with 5.1% (w/w) ionophore, 29.2% (w/w) PVC, and 65.7% (w/w) 2-nitrophenyl octyl ether (o-NPOE) as plasticizer displayed an anti-Hofmeister selectivity sequence % MathType!Translator!2!1!AMS LaTeX.tdl!TeX -- AMS-LaTeX!% MathType!MTEF!2!1!+-% feaafaart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX% garmWu51MyVXgatuuDJXwAK1uy0HwmaeHbfv3ySLgzG0uy0Hgip5wz% aebbnrfifHhDYfgasaacH8qrps0lbbf9q8WrFfeuY-Hhbbf9v8qqaq% Fr0xc9pk0xbba9q8WqFfea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qq% Q8frFve9Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeWaeaaakeaaca% qGOaGaae4uaiaaboeacaqGobWaaWbaaSqabeaacqGHsislaaGccqGH% +aGpcaqGtbGaaeyyaiaabYgadaahaaWcbeqaaiabgkHiTaaakiabg6% da+iaabMeadaahaaWcbeqaaiabgkHiTaaakiabg6da+iaaboeacaqG% SbGaae4tamaaBaaaleaacaqG0aaabeaakmaaCaaaleqabaGaeyOeI0% caaOGaeyOpa4JaaeOqaiaabkhadaahaaWcbeqaaiabgkHiTaaakiab% g6da+iaaboeacaqGSbWaaWbaaSqabeaacqGHsislaaGccqGH+aGpci% GGobGaai4tamaaBaaaleaacaGGZaaabeaakmaaCaaaleqabaGaeyOe% I0caaOGaeyOpa4JaaeOtaiaab+eadaWgaaWcbaGaaeOmaaqabaGcda% ahaaWcbeqaaiabgkHiTaaakiabg6da+iaabIeadaWgaaWcbaGaaeOm% aaqabaGccaqGqbGaae4tamaaBaaaleaacaqG0aaabeaakmaaCaaale% qabaGaeyOeI0caaOGaeyOpa4Jaae4uaiaab+eadaWgaaWcbaGaaein% aaqabaGcdaahaaWcbeqaaiaaikdacqGHsislaaGccaGGPaGaaiilaa% aa!67CA! $${ ext{(SCN}}^ - > { ext{Sal}}^ - > { ext{I}}^ - > { ext{ClO}}_{ ext{4}} ^ - > { ext{Br}}^ - > { ext{Cl}}^ - > operatorname{NO} _3 ^ - > { ext{NO}}_{ ext{2}} ^ - > { ext{H}}_{ ext{2}} { ext{PO}}_{ ext{4}} ^ - > { ext{SO}}_{ ext{4}} ^{2 - } )$$ , and exhibited near-Nernstian potential response to thiocyanate ranging from about 1.0×10−1 to 1.0×10−6 mol L−1 with a detection limit of 7.5×10−7 mol L−1 and a slope of 58.1±0.5 mV per decade in pH 3.0 phosphate buffer solution at 25 °C. This preferential response is believed to be associated with the unique coordination between the central metal of the carrier and thiocyanate.
Keywords: Zinc–phthalocyanine complex; Neutral carrier; Thiocyanate; Ion-selective electrode
Combining visible and near-infrared spectroscopy with chemometrics to trace muscles from an autochthonous breed of pig produced in Uruguay: a feasibility study by D. Cozzolino; A. Vadell; F. Ballesteros; G. Galietta; N. Barlocco (pp. 931-936).
Visible (Vis) and near-infrared reflectance (NIR) spectroscopy combined with chemometrics was explored as a tool to trace muscles from autochthonous and crossbreed pigs from Uruguay. Muscles were sourced from two breeds, namely, the Pampa-Rocha (PR) and the Pampa-Rocha x Duroc (PRxD) crossbreed. Minced muscles were scanned in the Vis and NIR regions (400–2,500 nm) in a monochromator instrument in reflectance. Principal component analysis (PCA), discriminant partial least square regression (DPLS), linear discriminant analysis (LDA) based on PCA scores and soft independent modelling of class analogy (SIMCA) were used to identify the origin of the muscles based on Vis and NIR data. Full cross validation was used as validation method when classification models were developed. DPLS correctly classified 87% of PR and 78% of PRxD muscle samples. LDA calibration models correctly classified 87 and 67% of muscles as PR and PRxD, respectively. SIMCA correctly classified 100% of PR muscles. The results demonstrated the usefulness of Vis and NIR spectra combined with chemometrics as rapid method for authentication and identification of muscles according to the breed of pig.
Keywords: Near-infrared spectroscopy; Principal component analysis; Linear discriminant analysis; Pig muscles; Traceability
Determination of volatile oak compounds in aged wines by multiple headspace solid-phase microextraction and gas chromatography–mass spectrometry (MHS-SPME–GC–MS) by José David Carrillo; María Teresa Tena (pp. 937-943).
Multiple headspace solid-phase microextraction (MHS-SPME) with gas chromatography–mass spectrometry is proposed for quantification of nine volatile oak compounds in aged wines. These compounds are formed and extracted by wine when it is matured in oak barrels and are responsible for particular organoleptic properties and the high quality of these wines. Some important variables of the extraction process, for example volume of sample and extraction time, were studied. Extraction of 50 μL wine was performed with a divinylbenzene–Carboxen–polydimethylsiloxane fibre at 55 °C for 60 min. For calibration the same conditions were used, except that the wine was substituted by 50 μL of a standard solution in synthetic wine. The linearity, detection limits, and repeatability of the method were determined by use of standard solutions in synthetic wine. Detection limits were between 0.01 and 10 μg L−1 (for eugenol and furfural, respectively) and repeatability, expressed as relative standard deviation, was from 2 to 6%. The method was used to analyse six red wines and the concentrations obtained were statistically compared with those obtained by the standard addition method for the same wines.
Keywords: Oak volatile compounds; Aged wine; Multiple headspace solid-phase microextraction; Gas chromatography–mass spectrometry
Redox-driven transport of copper ions in an emulsion liquid membrane system by Hiroaki Matsumiya; Yosuke Yatsuya; Masataka Hiraide (pp. 944-947).
A new redox-driven type of emulsion liquid membrane separation is described. Milligram amounts of copper(II) in 0.2 M hydrochloric acid were reduced to copper(I) in the presence of ascorbic acid (1 M≡1 mol l−1). The copper solution was emulsified with a (1+4) mixture of toluene and n-heptane using Span-80 (sorbitan monooleate) as an emusifier. The resulting water-in-oil emulsion was dispersed in 0.2 M hydrochloric acid containing hydrogen peroxide and neocuproine (2,9-dimethyl-1,10-phenanthroline) by stirring for 10 min. The copper in the internal aqueous phase was selectively transported to the external one, leaving other heavy metals (e.g., Mn, Co, Ni, Cd and Pb) in the internal aqueous phase. After collecting the dispersed emulsion globules, they were demulsified by heating and the metals in the segregated aqueous phase were determined by graphite-furnace atomic absorption spectrometry (GFAAS). The selective transport of copper offered the multielement separation of trace heavy metals from a copper matrix, allowing the GFAAS determination of impurities at the 0.01% level in copper metal.
Keywords: Separation; Emulsion liquid membrane; Redox reaction; Copper; Trace analysis
Capillary HPLC–ICP MS mapping of selenocompounds in spots obtained from the 2-D gel electrophoresis of the water-soluble protein fraction of selenized yeast by Laure Tastet; Dirk Schaumlöffel; Brice Bouyssiere; Ryszard Lobinski (pp. 948-953).
A method based on ICP collision-cell MS detection in capillary HPLC was developed to gain an insight into the purity and identity of selenium-containing proteins separated by 1-D and 2-D electrophoresis. The bands and spots obtained after the separation of water-soluble proteins in selenized yeast were digested with trypsin prior to chromatography. Selenium could be detected down to the subpicogram level. The method, assisted by information obtained by MALDI TOF MS on the 5000 Da cut-off fraction, permitted the purity of bands and spots to be estimated and the efficiency of tryptic digestion and the quantity of selenium present in individual peptides to be evaluated. Owing to the high sensitivity and the lack of matrix suppression effects, the method provided chromatograms with signal-to-noise ratios of 10–1000 in conditions where the common ES Q–TOF MS detection failed.
Keywords: Gel electrophoresis; Capillary HPLC; ICP MS; Selenium-containing proteins; Selenized yeast
Application of anodized aluminum in fluorescence detection of biological species by Pavel Takmakov; Ivan Vlassiouk; Sergei Smirnov (pp. 954-958).
Thin nanoporous alumina obtained by anodization of aluminum films offers promising advantages for application in fluorescence-based biological sensors including convenient preparation, increased density of binding sites, and improved collection efficiency of fluorescence. These advantages are illustrated in the detection of streptavidin using biotin covalently bound to the surface of alumina nanopores. Fluorescence intensity enhancement as high as 7 times is observed in nanopores in comparison to flat glass surface.
Keywords: Biosensors; Fluorescence/Luminescence; Nanoporous Aluminum Oxide; Biotin
Cu2+ and Cu+ bathocuproine disulfonate complexes promote the oxidation of the ROS-detecting compound dichlorofluorescin (DCFH) by Hilde Laggner; Marcela Hermann; Bernhard M. K. Gmeiner; Stylianos Kapiotis (pp. 959-961).
The water-soluble Cu+chelator bathocuproine disulfonate (BCS) is widely used to quantify Cu+ or detect Cu+ formation in Cu2+-initiated oxidation reactions. The dichlorofluorescin (DCFH) assay is commonly used to monitor free radical reactions, reactive oxygen species (ROS), or reactive nitrogen species (RNS). Upon oxidation the non-fluorescent DCFH is converted into the fluorescent compound dichlorofluorescein (DCF). In the present communication we show that the Cu+ reagent BCS strongly facilitated the oxidation of DCFH in the presence of Cu2+ or Cu+. In contrast, 2,2′-dipyridyl (DP), which is also a Cu+-complexing reagent, but not as well known and therefore not as commonly used as BCS, did not cause any oxidative modification of DCFH in the presence of Cu2+ or Cu+. We therefore recommend that DP should be used instead of BCS to complex Cu+ in reactions which are initiated by Cu2+ and when ROS/RNS are analyzed by the DCFH oxidation assay.
Keywords: Bathocuproine disulfonate; Dipyridyl; Dichlorofluorescin; Copper ions; Oxidation
Vanadium determination in chloride matrices using ICP-MS: finding the optimum collision/reaction cell parameters for suppressing polyatomic interferences by Vladislav Chrastný; Michael Komárek; Martin Mihaljevič; Jana Štíchová (pp. 962-970).
Efficiencies of He/NH3 and He/H2 collision gases were compared in a conventional type of hexapole cell of an inductively coupled plasma mass spectrometer (ICP-MS). The optimum conditions [hexapole and quadrupole bias voltage (VH and VQ) and collision/reaction gas flow rates] were tested for vanadium determination (51V) in chloride matrices. When the He/H2 mixture was used, the optimum values of VH and VQ were −10.0 and −8.0 V, respectively. This set-up corresponds to the kinetic energy discrimination effect. When the He/NH3 mixture was used, the optimum values of VH and VQ were +10.0 and −7.0 V, respectively. Positive VH values correspond to the ion kinetic energy effect, which allows the reactivity of the ions entering the collision/reaction cell with the reaction gas to be controlled. The obtained results showed that the He/H2 mixture is not optimal for V determination in samples containing chlorides due to the insufficient suppression of the polyatomic interference of 35Cl16O+. Data obtained from vanadium determination using the He/NH3 mixture were consistent for all selected Cl− concentrations, and the results were acceptable. The detection limit was comparable with detection limits obtained from ICP-MS equipped with a dynamic reaction cell. Analyses of elements forming interfering molecules, e.g., iron (56Fe), arsenic (75As) and selenium (80Se), were in good agreement with the certified values for both studied collision/reaction gas mixtures.
Keywords: Vanadium; Chloride matrix; ICP-MS; Collision/reaction cell; Hexapole bias; Quadrupole bias
Stoichiometry determination of (Pb,La)(Zr,Ti)O3-type nano-crystalline ferroelectric ceramics by wavelength-dispersive X-ray fluorescence spectrometry by Rafał Sitko; Beata Zawisza; Andrzej Kita; Małgorzata Płońska (pp. 971-974).
Analysis of small samples of lanthanum-doped lead zirconate titanate (PLZT) by wavelength-dispersive X-ray fluorescence spectrometry (WDXRF) is presented. The powdered material in ca. 30 mg was suspended in water and collected on the membrane filter. The pure oxide standards (PbO, La2O3, ZrO2 and TiO2) were used for calibration. The matrix effects were corrected using a theoretical influence coefficients algorithm for intermediate-thickness specimens. The results from XRF method were compared with the results from the inductively coupled plasma optical emission spectrometry (ICP-OES). Agreement between XRF and ICP-OES analysis was satisfactory and indicates the usefulness of XRF method for stoichiometry determination of PLZT.
Keywords: Ferroelectrics; PLZT; XRF; ICP-OES
Testing equivalence between two laboratories or two methods using paired-sample analysis and interval hypothesis testing by Shixia Feng; Qiwei Liang; Robin D. Kinser; Kirk Newland; Rudolf Guilbaud (pp. 975-981).
A modified interval hypothesis testing procedure based on paired-sample analysis is described, as well as its application in testing equivalence between two bioanalytical laboratories or two methods. This testing procedure has the advantage of reducing the risk of wrongly concluding equivalence when in fact two laboratories or two methods are not equivalent. The advantage of using paired-sample analysis is that the test is less confounded by the intersample variability than unpaired-sample analysis when incurred biological samples with a wide range of concentrations are included in the experiments. Practical aspects including experimental design, sample size calculation and power estimation are also discussed through examples.
Keywords: Equivalence; Interval hypothesis testing; Paired-sample analysis; Bioanalysis; Comparability