Forgot your password?
New user?
New Window Opens on the Secret Life of Microbes: Scientists Develop First Microbial Profiles of Ecosystems
CAS announces the release of SciFinder Scholar for Mac OS X
Press Releases
Press Releases
| Check out our New Publishers' Select for Free Articles |
Analytical and Bioanalytical Chemistry (v.365, #6)
Acoustic levitation device for sample pretreatment in microanalysis and trace analysis by Runar Eberhardt; Bernd Neidhart (pp. 475-479).
A sample preparation device for microanalysis and trace analysis based on acoustic levitation is described. Derivatization can be performed in a single levitated drop as part of the sample pretreatment in an analytical procedure. The applicability of the experimental setup is demonstrated. First results of the preconcentration of hexachlorobenzene are given.
Decision protocol for checking robustness with previous outlier detection in the validation of analytical methods by J. M. Bosque-Sendra; M. Nechar; L. Cuadros Rodríguez (pp. 480-488).
A general procedure based on variation of experimental design for checking robustness in the validation of analytical methods is presented. This procedure, which is easy to apply, consists in estimating the main total effects, in detecting outliers, checking the curvature and in determining the main side effects. Two methodologies based on the analysis of a) the residuals from the reduced model and b) the replicates from the reconstructed design were employed for the detection of outliers. In further studies, general experimental design principles were applied using two- and three-level factorial designs. In some cases, a dummy variable was introduced in order not to modify the structure of the designs utilized.
Multivariate statistical analysis of coastal sediment data by I. Stanimirova; S. Tsakovski; V. Simeonov (pp. 489-493).
Multivariate statistical analysis of sediment data (information matrix 123 × 16) from the Gulf of Mexico, USA shows that the data structure is defined by four latent factors conditionally called “inorganic natural”, “inorganic anthropogenic”, “bioorganic” and “organic anthropogenic” explaining 39.24%, 23.17%, 10.77% and 10.67% of the total variance of the data system, respectively. The receptor model obtained by the application of the PCR approach makes it possible to apportion the contribution of each chemical component for the latent factor formation. A separation of the contribution of each chemical parameter is achieved within the frames of “natural” and “anthropogenic” origin of the respective heavy metal or organic matter to the sediment formation process. This is a new approach as compared to the traditional “one dimensional” search with a limited number of preliminary selected tracer components. The model suggested divides natural from anthropogenic influences and allows in this way each participant in the sediment formation process to be used as marker of either natural or anthropogenic effects.
An electrochemical method for quantification of the radical scavenging activity of SOD by F. Lisdat; B. Ge; R. Reszka; E. Kozniewska (pp. 494-498).
An electrochemical technique for the determination of enzymatic superoxide scavenging activity is described. In amperometric mode of sensor operation ¶the oxidation current was altered by additions of superoxide dismutase (SOD). The 50% inhibition value (I50) corresponded to 0.165 U of the standard photometric test of McCord and Fridovich. Influence by inert proteins was much less than in the standard method: The SOD/BSA ratio was 4 × 105. Potentially interfering substances, e.g. ascorbic acid and glutathione, were tested. Plasma samples of rats which were treated with modified SOD during cerebral ischaemia, were assayed with the new method and the standard photometric test. A good correlation was found for the analysis in these physiological samples (r = 0.97).
Capillary zone electrophoresis for the determination of average hydrodynamic velocity and diffusion coefficient by Hongyi Zhang; Xiurong Song; Zhihong Shi; Gengliang Yang; Zhide Hu (pp. 499-503).
The determination of the average hydrodynamic velocity and diffusion coefficient by capillary zone electrophoresis is described. The present simple method only requires basic experimental data, such as peak area, peak height and migration time to complete the task of determining the diffusion coefficient and the average hydrodynamic velocity.
Kinetic spectrophotometric determination of trace amounts of selenium and vanadium by A. Safavi; H. R. Sedghy; E. Shams (pp. 504-510).
A sensitive kinetic spectrophotometric method has been developed for the determination of Se(IV) over the range of 45 to 4000 ng in 10 mL of solution. The method is based on the catalytic effect of Se(IV) on the reduction reaction of bromate by hydrazinium dichloride, with subsequent reaction of Ponceau S with products of the above reaction (chlorine and bromine), causing color changing of Ponceau S. Method development includes optimization of time interval for measurement of slope, pH, reagents concentration, and temperature. The optimized conditions yielded a theoretical detection limit of 33 ng/¶10 mL of solution of Se(IV). The interfering effects were studied and removed. The method was applied to the determination of selenium in spiked water, Kjeldahl tablet, selenium tablet, and shampoo. Vanadium(V) has an inhibition effect on the catalyzed reaction of bromate and hydrazine by selenium. Using this effect, V(V) can be determined in the range of 70 to 2500 ng in 10 mL of solution. The optimization procedure includes pH and selenium concentration. An extraction method was used for interference removal. The method was applied to the determination of vanadium in petroleum.
Copper(II)-selective membrane electrode based on a recently synthesized naphthol-derivative Schiff’s base by N. Alizadeh; S. Ershad; H. Naeimi; H. Sharghi; M. Shamsipur (pp. 511-515).
A PVC membrane electrode for copper(II) ions based on a recently synthesized naphthol-derivative Schiff’s base as membrane carrier was prepared. The sensor exhibits a Nernstian response for Cu2+ ions over a wide concentration range (5.0 × 10–6–5.0 × 10–2 mol/L) with a detection limit of 3.1 × 10–6 mol/L (0.2 μg/mL). It has a very short response time of about 5 s and can be used for ¶3 months without any divergence in potential. The proposed electrode revealed good selectivities over a wide variety of other cations including alkali, alkaline earth, transition and heavy metal ions and could be used in a pH range of 4.0–7.0. It was successfully applied to the direct determination and potentiometric titration of copper ion.
Photodissociation/gas-diffusion separation and fluorimetric detection for the analysis of total and labile cyanide in a flow system by E. Miralles; R. Compañó; M. Granados; M. D. Prat (pp. 516-520).
Total cyanide species are determined in a flow injection system which includes UV-photodissociation, gas-diffusion separation and spectrofluorimetric detection. Without the irradiation step, only cyanide easily released in acid medium, i.e. labile cyanide, is determined. Cyanide diffuses through a microporous PTFE membrane from an acid donor stream to a sodium hydroxide acceptor stream. Then, the transferred cyanide reacts with ¶o-phthalaldehyde and glycine to form a highly fluorescent isoindole derivative. Complete cyanide recoveries were obtained for the most important metal cyanide complexes found in environmental samples, excepting cobaltocyanide. The sampling frequency for total cyanide was 4 samples h–1 and the detection limit was 0.4 μg L–1. Recoveries of total cyanide from river water obtained with this method are about 90% of those obtained with APHA Method 4500-CN C for total cyanide.
A simple and mild derivatization method for hydroxyl compounds using condensation agent carbazole-9-N-(2-methyl)-acetyl-benzene-disulfonate and its application for the determination of volatile alcohols from plasma by HPLC with fluorescence detection by Jinmao You; Wenjian Lao; Qingyu Ou; Xuejun Sun (pp. 521-528).
A simple and sensitive HPLC method for the determination of hydroxyl compounds including volatile alcohols from spiked plasma, using a fluorescent condensation agent, namely carbazole-9-N-(2-methyl)-acetyl-benzene-disulfonate (CMABS), has been developed. A mixture of alcohols and pyridine in dichloromethane was treated with CMABS to give a quantitative yield of esters. The maximum fluorescence emissions for the derivatized alcohols are at 365 nm (λex 335 nm). Studies on derivatization conditions indicate that alcohols react very fast with CMABS in presence of pyridine in dichloromethane to give the corresponding fluorescent derivatives. The method, in conjunction with a multi-step gradient, offers a baseline resolution of the common alcohol derivatives on a reversed-phase C18 column, which is more convenient and more efficient than previous methods which require the prior conversion of the carboxylic acids to the acyl chlorides. The application of this method to the analysis of volatile alcohols in plasma was also investigated. The LC separation shows good selectivity and reproducibility for alcohol derivatives. The relative standard deviations ¶(n = 5) for 100 pmol of each alcohol are < 4%. The detection limits are at the fmol level for C1–C3 alcohols and pmol level for C4–C9 alcohols.
Chlorinated di- and triphenylmethanes in sediments of the Mulde and Elbe rivers by J. Schwarzbauer; S. Franke; W. Francke (pp. 529-536).
Congeneric groups of chlorinated diphenylmethanes (ClDPM) and triphenylmethanes (ClTPM) identified by coupled GC/MS investigations of Elbe and Mulde river sediments were not as yet noticed as environmental contaminants of aquatic sediments. ClDPM and ClTPM are structurally related to other polychlorinated aromatic compounds and form complex mixtures of congeners. Individual ClDPM/ClTPM as well as mixtures of congerers were synthesized, and served as reference compounds for isomer identification and quantitative analysis. In addition to mass spectra, GC/FTIR-investigations and retention indices proved to be valuable for structural assignments. Sediments from the Mulde river contained up to 220 μg/kg ClTPM and 170 μg/kg ClDPM. The spatial distribution of ClDPM/TPM concentrations indicated a strong localized source of emisson at the lower Mulde river, from where the compounds enter sediments and suspended matter of the Elbe river. The occurrence of ClTPM in the Hamburg harbour at comparable levels in samples of recent and older sediments indicates emissions over a prolonged period.
Chemiluminescent lipase determination based on the enhanced luminol/H2O2/horseradish peroxidase/fluorescein diacetate energy transfer system by A. Navas Díaz; F. G. Sanchez; M. C. Torijas; J. Lovillo (pp. 537-540).
A methodology for the determination of lipase, based on the coupled processes of energy transfer and enhancement of the chemiluminescence of the luminol-H2O2-horseradish peroxidase (HRP) system has been developed. Fluorescein diacetate (FDA) was hydrolyzed to fluorescein by the action of the enzyme lipase, and this compound acted as an enhancer of the chemiluminescent process and acceptor of the chemiluminescent emission from the luminol-H2O2-HRP system. By measuring the transferred emission to fluorescein at 525 nm, lipase (range 0.2–1.5 U/mL, RSD 2.3%) was determined. This methodology permited the determination of every compound of the system, thus, H2O2 (range 0.5–2 mM, RSD 6.9%) and HRP (range 5.5–49.5 U/mL, RSD 3.6%) could also be determined. Lipase was determined in rabbit serum with 96.7 ± 3.3% and 102.9 ± 5.4% recoveries for two different lipase concentrations. Besides, H2O2 was determined in the disinfectant solution for contact lenses.
Comparison of enantioseparation of amino acid derivatives in aqueous and mixed aqueous-organic media by capillary zone electrophoresis by Lili Yang; Zhuobin Yuan (pp. 541-544).
The chiral separation of dansyl-amino acids has been performed by capillary zone electrophoresis using ¶β-cyclodextrin as a chiral selector, urea as an additive and 2-propanol and methanol as organic modifiers. The enantiomeric separations of dansyl-amino acids were investigated in aqueous medium and compared with the separation in mixed aqueous-organic medium as background electrolytes. The separation conditions, (concentration of buffer, β-cyclodextrin, methanol, urea and the pH value of buffer) were optimized. In the absence of organic modifier, only five pairs of 8 separated dansyl-amino acids were resolved when run separately. A mixture of up to eight chiral amino acids can be baseline resolved in less than 19 min by β-cyclodextrin-modified capillary zone electrophoresis with a buffer of 60 mmol L–1 H3BO3-KCl/40 mmol L–1 NaOH (pH 9.0), 4 mol L–1 urea, 100 mmol L–1β-cyclodextrin and 10% (v/v) methanol.
Combination of various analytical techniques for speciation of low molecular weight aluminium complexes in plant sap by T. Bantan; R. Milačič; B. Mitrović; B. Pihlar (pp. 545-552).
The possibilities for speciation of low molecular weight aluminium organic acid complexes (LMW-Al) in plant sap were investigated by applying a combination of various chromatographic and spectroscopic techniques. The behavior of different LMW-Al complexes was investigated in synthetic aqueous solutions on anion and cation exchange fast protein liquid chromatography (FPLC) columns with inductively coupled plasma – atomic emission spectrometry (ICP-AES) or electrothermal atomic absorption spectrometry (ETAAS) detection. Plant sap of Sempervivum tectorum with a high concentration of Al (9.3 μg cm–3) and Sansevieria trifasciata with an appreciably lower Al concentration (0.065 μg cm–3) were analyzed. The speciation study in plant sap indicated that the species present in these samples, existed as negatively charged LMW-Al complexes which were eluted at the retention time typical for Al-citrate and Al-aconitate. In order to identify Al binding ligands eluted under the chromatographic peak analysis by electrospray ionization (ESI)-MS technique using Z spray ion source were also applied. The predominant LMW-Al negatively charged complexes in Sempervivum tectorum and Sansevieria trifasciata were found to be Al-citrate and Al-aconitate. It was shown that other LMW organic acids do not form complexes with Al in the samples studied.
Analysis of O-glucuronide conjugates in urine by electrospray ion trap mass spectrometry by J. K. Gu; D. F. Zhong; X. Y. Chen (pp. 553-558).
The application of electrospray ionization (ESI) ion trap mass spectrometry in the characterization of O-glucuronide conjugates of some drugs in urine is described. The conjugated metabolites formed in rabbit and human were separated by reversed-phase high-performance liquid chromatography (HPLC) and characterized by multi-stage mass spectrometry (MSn) experiments in negative ion mode. The ESI mass spectra showed a deprotonated molecule [M–H]–, which was chosen as precursor ion. Collision-induced dissociation (CID) of [M–H]– in MSn experiments resulted in the appearance of glucuronate ‘fingerprint’ ions at m/z 175 and 113 as well as prominent aglycone ions which were the same as those produced from authentic specimens. This information can be used to identify this type of compound directly without the need for derivatization or hydrolysis of enzymes, providing a rapid and specific method for guiding the isolation and characterization of similar compounds in complex matrices with LC/MS.
Classification of ancient proteinaceous painting media by the joint use of pattern recognition and factor analysis on GC/MS data by R. Aruga; P. Mirti; A. Casoli; G. Palla (pp. 559-566).
Reference proteinaceous binding media of the kinds historically used in painting (specially prepared for this study) and samples collected from ancient polychrome works of art were analysed by gas chromatography – mass spectrometry. The data have been processed by several multivariate chemometric techniques, such as cluster analysis, principal component analysis, factor analysis and SIMCA technique in order to classify the binding media of the ancient works of art on the basis of the proteinaceous material used. The characterisation of ancient samples was possible by the joint use of SIMCA technique and factor analysis. The latter, in particular, has made it possible to point into evidence the presence of at least two latent factors. The first factor seems to be connected with the chemical composition of the painting media, while the second factor is likely to be connected with ageing processes.