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 |
Analytica Chimica Acta (v.545, #1)
Multiple factor analysis in environmental chemistry by I. Stanimirova; B. Walczak; D.L. Massart (pp. 1-12).
In environmental chemistry studies, it may be necessary to analyze data sets constituted by different blocks of variables, possibly of different types, measured on the same samples. Multiple factor analysis (MFA) is presented as a tool for exploring such data. The most important features of MFA are shown on a real environmental data set, consisting of two blocks of data, namely heavy metals and polycyclic aromatic hydrocarbons, measured for sediment samples. They are discussed and compared to principal component analysis (PCA). The usefulness of the weighting scheme used in MFA as a preprocessing step for other chemometric methods, such as clustering, is also highlighted.
Keywords: Exploratory analysis; MFA; Weighting; Procrustes analysis; Matching data tables; STATIS
Rapid screening of precursor and degradation products of chemical warfare agents in soil by solid-phase microextraction ion mobility spectrometry (SPME–IMS) by Preshious Rearden; Peter B. Harrington (pp. 13-20).
The use of solid-phase microextraction (SPME) coupled to ion mobility spectrometry (IMS) to detect precursor and degradation products of chemical warfare agents (CWAs) as soil contaminants was investigated. The development and characterization of a system to interface a thermal desorption solid-phase microextraction inlet with a hand held ion mobility spectrometer was demonstrated. The analytes used in this study were diisopropyl methylphosphonate (DIMP), diethyl methylphosphonate (DEMP), and dimethyl methylphosphonate (DMMP). Two SPME fibers with different stationary phases, 100μm polydimethylsiloxane (PDMS) and 65μm polydimethylsiloxane divinylbenzene (PDMS/DVB), were evaluated in this study to determine the optimal fiber and extraction conditions. Better results were obtained with the PDMS fiber. SPME–IMS offered good repeatability and detection of the precursor and degradation products in spiked soil at concentrations as low as 10μg/g. Sample analysis time was less than 30min for all the precursor and degradation products.
Keywords: Chemical warfare agent; Solid-phase microextraction; Ion mobility spectrometry; Headspace analysis
Electrochemical DNA biosensors based on platinum nanoparticles combined carbon nanotubes by Ningning Zhu; Zhu Chang; Pingang He; Yuzhi Fang (pp. 21-26).
Platinum nanoparticles were used in combination with multi-walled carbon nanotubes (MWCNTs) for fabricating sensitivity-enhanced electrochemical DNA biosensor. Multi-walled carbon nanotubes and platinum nanoparticles were dispersed in Nafion, which were used to fabricate the modification of the glassy carbon electrode (GCE) surface. Oligonucleotides with amino groups at the 5′ end were covalently linked onto carboxylic groups of MWCNTs on the electrode. The hybridization events were monitored by differential pulse voltammetry (DPV) measurement of the intercalated daunomycin. Due to the ability of carbon nanotubes to promote electron-transfer reactions, the high catalytic activities of platinum nanoparticles for chemical reactions, the sensitivity of presented electrochemical DNA biosensors was remarkably improved. The detection limit of the method for target DNA was 1.0×10−11moll−1.
Keywords: Carbon nanotubes; Platinum nanoparticles; Electrochemical DNA biosensor
Direct electrochemical assay of glucose using boron-doped diamond electrodes by Joowook Lee; Su-Moon Park (pp. 27-32).
We report linear sweep and square wave voltammetric studies on glucose oxidation at boron-doped diamond (BDD) electrodes in an alkaline medium in efforts to evaluate the techniques for electrochemically assaying glucose. The bare BDD electrode showed good linear responses to glucose oxidation for a concentration range from 0.5 to 10mM glucose, which well encompasses the physiological range of 3–8mM. The BDD electrodes did not experience interferences from ascorbic acid or uric acid during glucose detection. This method, when applied to real blood samples, gave results similar to those obtained by a commercial glucose monitor.
Keywords: Boron-doped diamond electrodes; Non-enzymatic glucose analysis
Identification of chiral selectors for improved enantioseparation based on molecular interaction fields by Maria Luiza C. Montanari; Quezia B. Cass; Adriano D. Andricopulo; Andrei Leitão; Carlos A. Montanari (pp. 33-45).
Chiral sulfoxide drugs such as omeprazole, lansoprazole and pantoprazole were chromatographed on three chiral stationary phases (CSP), using amylose tris-(phenylcarbamate) derivatives in the reversed-phase mode. The retention factors ( k) and chromatographic partition coefficients ( kw), obtained by extrapolation of the first according to the linear Snyder equation, were analyzed employing molecular interaction fields (MIF) of eluted analytes. Based on the generated MIF, chiral selectors could be identified for improving enantiomeric separation performance of the respective sulfoxides. The method is useful for predicting the complementarities between CSP and analytes, and thus to help the selection of appropriate stationary phases prior to their preparation.
Keywords: Principal component analysis; Chiral selector selection; Hydrophobicity; Sulfoxide drugs
Seasonal and chemotype influences on the chemical composition of Lantana camara L. by Jean-Aimé Randrianalijaona; Panja A.R. Ramanoelina; Jean R.E. Rasoarahona; Emile M. Gaydou (pp. 46-52).
Yellow-orange and pink-violet colours of flower plants of Lantana camara from Madagascar were studied with a focus on essential oil (EO) in order to characterize chemotype EO variability. The chemical composition of 73 samples of aerial part EO of L. camara collected each month of the year, at various location, have been characterized by gas chromatography-mass spectrometry (GC-MS). Among the 50 peaks characterized, 43 were identified. The main components changed within the two flower colour types. EO from yellow-orange colour of flowers compared to pink-violet flowers is characterized by high content in terpenic compounds and lower amount in oxygenated compounds. Similar results were observed during seasons, showing that the chemical composition is relatively stable all year long. The components characterizing the pink-violet flower chemotype are: sabinene (9.4–11.3%), 1,8-cineole (3.7–4.6%), linalool (4.8–6.1%), β-caryophyllene (11.3–13.6%), α-humulene (4.4–5.2%), β-bisabolene (1.7–2.3%), γ-cadinene (0.1–0.4%), ar-curcumene (1.0–1.6%), caryophyllene oxide (1.2–0.7%) and davanone (22.6–25.9%). The components characterizing the yellow-orange flower chemotype are: sabinene (9.0–14.3%), 1,8-cineole (0.8–1.0%), linalool (0.4–1.4%), β-caryophyllene (25.8–30.8%), α-humulene (2.4–2.6%), β-bisabolene (13.6–14.9%), γ-cadinene (0.6–5.2%), ar-curcumene (0.7–2.8%), caryophyllene oxide (0.1–0.4%) and davanone (0.0–0.6%). Chemical composition of nine L. camara industrial EO show that they are composed of mixture of yellow-orange and pink-violet colour of flower chemotypes. Davanone is found in all samples with a mean of 12.4%, linalool (5.4%) and 1,8-cineole (4.1%). For sesquiterpenes, the main are β-caryophyllene (15.9%), β-bisabolene (1.8%) and γ-muurolene (1.4%).
Keywords: Lantana camara; Verbenaceae; Chemotype; Davanone; β-Caryophyllene; β-Bisabolene; Sabinene; Linalool
Preprocessing and exploratory analysis of chromatographic profiles of plant extracts by Margriet M.W.B. Hendriks; Leyre Cruz-Juarez; Dries De Bont; Robert. D. Hall (pp. 53-64).
The characterization of herbal extracts to compare samples from different origin is important for robust production and quality control strategies. This characterization is now mainly performed by analysis of selected marker compounds. Metabolic fingerprinting of full metabolite profiles of plant extracts aims at a more rapid and thorough screening or classification of plant material. We will show that HPLC is an appropriate technique for metabolic fingerprinting of secondary metabolites, given that adequate preprocessing of raw profiles is performed. Additional variation, which results from sample preparation and changing measurement conditions, usually obscures the information of interest in these raw profiles. This paper illustrates the importance of preprocessing of chromatographic fingerprinting data. Different alignment methods are discussed as well as the influence of normalization. Weighted principal component analysis is introduced as a valuable alternative to autoscaling of data. LC–UV data on Willow ( Salix sp.) extracts is used to evaluate these preprocessing methods and their influence on exploratory data analysis.
Keywords: Metabolic profiling; Metabolomics; Preprocessing; Alignment; Weighted principal component analysis; Liquid chromatography; Plant extracts; Willow (; Salix; sp.)
Determination of naproxen with flow injection chemiluminescence of Ru(bpy)32+–PbO2 system and its application for the binding study of naproxen to protein by Shoulian Wei; Lixia Zhao; Xianglei Cheng; Jin-Ming Lin (pp. 65-73).
A flow injection method based on Ru(bpy)32+–PbO2 chemiluminescence system was developed for the determination of naproxen. The factors affecting the CL intensity were performed including the amount of PbO2 and H2SO4, pH of buffer and concentration of Ru(bpy)32+. Under the optimum conditions, naproxen has a linear calibration graph in the range of 2×10−8–6×10−6mol/L with a limit of detection ( S/ N=3) of l.0×10−8mol/L, The correlation coefficient was 0.9976 ( n=12) with a relative standard deviation of 3.4% for 15 determinations of l×10−6mol/L of naproxen. Combining with ultrafiltration, this method was successfully applied to study naproxen–protein interaction. The binding constants ( K) to bovine serum albumen (BSA) were K1=2.06×106L/mol and K2=2.18×107L/mol, and to human serum albumen (HSA) were K1=4.80×106L/mol and K2=l.25×107L/mol, respectively. The correlation coefficients given by Scatchard plot and Klotz plot were satisfied, indicating that studied drug has two types of binding site in the molar ratio range studied. The number of the binding site ( n) on one molecule of BSA were n1=6.79 and n2=1.88, and of HSA were n1=1.22 and n2=1.80, respectively. The proposed method provided a sensitive, reliable and simple technique for studying naproxen–protein interaction and was for the first time applied to the determination of the unbound fraction of naproxen in its human serum albumin equilibrated solution.
Keywords: Chemiluminescence; Flow injection; Naproxen; Drug–protein binding; Ultrafiltration
2-[4-(Dimethylamino)phenyl]-3-hydroxy-4 H-chromene-4-one: A H-bond-sensitive fluorescent probe for investigating binary mixtures of organic solvents by V.G. Pivovarenko; A. Wróblewska; J. Błażejowski (pp. 74-78).
Molecules of electronically excited 2-[4-(dimethylamino)phenyl]-3-hydroxy-4 H-chromene-4-one (a fluorescent probe) co-exist in the normal (N*) and tautomeric (T*) forms and emit radiation in different spectral regions. The positions (expressed in wave numbers, ν) and intensities ( I) of the emission bands are strongly affected by the ability of the medium's molecules to participate in hydrogen bonding with the probe. In such cases, IN*, IN*/ IT*, νN*, νN*+ νT* or νN*− νT*, depend on the concentration (over a certain range) or its base-10 logarithm (log) of the component interacting with the probe. These relationships form the basis for a quantitative assay of such compounds in binary mixtures. On the other hand, the log( IN*/ IT*) versus νN*+ νT* or νN*− νT* relationships demonstrate unique features that can be used to distinguish components (alcohols) interacting with the probe and to quantify their contents. The prospects for the analytical application of these findings are outlined briefly.
Keywords: 2-[4-(Dimethylamino)phenyl]-3-hydroxy-4; H; -chromene-4-one; Hydrogen bonds; Fluorescent probe; Assay of components in binary liquids
Optimization of selenium determination in plant samples by hydride generation and axial view inductively coupled plasma atomic emission spectrometry by P. Masson; D. Orignac; T. Prunet (pp. 79-84).
The use of hydride generation coupled with axial view inductively couple plasma atomic emission spectrometry was presented for the determination of selenium in plant samples. The chemical factors affecting potentially the hydride generation efficiency (hydrochloric acid, sodium borohydride and sodium hydroxide concentrations) were assessed through investigation of chemical interference, accuracy and repeatability. The accuracy of measurements was not affected by elements present in high concentration in the plant matrix (K, Ca, Mg, and P). No interference was also observed with transition metals. Using a real sample (maize) with standard additions, decreases of recoveries were sometimes observed for 0.1% (m/v) NaOH, and attained 13.8% in the most unfavourable case. The final accuracy of the method was verified by using two certified reference materials: CRM 402 (white clover) and CRM 279 (sea lettuce). No statistically significant differences were obtained between the measured concentrations and the certified values. The optimized method was found sensitive (detection limit 0.15μgl−1), reliable and repeatable (R.S.D. between 1.3% and 4.0%).
Keywords: Selenium analysis; Plant samples; Hydride generation; Inductively coupled plasma atomic emission spectrometry
Direct determination of lead in produced waters from petroleum exploration by electrothermal atomic absorption spectrometry X-ray fluorescence using Ir–W permanent modifier combined with hydrofluoric acid by Eliane P. Oliveira; Ricardo E. Santelli; Ricardo J. Cassella (pp. 85-91).
The present work reports the development of a methodology for the direct determination of lead in high saline waters derived from petroleum exploration employing electrothermal atomic absorption spectrometry with permanent Ir–W and HF as modifiers. These waters, so-called produced waters, have complex composition containing several types of organic and inorganic substances. In order to attain best conditions (highest analytical signal besides lowest background) for the methodology studies about the effect of several variables and the convenient calibration strategy were performed. Also, the efficiency of other modification approaches was evaluated. At best conditions, pyrolysis and atomization temperature were 800 and 2200°C, respectively, when the modifiers cited above were utilized. Obtained results indicate that, in this kind of sample, lead can be determined by standard addition method or employing external calibration with standard solutions prepared in 0.8moll−1 NaCl medium. In order to evaluate the accuracy of the procedure, a recovery test was performed with six spiked samples of produced waters. The detection limit, quantification limit and the relative standard deviation in 0.8moll−1 NaCl were also calculated and the values are 1.5μgl−1, 5.0μgl−1 and 5.0% (at 10μgl−1 level), respectively.
Keywords: Lead; Produced waters; Electrothermal atomic absorption spectrometry; HF; Ir–W permanent modifier
The influence of scattering processes in quantitative X-ray fluorescence analysis by M. Bos; J.A. M. Vrielink (pp. 92-98).
Existing theory was used to develop a fundamental parameter (FP) computer program for quantitative X-ray fluorescence (XRF) spectrometry in which scattering interactions are taken into account. The program is suited for polychromatic radiation and composite samples and is used to estimate the errors that result from neglecting the scattering contributions in the analysis of samples in a low Z matrix when the spectrometer is calibrated either on pure elements or on standards similar to the samples.
Keywords: Quantitative XRF Rayleigh Compton scattering
Attenuated Total Reflection-Fourier transform infrared analysis of the fermentation process of pineapple by Sergio Armenta; Salvador Garrigues; Miguel de la Guardia; Philippe Rondeau (pp. 99-106).
A direct and reagent free procedure has been developed to monitor the fermentation process of pine apple nectar using Attenuated Total Reflectance Fourier-transform mid-infrared spectrometry (FT-IR) and multivariate analysis. A classical 42 design for standards was employed for calibration using the information in the spectral range from 907 to 1531cm−1 of the first order derivative spectra after mean centering of infrared data. The root mean square error of calibration (RMSEC) of 0.040, 0.021, 0.063 and 0.074% w/w were obtained for glucose, fructose, saccharose and ethanol, respectively, and a mean relative validation error of 2.9, 2.1, 2.6 and 3.6% was achieved for glucose, fructose, saccharose and ethanol. Results obtained by the proposed procedure for the alcohol content at different fermentation levels were statistically comparable with those obtained by a reference spectrometric method. So, FT-IR spectrometry provides a fast alternative to long and tedious classical procedures to ethanol determination and sugar enzymatic analysis.
Keywords: FT-IR; ATR; PLS; PCA; Monitorization; Fermentation; Bioprocess
2,2′,3,4-Tetrahydroxy-3′-sulpho-5′-nitroazobenzene for spectrophotometric determination of aluminium in pharmaceutical suspensions and granite by Tufan Guray; Ülkü Dilek Uysal; Tevfik Gedikbey; A. Ali Huseyinli (pp. 107-112).
A selective and sensitive new spectrophotometric method has been developed for the determination of aluminium. 2,2′,3,4-Tetrahydroxy-3′-sulpho-5′-nitroazobenzene (tetrahydroxyazon SN) formed an orange chelate with aluminium at pH 4. Molar absorptivity of the complex in 1:2 is 5.46×104lmol−1cm−1 at 479nm. The method obeys Beer's law in the range of 0.005–1.079μgml−1. The determination of aluminium is not interfered with by earth alkaline, alkaline elements, rare earth elements, halides, phosphates, sulphates, urea, ascorbic acid, Sn2+, Sr2+, Cr3+, Cd2+, Hg2+, or Mn2+. The proposed method is rapid and simple, and it has been successfully applied to the determination of aluminium in certified pharmaceutical suspension and granite.
Keywords: Aluminium; 2,2′,3,4-Tetrahydroxy-3′-sulpho-5′-nitroazobenzene; Tetrahydroxyazon SN; Spectrophotometric determination; Granite; Pharmaceutical analysis
Implementation of multicommutation principle with flow-through multioptosensors by E.J. Llorent-Martínez; A. Domínguez-Vidal; P. Ortega-Barrales; M. de la Guardia; A. Molina-Díaz (pp. 113-118).
For the first time, the combination of multicommutation concept with flow-through multioptosensors is exploited and a biparameter multicommutated UV sensor is developed. A very easy-operated and automated sensing device is proposed here and demonstrated to be useful in the routine analysis by applying it to the determination of two widely used pharmaceuticals chosen as model analytes: salicylamide and caffeine. The particulated solid phase used performs two functions: (a) states selectivity conditions by itself in the flow cell and (b) provides appropriate separation of the analytes in the on-line precolumn, thus making possible the sequential arrival of the analytes to the detection zone. Both carrier and eluting solutions chosen allow (with a very simple solenoid valve configuration and operation) the transitory signals to be developed in a completely automated device. Drastic reduction of carrier and eluting solutions used are achieved as compared to typically FIA optosensor configuration. The sensor responds linearly in the range 2–30 and 1–14μgml−1 for SLC and CF, with detection limits of 0.33 and 0.15μgml−1, respectively. Solution savings between 50 and 85% were obtained when comparing to typical flow injection analysis (FIA).
Keywords: Multicommutation; Pharmaceuticals; Flow-through optosensor