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.361, #5)
Analytical science – a discipline between chemistry and metrology by K. Doerffel (pp. 393-394).
After Karel Eckschlager (Prague) introduced information theory into analytical chemistry in the mid 60s, its usage and importance to the discipline has grown exponentially. One wonders whether it is the chicken or the egg in this case as well, but without informatics the immense amount of data produced in analytical measurements today could not be digested, filtered, and understood.Klaus Doerffel (Deceased, formerly of Leipzig) was an active and driving participant in the development of informatics and its use in analytical chemistry. He has summarized the field up to 1995 in a work entitled: “Analytical science – A discipline between chemistry and metrology.” The work is too large to permit full publication in this journal. Therefore, the important points are summarized here, and the full text can be obtained by written request to the Editorial Office.
Quantification of the expected shelf-life of certified reference materials by J. Pauwels; A. Lamberty; H. Schimmel (pp. 395-399).
Stability testing and -monitoring are of the highest importance for the certification of reference materials. However, in general the results of these measurements are only assessed in a qualitative way, and no effort is made to quantify the period of certification or the shelf-life of the CRM. However, the revised ISO Guide 31 “Contents of Certificates, Certification Reports and Labels of Reference Materials” will most probably contain the explicite obligation to mention an expiry date “for all CRMs where instability has been demonstrated or is considered possible”. Therefore a method is proposed for quantifying the expected shelf-life on the basis of linear regression and determination of the intersection of the lower confidence limit of the certified value with the 95% lower confidence bound of the mean degradation curve.
Preparation and certification of new thorium isotopic reference materials by K. Raptis; K. Mayer; F. Hendrickx; P. De Bièvre (pp. 400-403).
Preparation of two Isotopic Reference Materials of thorium has been performed, starting from highly enriched 232Th (99.99%) and 230Th (99.8%). After full characterization (chemical and isotopic) of these purified base materials the thorium nitrate was transformed to thorium dioxide. Accurately weighed amounts of the two isotopes in the dioxide form were subsequently dissolved in nitric acid and resulted in solutions with amount ratios n(230Th)/n(232Th) close to 10–5 (IRMM-035) and 3 · 10–6 (IRMM-036). These gravimetrically prepared ratios were finally verified by means of Thermal Ionization Mass Spectrometry (TIMS). The purpose of the Reference Materials is to calibrate thorium isotope amount ratio measurements.
Pesticide analysis in ground water. Statistical evaluation of certification data of a multicomponent reference material by K. Schramm-Nielsen; J. Merry; B. A. Nyeland; N. H. Spliid; H. Spliid (pp. 404-409).
21 laboratories participated in the certification of a multicomponent ampouled reference material containing 24 pesticides. This paper describes the statistical analysis of the unbalanced data set returned by the participants in the certification. The simplest method of certification is achieved when laboratories report all the required data. In practice, however, with complex analytical methods such as multicomponent analyses of organic compounds, laboratories are not able to report all the required data. The response for each determinand in the material has been modelled in a three-factor nested model. For computational comfort the model has been rephrased into a general linear model. The statistical problems with unbalanced data are discussed in relation to ISO 5725 and ISO Guide 35. Tests for homogeneity are exact and uninfluenced by the unbalance in data. Unbalanced data cause dependencies between mean squares above the second lowest level of the model, thus exact hypothesis testing is not possible at higher levels. Approximate tests for variation between rounds and laboratories has been constructed by means of Satterthwaite’s formula [1]. A graphical plot of deviances from certified values has been applied to illustrate laboratory performance.
Accurate and rapid estimation on spectral interferences in routine analysis by ICP-AES: use of mutual interference coefficients by Yûetsu Danzaki; Kunio Takada; Kazuaki Wagatsuma; Masaoki Oku (pp. 410-418).
A practical method to estimate spectral interferences and to select optimum analytical lines in ICP-AES is suggested. Depending on the matrix composition and the amounts of the analyte, the analytical lines suffering from little interferences and the limit of determination can be determined from calculation using spectral interference coefficients. For this calculation, the spectral interference coefficients, which are defined as apparent mass of the analyte equivalent to the spectral interference from unit mass of the interferent, are obtained experimentally for 639 emission lines of 68 elements. There is a good correlation between the coefficients obtained on two spectrometers having different resolutions.
Study on the systematic optimization of capillary electrophoresis using a controlled weighted centroid variable size simplex algorithm by H. Wang; Jun-Ling Gu; Han-Fang Hu; Tian-Hui Ding; Ruo-Nong Fu (pp. 419-423).
The systematic optimization of capillary electrophoretic separations using a dynamic scouting optimum method-controlled weighted centroid variable size simplex algorithm is described. The factors affecting the efficiency of the separation are simultaneously considered during the optimization procedures. The established optimization method is applied to amino acid separation by capillary zone electrophoresis (CZE) with on-column indirect UV detection and to the separation of local anesthetics by micellar electrokinetic chromatography (MECC) with on-column UV detection. The optimization procedures include the pH and the background absorption electrolyte (BGAE) concentrations together with the applied voltage in the CZE separation of amino acids. The pH, the SDS concentrations together with the percentage of methanol are considered in the MECC separation of local anesthetics. Two methods, i.e., the Long Coefficient and Uniform Design Table, are used to define the start vertexes during the optimization procedure and similar final experimental conditions for the separations are achieved. Thirteen native amino acids are baseline separated by CZE and 4 local anesthetics are satisfactorily separated by MECC.
Adsorption studies of dodecylamine at the quartz interface using an electrode-separated piezoelectric sensor by Dazhong Shen; Songmin Peng; Qi Kang; Yanhui Xue (pp. 424-428).
The adsorption process of dodecylammonium chloride (DAC) from aqueous solutions onto a quartz crystal interface was investigated in situ using an electrode-separated piezoelectric sensor (ESPS). Increasing amounts of DAC adsorbed onto a quartz crystal surface resulted in linearly decreasing oscillating frequencies of the ESPS. The adsorption density can be monitored by the frequency decrease. The adsorption density obtained by calculation using the Sauerbrey equation in the ESPS method is greater than that in solution depletion method. A calibration coefficient is added into the Sauerbrey equation to correct the influence of surface roughness of the quartz crystal on the adsorption density. The influence of solution properties on the adsorption density measurement was discussed. A dependence of the adsorption density on pH was reported.
On atomization of uranium in plutonium matrix using ETA-AAS by Neelam Goyal; Paru J. Purohit; A. G. Page (pp. 429-432).
Atomization processes for uranium in aqueous media and in the presence of a plutonium matrix have been studied and a chemical mechanism is proposed. These studies have been utilized for the determination of uranium in plutonium by Electrothermal Atomization- Atomic Absorption Spectrometry (ETA-AAS) within the constraints of its stable carbide forming tendency and complexity caused by formation of plutonium suboxide at high temperatures. In spite of these limitations the analytical range obtained for determination of uranium is 2.5–100 ng with a sample aliquot of 5 μL containing 5 mg/mL plutonium concentration. The precision of the method is evaluated as 9% RSD.
Emission of secondary ions from 3d, 4d, and 5d transition metals under chloro-trifluoro-methane CClF3 as reactant gas by Björn Schlosser; W. Seidel (pp. 433-436).
Surface interactions of CClF3 with polycrystalline samples of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Nb, Mo, Rh, Pd, Ag, Ta, W, Re, Ir, and Pt were investigated by means of moderate dynamic SIMS. As observed with other reactant gases these transition metals in most cases appear to be discernible into “dissociative” and (partial) “molecular” adsorbents. Small signals of oxidic secondary ions which are detectable for residual gas conditions vanished under the action of CClF3. However, due to strong polarization by either of the halogens, the emission of Me2+ ions is enhanced for Ti, V, and Nb.
Thiocyanate-selective electrode based on cobalt(II) complexes of pyrazolone heterocyclic Schiff bases by Min Ying; R. Yuan; Zhi-Qiang Li; You-Qiang Song; W.-X. Li; H.-G. Lin; G.-L. Shen; R.-Q. Yu (pp. 437-441).
A new solvent polymeric membrane electrode based on pyrazolone heterocyclic Schiff base complexes of Co(II) is described. It shows a preferential response towards thiocyanate over a range of 2.0 × 10–6 to 1.0 × 10–1 mol L–1 with a slope of –60.2 ± 0.6 mV/dec. The selectivity sequence observed is thiocyanate > hydroxide > nitrite > iodide > perchlorate > citrate > bromide > fluoride > chloride > nitrate > acetate > borate > sulfate > phosphate. The selectivity behavior is discussed in view of axial coordination by uv/vis spectroscopy and the transfer process of thiocyanate across the membrane interface is investigated by the ac impedance technique. The electrode was successfully applied to the determination of thiocyanate in human urine as an indicator for distinguishing between smokers and non-smokers.
Determination of sulfur in metal sulfides by bromine water-CCl4 oxidative dissolution and modified EDTA titration by Tsembel Darjaa; Kohta Yamada; Nobuaki Sato; T. Fujino; Yoshio Waseda (pp. 442-444).
The sulfur content in metal sulfides can be determined after oxidative dissolution with bromine water-CCl4 at 50 °C by modified EDTA titration. The sulfides were quantitatively oxidized to SO4 2– without evolving H2S, and the metal cations were removed by cation exchange on an H-type column. Sulfate was precipitated as BaSO4, and the remaining Ba2+ was subsequently titrated with EDTA at pH = 10. The standard deviation for the determined sulfur in the metal sulfides, some of which can be hardly dissolved in usual mineral acid media, is about a few %. The method can be carried out with sample amounts containing as little as 1.5–2 mg sulfur.
Flow injection on-line sorption preconcentration of platinum in a knotted reactor coupled with electrothermal atomic absorption spectrometry by E. Ivanova; F. Adams (pp. 445-450).
A flow injection on-line sorption preconcentration method for the electrothermal AAS determination of platinum has been developed. The pyrrolidine dithiocarbamate complexes of either Pt4+ or Pt2+, formed in 0.7 mol L–1 HNO3, are on-line adsorbed on the inner walls of a PTFE knotted reactor and subsequently eluted with methanol. An enhancement factor of 112 and a detection limit (3 σ) of 10 ng L–1 along with a sampling frequency of 21 h–1 are achieved with a 90 s preconcentration time at a sample flow rate of 8.8 mL min–1. The relative standard deviation is 2.5% for 0.4 μg L–1 Pt. The method has been applied to the determination of platinum in blood samples.
Preconcentration and determination of trace amounts of lead (II) as thenoyltrifluoroacetone complex with dibenzo-18-crown-6 by synergistic extraction and atomic absorption spectrometry by K. Z. Hossain; T. Honjo (pp. 451-454).
A new method for the preconcentration and determination of trace amounts of lead at the μg/L level in natural waters has been established based on the formation of the thenoyltrifluoroacetone (TTA) complex with dibenzo-18-crown-6 (DB18C6) by means of synergistic extraction and back-extraction combined with atomic absorption spectrometry (AAS). The effect of various factors (synergism with TTA and DB18C6, shaking time, preconcentration factor, composition of the extracted species, and foreign ions etc.) on the extraction and back-extraction of lead has been investigated in detail. The lead-TTA chelate in o-dichlorobenzene forms a stable adduct with DB18C6 as Pb(TTA)2 DB18C6. The stability constant (β) of the adduct determined by curve fitting method was log β = 4.2. The amount of lead in natural waters such as tap water (Kanazawa University) and Kakehashi river (Komatsu City) determined by the present method was found to be 0.64 ± 0.02 μg/L and 5.10 ± 0.03 μg/L, respectively.
Preconcentration of phenols by adsorption on organo-clay followed by capillary electrophoretic determination by F. B. Erim; I. Alemdar (pp. 455-458).
The organo-clay adsorbent used was prepared by modification of montmorillonite from Kurşunlu, Turkey with the cationic surfactant cetyltrimethlyammonium bromide. The modification process involves replacing the inorganic exchange cations of the clay by organic cations containing long chain alkyl groups. The retention of phenolic compounds from aqueous solution on the organo-clay was studied. The analytes are quantitatively retained on the proposed adsorbent at pH 7 and recovered by elution with ethanol. The determination of phenols was performed by capillary electrophoresis.
Determination of anionic trace impurities in acetic acid by two-dimensional capillary isotachophoresis by T. Meißner; F. Eisenbeiß; B. Jastorff (pp. 459-464).
Potential impurities such as nitrate, sulfate, nitrite, fluoride, formate, phosphate and oxalate were detected up to an analyte-to-excess ratio (ATER) of 1:3 · 105 using an online two-dimensional isotachophoretic system. With the developed electrolyte system, consisting of two different leading electrolytes, limits of detection (LOD) in the nmol/L range were realised by conductivity detection. These optimized conditions were applied to the determination of these anionic impurities in different types of acetic acid and acetate salts in order to evaluate and to verify their quality. Without sample preparation and or preconcentration, we were able to determine the above mentioned analytes in the range of 0.00032–0.001% within 20 min. The results were compared with those obtained by classical methods.
Simultaneous spectrophotometric determination of Tartrazine, Sunset Yellow and Ponceau 4R in commercial products by partial least squares and principal component regression multivariate calibration methods by J. J. Berzas Nevado; J. Rodríguez Flores; M. J. Villaseñor Llerena (pp. 465-472).
Three multivariate calibration methods, partial least squares (PLS-1 and PLS-2) and principal component regression (PCR), were proposed and successfully applied to the simultaneous determination of three dyes, Tartrazine (E-102), Sunset Yellow (E-110) and Ponceau 4R (E-124) in mixtures by ultraviolet-visible absorption spectrophotometry. The designed and optimized training set of calibration was applied to the determination of the three dyes in several synthetic mixtures, containing 1.6–20.0 mg/L of Tartrazine, 3.2–40.0 mg/L of Sunset Yellow and 3.2– 36.0 mg/L of Ponceau 4R. 94.5–105.3% recovery values were obtained. Three commercial foods that contained the three dyes were also satisfactorily analyzed without separation step. The results obtained by the application of the three chemometric approaches in the commercial products are discussed and compared with those obtained by an HPLC method and very similar values were found by all methods. Repeatability and reproducibility studies (with the Student’s and F tests) were achieved over two series of nine standards for each dye, showing no significant differences at the 95% confidence level.
Quantitative analysis of malto-oligosaccharides by MALDI-TOF mass spectrometry, capillary electrophoresis and anion exchange chromatography by Thomas Kazmaier; Sunhilde Roth; Jürgen Zapp; Michael Harding; Reinhard Kuhn (pp. 473-478).
The analysis of malto-oligosaccharides by MALDI-TOF mass spectrometry (MS), capillary electrophoresis (CE) and anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) is described. Appropriate methods were developed which enabled the resolution of the oligosaccharides and quantification of the peak areas. It could be shown that each technique provided a different distribution profile of the maltodextrins. Using MALDI-TOF MS signals of higher molecular weight oligomers were enhanced while low molecular weight analogues were discriminated. Thus, the response factor depends on the degree of polymerization (DP) of the carbohydrates. Homologues up to DP-15 could be detected. Analysis of the maltodextrins by CE was accomplished by derivatization of the sugars with 4-aminobenzonitrile (ABN) and 8-aminonaphthalene-1,3,6-trisulfonic acid, respectively. By using the latter reagent oligosaccharides up to DP-13 were detected while derivatization with ABN allowed detection up to DP-9. The molecular weight distribution obtained by both approaches were the same. HPAEC-PAD enabled the determination of oligomers up to DP-9. The distribution obtained by this technique showed somewhat lower signals of the small homologues than those found by CE while the opposite held for higher molecular weight compounds. Hydrolysis of the carbohydrates by the derivatization reaction prior to CE analysis, which increased the proportion of low molecular weight homologues, may account for these findings.
Study of the acid-base properties of leaf litter extracts by J. C. G. Esteves da Silva; A. A. S. C. Machado; M. A. Ferreira; Francisco Rey (pp. 479-486).
The acid-base properties of four leaf litter extracts, LLE (eucalyptus, fern, oak and chestnut coverture), were characterized by synchronous fluorescence (SyF) spectroscopy and compared with those of two fulvic acids (FA) extracted from two different horizons (0–5 and 5–15 cm) of an oak forest soil. The characterization was based on the variation with the pH of the properties of the fluorescent structures present in the samples, which function as probes and provide a macroscopic image of their acid-base properties. These sets of SyF spectra collected as a function of the pH show fingerprinting potential. They were treated by a self-modeling curve resolution procedure, evolving factor analysis with a gradient concentration window (EFA-GCW), to reduce the raw spectral data to the number of components, their spectra, and SyF intensity profiles (pH distribution diagrams). Four acid-base systems were detected for all samples of LLE and FA with pKas ranging from 2.5 to 10.0 (pKas about 3, 5, 7 and 9, except for the fern LLE sample which showed pKas about 5, 7, 9 and 10). A similarity analysis of the spectra of the components, performed by cluster analysis, showed that the most acidic fluorescent structures of the LLE are not similar to those of the soil FA, but the less acidic are.
Capabilities of double focussing magnetic sector-ICP-MS for the determination of trace elements in body fluids (blood, blood serum, urine) at the example of control materials by P. Schramel; I. Wendler (pp. 487-491).
The capability of double focussing magnetic sector inductively coupled plasma mass spectrometry (HR-ICP-MS) for the determination of trace elements in different body fluids was investigated in commercially available control materials. The elements included in this study were: Al, As, Cd, Cr, Co, Cu, Hg, Mn, Ni, Pb, Sb, Se, Tl and Zn. Sample preparation, instrument stability and the results, which are in very good agreement to the given values, are presented and discussed.
Sensitive synchronous spectrofluorimetric methods for the determination of naproxen and diflunisal in serum by T. Pérez-Ruiz; C. Martínez Lozano; V. Tomás; J. Carpena (pp. 492-495).
The interaction of diflunisal and naproxen with several surfactants was studied. Spectrofluorimetric methods were developed for the determination of both drugs in sodium dodecylsulfate micellar medium. The mixture of these drugs was resolved by synchronous fluorescence spectrometry using two scans. At Δλ = 20 nm, only naproxen yields a detectable signal that is unaffected by the presence of diflunisal. At Δλ = 110 nm the signal of diflunisal is not influenced by the presence of an up to 3-fold excess of naproxen. Mixtures containing naproxen/ diflunisal in ratios from 50:1 to 1:50 were analyzed with good results. The linear calibration ranges of both drugs were ca 0.02–2.0 μg mL–1. The method has satisfactorily been applied to a mixture of both drugs in serum.
Determination of titanium and zirconium wear debris in blood serum by means of HNO3/HF pressurized digestion using ICP – optical emission spectrometry by J. Kunze; M. A. Wimmer; S. Koelling; E. Schneider (pp. 496-499).
A ‘one bottle’ method to determine particulate debris of titanium and zirconium in blood serum was developed. Inductively coupled plasma – optical emission spectrometry (ICP-OES) was used to simultaneously detect both elements at concentrations above 50 ng/mL. Pressurized digestion by means of nitric and hydrofluoric acid in PTFETM-containers in a specific time-heat-pressure protocol apparatus was applied to assure complete solvation of particles including oxides. Total decomposition of the matrix was achieved and reasonable detection limits were accomplished. The amount of remaining carbon did not cause any matrix problems during measurement.
Quantitative determination of glucose in blood plasma by homonuclear proton decoupled water attenuation transverse relaxation Carr-Purcell-Meiboom-Gill (WATR-HDCPMG) NMR spectroscopy by W. Y. Choy; S. C. F. Au-Yeung; S. Y. Fan; W. L. A. K. Chiu; C. S. Cockram (pp. 500-503).
Glucose in 5% D2O/95% H2O solution was successfully determined quantitatively by measurements of the 1H NMR peak height (intensity) of the single peaks at δ(1H) = 5.22 and 4.64 ppm corresponding to the α-D and the β-D-glucose spectrum, respectively. The single peaks were obtained from decoupling of the high field part of the AX spectrum of the α-D- or the β-D-glucose by incorporation of time shared homonuclear decoupling in the WATR-CPMG method (WATR-HDCPMG) without re-attenuation of the water peak. The method was applied to the determination of total glucose in blood plasma from human subjects undergoing oral glucose tolerance test (OGTT) in the teaching hospital. The results compared favorably with those obtained from the standard glucose oxidase method obtained in a hospital pathology laboratory. The accuracy of the results obtained using the WATR-HDCPMG method was within 3.5% of the glucose oxidation method.
Influence of pressure and atomizer length on absorption curves in ETA-AAS measurements for standardless analysis by F. N. Rossi; D. Melucci; C. Locatelli; P. Reschiglian; G. Torsi; A. Millemaggi (pp. 504-506).
A new method for standardless analysis in electrothermal atomic absorption spectroscopy has been recently proposed whose implementation requires the use of special atomizers and power supplies not available in the market. Up to now, with the proposed method, only volatile elements have been determined with good results because it can be applied only if all atoms injected are simultaneously present in the atomizer for a time interval sufficiently long that a good value of absorbance can be measured. This can be obtained if the heating rate is sufficiently high and the removal of atoms from the atomizer slow. From a theoretical model based only on diffusion, it can be deduced that the possibility of standardless analysis in the mode described above can be enhanced if the length of the atomizer is increased and the diffusion coefficient of the analyte is decreased. From the results obtained by comparing data from atomizers of 36 and 50 mm in length and at different pressures, it can be inferred that the removal mechanism is basically controlled by diffusion but that other mechanisms, like convection, are also present.
Anodic stripping voltammetric determination of Zn, Pb and Cu traces in whisky samples by P. J. S. Barbeira; Nelson R. Stradiotto (pp. 507-509).
The simultaneous “in natura” determination of trace Zn, Pb and Cu in whisky samples by anodic stripping voltammetry (ASV), using a hanging mercury drop electrode, without previous treatment or addition of supporting electrolyte is described. The choice of an appropriate stripping voltammetric method and deposition potential minimizes the influence of the organic content and ensures a good reproducibility of the measurements. The reliability of the method was tested comparing the results with those of atomic absorption spectroscopy (AAS), with differences of about 10%. The method allows the determination of heavy metal ions in the μg L–1 range.
Determination of Cr(III) in urine, blood serum and hair using flow injection chemiluminescence analysis by R. Escobar; M. S. García-Domínguez; A. Guiraúm; F. F. de la Rosa (pp. 509-511).
A flow injection (FI) chemiluminescence method for the determination of Cr(III) in blood serum, urine and hair samples is reported. It is based on the chromium-catalyzed light emission from the luminol oxidation by hydrogen peroxide. The apparatus consists of an FI system with a flow cell formed by a coiled transparent tube suitable for chemiluminescence detection. The specificity of the method is achieved in presence of EDTA. The detection limit under optimum conditions is 0.01 μg L–1 of Cr(III). Precision and accuracy were evaluated by determining Cr(III) concentrations in urine standards from the National Institute of Standard and Technology (NIST).