Towards more fair and effective doping tests based on chromatography with mass spectrometric detection

Van Eenoo and Delbeke in Accred Qual Assur (2009) have criticized Faber (in Accred Qual Assur, 2009) for not taking “all factors under consideration when making his claims”. Here, it is detailed that their criticism is based on a misunderstanding of examples that were merely intended to be illustrative. Motivated by this criticism, further discussion is provided that may help in the pursuit of more fair and effective doping tests, here exemplified by chromatography with mass spectrometric detection. Surely, any doping test can only be improved or even optimized if the risks of false positives and false negatives are well defined. This requirement is consistent with a basic principle concerning mathematical approximations (Parlett in “The symmetric eigenvalue problem”, Prentice-Hall, Englewood Cliffs, 1980): apart from just being good, they should be known to be good. Author’s reply to the response on “Regulations in the field of residue and doping analysis...” Papers published in this section do not necessarily reflect the opinion of the Editors, the Editorial Board and the Publisher.     

Estimation in multiple measurements

A recent paper by Nam et al. (Accred Qual Assur 14:43–47, 2009) considers the issue of repeated measurements of a same measurand. The paper is a follow-up of two previous papers (Choi et al. in Accred Qual Assur 8:13–15, 2003, 8:205–207, 2003) on the same topic. The first two papers show a well-known fact, i.e., that systematic effects are not reduced by repeating measurements, and give formulae for the uncertainty of the estimate of the average from repeated measurements in the case that the differences between individual results are not (Choi et al. in Accred Qual Assur 8:13–15, 2003) or are (Choi et al. in Accred Qual Assur 8:205–207, 2003) statistically significant, respectively. The last paper addresses a more interesting issue, that is, a difference in the estimate average for non-linear models depending on how raw data is processed in the model. In the present paper, I re-discuss the whole issue of multiple measurements, trying to clarify the various aspects of the topic. Papers Published in this section do not necessarily reflect the opinion of the Editors, the Editorial Board, and the Publisher.     

Key metrological issues in proficiency testing––response to “Metrological compatibility-a key issue in further accreditation” by K. Heydorn

A discussion of proficiency testing (PT) topics started by Heydorn (Accred Qual Assur 15:643–645, 2010) is continued in the present paper. The role of PT in the accreditation of testing/analytical laboratories, the use of consensus values (average or weighted average, median, observed standard deviation, etc.) and a metrological background of PT schemes are discussed. It is shown that metrological traceability, comparability, and compatibility, as well as commutability of a reference material, are the key issues of any PT scheme that applies certified reference material as test items. Metrological compatibility of PT results in such schemes is a property demonstrating the closeness of the PT results to the certified value in comparison with the measurement uncertainty of their difference. The metrological background is especially important for the selection and use of PT schemes for a limited number of participants (fewer than 30) as detailed in IUPAC/CITAC Guide on the topic published in 2010 in Pure Appl Chem 82(5):1099–1135.     

Comments on “Lectures for chemists on statistics II. The normal distribution: a briefer on the univariate case”

A recent paper of Meinrath (Accred Qual Assur 13:179–192, 2008) addresses matters of statistical analysis when the data are thought to have been drawn from a normal distribution with unknown mean and variance. In this comment we clarify, correct and enlarge upon points made there.     

Uncertainty in repeated measurement of a small non-negative quantity: explanation and discussion of Bayesian methodology

This article considers the problem of uncertainty evaluation when there are repeated measurements of a small quantity known to be non-negative. A solution to this problem has recently been put forward by the Analytical Methods Committee of the Royal Society of Chemistry (Accred Qual Assur 13:29–32). The Bayesian statistical basis of this solution is explained and discussed. It is shown that the performance of this procedure can be poor in an important subset of measurement situations.     

Nonparametric assessment of comparability of analytical results obtained in proficiency testing based on a metrological approach

A nonparametric sign test is implemented for assessment of comparability of proficiency testing (PT) results when their distribution differs from the normal or other known distribution. It allows testing the null hypothesis about insignificance of the bias of median of results obtained in PT from the traceable certified value of the reference material used in PT as test items, i.e., the hypothesis stating that comparability of the PT results is successful. Probability of type I error of rejecting the null hypothesis when it is true, and probability of type II error of it not rejecting when it is false (the alternative hypothesis about unsuccessful comparability is true) are considered. The test can be helpful for PT providers and laboratory accreditation bodies in analysis of PT results when the comparability criterion developed for a normal results distribution (Accred. Qual. Assur. 10:466–470) is not applicable.     

Measurement of small quantities: further observations on Bayesian methodology

This article discusses the measurement of the sum of small positive quantities each estimated in separate analyses. It extends criticism recently given of ‘objective Bayesian’ methodology (Accred Qual Assur 15:181–188, 2010) and identifies two troublesome effects: the inherent bias in an analysis for a single quantity is compounded when the measurand is the sum of such quantities, and the precaution of overestimating measurement variability can actually make the resulting interval of measurement uncertainty less reliable! Unacceptable results are obtained. A cause of this behavior is identified, and a distinction between ‘objective’ and ‘subjective’ Bayesian statistics is discussed.     

Feasibility study for the preparation of certified reference materials part I – mineral oil contaminated soils

The international joint project HYCREF (Contract No. G6RD-CT-2002-00854), funded by the European Commission in the 5th Framework programme, aimed to develop methods to prepare homogeneous and stable reference materials of water, soil, and waste contaminated with mineral oil hydrocarbons and to certify the mineral oil content by gas chromatographic methods. The results of a feasibility study for the preparation of three soil reference materials are discussed in this paper, and for the preparation of three waste reference materials in the second part (Koch et al., Accred Qual Assur submitted for publication). The soil materials were selected to represent different soil types and contamination levels. The project plan set three requirements for these reference materials: uncertainty in the mineral oil content resulting from the certification exercise <5%, a sample inhomogeneity of <3% and a minimum long-term stability of 5 years. For the most part, these requirements were met within this project.     

Use of uncertainty information for estimation of certified values. Comparison of four approaches using data from a recent certification exercise

Four approaches for estimation of reference values and their respective uncertainties of characterisation were compared using data from the recently finalised certified reference materials ERM-EC680k and ERM-EC681k, elements in plastics. Reference values and uncertainties of characterisation were estimated as mean of laboratory means and their respective standard deviations, using equal weights and the weighting procedure of Mandel–Paule. In addition, two approaches taking into consideration uncertainty information reported by the participants, namely the consistency check and simulation procedure proposed by Cox for CCQM Key comparisons and an approach suggested by Pauwels et al. (Accred Qual Assur 3:180–184, 2000) were used. No difference between the equally-weighted and Mandel–Paule consensus means was observed and the reference value from the Cox approach was in all cases within ±2 u _char of each consensus mean. Uncertainties varied between the three approaches. Uncertainties derived from equally-weighted mean of means approach are on average 14% above uncertainties using the Mandel–Paule consensus mean, 36% above the uncertainties estimated by Pauwels et al., and 54% above the uncertainties from the Cox approach. Robustness of the uncertainty estimation against incorrect estimation of uncertainties was assessed. Assumption of a 50% uncertainty of the individual uncertainties resulted in an uncertainty of 30% of the uncertainty of characterisation. Differences between the four approaches are negligible for this dataset when combined with the uncertainty contribution from heterogeneity and stability as prescribed in ISO Guide 35. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Van der Waals Radii of Hydrogen in Gas-Phase and Condensed Molecules

Van der Waalsa radii of hydrogen in the different gas-phase and condensed molecules are determined and shown that a value of the van der Waals radius depends on the effective charge of the H atom. Is described also the van der Waals anisotropy of H in some molecules.     

Van der Waals radii of elements from the data of structural inorganic chemistry

Van der Waals radii of elements were determined from the data of the structural inorganic chemistry: from intersitial distances in CdX₂- and graphite-type structures, bond lengths in van der Waals molecules, molar volumes of A₂-type substances, refractometry data, and from quantum chemical and correlation ratios. The recommended values of van der Waals radii of elements are tabulated.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 24–29, January, 1995.The author is grateful to the administration of the Department of Chemistry at the University of Durham (Great Britain) for the opportunity to perform this work and to Prof. J. Howard and Prof. K. Wade for useful discussions.     

Electrochemical characterization of Ni–Fe alloy codeposition under MHD control

The nickel–iron alloy electrodeposition is affected by a superimposed magnetic field. Some previous papers [Msellak et al., Magnetohydrodynamics, 39:487–493, 2003 and Msellak et al., J Magn Magn Mat, 281:295–304, 2004] have exhibited some dramatic changes in iron amount and morphology of these deposits. As it is usual for a magnetic field up to 1 T, no charge transfer effect can be expected, and the observed modifications can be explained by the magnetohydrodynamic convection that controls the iron species flux during the electrochemical reaction. By electrochemical impedance spectroscopy and physical investigations (scanning electron microscopy, X-ray diffraction, and inductively coupled plasma), the reduction process is analyzed, the characteristic parameters of the mechanism are determined, and the magnetic field effects can be quantified. Contribution to special issue on “Magnetic field effects in Electrochemistry”.     

CEPA calculations of potential energy surfaces for open-shell systems.: III. Van der Waals interaction between O(3P) and He(1S)

Quantum-chemical ab initio calculations have been performed for the van der Waals interaction between helium and oxygen atoms in their respective ground states: He(¹S)+ O(³P). As long as fine-structure effects are neglected, there are two low-lying electronic states, ³Σ^? and ³Π resulting from the degeneracy of the O(³P) ground state. Both states are purely repulsive at the SCF level, after inclusion of electronic correlation by the CEPA method they exhibit shallow van der Waals (dispersion) minima at large interatomic separation: R_? = 3.61 Å, ? = 1.0 meV (³Σ^?) and R_? = 3.05 Å, ? = 2.3 meV (³Π). The analysis of the results shows the very slow convergence of the dispersion interaction with increasing basis size, while SCF repulsion and the repulsion due to the change of the intra-atomic correlation are obtained reasonably accurately with moderate basis stes. Van der Waals coefficients C₆, C₈, C₁₀, potential curves of the type HFD (i.e. Hartree-Fock plus damped dispersion) and the influence of fine-structure effects (mainly spin-orbit coupling) on the shape of the adiabatic potential curves are discussed as well.     

Synthesis,characterization, cytotoxicity,DNA binding and computational studies of an anionic palladium(II) complex derived from 8-hydroxyquinoline and 1,1-cyclobutanedicarboxylate

A novel 1,1-cyclobutanedicarboxylato-8-hydroxyquinolinatopalladate(II), Na[Pd(8-QO)(cbdca)] (8-QO = 8-hydroxyquinoline and cbdca = 1,1-cyclobutanedicarboxylate) has been designed and synthesized. The structure of the complex has been characterized by elemental analysis, molar conductance, FT-IR, UV–Vis, ¹³C NMR, ¹H NMR spectroscopy. The cytotoxic activities of the complex have been tested against human foreskin fibroblast normal cell line, HFFF2 and two human breast cancer cell lines, T47D and MCF-7 by MTT assay techniques. The binding properties of the antitumor complex with calf thymus DNA (ctDNA) have been investigated under physiological condition in Tris–HCl buffer solution at pH 7.0 by absorption spectroscopy, fluorescence titration spectra, EB displacement and gel chromatography studies. All these results demonstrate that the water soluble complex can cooperatively bind to ctDNA at low concentrations through a static quenching procedure. Thermodynamic parameters were calculated according to Van’t Hoff equation which indicated that hydrogen bond and van der Waals force play predominant roles in the binding process. Finally, the results of molecular docking calculations clarify the binding mode which is in good accordance with experimental results.     

Cellophan und Kuprophan als Membranen fÜr die Dialyse und Elektrodialyse

Zusammenfassung Die zur Zeit als Verpackungsmaterial in den Handel kommende Zellulosefolie Kuprophan wurde auf ihre Verwendbarkeit als Dialysenmembran untersucht. Es ergab sich, da? die „Durchl?ssigkeit“ von Kuprophan etwa doppelt so gro? ist wie die von Cellophan Qual. 300 und etwa achtmal so gro? wie die von Pergamentpapier zur Dialyse C 155∶100, da? also bei Anwendung der Kuprophanmembran die Dialyse in der H?lfte der bei Verwendung von Cellophan Qual. 300 und im achten Teil der bei Gebrauch von Pergamentpapier als Membran erforderlichen Zeit beendet ist. Die mechanische Festigkeit von Kuprophan ist gut, trotz der nur geringen St?rke von 10Μ. Kuprophan ist daher, neben Cellophan Qual. 300, als hervorragend geeignetes Membran-material anzusprechen.     

New flavonoid-containing derivatives of lupinine

An oxazine ring was annelated to benzopyran-4-one and benzopyran-2-one cores by reacting 7-hydroxyisoflavones and 7-hydroxycoumarins with lupinylamine and formalin. The new derivatives 9,10-dihydro4H,8 H-chromeno[8,7-e][1,3]oxazin-4-one and 9,10-dihydro-2 H,8 H-chromeno[8,7-e][1,3]oxazin-2-one containing a lupinine moiety in the 9-position were prepared.     

Global dynamics of the smallest chemical reaction system with Hopf bifurcation

The global behavior of solutions is described for the smallest chemical reaction system that exhibits a Hopf bifurcation, discovered in [12]. This three-dimensional system is a competitive system and a monotone cyclic feedback system. The Poincaré–Bendixson theory extends to such systems [2,3,6,8] and a Bendixson criterion exists to rule out periodic orbits [4].     

The increasing demands of quality assurance in chemical testing

The chemical and microbiological testing community is going through a rather difficult period of change. Publication of ISO/IEC 17025 (General requirements for the competence of Calibration and Testing Laboratories, 1999) [1] is placing additional demands on testing laboratories to ensure traceability and estimate uncertainty in their measurements. At the same time, laboratories must remain mindful of the need to provide relevant, timely and economic services to their clients. International Accreditation New Zealand (IANZ) and its accredited laboratories are currently focussing on establishing realistic methods for ensuring traceability to national and international standards and estimating measurement uncertainty. To this end, IANZ recognizes that it has an important role in providing as much advice and assistance as possible, not only to its accredited chemical laboratories but also to all those contemplating accreditation in New Zealand.

The photodissociation of H2S: A study of indirect photodissociation

We have performed calculations for the photodissociation of H₂S using surfaces constructed to test a model proposed by van Veen et al., in which the dissociation occurs via predissociated levels of the bound ¹B₁ excited state. Total Franck-Condon factors for the photodissociation and partial Franck-Condon factors for the product vibrational distributions are presented.     

Ionic Liquids: Dissecting the Enthalpies of Vaporization

We calculate the heats of vaporisation for imidazolium‐based ionic liquids [C_nmim][NTf₂] with n=1, 2, 4, 6, 8 by means of molecular dynamics (MD) simulations and discuss their behavior with respect to temperature and the alkyl chain length. We use a force field developed recently. The different cohesive energies contributing to the overall heats of vaporisations are discussed in detail. With increasing alkyl chain length, the Coulomb contribution to the heat of vaporisation remains constant at around 80 kJ mol^?1, whereas the van der Waals interaction increases continuously. The calculated increase of about 4.7 kJ mol^?1 per CH₂‐group of the van der Waals contribution in the ionic liquid exactly coincides with the increase in the heats of vaporisation for n‐alcohols and n‐alkanes, respectively. The results support the importance of van der Waals interactions even in systems completely composed of ions.