Inter-comparison exercises as a tool for teaching quality assessment: an experience in Spanish universities

Since the academic year 2001–2002, inter-laboratory trials for students of Analytical Chemistry in Spanish Universities have been organised by the Department of Analytical Chemistry at the University of Barcelona in collaboration with the Complutense University of Madrid, the University of Cordoba and the University of Huelva. The aim of these exercises is to train students in the use of tools for the assessment and improvement of quality in analytical laboratories.Representative samples of environmental and food analysis, agricultural soils and a type of beer were selected. The ethanol content of the beer and the pH, conductivity, and extractable phosphorus and potassium content in the soil were the chosen analytical parameters.Sample preparation, homogeneity and stability studies, as well as the statistical treatment of data from participants, were carried out by the laboratory Mat Control of the Department of Analytical Chemistry of the University of Barcelona.The paper presented heregives the results obtained after two years of experience.Presented at BERM-9—Ninth International Symposium on Biological and Environmental Reference Materials, June 15–19, 2003, Berlin, Germany.     

A practical approach to assessment of sampling uncertainty

The paper reports the approach followed in the SOILSAMP project, funded by the National Environmental Protection Agency (ANPA)of Italy. SOILSAMP is aimed at assessing uncertainties associated with soil sampling in agricultural, semi-natural, urban, and industrial environments. The uncertainty assessment is based on a bottom-up approach, according to the Guide to the Expression of Uncertainty in Measurement published by the International Organization for Standardization (ISO). A designated agricultural area, which has been characterized in terms of elemental spatial distribution, will be used in future as a reference site for soil sampling intercomparison exercises. Received: 19 November 2001 Accepted: 6 January 2002     

Determination of polynuclear aromatic hydrocarbons in aerosol by solid-phase extraction and gas chromatography-mass spectrum

The optimum procedures for clean up aerosols in silica solid-phase extraction (SPE) cartridge prior to the analysis of polynuclear aromatic hydrocarbons (PAHs) by gas chromatography–mass spectrum (GC–MS) in selected ion monitoring detection mode have been investigated. The silica SPE cartridge is activated by dichloromethane and hexane, and then dried up by vacuum in SPE instrument for about 5 min. The sample volume loaded on the cartridge is 3 ml and after loading the sample the cartridge was dried in vacuum for 5 min. The PAHs were eluted from the cartridge by 3 ml 20% dichloromethane in hexane. The flow-rate of sample loading and eluting was controlled in about 1 ml min⁻¹. The aerosols collected on the campus of Beijing Normal University from August 2001 to July 2002 have been processed with these optimum procedures and 16 EPA priority pollution PAHs in the aerosols have been quantitatively determined.     

Electron-pairing analysis from localization and delocalization indices in the framework of the atoms-in-molecules theory

This article presents an overview of recent advances in the study of electron pairing through the use of localization and delocalization indices obtained from double integration over atomic basins of the exchange–correlation density in the framework of the atoms-in-molecules theory. These localization and delocalization indices describe the intra- and interatomic distribution of the electron pairs in a molecule. The main results of the application of these second-order indices to the analysis of molecular structure and chemical reactivity are briefly reviewed. It is shown that localization and delocalization indices represent a powerful tool to describe the electron-pair structure of molecules, which, in turn, provides deeper insight into relevant chemical phenomena such as electron correlation effects and the formation of localized α, β electron pairs. Received: 8 April 2002 / Accepted: 26 June 2002 / Published online: 6 September 2002 Acknowledgements. Financial help was furnished by the Spanish DGES projects no. PB98-0457-C02-01 and BQU2002-04112-C02-02. J.P. thanks the Departament d'Universitats, Recerca i Societat de la Informació de la Generalitat de Catalunya for benefiting from a doctoral fellowship, no. 2000FI-00582. M.S. is indebted to the Departament d'Universitats, Recerca i Societat de la Informació of the Generalitat de Catalunya for financial support through the Distinguished University Research Promotion, 2001. We also thank the Centre de Supercomputació de Catalunya for providing us with computing facilities. Correspondence to: M. Solà e-mail: miquel.sola@udg.es     

Liquid chromatography-mass spectrometry approach for the characterization and purification of crude synthetic peptide hormones

In this study, conditions for the optimal separation by LC-UV and characterisation by LC-ES-MS of crude mixtures generated during SPPS of several peptide hormones are compiled. The linear solvation energy relationship (LSER) methodology has been used to predict the retention of the target peptides and their side products and then to develop a separation LC methodology with applicability on both the analytical and preparative scale. Identification of these side products by LC-ES-MS analysis has been made on the basis of their calculated molecular masses. This method may be regarded as a key tool for the optimisation of the synthetic procedures and for complying with regulatory agencies' requirements before commercialisation of a safe and effective peptide-based pharmaceutical drug.Awarded a prize as outstanding poster on the occasion of Jornadas de Análisis Instrumental (JAI), November 26 to 29, 2002, Barcelona, Spain     

发光分析

评述在 2 0 0 1年 1月～ 2 0 0 2年 12月间我国发光分析的发展概况 ,内容包括荧光、磷光、化学发光和电化学发光分析等。引用文献 32 9篇。     

Partial Hessian vibrational analysis: the localization of the molecular vibrational energy and entropy

The partial Hessian vibrational analysis (PHVA), in which only a subblock of the Hesssian matrix is diagonalized to yield vibrational frequencies for partially optimized systems, is extended to the calculation of vibrational enthalpy and entropy changes for chemical reactions. The utility of this method is demonstrated for various deprotonation reactions by reproducing full HVA values to within 0.1–0.4 kcal/mol, depending on the number atoms included in the PHVA. When combined with the hybrid effective fragment potential method [Gordon MS, et al. (2001) J Phys Chem A 105:293–307], the PHVA method can provide (harmonic) free-energy changes for localized chemical reactions in very large systems. Received: 21 September 2001 / Accepted: 30 October 2001 / Published online: 22 March 2002     

Comments on “Some fundamental problem with zero flux partitioning of electron densities”

 The article by P. Cassam-Chena? and D. Jayatilaka (Theor Chem Acc (2001) 105: 213) is critically analyzed. Received: 18 April 2001 / Accepted: 9 September 2001 / Published online: 3 June 2002     

Self-assembly of frame structures. 10. Stereochemistry of 2,5-dioxabicyclo [2.2.1]heptane-3,6-digne

By optimization of the geometry of 2, 5-dioxabicyclo[2. 2.1]heptane-3.6-dione (1) with an ab initio (RHF/6-31 G') calculation, we have found that a single synchro(+, +)-twist form (A) corresponds to the (1 R,4R)-enantiomer (the dihedral angles of the lactone bridges are ₀ = 2.6°). According to MM2(91) and MM3(92) calculations, (1R,4R)-1 exists as the s-ynchro(+, +)-A-twist ( ₀ = 3.9°) and the synchro(-, -)-B-twist ( = -3.8°) forms, respectively. Investigating the torsional energy surface of the dilactone 1 (MM2(91)), we found only the (1R,4R,P)-diastereomeric form (A), which is stabilized compared with the (1R,4P,M) form (B) (probably as a result of the more preferred dipole-dipole interaction of the carbonyl groups). According to the calculated puckering coordinates, the five-membered and six-membered moieties of the bicycle 1 are flattened compared with norbornane.Institute of Chemical Physics at Chernogolovka. Russian Academy of Sciences, Chernogolovka, Moscow Oblast 142432. Department of Chemistry, University of Calgary, Alberta, Canada T2N 1N4. Department of Chemistry, College of Sciences, Autonomous University of Barcelona, Bellaterra 08193, Spain. Laboratory of Organic Chemistry, College of Pharmacy, University of Barcelona, Barcelona 08028, Spain. N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, Moscow 117977. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1479-1488, November, 1995.     

Can STO basis sets do a good job in evaluating molecular electromagnetic properties? I. First hyperpolarizability of H2O, CH4, and NH3 according to the TDHF theory

The performance of STO basis sets for the ab initio estimation of the nonlinear electromagnetic response properties of molecules, in terms of a time-dependent Hartree–Fock procedure, is investigated. Applications to the case of the first dynamic hyperpolarizability of three simple polyatomics (H₂O, CH₄, NH₃) adopting several extended basis sets are reported and discussed. Independent estimates for the observables investigated obtained by the same approach in terms of Gaussian basis sets are confronted with our findings in the search for recipes of possible utility.Acknowledgements This research has been partially supported by funds provided by the Italian Consiglio Nazionale delle Ricerche (contribution n. CTB 00.00650.PF34) and Pisa University (fondi di Ateneo, ex 60%, years 2001–2002).Contribution to the Jacopo Tomasi Honorary Issue     

Some confusion concerning integral isoconversional methods that may result from the paper by Budrugeac and Segal “Some Methodological Problems Concerning Nonisothermal Kinetic Analysis of Heterogeneous Solid–Gas Reactions”

Budrugeac and Segal (Int. J. Chem. Kinet. 33 , 564, 2001) have generally criticized the integral isoconversional methods for producing a systematic error in the activation energy, whose value varies with the extent of conversion. We stress that this error is practically eliminated in the advanced integral isoconversional methods when using integration over small time segments (Vyazovkin, S. J. Comput Chem. 22 , 178, 2001) © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 418–420, 2002     

Bader's interatomic surfaces are unique

 In this work we comment on the statement about the nonuniqueness of the solution of Bader's equation for defining atoms in molecules reported in the article of P. Cassam-Chena? and D. Jayatilaka in Theoretical Chemistry Accounts (2001) 105: 213–218 Received: 10 May 2001 / Accepted: 7 September 2001 / Published online: 3 June 2002     

Use of Imidazole 4,5-Dicarboxylic Acid Resin in Vanadium Speciation

 A new resin has been synthesized by functionalisation of polystyrene-divinylbenzene (8%) with imidazole 4,5-dicarboxylic acid through –N=N– bonding. The resulting resin has been characterised by elemental analysis, thermogravimetric analysis, infrared spectroscopy, hydrogen ion capacity and metal ion capacity. The speciation study of vanadium has been studied by using this resin and the maximum exchange capacity was found to be 0.45 mmol g⁻¹ for V⁴⁺ and that for V⁵⁺ was 1.57 mmol g⁻¹ at pH 3 for both. The eluents malonic acid and sodium hydroxide have been used for the selective separation of vanadium(IV) and vanadium(V) species respectively. The effects of diverse ions on the sorption and recovery of each species have been studied. Finally, the developed method has been applied for the speciation and determination of these two species in natural water samples. Correspondence: Department of Chemistry, The University of Burdwan, Burdwan, India. e-mail: akdas100@yahoo.com Received December 20, 2001; accepted October 11, 2002     

External proficiency testing exercises on human leukocyte antigen typing in Italy between 1998 and 2002

External proficiency testing exercises are essential tools for measuring the quality of different kinds of performances related to health care and to ensure that they are uniform throughout a region. For many years, the Italian National Transplant Centre and the Italian National Institute of Health have been organizing external proficiency testing exercises for serological and genomic human leukocyte antigen (HLA) typing, following the rules of the European Federation of Immunogenetics. This society provides accreditation for immunogenetical tests to those European countries which want to collaborate on programmes on solid organ and bone marrow transplantation. The results of the Italian external proficiency testing exercises are very satisfactory because of the progressive improvement of the quality of HLA typing seen in Italian laboratories between 1998 and 2002. The attained outcome will certainly guarantee a more reliable service in clinical practice, and will contribute to the process of approaching the highest quality in health care.     

Molecular structure and Bader's theory

 It is shown that a supposed catastrophe of Bader's theory of atoms in molecules, suggested by Cassam-chena? and Jayatilaka [Theor Chem Acc (2001) 105: 213] is merely a consequence of the approximate character of the adiabatic Born–Oppenheimer theory of molecular structure, and that nonadiabatic approaches could be in accordance with Bader's ideas. Received: 4 April 2001 / Accepted: 5 September 2001 / Published online: 3 June 2002     

Linear stability analysis of a reaction–diffusion model of solid-phase combustion

 The dynamic behavior of a reaction–diffusion model of solid-phase combustion is investigated by using the linear stability analysis method. The diffusion coefficients of the oxygen gas and the vapor of the combustible solid (Mg) are taken as two controlling parameters in the analysis. The bifurcation map obtained shows three dynamic regions. Region I only shows stable combustion. Regions II and III both show stable combustion and oscillatory combustion depending on the ratio of the two diffusion coefficients. Interestingly region II also shows a small range of a bistable state consisting of a stable focus and an oscillating state, which is like the critical phenomena in phase transitions. The results indicate that the occurrence of oscillating combustion requires that the value of the diffusion coefficient of the Mg vapor should be comparable to or less than that of the oxygen gas at the same temperature. Received: 6 November 2001 / Accepted: 25 March 2002 / Published online: 13 June 2002     

Correlated electron-pair properties of the Li atom in momentum space

On the basis of multiconfiguration Hartree–Fock calculations, correlated electron-pair intracule (relative motion) and extracule (center-of-mass motion) properties are reported for the Li atom in momentum space. The present results are more accurate and consistent than those in the literature. Received: 10 September 2001 / Accepted: 11 December 2001 / Published online: 22 March 2002