A rapid method for the determination of the Fusarium mycotoxinbeauvericin in maize

The development of a rapid method for the determination of the Fusarium mycotoxin beauvericin (BEA) in corn and cereals is described. This method allows to prepare at least 5 times more samples simultaneously with similar analytical performance characteristics as previously published analytical methods. Received: 14 May 1998 / Revised: 9 July 1998 / Accepted: 14 July 1998     

Ultra-trace analysis of nitrite in food samples by flow injection with spectrophotometric detection

A flow injection system with spectrophotometric detection is proposed for the determination of low levels of nitrite based on its catalytic effect on the oxidation of gallocyanine by bromate in acidic media. Various analytical parameters such as acidity, reagent concentration, flow rate, sample size, time, temperature, and interfering species were studied. The calibration graph was linear for 0.020–0.500 μg/mL of nitrite. The method is successfully applied to food samples. Up to 30 ± 5 samples can be analyzed per hour. Received: 8 April 1998 / Revised: 3 June 1998 / Accepted: 31 July 1998     

Ultra-trace analysis of nitrite in food samples by flow injection with spectrophotometric detection

A flow injection system with spectrophotometric detection is proposed for the determination of low levels of nitrite based on its catalytic effect on the oxidation of gallocyanine by bromate in acidic media. Various analytical parameters such as acidity, reagent concentration, flow rate, sample size, time, temperature, and interfering species were studied. The calibration graph was linear for 0.020–0.500 μg/mL of nitrite. The method is successfully applied to food samples. Up to 30 ± 5 samples can be analyzed per hour. Received: 8 April 1998 / Revised: 3 June 1998 / Accepted: 31 July 1998     

Study of flexible joints and permanent bends in DNA fragments by brownian dynamics simulations

The use of Brownian dynamics simulations to investigate the presence of structural (kinks) and dynamic (bulges) anomalies in short DNA stretches is analyzed in connection with a string-of-beads model. A scaling method to choose the hydrodynamic translational and rotational parameters of the beads is proposed and tested on straight, kinked and bulged DNA fragments 17 nm long. The model reproduces the rigid-body rotational diffusion for the straight DNA and for the fluorescence polarization anisotropy decay of the kinked and bulged DNAs the model predicts a different behavior which is found experimentally. Received: 24 March 1998 / Accepted: 3 September 1998 / Published online: 23 November 1998     

Biomonitoring of benzene and toluene in human blood by headspace-solid-phase microextraction

A simple and rapid method for the determination of benzene and toluene in whole blood by headspace-solid-phase microextraction (HS-SPME) is described. Using SPME fibres coated with 65 μm carboxene/polydimethylsiloxane, limits of quantification (LOQ) of 5 ng/L for benzene and 25 ng/L for toluene are achieved. As a result of its large linear range (i.e. 5–5000 ng/L for benzene) the method is suitable for biomonitoring of both occupationally and environmentally exposed people. The reproducibility of the determination of benzene is ≤ 8%. An interlaboratory comparison demonstrated that the method proposed here compares favorably with existing methods (dynamic headspace, purge and trap). Received: 9 February 1998 / Revised: 6 July 1998 / Accepted: 18 July 1998     

Speciation of activators in electroluminescent thin films: an EXAFS study of cerium and terbium doped strontium sulfide

Extended X-ray absorption fine structure (EXAFS) was used to determine the local structure of the luminescent centers in Tb³⁺ and Ce³⁺ -doped strontium sulfide thin films deposited by Atomic Layer Epitaxy (ALE). The rare earths were observed to enter mainly the substitutional sites but at the same time a part of the atoms form RES clusters (RE = rare earth). The presence of both substitutional sites and RES clusters has been observed for the first time in this study for rare earths in II–VI compounds. Received: 9 February 1998 / Revised: 22 May 1998 / Accepted: 29 May 1998     

FIA determination of pyruvate in serum based on direct chemiluminescence oxidation

Chemiluminescence was observed by mixing acidic potassium permanganate solution with pyruvate in the presence of quinine. A new simplified method for pyruvate determination based on this phenomenon was established. The chemiluminescence intensity is a linear function of the concentration of pyruvate in the range of 2 × 10^–6 to 1 × 10^–3 g/mL with a detection limit of 0.8 μg/mL and a relative standard deviation of less than 2.3%. The method has been successfully used to determine pyruvate in serum. Received: 3 April 1998 / Revised: 20 July 1998 / Accepted: 17 September 1998     

Need for quality management in research and development

 There is growing interest in setting up a general concept for quality management and quality control in research and development, which in this case means, for example, research in the fields of medicine and social sciences. This article is a strong plea for a quality management system in all fields of research and development and will probably initiate broad discussion on this delicate topic. Received: 28 June 1998 · Accepted: 13 July 1998     

Certification of reference materials for the quality control of major element determinations in groundwater Part 2: Certification

The quality control of groundwater monitoring requires the availability of representative CRMs. This paper describes the preparation of two artificial groundwater reference materials, CRM 616 (high carbonate content) and CRM 617 (low carbonate content), the homogeneity and stability studies and the analytical work performed for the certification of a range of major elements (Ca, Cl, Fe, K, Mg, Mn, Na, NO₃, PO₄ and SO₄). Received: 15 May 1998 / Revised: 25 June 1998 / Accepted: 1 July 1998     

Iodine determination in biological materials Options for sample preparation and final determination

This paper describes the development of various new acid sample decomposition methods, as well as an extraction (leaching) method and compares them with the “Sch?niger Combustion” technique. The methods have been developed as sample preparation techniques for iodine determination in biological materials, especially in solid samples. ICP-MS (inductively coupled plasma mass spectrometry) and a catalytic technique are employed and discussed for the final determination of iodine concentrations. Accuracy and reliability of the different analytical methods are shown in the examples of different CRMs (certified reference materials) available for iodine. The results of an interlaboratory comparison are specifically presented for the extraction (leaching) method. Received: 11 May 1998 / Revised: 14 June 1998 / Accepted: 16 June 1998     

Direct subduction of Q-conjugacy representations to give characteristic monomials for combinatorial enumeration

Characteristic monomials for a finite group are obtained by direct subductions of Q-conjugate representations. They are shown to give a generating function that is capable of solving enumeration problems. Received: 1 May 1998 / Accepted: 16 July 1998 / Published online: 18 September 1998     

Determination of EDTA in used fixing solutions by capillary electrophoresis

A capillary electrophoretic method for the determination of EDTA has been developed. EDTA was converted to Ni(II)-EDTA prior to separation, separated from Fe(III)-EDTA, thiosulphate, bromide and polythionates using a fused silica capillary (57 cm × 75 μm I.D.) filled with a borate buffer (50 mmol L^–1; pH 8.5; applied voltage, 30 kV) and detected at 214 nm. The separation time is about 6 min. The detection limit achieved is 2 × 10^–6 mol L^–1 for EDTA. This method was applied for the determination of free EDTA in used fixing solutions. Received: 27 February 1998 / Revised: 28 April 1998 / Accepted: 20 May 1998     

Determination of traces of metals in wines from Macedonia

A new method for the determination of chromium and manganese in wines using square-wave voltammetry was developed. For chromium, acrylic acid was chosen as supporting electrolyte and for manganese a mixture of NH₄OH and NH₄Cl. The experimental conditions (initial and final potential, frequency, pulse height, scan increment, scan rate and equilibrium and deposition time) were optimized. Chromium and manganese were determined in the Macedonian wines Kratošija, Kavadarka, Ohridija and Smederevka. The results agreed well with those obtained by standard UV/VIS spectrophotometry. A statistical treatment of the experimental data was performed using STATGRAPH and MATHCAD software packages. Received: 13 February 1998 / Revised: 19 May 1998 / Accepted: 25 May 1998     

Integral sorption in rubbery polymers

Simple equations are derived that describe integral sorption and desorption experiments under conditions where moving boundary effects in polymer films and spheres can be large because of high solvent concentrations. General conclusions are formulated about the nature of sorption and desorption experiments for both rectangular and spherical geometries. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36 : 171–180, 1998     

Periodic orbits and vibrational wave functions for DCP: nonlinear resonances in isotopically substituted molecules

We investigate, by means of classical and quantum mechanics, how isotopic substitution (H/D) affects the vibrational dynamics of HCP. The analysis of periodic orbits, including the location of the principal families as well as saddle node bifurcations, reveals a totally different picture for the phase-space resonance structure for HCP and DCP. While HCP is characterized by a 1:2 resonance between the CP stretch and the bending mode, DCP shows a 1:2 resonance between the two stretching degrees of freedom. Saddle node bifurcations, which are associated with large-amplitude motion of H/D moving from the C- to the P-end, appear at considerably higher energies in DCP than in HCP. These results are in accord with exact quantum mechanical calculations of the vibrational levels. Received: 24 June 1998 / Accepted: 10 August 1998 / Published online: 9 October 1998     

Determination of EDTA in used fixing solutions by capillary electrophoresis

A capillary electrophoretic method for the determination of EDTA has been developed. EDTA was converted to Ni(II)-EDTA prior to separation, separated from Fe(III)-EDTA, thiosulphate, bromide and polythionates using a fused silica capillary (57 cm × 75 μm I.D.) filled with a borate buffer (50 mmol L^–1; pH 8.5; applied voltage, 30 kV) and detected at 214 nm. The separation time is about 6 min. The detection limit achieved is 2 × 10^–6 mol L^–1 for EDTA. This method was applied for the determination of free EDTA in used fixing solutions. Received: 27 February 1998 / Revised: 28 April 1998 / Accepted: 20 May 1998     

Certification of total arsenic, dimethylarsinic acid and arsenobetaine contents in a tuna fish powder (BCR-CRM 627)

Tuna fishes were collected in the Straits of Messina (Italy), were dissected and dorsal muscles minced, freeze-dried, ground and sieved. The obtained powder was stabilised by γ-irradiation and filled into brown glass bottles. The homogeneity and stability at +20 °C and +40 °C were verified with regards to the total arsenic, dimethylarsinic acid and arsenobetaine contents. Ten laboratories participated in the certification study. All participants had demonstrated beforehand their ability to produce accurate results for the As speciation in fish tissue. The certified values are: total arsenic (4.8 ± 0.3) mg/kg, arsenobetaine (52 ± 3) μmol/kg, dimethylarsinic acid (2.0 ± 0.3) μmol/kg. The material is available from the BCR since early 1998. Received: 31 March 1998 / Revised: 20 July 1998 / Accepted: 25 July 1998     

Liquid-chromatographic determination of sulfadimidine in milk and eggs

A method for the determination/identification of residual sulfadimidine (SDD) in milk and eggs by high-performance liquid chromatography (HPLC) with a photo-diode array detector was developed. The sample preparation was performed by shaking with a mixture of 20% (w/v) trichloroacetic acid-methanol (4:1, v/v) followed by ultra-filtration using Molcut II^?. A LiChrospher^? 100 RP-8 (e) column and a mobile phase of 4% (v/v) acetic acid solution-acetonitrile (6:4, v/v) were used. The average recoveries from spiked SDD samples were 80.8–88.0% with coefficients of variation of 2.8–5.5%. The limits of detection in milk and eggs were 0.01 μg/mL and 0.01 μg/g, respectively. The total time required for the analysis of one sample was less than 20 min. Received: 7 October 1998 / Revised: 29 December 1998 / Accepted: 30 December 1998     

Preconcentration of some metals using metalfix chelamine resin prior to ICP-AES analysis

Preconcentration and separation of Ni, Pb and Cd have been investigated using the metalfix chelamine resin prior to inductively coupled plasma – atomic emission spectrometry (ICP-AES) under various experimental conditions. The recoveries of the analytes obtained with 95% confidence level were 92 ± 1% for Ni, 100 ± 4% for Pb and 93 ± 3% for Cd. Received: 5 February 1998 / Revised: 30 April 1998 / Accepted: 12 June 1998     

Variational solution of the single-particle Dirac equation in the field of two nuclei using relativistically adapted Slater basis functions

A variational method for solving the time-independent single-particle Dirac equation in the Coulomb field of two nuclei is described. A minimax variational principle and basis functions that have the proper analytic behavior, i.e. behave like r ^γ,γ non-integer, in the neighborhood of a nucleus, are used. A momentum space integration scheme for computing the necessary two-center integrals is described. Results are given for a standard test problem on two nuclei with Z=90 with an internuclear separation of 2.0/Z. The results confirm those of a previous calculation [F.A. Parpia and A.K. Mohanty, Chem Phys Lett 238: 209 (1995)]. Received: 13 May 1998 / Accepted: 22 June 1998 / Published online: 28 August 1998