Determination of polycyclic aromatic hydrocarbons in industrial waste water at the ng/ml. level

A combination of column, thin-layer and capillary gas chromatography was investigated as a quantitative method for determination of polycyclic aromatic hydrocarbons in industrial waste water at the 10-100 ng/ml level. The method gives 90-95% overall recovery. Analytical results for polycyclic aromatic hydrocarbons in waste water from a Norwegian aluminium plant are presented.     

Noise sustained waves in subexcitable media: From chemical waves to brain waves

We discuss a novel type of spatiotemporal pattern that can be observed in subexcitable media when coupled to a thermal environment. These patterns have been recently observed in several different types of systems: a subexcitable photosensitive Belousov-Zhabotinsky reaction, hippocampal slices of rat brains, and astrocyte syncytium. In this paper, we introduce the basic concepts of subexcitable media, describe recent experimental observations in chemistry and neurophysiology, and put these observation into context with computer simulations. (c) 1998 American Institute of Physics.     

Developmental toxicity of benzotriazole in the protochordate Ciona intestinalis (Chordata, Ascidiae)

Benzotriazoles (BT) are applied as anticorrosive and de-icing agents and have been detected in a variety of aquatic ecosystems and municipal wastewater effluents. We have assessed the developmental effects of benzotriazole (CAS number 95-14-7) to the marine invertebrate Ciona intestinalis (Chordata, Ascidiae). At 15 ± 1 °C, the 24 h No-Observed Effect Concentration (NOEC) and Lowest Observed Effect Concentration (LOEC) values based on embryo morphological development were 100 and >100 mg L⁻¹, respectively (nominal concentration under static conditions). After 48 h, the NOEC and LOEC values were 10 and 32 mg L⁻¹, respectively. Light and electron microscopy studies on benzotriazole-exposed larva indicated that the primary target cells were the extra-embryonic test cells, which are known to play a significant apoptotic role during ascidian metamorphosis. The visible decline of test cells in benzotriazole-exposed larvae raises the possibility that the compound interferes with the regulation of embryo development in protochordates such as C. intestinalis. Further research is warranted to assess the potential longer term sublethal impacts of benzotriazole in aquatic organisms.     

Formation and evolution of scroll waves in photosensitive excitable media

Experimental and computational studies of the formation and evolution of scroll waves in three-dimensional excitable media are presented. Scroll waves are initiated in the photosensitive Belousov-Zhabotinsky reaction by perturbing traveling waves transverse to their direction of propagation. Scroll rings are generated by perturbing circular waves, which expand or contract depending on the strength of an imposed excitability gradient and its direction relative to the rotational direction of the scroll wave. (c) 1998 American Institute of Physics.     

Determination of calcium, magnesium, sodium, and potassium in foodstuffs by using a microsampling flame atomic absorption spectrometric method after closed-vessel microwave digestion: method validation

This paper describes a validation process in compliance with the NFIEN ISO/IEC 17025 standard for the determination of the macrominerals calcium, magnesium, sodium, and potassium in foodstuffs by microsampling with flame atomic absorption spectrometry after closed-vessel microwave digestion. The French Standards Commission (Agence Francaise de Normalisation) standards NF V03-110, NF EN V03-115, and XP T-90-210 were used to evaluate this method. The method was validated in the context of an analysis of the 1322 food samples of the second French Total Diet Study (TDS). Several performance criteria (linearity, LOQ, specificity, trueness, precision under repeatability conditions, and intermediate precision reproducibility) were evaluated. Furthermore, the method was monitored by several internal quality controls. The LOQ values obtained (25, 5, 8.3, and 8.3 mg/kg for Ca, Mg, Na, and K, respectively) were in compliance with the needs of the TDS. The method provided accurate results as demonstrated by a repeatability CV (CVr) of < 7% and a reproducibility CV (CVR) of < 12% for all the elements. Therefore, the results indicated that this method could be used in the laboratory for the routine determination of these four elements in foodstuffs with acceptable analytical performance.     

Optimisation of ICP-MS collision/reaction cell conditions for the determination of elements likely to be interfered (V, Cr, Fe, Co, Ni, As and Se) in foodstuffs

A strategy for the accurate determination in foodstuffs of seven elements liable to be interfered with (V, Cr, Fe, Co, Ni, As and Se), was successfully applied. Firstly, to reduce spectroscopic interferences, four influential factors (hexapole and quadrupole bias, helium and hydrogen flows) of the collision/reaction cell device were optimised through the experimental design methodology. Secondly, non-spectroscopic interferences, which may severely disturb the analysis of matrices containing large amounts of non-target elements, were significantly reduced by a limited decrease in the flow rate of the optimum initial nebuliser rather than with a specific time-consuming dilution. Finally, the optimised multi-element method was subjected to a full validation that demonstrated its acceptable analytical performance.     

Reduction of in-source collision-induced dissociation and thermolysis of sulopenem prodrugs for quantitative liquid chromatography/electrospray ionization mass spectrometric analysis by promoting sodium adduct formation

Six chromatographically resolved sulopenem prodrugs were monitored for their potential to undergo both in-source collision-induced dissociation (CID) and thermolysis. Initial Q1 scans for each prodrug revealed the formation of intense [Prodrug2 + H]+, [Prodrug2 + Na]+, [Prodrug + Na]+, and [Sulopenem + Na]+ ions. Non-adduct-associated sulopenem ([Sulopenem + H]+) along with several additional lower mass ions were also observed. Product ion scans of [Prodrug3 + Na]+ showed the retention of the sodium adduct in the collision cell continuing down to opening of the beta-lactam ring. In-source CID and temperature experiments were conducted under chromatographic conditions while monitoring several of the latter ion transitions (i.e., adducts, dimers and degradants/fragments) for a given prodrug. The resulting ion profiles indicated the regions of greatest stability for temperature and declustering potential (DP) that provided the highest signal intensity for each prodrug and minimized in-source degradation. The heightened stability of adduct ions, relative to their appropriate counterpart (i.e., dimer to dimer adduct and prodrug to prodrug adduct ions), was observed under elevated temperature and DP conditions. The addition of 100 microM sodium to the mobile phase further enhanced the formation of these more stable adduct ions, yielding an optimal [Prodrug + Na]+ ion signal at temperatures from 400 to 600 degrees C. A clinical liquid chromatography/tandem mass spectrometry (LC/MS/MS) assay for sulopenem prodrug PF-04064900 in buffered whole blood was successfully validated using sodium-fortified mobile phase and the [PF-04064900 + Na]+ ion for quantitation. A conservative five-fold increase in sensitivity from previously validated preclinical assays using the [PF-04064900 + H]+ precursor ion was achieved.