Determination of Phenolic Endocrine Disruptors in Cosmetics by High-Performance Liquid Chromatography Mass Spectrometry

An analytical method for the simultaneous determination of bisphenol A, 4-t-octylphenol, 4-n-octylphenol, and 4-n-nonylphenol in cosmetic samples has been developed. These compounds have toxic effects on human health as they have shown to produce endocrine disrupting properties. Therefore, their presence in cosmetics should be avoided according to the current European Regulations on cosmetic products. The method is based on high-performance liquid chromatography coupled to mass spectrometry (HPLC-MS) detection. Standard addition calibration was used to avoid matrix effects. The limits of detection values ranged between 7 and 15?ng?mL^?1 (threefold of the residual standard deviation of regression lines). The proposed method was validated, and good recovery (90–106%) and repeatability values (2.7–8.2%) were obtained. Finally, the method was successfully applied to ten commercially available cosmetic samples. The good analytical features of the proposed method make it useful to carry out the quality control of cosmetic products and raw materials to assure the safety of users.     

Modelling hydrological data with and without long memory

The paper focuses on the problem of long-range dependence when analysing time series of hydrological data. Three time series are analysed: the monthly rainfall in the town of Florence, Italy; the daily minimum temperatures in the same town; and, finally, the daily water inflow to Lake Maggiore, Italy. Heuristic methods and maximum likelihood estimation of a parametric model are used to investigate the Hurst phenomena and to detect whether long-range dependence is present in any of the time series. We found that long-range dependence is not present in the first series but it is present in the last two. The daily water inflow to Lake Maggiore was modelled by a fractionally differenced arima model (farima) which contains a long-range dependence component. It is shown that the fit is much better than the one provided by more traditional arima models that do not have such a component.

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Sommario Lo studio considera il problema dell'identificazione dei fenomeni di dipendenza a lungo termine (long range dependence) nelle serie temporali di dati idrologici. Allo scopo sono state analizzate tre serie temporali, rispettivamente quella dei totali mensili di precipitazione rilevati alla stazione dell'Osservatorio Ximeniano de Firenze, quella delle temperature minime giornaliere per la stessa stazione e quella degli afflussi giornalieri al Lago Maggiore. Per identificare la presenza di fenomeni di dipendenza long range, attraverso la valutazione della consistenza del fenomeno di Hurst, sono stati utilizzati sia metodi euristici, sia la stima a massima verosimiglianza di un modello parametrico. Due delle tre serie analizzate sono risultate caratterizzate da tale dipendenza. Per la serie degli afflussi al Lago Maggiore, si è inoltre proceduto alla simulazione attraverso un modello arima a differenziazione frazionaria (farima), la cui struttura contiene una componente long-range. I risultati ottenuti, mostrano che tale modello fornisce risultati significativamente migliori dei tradizionali modelli arima, privi di tale componente.

     

2-Naphthol-phosphatidylethanolamine: A fluorescent phospholipid analogue for excited-state proton transfer studies in membranes

The fluorescence properties of the phospholipid derivative,N-[1-(2-naphthol)]-phosphatidylethanolamine (NAPH-PE), have been studied by steady-state and time-resolved fluorescence techniques. The new probe is a naphthol adduct of phosphatidylethanolamine. The emission spectrum of the fluorescent phospholipid depends on the pH and on the proton acceptor concentration as expected for a typical two-state excited-state proton transfer reaction. In ethanol solutions at an apparent pH of 6.7 and in the presence of acetate anion (0.14M), a biexponential decay is obtained from global analysis of the data. The lifetimes, ₁=3.9 ns and ₂=6.2 ns. are constant across the spectral region 350–460 nm. The decay-associated spectra and the species-associated spectra reproduce well the profiles reported for a two-state excited-state proton transfer reaction. The fluorescent phospholipid has been incorporated into dimyristoyllecithin and dipalmitoyllecithin vesicles. Although lower proton transfer is found, the reaction appears to be dependent on the gel-to-liquid-crystalline phase transition of the lipid membrane. In addition, the steady-state anisotropy of NAPH-PE measured as a function of temperature trace the phase transition of the two vesicle systems. Thus, it is shown that the physical state of the bilayer affects a reaction which takes place at the membrane surface. In the presence of acetate ions (0.3M), global analysis, performed in terms of fluorescence decay parameters, recovers preexponential coefficients that are consistent with an excited-state proton transfer reaction. The short lifetime drops from 3.9 to 0.44 ns without significant changes of the longer-lifetime component.     

Witnessing differences without redundancies

We show that elements suffice to witness the differences of pairwise distinct sets, and provide sufficient conditions for an infinite family of pairwise distinct sets to have a minimal collection of elements witnessing the differences between any two of its members.

     

Oxidative Cyclization of Iodo Ketones. Synthesis of 6-Oxa-5alpha-pregnane-3,20-dione

The steroidal delta- and gamma-iodo ketones 1 and 9 were converted to the cyclic hemiketals 3 and 10, by oxidation to the iodoso derivatives with m-CPBA. Spontaneous cyclization of the latter intermediates to the corresponding oxocarbenium ions, followed by stereoselective addition of water, rendered the hemiketals. Depending on the reaction conditions, the five-membered oxocarbenium ion derived from the gamma-iodo ketone 9 may add H(2)O or m-CPBA to give either the hemiketal or a Baeyer-Villiger type product 12, while the oxocarbenium derived from 1 gives exclusively the hemiketal. When the reaction was carried out in dry methanol, methyl ketals were formed. Use of this methodology allowed us to synthesize 6-oxa-5alpha-pregnanes with and without functionalization at C-19.     

Detection and quantitation of sulfonylurea herbicides in soil at the ppb level by capillary electrophoresis

A multi-residue analytical method based on solid-phase extraction enrichment combined with capillary electrophoresis (CE), using micellar electrokinetic capillary chromatography, was developed to isolate, recover and quantitate three sulfonylurea herbicides (chlorsulfuron, chlorimuron and metasulfuron) from soil samples. Optimization for CE separation was achieved using an overlapping resolution map scheme. The recovery of each herbicide was >80% and the limit of detection was 10 ppb. The capability of CE in providing quantitative analysis of sulfonylureas in soil samples at the ppb level has been demonstrated.     

Titrimetric semimicro determination of reducing sugars in wines and liquors

Summary A semimicro modification of the method ofFehling-Causse-Bonnams is described for the determination of invert sugar in wines and liquors. A relative standard deviation of 4 parts per thousand is obtained by closely adhering to a standardized procedure which is also required for the attainment of accuracy.

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Zusammenfassung Ein Halbmikroverfahren der Methode vonFehling-Causse-Bonnams wird für die Bestimmung von Invertzucker in Wein und Likören beschrieben. Der relative mittlere Fehler konnte durch Konstanthaltung der Versuchsbedingungen auf 0,4% beschränkt werden, eine Maßregel, die für die Erzielung richtiger Ergebnisse erforderlich ist. Die zur Entfärbung verwendete Pflanzenkohle adsorbiert auch etwa 2% des reduzierenden Zuckers pro 50 mg Kohle und der dadurch bedingte Korrektionsfaktor muß durch Kontrollanalysen mit Invertzuckerlösungen bekannten Gehaltes für jede Kohlesorte bestimmt werden.

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Résumé On décrit un procédé semi-micro pour la méthode deFehling-Causse-Bonnams pour le dosage du sucre interverti dans le vin et les liqueurs. L'erreur relative moyenne a pu être limitée à 0,4% par maintien constant des conditions de l'expérience; cette mesure est nécessaire pour l'obtention de résultats corrects. Le charbon végétal utilisé pour décolorer adsorbe environ 2% de sucre réducteur pour 50 mg de charbon et le facteur de correction qui en résulte doit, dans les analyses de contrôle, être déterminé pour chaque qualité de charbon avec des solutions de sucre interverti de teneur connue.

     

Application of technetium and rhenium carbonyl chemistry to nuclear medicine. Preparation of [NEt4]2[TcCl3(CO)3] from [NBu4][TcO4] and structure of [NEt4][Tc2(μ-Cl)3(CO)6]; structures of the model complexes [NEt4][Re2(μ-OEt)2(μ-OAc)(CO)6] and [ReBr({-CH2S(CH2)2Cl}2)(CO)3]

Transition Metal Chemistry - A detailed investigation of the one-pot synthesis of [NEt4]2[MX3(CO)3] [M=Tc (1a) or Re (1b); X= Cl?, Br?] is presented. The intermediates...     

The development of solid-surface fluorescence characterization of polycyclic aromatic hydrocarbons for potential screening tests in environmental samples

This paper presents the characterization of polycyclic aromatic hydrocarbons (PAHs) in solid-surface fluorescence as the first step for obtaining new optical sensors for PAHs screening. The fluorescence properties of the EPA-PAHs (naphthalene, acenaphthene, acenaphthylene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, chrysene, benzo[a]anthracene, benzo[k]fluoranthene, benzo[b]fluoranthene, benzo[a]pyrene, indeno [1,2,3-cd]pyrene, benzo[g,h,i]perylene and dibenzo[a,h]anthracene) on five types of solid-surfaces were evaluated. The experimental variables (pH and percentage of organic solvent in samples) were studied, obtaining different possibilities for making individual sensors for some of these PAHs and the best conditions for developing sensors for PAH screening were also studied.     

Controlling multivalent interactions in triply-threaded two-component superbundles

We have investigated the (1)H NMR spectra, the absorption spectra, the fluorescence spectra and decays, and the electrochemical properties of i). a tritopic receptor in which three benzo[24]crown-8 macrorings are fused onto a triphenylene core, ii). a trifurcated trication wherein three dibenzylammonium ions are linked 1,3,5 to a central benzenoid core, and iii). their 1:1 adduct which constitutes a triply-threaded, two-component supramolecular bundle. X-Ray crystallography has established the precise geometry of this paucivalent recognition motif in the solid state. In addition to [N(+)-H...O] hydrogen bonding and [C-H...O] interactions between the NH(2) (+) centers on the three dibenzylammonium ion containing arms of the trication and the three crown ether rings in the tritopic receptor, there is a stabilizing [pi...pi] stacking interaction between the two aromatic cores. Mass spectrometry and (1)H NMR spectroscopy have confirmed the integrity of the 1:1 adduct beyond the solid state, provided the solvents are relatively apolar (e.g., chloroform and acetonitrile). The intense fluorescence emissions of the two recognition components are quenched upon association with the concomitant appearance of a lower energy, broad fluorescence band originating from the pi-pi stacking in the 1:1 adduct of the aromatic cores in the two matching components. Titration experiments, including Job plots, establish the 1:1 stoichiometry of the adduct, an observation which is also confirmed by electrochemical experiments. The electrochemical results show that, both in the tritopic receptor and in the superbundle itself, the first oxidation process is associated with the hexaalkoxytriphenylene core. The successive oxidation processes of the peripheral dioxybenzene units are affected by charge-transfer interactions in the tritopic receptor, whereas, in the superbundle, such units are not interacting. In acetonitrile solution, dethreading/rethreading of the 1:1 adduct can be controlled quantitatively by addition of base and acid. Dethreading and rethreading is also observed by (1)H NMR spectroscopy when dimethylsulfoxide is added to a solution of the 1:1 adduct in equal volumes of acetonitrile and chloroform. A trifurcated trication where methyl groups are located on the para positions of the three dibenzylammonium ions, which are linked 1,3,5 to the neutral benzenoid core, has been employed to demonstrate that dethreading of the 1:1 adduct involves doubly-threaded and singly-threaded species, that is, the paucivalent site is dismembered in a sequence of logical steps involving stable intermediates. This molecular recognition system is a rare example of a supramolecular entity based on a cooperative binding motif that can be switched on and off by chemical means.