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11.
Lattice Monte Carlo simulations are used to study the effect of nonionic surfactant concentration and CO2 density on the micellization and phase equilibria of supercritical CO2/surfactant systems. The interaction parameter for carbon dioxide is obtained by matching the critical temperature of the model fluid with the experimental critical temperature. Various properties such as the critical micelle concentration and the size, shape, and structure ofmicelles are calculated, and the phase diagram in the surfactant concentration-CO2 density space is constructed. On increasing the CO2 density, we find an increase in the critical micelle concentration and a decrease in the micellar size; this is consistent with existing experimental results. The variation of the micellar shape and structure with CO2 density shows that the micelles are spherical and that the extension of the micellar core increases with increasing micellar size, while the extension of the micellar corona increases with increasing CO2 density. The predicted phase diagram is in qualitative agreement with experimental phase diagrams for nonionic surfactants in carbon dioxide. 相似文献
12.
Angelo Zinellu Salvatore Sotgia Elisabetta Pisanu Bastianina Scanu Manuela Sanna Maria Franca Usai Roberto Chessa Luca Deiana Ciriaco Carru 《Analytical and bioanalytical chemistry》2010,398(5):1973-1978
The role of neurotransmitter amino acids (NAAs) in the functioning of the nervous system has been the focus of increasingly
intense research over the past several years. Among the various amino acids that have important roles as neurotransmitters,
there are alanine (Ala), glutamic acid (Glu), aspartic acid (Asp), serine (Ser), taurine (Tau) and glycine (Gly). NAAs are
present in plasma, cells and—at trace levels—in all biological fluids, but complex components in biological matrices make
it difficult to determine them in biological samples. We describe a new capillary electrophoresis (CE) method with laser-induced
fluorescence detection by which analytes are resolved in less than 12 minutes in a 18 mmol/L phosphate run buffer at pH 11.6.
The use of elevated temperatures during sample derivatization leads to a drastic reduction in the reaction time, down to 20 min,
compared to the 6–14 h usually described for reactions between FITC and amino acids at room temperature. In order to demonstrate
its wide range of applications, the method was applied to the analysis of NAA in human plasma and in other sample types, such
as red blood cells, urine, cultured cells, cerebrospinal fluid, saliva and vitreous humor, thus avoiding the typical limitations
of other methods, which are normally suitable for use with only one or two matrix types. 相似文献
13.
Angelo Zinellu Valeria Pasciu Salvatore Sotgia Bastianina Scanu Fiammetta Berlinguer Giovanni Leoni Sara Succu Ignazio Cossu Eraldo Sanna Passino Salvatore Naitana Luca Deiana Ciriaco Carru 《Analytical and bioanalytical chemistry》2010,398(5):2109-2116
We describe a new capillary electrophoresis laser-induced fluorescence (CE-LIF) method for the quantification of adenosine 5′-triphosphate (ATP) in spermatozoa and oocytes. The optimization of the precapillary derivatization reaction between ATP and 4,4-difluoro-5,7-dimethyl-4-bora-3a,4adiaza-s-indacene-3-propionyl ethylene diamine hydrochloride (BODIPY FL EDA) has been described. BODIPY-ATP conjugate was analysed in an uncoated fused silica capillary of 75 μm ID and 50 cm effective length using a 10 mmol/L tribasic sodium phosphate buffer, pH 11.5, at 22 kV in <5 min. A good reproducibility of intra- and inter-assay tests was obtained (CV?=?4.55% and 7.14%, respectively). With respect to our previous CE-UV assay, the new method showed an improvement in sensitivity that was about 120-fold (limit of quantification, 0.15 vs 18 μmol/L). Method applicability was proven on the reproductive cells of several animal species (roosters, horses, sheep and goats). Due to the elevated sensitivity, the new assay allows the measurement of adenosine 5′-triphosphate levels from just 20 oocytes. Considering that ATP concentration in reproductive cells is related to the mitochondrial integrity after cryopreservation, the proposed method could be a useful tool in assisted reproductive technologies. 相似文献
14.
Paola Manca Maria I. Pilo Giovanni Casu Serafino Gladiali Gavino Sanna Roberta Scanu Nadia Spano Antonio Zucca Chiara Zanardi Diego Bagnis Luca Valentini 《Journal of polymer science. Part A, Polymer chemistry》2011,49(16):3513-3523
A novel polythiophene bearing a pendant terpyridine moiety has been synthesized by electrochemical polymerization of a new thiophene monomer, namely 4′‐(2,2′:5′,2″‐terthien‐3′‐ethynyl)‐2,2′:6′,2″‐terpyridine (TAT). The insertion of a conjugated ethynyl spacer between the terthiophene and the terpyridine fragments provides for an effective extension of the delocalization of electrons within the structural unit and the polymer as a whole. The synthesis and characterization of the relevant monomer, the electrosynthesis of the corresponding polymer and its electrochemical, UV–visible spectroelectrochemical and IR characterization are described. Finally, a comparison between the electrochemical, spectroscopic, and spectroelectrochemical properties of PTAT and the analogue, saturated‐spacer PTTT (TTT = 4′‐[(2,2′:5′,2″‐terthien‐3′‐yl)methoxy]‐2,2′:6′,2″‐terpyridine) polymer is discussed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
15.
Chennamsetty N Bock H Scanu LF Siperstein FR Gubbins KE 《The Journal of chemical physics》2005,122(9):094710
The impact of alcohol additives on the self-assembly of surfactants in supercritical carbon dioxide is investigated using lattice Monte Carlo simulations. We observe that all studied (model) alcohols reduce the critical micelle concentration. The reduction is stronger the longer the hydrocarbon chain of the alcohol, and the higher the alcohol concentration. Short-chain alcohols are found to concentrate in the surfactant layer of the aggregates, replacing surfactant molecules and leading to a strong decrease of the aggregation number and a large increase of the number of aggregates. On the other hand, only a small number of alcohol molecules with longer chain length are found in the aggregates, leading to a slight increase in the aggregation number. However, structural properties such as size and density profiles of aggregates at the same aggregation number are not influenced markedly. Consequently, short-chain alcohols act as cosurfactants, directly influencing the properties of the aggregates, while alcohols with longer hydrocarbon chains work as cosolvents, altering the properties of the solvent. However, the transition between both extremes is gradual. 相似文献
16.
Spano N Casula L Panzanelli A Pilo MI Piu PC Scanu R Tapparo A Sanna G 《Talanta》2006,68(4):1390-1395
The use of the RP-HPLC official method of the International Honey Commission (IHC) for the determination of 5-hydroxymethylfurfural (HMF) in strawberry tree honey (Arbutus unedo, a typical Sardinian honey) has brought to light a specific and heavy chromatographic interference that prevents accurate quantification. The interference has been identified as homogentisic acid (HA), i.e. the marker of the botanical origin of the honey. For this reason, an alternative RP-HPLC method is proposed. The bias-free method allows a complete separation of HMF from HA to the baseline level and is faster and more precise than the RP-HPLC official method: the detection and quantification limits are 1.9 and 4.0 mg kg−1, respectively, whereas the repeatability is ca. 2% in the HMF concentration range of 5-140 mg kg−1. 相似文献