Determination of total arsenic by batch hydride generation atomic absorption spectrometry in injectable drugs containing high levels of Sb(V) as N-methylglucamine antimonate

A procedure for the determination of arsenic by batch hydride generation atomic absorption spectrometry (HG AAS) in commercial samples of injectable drugs, containing high concentrations of Sb(V), is described. The procedure is based on the complexing effect for Sb of citric, oxalic and acetic acids as reaction media. Aqua regia was used for sample digestion prior to As determination by HG AAS. The following experimental conditions for the determination of total As, as As(V), were evaluated: the acid medium and its concentration, sodium tetrahydroborate concentration, purge time, and influence of the different oxidation states of As. The effect of the delay time after mixing of sample and acid solution was also studied. Optimized conditions were: 10% (m/v) citric acid, 1.5% (m/v) sodium tetrahydroborate solution and 30 s for purge time. A delay time of 1 h was required after the digested sample had been mixed with citric acid, before As determination could be carried out. No interference on As(III) and As(V) signals was observed in the presence of up to 1 mg Sb(V). The tolerance limits for Ni(II), Cu(II) and Pb(II) were 1 mg, 100 μg and 100 μg, respectively. Recovery tests for As(III) and As(V) resulted in values between 97 and 101%. Characteristic mass and detection limit (3σ), using the recommended conditions, were 0.52 and 0.8 ng, respectively, for total As.     

Reactions of nitrogen oxides with heme models. Characterization of NO and NO2 dissociation from Fe(TPP)(NO2)(NO) by flash photolysis and rapid dilution techniques: Fe(TPP)(NO2) as an unstable intermediate

Described are studies directed toward elucidating the controversial chemistry relating to the solution phase reactions of nitric oxide with the iron(II) porphyrin complex Fe(TPP)(NO) (1, TPP = meso-tetraphenylporphinato2-). The only reaction observable with clean NO is the formation of the diamagnetic dinitrosyl species Fe(TPP)(NO)2 (2), and this is seen only at low temperatures (K(1) < 3 M(-1) at ambient temperature). However, 1 does readily react reversibly with N2O3 in the presence of excess NO to give the nitro nitrosyl complex Fe(TPP)(NO2)(NO) (3), suggesting that previous claims that 1 promotes NO disproportionation to give 3 may have been compromised by traces of air in the nitric oxide sources. It is also noted that 3 undergoes reversible loss of NO to give the elusive nitro species Fe(TPP)(NO2) (4), which has been implicated as a powerful oxygen atom transfer agent in reactions with various substrates. Furthermore, in the presence of excess NO2, the latter undergoes oxidation to the stable nitrato analogue Fe(TPP)(NO3) (5). Owing to such reactivity of Fe(TPP)(NO2), flash photolysis and stopped-flow kinetics rather than static techniques were necessary for the accurate measurement of dissociation equilibria characteristic of Fe(TPP)(NO2)(NO) in 298 K toluene solution. Flash photolysis of 3 resulted in competitive NO2 and NO dissociation to give Fe(TPP)(NO) and Fe(TPP)(NO2), respectively. The rate constant for the reaction of 1 with N2O3 to generate Fe(TPP)(NO2)(NO) was determined to be 1.8 x 10(6) M(-1) s(-1), and that for the NO reaction with 4 was similarly determined to be 4.2 x 10(5) M(-1) s(-1). Stopped-flow rapid dilution techniques were used to determine the rate constant for NO dissociation from 3 as 2.6 s(-1). The rapid dilution experiments also demonstrated that Fe(TPP)(NO2) readily undergoes further oxidation to give Fe(TPP)(NO3). The mechanistic implications of these observations are discussed, and it is suggested that NO2 liberated spontaneously from Fe(P)(NO2) may play a role in an important oxidative process involving this elusive species.     

Modified capillary GC/MS system enabling dynamic headspace sampling with on-line cryofocusing and cold on-column injection of liquid samples

The paper describes a capillary GC/MS hardware arrangement allowong either:

• (a) on-line injection of sample of gases and vapors coming from dynamic headspace or purg & trap samplers and their subsequent cryofocusing/thermal desorption prior to the analytical capillary column (first column):
• (b) direct injection of liquid samples through a cold on-column injector into a second analytical column (counted in series with the first).

Chromatographic profiles of acacia honey aromas provide condirmation of the suitability of this system.     

Divisible designs from twisted dual numbers

The generalized chain geometry over the local ring $K(\varepsilon ; \sigma)The generalized chain geometry over the local ring of twisted dual numbers, where K is a finite field, is interpreted as a divisible design obtained from an imprimitive group action. Its combinatorial properties as well as a geometric model in 4-space are investigated. Dedicated to Helmut M?urer on the occasion of his 70th birthday     

Biological applications of gold nanoparticles

This critical review gives a short overview of the widespread use of gold nanoparticles in biology. We have identified four classes of applications in which gold nanoparticles have been used so far: labelling, delivering, heating, and sensing. For each of these applications the underlying mechanisms and concepts, the specific features of the gold nanoparticles needed for this application, as well as several examples are described (142 references).     

Luminescent Single-Molecule Magnets as Dual Magneto-Optical Molecular Thermometers

Luminescent thermometry allows the remote detection of the temperature and holds great potential in future technological applications in which conventional systems could not operate. Complementary approaches to measuring the temperature aiming to enhance the thermal sensitivity would however represent a decisive step forward. For the first time, we demonstrate the proof-of-concept that luminescence thermometry could be associated with a complementary temperature readout related to a different property. Namely, we propose to take advantage of the temperature dependence of both magnetic (canonical susceptibility and relaxation time) and luminescence features (emission intensity) found in Single-Molecule Magnets (SMM) to develop original dual magneto-optical molecular thermometers to conciliate high-performance SMM and Boltzmann-type luminescence thermometry. We highlight this integrative approach to concurrent luminescent and magnetic thermometry using an air-stable benchmark SMM [Dy(bbpen)Cl] (H₂bbpen=N,N′-bis(2-hydroxybenzyl)-N,N′-bis(2-methylpyridyl)ethyl-enediamine)) exhibiting Dy³⁺ luminescence. The synergy between multiparametric magneto-optical readouts and multiple linear regression makes possible a 10-fold improvement in the relative thermal sensitivity of the thermometer over the whole temperature range, compared with the values obtained with the single optical or magnetic devices.     

Au-Ir催化剂用于生物质衍生物加氢

采用沉积-沉淀法制备了TiO2负载的Au-Ir和Au-Ru催化剂,用于乙酰丙酸加氢制γ-戊内酯反应,并与相应的单金属催化剂性能进行了比较。有趣的是, Ir/TiO2中添加Au抑制了催化剂活性,而添加Ru则表现出正效应的协同作用。这两个催化剂均在H2中还原,使得M0–Au0间相互作用增强。结合以前的密度泛函理论计算和催化反应结果,我们认为, Au-Ir/TiO2催化剂活性低于Ir/TiO2催化剂是由于Au影响了Ir原子的氧化还原过程。     

Determination of Flavonoids and Resveratrol in Wine by Turbulent-Flow Chromatography-LC-MS

Turbulent-flow chromatography (TFC) on-line coupled to liquid chromatography mass spectrometry (LC-MS) is used to determine flavonoids and resveratrol in different types of wines. A fully automated system was developed in which 10 mL of sample (diluted wine) was passed over a TFC column, after which the retained analytes were separated by reversed-phase LC and detected by negative ion mode atmospheric-pressure chemical ionization (APCI) MS. The method proved to be fast, non-laborious, robust and sensitive. The feasibility of the method was tested on several red, white and rose wines. Quantitation of resveratrol was possible using the standard addition procedure. Red wine showed the highest amount of resveratrol (4 mg L⁻¹), while rose and white wine contained concentrations which were about ten fold lower.     

High Resolution Gel Permeation Chromatography Followed by GC–ECD for the Determination of Pesticide Residues in Soybeans

An efficient and validated approach for the determination of pesticide residues in soybeans using high-resolution gel permeation chromatography in combination with gas chromatography and electron capture detection is described. Gel permeation chromatography was used to remove interfering fatty components of soybeans before gas chromatographic analysis. The limit of quantification for the seven pesticides studied was between 9 and 46 μg kg^?1. The method was applied to different soybean varieties and recoveries were determined to be between 93 and 118% with RSD values below 10%.     

On the Coexistence of Superconductivity and Magnetic Ordering in Unconventional Superconductors

It is demonstrated that the coexistence of superconductivity and magnetic ordering, occurring, for instance, in iron-based pnictides and uranium compounds, is not forbidden by classical Maxwell’s equations and London-type equations. It predicts simply that internal magnetization is allowed but localized magnetic moments are screened at distances of the order of the London penetration depth. A microscopic theory is considered for the case of ferromagnetic ordering, described in simple terms by electron-magnon coupling. For the sake of simplicity, we assume that itinerant electrons are not responsible for the magnetic ordering, but interact with phonon and magnon excitations, leading to an alternative Cooper pair channel. The temperature dependence and the isotope effect of the superconducting gap is also analysed.