Superacid mediated hydroxyalkylation reaction of 1,2,3‐indanetrione: a theoretical study

Energies of mono‐ and multiprotonation for 1,2,3‐indanetrione and ninhydrin in triflic acid (TFSA) media were estimated at PBE0/aug‐cc‐pvtz//6‐31+G** level of theory. The reactivity of formed intermediates in the reaction of aromatic electrophilic substitution has been studied at the same level of theory. It appears that the basicity of carbonyl groups in 1,2,3‐indanetrione is extremely low due to mutual influences of carbonyl groups. Carbonyl 2 is the least basic but the most reactive in accordance with experiment. Calculations demonstrated that monoprotonated intermediates are the principal reactive species in the reaction of hydroxyalkylation of 1,2,3‐indanetrione in TFSA. A new isomerization mechanism of 2,2‐diaryl‐1,3‐indanediones to 3‐(diarylmethylene)isobenzofuranones in TFSA media has been proposed. Copyright © 2010 John Wiley & Sons, Ltd.     

Charge dynamics,Majorana condition and the topology of the interacting electromagnetic field

In previous works [1, 2], the 2-dimensional charge transport with parallel (in plane) magnetic field was considered from the theoretical point of view showing explicitly that the specific form of the emergent equation enforces the respective field solution to fulfil the Majorana condition. In this paper we review, explain and analyze these important results in the context of the generated physical effects, namely, the quantum ring as spin filter, the quantum Hall effect and a new one of pure topological origin (as the described by the Aharonov–Casher theorems). The link with supersymmetrical models is briefly discussed.     

Evaluation of methoxy polyethylene glycol‐polylactide diblock copolymers as additive in hypromellose film coating

This paper deals with a new application of diblock methoxy polyethylene glycol‐polylactide block copolymers, a class of synthetic biomaterials largely studied in the pharmaceutical and biomedical fields owing to their favorable properties such as biocompatibility, biodegradability, low immunogenicity, and good mechanical properties. In this work, these materials were evaluated as additives for gastro‐soluble pharmaceutical coating aimed to reduce film stiffness and water permeability. Two copolymers with different polylactide chain lengths were synthesized and characterized in term of molecular weight and solid‐state properties. A series of free films with different hypromellose/copolymers ratio were prepared and characterized in terms of appearance, components miscibility, plasticity, and water vapor permeability. The obtained results demonstrate that copolymers effectively influence hypromellose film properties according to their concentration and molecular weight. Specifically, the addition of the copolymer with a molecular weight of 6.5 kDa in a ratio hypromellose:polymer 5:1, allowed to obtain films with good appearance, improved plasticization, and water permeability properties. For higher molecular weight, copolymer or different ratios was not possible to observe the improvement of all the properties at the same time. The results also make possible to define the critical features to improve in order to use block copolymers as additive in hypromellose film coating. The availability of new water‐soluble additives able to work as plasticizer and moisture sealer in polymeric films represents an important progress not only in the field of pharmaceutical coating but also in that of food coatings, as for example in the formulation of edible films. Copyright © 2013 John Wiley & Sons, Ltd.     

A multiresidual method based on ion-exchange chromatography with conductivity detection for the determination of biogenic amines in food and beverages

In the present work a sensitive and accurate method by ion chromatography and conductimetric detection has been developed for the determination of biogenic amines in food samples at microgram per kilogram levels. The optimized extraction procedure of trimethylamine, triethylamine, putrescine, cadaverine, histamine, agmatine, spermidine, and spermine from real samples, as well as the separation conditions based on a multilinear gradient elution with methanesulfonic acid and the use of a weak ionic exchange column, have provided excellent results in terms of resolution and separation efficiency. Extended calibration curves (up to 200 mg/kg, r?>?0.9995) were obtained for all the analyzed compounds. The method gave detection limits in the range 23–65 μg/kg and quantification limits in spiked blank real samples in the range 65–198 μg/kg. Recovery values ranged from 82 to 103 %, and for all amines, a good repeatability was obtained with precision levels in the range 0.03–0.32 % (n?=?4). The feasibility and potential of the method were tested by the analysis of real samples, such as tinned tuna fish, anchovies, cheese, wine, olives, and salami.

Synthesis of 3-iodothiophenes via iodocyclization of (Z)-thiobutenynes

A simple synthesis of 3-iodothiophenes was demonstrated using a wide range of (Z)-thioenynes. The key step in the iodocyclofunctionalization was the selective reduction of the triple bond in (Z)-thioenynes by the addition of iodine as an electrophilic agent. The 3-iodothiophenes were obtained in good to excellent yields of 61–92%. The 3-iodothiophenes were used as substrates in Sonogashira cross-coupling reactions to obtain thiophene acetylenes.     

Comprehensive two‐dimensional gas chromatography coupled with static headspace sampling to analyze volatile compounds: Application to almonds

The hyphenation of static headspace sampling with comprehensive 2D GC equipped with a modulator based on capillary flow technology and a flame ionization detector was used to separate and identify 43 representative target volatile compounds (light hydrocarbons, carbonyls, pyrazines, alcohols, furans, and benzenes) frequently detected in the roasting process of nuts. Five column combinations with differing degrees of orthogonality (one conventional and four inverted phase sets) were tested in order to obtain the best conditions for analyzing these volatile compounds. Optimization of the working conditions for each of the different column combinations was performed by means of a central composite design. The best results in terms of separation and differentiation among the different chemical groups were achieved with a combination of inverted phase columns (first dimension: highly polar, INNOWax; second dimension: mid‐polar, ZB‐35). Additionally, a reference template was developed to provide an effective and rapid analysis of the target compounds. Finally, the proposed method was successfully employed to identify volatile compounds in raw and roasted almond samples from the Spanish cultivar Largueta.     

Multiresidue method for the fast determination of pesticides in nutraceutical products (Camellia sinensis) by GC coupled to triple quadrupole MS

A method based on QuEChERS (quick, easy, cheap, effective, rugged, and safe) has been developed and validated for the determination and quantification of more than 140 pesticides in nutraceutical products obtained from green tea (Camellia sinensis). Extraction was performed with acidified acetonitrile (acetic acid 1%, v/v) and a clean‐up step using primary secondary amine (50 mg), graphitized black carbon (100 mg) and magnesium sulfate (200 mg) was needed. Pesticide determination was achieved utilizing GC coupled to triple quadrupole MS/MS using the selective‐reaction monitoring mode. The total run time was 23 min. Pesticides were quantified using matrix‐matched calibration. Recoveries ranged from 70 to 120% and relative SD was lower than 25% at 10, 50, and 100 μg/kg. LOQs were lower than 10 μg/kg. 148 pesticides were validated. The validated method was applied to commercial nutraceutical products, detecting 4,4‐dichlorobenzophenone (28 μg/kg), o,p′‐dicofol (38 μg/kg) and p,p‐dicofol (44 μg/kg) in a few samples.     

A validated stability-indicating LC method for simultaneous determination of quinapril and hydrochlorothiazide in pharmaceutical samples

A stability-indicating liquid chromatographic method was developed and validated for simultaneous determination of quinapril and hydrochlorothiazide in drug substances and dosage forms. Chromatographic separation of quinapril, hydrochlorothiazide and its degradation products was achieved on a RP-18 column, using acetonitrile and phosphate buffer (pH 4.6) as mobile phase in a gradient mode and detection at 216 nm. Stress testing was performed under hydrolytic, oxidative, thermal and photolytic conditions. The degradation products were well resolved from main peaks, proving the stability-indicating power of the method. The assay was linear for quinapril and hydrochlorothiazide concentrations of 40–200 µg mL^?1 and 25–125 µg mL^?1, respectively. The developed method was selective, accurate and precise for quinapril and hydrochlorothiazide determination. This method was used to quantify both drugs in combined commercial tablets. The results showed that the proposed method was found to be suitable for quantitative determination and the stability study of quinapril and hydrochlorothiazide in pharmaceutical samples.