Determination of Point of Zero Charge of Tunisian Kaolinites by Potentiometric and Mass Titration Methods

This paper deals with determining points of zero charge of natural and Na+-saturated mineral kaolinites using two methods: (1) acid-base potentiometric titration was employed to obtain the adsorption of H+ and OH- on amphoteric surfaces in solutions of varying ionic strengths in order to determinate graphically the point of zero net proton charge (PZNPC) defined equally as point of zero salt effect (PZSE); (2) mass titration curve at different electrolyte concentrations in order to estimate PZNPCs by interpolation and to compare with those determined by potentiometric titrations. The two methods involved points of zero charge approximately similar for the two kaolinites between 6.5-7.8, comparable to those reported previously and were in the range expected for these clay minerals. The comparison of potentiometric surface titration curves obtained at 25 °C and those published in the literature reveals significant discrepancies both in the shape and in the pH of PZNPCs values.

On Combining Morphological Component Analysis and Concentric Morphology Model for Mammographic Mass Detection

Mammographic mass detection is an important task for the early diagnosis of breast cancer. However, it is difficult to distinguish masses from normal regions because of their abundant morphological characteristics and ambiguous margins. To improve the mass detection performance, it is essential to effectively preprocess mammogram to preserve both the intensity distribution and morphological characteristics of regions. In this paper, morphological component analysis is first introduced to decompose a mammogram into a piecewise-smooth component and a texture component. The former is utilized in our detection scheme as it effectively suppresses both structural noises and effects of blood vessels. Then, we propose two novel concentric layer criteria to detect different types of suspicious regions in a mammogram. The combination is evaluated based on the Digital Database for Screening Mammography, where 100 malignant cases and 50 benign cases are utilized. The sensitivity of the proposed scheme is 99% in malignant, 88% in benign, and 95.3% in all types of cases. The results show that the proposed detection scheme achieves satisfactory detection performance and preferable compromises between sensitivity and false positive rates.

Mass transfer resistance in the production of high impact polypropylene

Mass transfer resistance in the production of high impact polypropylene (hiPP) produced by a two-stage slurry/gas polymerization was investigated by field-emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. It is found that the formation of ethylene-propylene copolymer (EPR) phases in polypropylene (iPP) particle produced in the first stage slurry polymerization exhibits a developing process from exterior to interior

Evaluation of flavonoids binding to DNA duplexes by electrospray ionization mass spectrometry

In this study, electrospray ionization mass spectrometry (ESI-MS) was used to investigate the binding interactions of ten flavonoid aglycones and ten flavonoid glycosides with DNA duplexes. Relative binding affinities of the flavonoids toward DNA duplexes were estimated based on the fraction of bound DNA. The results revealed that the 4'-OH group of flavonoid aglycones was essential for their DNA-binding properties. Flavonoid glycosides with sugar chain linked on ring A or ring B showed enhanced binding toward the duplexes over their aglycone counterparts, whereas glycosylation of the flavonol quercetin on ring C exhibited a less pronounced effect.

Structural characterization and identification of dibenzocyclooctadiene lignans in Fructus Schisandrae using electrospray ionization ion trap multiple-stage tandem mass spectrometry and electrospray ionization Fourier transform ion cyclotron resonance multiple-stage tandem mass spectrometry

The electrospray ionization ion trap multiple-stage tandem mass spectrometry (ESI-MSn) and electrospray ionization Fourier transform ion cyclotron resonance multiple-stage tandem mass spectrometry (ESI-FT-ICR-MSn) have been applied successfully to the direct investigation of a number of dibenzocyclooctadiene lignan constituents from the methanol extracts of the Fructus Schisandrae in the positive ion mode. The detailed structural characterization of the same skeleton and different peripheral substituents had been studied and the precise elemental compositions of ions at high mass resolution had been obtained. So the fragmentation mechanisms could be clarified.

Qualitative and semi-quantitative analysis of quaternary alkaloids in Coptis-scute herb couple by Electrospray mass Spectrometry

A practical solution of qualitatively analyzing quaternary alkaloids in coptis-scute herb couple by electrospray ionization mass spectrometry(ESI-MS) was developed. Without the complicated pretreatment of sample, the active ingredients including berberine, palmatine, coptisine, jatrorrhizine, epiberberine, and columbamine were identified and some relative content changing rules of alkaloids in coptis-scute couple were summarized in this article. The overall profiles of the complex extracts were obtained.

Studies on the stability of diester-diterpenoid alkaloids from the genus Aconitum L. by high performance liquid chromatography combined with electrospray ionisation tandem mass spectrometry (HPLC/ESI/MSn)

The stability of diester-diterpenoid alkaloids (DDA) from plants of the genus Aconitum L. has been studied in different solvents and pH buffers. The HPLC/ESIMS method for analysing the concentration of DDA was established and DDA's decomposition products were elucidated by HPLC/ESI-MS/MSn. In different solvents, e.g. dichloromethane, ether, methanol and distilled water, the decomposition pathways of DDA are quite different and their difference in stabilities depends on the difference of their structures, in which substituents at the N atom and substituents at C-3 are different. The pyrolytic products of DDA, such as deacetoxy aconitine-type alkaloids, have been observed in the above solvents, whereas 8-methoxy-14-benzoyl aconitine-type alkaloids have been obtained only in methanol.

Studies on alkaloids binding to GC-rich human survivin promoter DNA using positive and negative ion electrospray ionization mass spectrometry

Electrospray ionization mass spectrometry (ESI-MS) was used to investigate the binding of 13 alkaloids to two GC-rich DNA duplexes which are critical sequences in human survivin promoter. Negative ion ESI-MS was first applied to screen the binding of the alkaloids to the duplexes. Six alkaloids (including berberine, jatrorrhizine, palmatine, reserpine, berbamine, and tetrandrine) show complexation with the target DNA sequences. Relative binding affinities were estimated from the negative ion ESI data, and the alkaloids show a binding preference to the duplex with higher GC content. Positive ion ESI mass spectra of the complexes were also recorded and compared with those obtained in negative ion mode.

Studies of the intermolecular DNA triplexes of C+center dot GC and T center dot AT triplets by electrospray ionization Fourier-transform ion cyclotron resonance mass spectrometry

Formation and stabilities of four 14-mer intermolecular DNA triplexes, consisting of third strands with repeating sequence CTCT, CCTT, CTT, or TTT, were studied by electrospray ionization Fourier-transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) in the gas phase. The gas-phase stabilities of the triplexes were compared with their CD spectra and melting behaviors in solution, and parallel correlation between two phases were obtained. In the presence of 20 mm NH4+ (pH 5.5), the formation of the TTT triplex was not detected in both solution and the gas phase.

Interactions of mitoxantrone with duplex and triplex DNA studied by electrospray ionization mass spectrometry

We have examined interactions between mitoxantrone (MXT) and DNA duplexes or triplexes with different base compositions by using electrospray ionization mass spectrometry (ESI-MS), respectively. MXT interacts preferentially with DNA duplexes compared to the triplexes. In the mass spectrum of the duplex-MXT mixture, the complex peaks dominated in the ratios of duplex/MXT of 1:1, 1:2 and 1:3, and the 1:2 duplex/MXT peak was the most abundant. In contrast, only 1:1 triplex-MXT complexes were observed in the mass spectrum of the triplex-MXT mixture, and the most intensive peak was a free triplex ion without MXT.

Mass transfer kinetics of neodymium(III) extraction by calix[4]arene carboxylic acid using a constant interfacial area cell with laminar flow

BACKGROUND: Thermodynamics and kinetics data are both important to explain the extraction property. In order to develop a novel separation technology superior to current extraction systems, many promising extractants have been developed including calixarene carboxylic acids. The extraction thermodynamics behavior of calix[4]arene carboxylic acids has been reported extensively. In this study, the mass transfer kinetics of neodymium(III) and the interfacial behavior of calix[4]arene carboxylic acid were investigated.

A method for quantitative analysis of nitrogen oxides and N2 by means of mass spectrometry with the assistance of a catalytic technique for the reduction of NO with CO or hydrocarbons

Mass spectrometry is not able to differentiate NOx and N2 from other interferences (e.g. CO and C2H4) in the deNOx reactions. In the present study, a quantitative method for analysis of NOx and N2 simultaneously in these reactions with an assisted converter operated at higher temperature under O2-rich condition, which eliminates the interferences, is developed. The NOx conversion from this method is comparable to the one from an Automotive Emission Analyser equipped with NOx electrochemical sensor. Two types of deNOx reactions are tested in terms of selectivity of N2 production. The application of this method is discussed.

Studies on the Biotransformation of Arctigenin Using Electrospray Ionization Mass Spectrometry

To study the biotransformation of arctigenin, arctigenin was anaerobically incubated with Eubacterium sp. ARC-2 of human intestinal bacteria in vitro. Arctigenin formed a molecular ion [M-H](-) in negative ion mode. The arctigenin and its metabolites were investigated directly by the electrospray ionization tandem mass spectrometry ion trap and Fourier transform ion cyclotron resonance. Arctigenin was transformed to 4',4 ''-dihydroxylenterolactone by E sp. ARC-2 through 3 types of demethylation products.