Application of adsorptive stripping voltammetry for indirect measurement of nonelectroactive ions using competitive complex formation reactions

It is shown that adsorptive stripping voltammetry can be used for indirect determinations of non-electroactive species. Determination of fluoride was selected to demonstrate this concept which can be used in environmental, clinical and other applications.The fluoride determination is based on competitive complex formation reactions between zirconium and organic ligands, viz. Alizarin Red S (ARS) and Acid Alizarin Violet N (AAVN) and fluoride ions in acidic media (0.1M HNO₃ or HClO₄). Free ARS ligand is adsorbable on mercury electrode and its voltammetric peak increases with fluoride concentration due to ARS displacement from the Zr-ARS complexes with fluoride forming more stable Zr-fluoride complexes. Using AAVN as a ligand Zr-AAVN complexes are adsorbable on a mercury electrode and the voltammetric peak decreases with increasing fluoride concentration due to formation of more stable Zr-fluoride complexes.The sensitivity of the method is down to 0.1 M of fluoride. Overall fluoride recovery from synthetic water samples at micromolar concentration level was within 1% of the concentration added, with overall reproducibility of 5 independent measurements of ± 2.5% and ± 1.8% with ARS and AAVN ligand, respectively. Some interferences possibly present in water have been investigated.     

磁性Co/C纳米复合材料的合成及其对水中刚果红吸附性能研究

This comprehensive experiment has successfully introduced the frontier of scientific research into undergraduate laboratory teaching. A magnetic Co/C nanocomposite was synthesized by using ZIF-67 as the precursor. Upon calcination at high temperature in inert atmosphere, ZIF-67 was degraded and carbonized to form Co/C nanocomposite. The adsorption performance of Co/C nanocomposite for Congo Red was investigated in detail. The structure and composition of the nanocomposite were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). The concentration of Congo Red was determined by UV-Vis spectrophotometry. The kinetics data was fitted with the pseudo-first-order and pseudo-second-order kinetic models. The adsorption isotherms were analyzed according to Langmuir and Freundlich isotherm models. This experiment covers the synthesis of inorganic-organic hybrid material, characterization of materials, concentration determination of dyes, analysis of dynamics data and adsorption isotherms. Therefore, this experiment enables students to practice their experimental skills, increase their interest in scientific research, and broaden their professional knowledge.     

Organometallic emitting dyes: Palladium(II) nile red complexes

The Nile Red dye, H(NR), forms cyclometalated R₂-disubstituted-acetylacetonato square planar Pd(II) complexes (1-3; R = CH₃, CF₃, C₆H₅ respectively) whose photophysical properties were tested in cyclohexane, dichloromethane or methanol solutions. In cyclohexane 1-3 emit in the range 580-650 nm with a quantum yield ranging from 0.12 (R = CH₃) to 0.50 (R = CF₃) and lifetimes between 0.88 and 4.46 ns. These complexes form a new family of notably efficient red emitting organometallic dyes which could be of interest for practical applications.     

Synchronous fluorescence and UV-vis spectrometric study of the competitive interaction of chlorpromazine hydrochloride and Neutral Red with DNA using chemometrics approaches

In this study, we have shown with the use of UV–vis spectrophotometry and the constant wavelength synchronous fluorescence spectroscopy (CW-SFS) techniques that the pharmaceutical drug, chlorpromazine hydrochloride (CPZ), intercalates into the deoxyribonucleic acid (DNA) double helix by partial exchange with the Neutral Red (NR) molecular probe.

We have also demonstrated that with the use of three-way data plots, it is clear that it is important to have well-defined methodology for the selection of the important CW-SFS method parameter, Δλ. Ad hoc selection of this parameter, or even that based on experience, can readily lead to serious errors, which subsequently can be transferred to the interpretation of results. The said three-way plots provide a straightforward diagrammatic method, which improves the selection process of a satisfactory value for Δλ.

Finally, we used PARAFAC modeling to resolve the complex three-way CW-SFS data, which provided simultaneously the concentration information for the three reaction components, NR, CPZ and NR-DNA, for the system at equilibrium. This PARAFAC analysis indicated that the intercalation of the CPZ molecule into the DNA proceeds by exchanging with the NR probe, and can be attributed to two parallel reactions.     

New pyrrolopyridazine derivatives as blue organic luminophors

New pyrrolopyridazine derivatives were synthesized as potential blue organic luminophors. Three different classes of pyrrolopyridazine derivatives were made, for example, aryl groups directly connected to the core PPY (pyrrolo[1,2-b]pyridazine-5,6,7-tricarboxylic acid trimethyl ester) moiety, aryl groups connected to the PPY via a vinylene linker and aryl groups connected to the PPY via an acetylene linker. Their optical and electrochemical properties were productively compared. One of the derivatives 2 showed a relative quantum yield as high as 0.9. Compound 8 in the vinyl bridged pyrrolopyridazine series has been characterized by its X-ray crystal structure analysis.     

系数倍率导数光谱法定量测定纤维上染料

本文介绍了用系数倍率导数光谱法同时测定黄棕色涤纶上的分散黄ＲＧＦＬ，分散棕２ＲＬ，分散红Ｓ－ＢＷＦＬ的配比。这三种染料吸收峰重叠大，用该法可以完全消除彼此的干扰而不用分离，测得三种染料的配比与工艺配方中的比例一致，结果准确，可靠，回收率较好。这个方法操作简便，快速，可用于纵上染料的测定。     

Adiabatic compressibility of red blood cell membrane: influence of skeleton

Measurements of ultrasound velocity and density were used for determination of the adiabatic compressibility of red blood cells (RBC) during detachment of the membrane skeleton. Skeleton detachment was induced by addition of nystatin into a low ionic strength RBC suspension resulting in an increase (10%) of the ultrasound velocity concentration increment, [u], while the specific volume of cells, phi(v) did not change significantly. Changes of the concentration increment had rather long kinetics and were not completed even after 60 min. Both [u] and phiV values were used for calculation of the specific apparent adiabatic compressibility of RBC, phiK/beta0. The value of the specific apparent compressibility decreases following addition of nystatin. This corresponds to an increase in the volume elastic modulus of RBC membranes during detachment of the membrane skeleton. Control experiments with large unilamellar liposomes at conditions similar to that performed with the RBC did not reveal significant changes of [u] after the addition of nystatin. Our results show that the role of the membrane skeleton probably consists in maintaining higher compressibility of the RBC membranes. This may partly provide conditions for conformational changes of RBC membrane proteins.     

Application of reversed-phase and ion-pair HPLC for investigation of nucleotide metabolism in erythrocytes,reticulocytes and tumour cells

Summary The determination of nucleotides, nucleosides, and nucleobases was carried out in cells of different metabolic complexity: in mature and immature red blood cells, in Ehrlich ascites tumour cells from different proliferation stages, and in other tumour cells. The maturation of reticulocytes to erythrocytes is accompanied by loss of organelles and energy-requiring processes as well as the switch from aerobic to anaerobic ATP production. The profile of purine nucleotides, nucleosides, bases, and pyridine dinucleotides, by reversed-phae HPLC, shows large concentration changes during the maturation of red blood cells. The concentrations of purine mono and triphosphates are two to four times greater in reticulocytes in comparison with erythrocytes; the difference in the concentrations of nucleosides and nucleobases between reticulocytes and erythrocytes is even greater. Application of ion-pair HPLC showed that the Ehrlich ascites cells loose major portions of purine mono-, diand triphosphates between the 7th and 11th day after inoculation. Fast growing solid sarcoma tumours of rats (MV 202 Ner) contain higher amounts of nucleotides than slowly growing tumours of identical cell type.     

Identification and quantitative determination of diphenylarsenic compounds in abandoned toxic smoke canisters

Knowledge of the exact nature of the constituents of abandoned chemical weapons (ACW) is a prerequisite for their orderly destruction. Here we report the development of analytical procedures to identify diphenylchloroarsine (DA/Clark I), diphenylcyanoarsine (DC/Clark II) and related substances employed in one of the munitions known as "Red canister". Both DA and DC are relatively unstable under conventional analytical procedures without thiol derivatization. Unfortunately however, thiol drivatization affords the same volatile organo-arsenic derivative from several different diphenylarsenic compounds, making it impossible to identify and quantify the original compounds. Further, diminishing the analytical interference caused by the celluloid powder used as a stacking material in the weapons, is also essential for accurate analysis. In this study, extraction and instrumental conditions have been evaluated and an optimal protocol was determined. The analysis of Red canister samples following this protocol showed that most of the DA and DC associated with pumice had degraded to bis(diphenylarsine)oxide (BDPAO), while those associated with celluloid were dominantly degraded to diphenylarsinic acid (DPAA).     

Profile characterization and biological activities of cold pressed Garden Cress (Lepidium sativum) seed oil

Lepidium sativum is cultivated mainly for the edible oil from its seeds, and considered as an unutilized and neglected crop despite its important properties. Its oil fraction is used to produce soap and stabilize linseed oil when it is mixed with wild mustard seed oil. Once converted into fatty acid methyl esters, it represents a good substitute for imported petroleum diesel after alkaline transesterification reaction. In the current study, Lepidium sativum seeds cultivated in Tunisia and the physicochemical properties and nutrient profile of its cold pressed seed oil were investigated. The antioxidant, antibacterial, and anti-inflammatory activities of the above oil were also assessed. Lepidium sativum seed oil was abundant in both linolenic (35.59 ± 1.9%) and oleic (21.14 ± 0.63%) acids, and high amounts of β-sitosterol (42.57 ± 2.96 mg/100 g), campesterol (20.04 ± 1.4 mg/100 g) and Δ 5,24 stigmastadienol (11.82 ± 0.45 mg/100 g) were detected. The total tocopherol content of Lepidium sativum seed oil reached 136.83 ± 7.6 mg/100 g with a predominance of γ-tocopherol (86.23%). Its seed oil exhibited an IC₅₀ of 10.33 ± 0.05 mg/mL and a radical scavenging activity of 415.6 ± 40 Trolox Equivalent Antioxidant Capacity (TEAC) for the DPPH and the ABTS assays, respectively. While the thermal analysis proved a high thermal stability of Lepidium sativum seed oil, that of eight bacteria and one fungal strain showed no noticeable bacterial or antifungal effects. It was also revealed that Lepidium sativum seed oil held a remarkable anti-inflammatory activity. Hence, the obtained results evidenced remarkable chemical, antioxidant and anti-inflammatory properties of Lepidium sativum seed oil, which might potentially be promising for enhancing human health and preventing age-related diseases.