Estimation of platinum in environmental water samples with solid phase extraction technique using inductively coupled plasma mass spectrometry

A solid phase extraction technique for the determination of platinum(IV) at trace levels by inductively coupled plasma mass spectromA solid phase extraction technique for the determination of platinum(IV) at trace levels by inductively coupled plasma mass spectrometry (ICP-MS) was developed. The method was based on retention of platinum in a sample on silica gel modified with aminepropyl groups. The retention of platinum(IV) from the sample solution and the recovery of platinum with 1.0 mol L⁻¹ thiourea solution were quantitative. The relative standard deviation (RSD) was calculated as 5% (n = 7) at the 10 ng L⁻¹ level. The enrichment factor was found to be (50-fold) for 250 mL of water sample. Under optimum conditions, the method detection limit (MDL) was found to be 1 ng L⁻¹ for platinum in water matrices. Recoveries of Pt from spike addition to atmospheric water samples were quantitative (80–95%). The present method was used for the determination of platinum in precipitation, throughfall and runoff water samples.      

Tuning the spin ground state in heterononanuclear nickel(II)-copper(II) cylinders with a triangular metallacyclophane core

Two new heterometallic Ni(II)(n)Cu(II)((9-n)) complexes [n = 1 (2) and 2 (3)] have been synthesized following a multicomponent self-assembly process from a n:(3 - n):2:6 stoichiometric mixture of Ni(2+), Cu(2+), L(6-), and [CuL'](2+), where L and L' are the bridging and blocking ligands 1,3,5-benzenetris(oxamate) and N,N,N',N',N'-pentamethyldiethylenetriamine, respectively. Complexes 2 and 3 possess a unique cyclindrical architecture formed by three oxamato-bridged trinuclear linear units connected through two 1,3,5-substituted benzenetris(amidate) bridges, giving a triangular metallacyclophane core. They behave as a ferromagnetically coupled trimer of two (2)/one (3) S = (1)/(2) Cu(II)(3) plus one (2)/two (3) S = 0 Ni(II)Cu(II)(2) linear units with overall S = 1 Ni(II)Cu(II)(8) (2) and S = (1)/(2) Ni(II)(2)Cu(II)(7) (3) ground states.     

Preliminary pharmaceutico-analytical evaluation of transkarbam 12 using liquid chromatography

This paper deals with the search for optimal conditions for the identification of Transkarbam 12 (T 12) as a substance used for acceleration of transdermal penetration. Such substances are used in cases when drugs do not pass through the skin barrier under normal conditions. Other advantages are that they do not irritate the digestive system, provide continuous administration to an organism, and reduce fluctuations of drug concentration in blood. TLC and HPLC were used for identification. In the case of TLC, Silufol UV254 was used as stationary phase and the mobile phase consisted of chloroform, ethanol, and acetic acid. Detection was performed with iodine vapour. In the case of HPLC, the following three chromatographic columns were tested for the analysis of T 12: Silasorb SPH C 18, Silasorb SPH nitrile, and LiChrosorb Si-60. Because of the absence of any chromophore in the structure of T 12, work was performed on the derivatized compound. Detection was carried out at 230 nm. Quantification was studied on LiChrosorb Si-60 and the linearity, precision, and accuracy were evaluated.     

Atomic absorption spectrometric determination of mercury in soil standard reference material following microwave sample pretreatment

Several decomposition procedures and their influence on the determination of mercury by electrothermal (ET) and cold vapour (CV) atomic absorption spectrometry (AAS) have been studied. Soil samples were decomposed by microwave digestion in closed and open vessels as well as by digestion under reflux according to German standard. The use of different acids (HNO₃, HCl or aqua regia) was evaluated and compared in respect to their influence on the determination of mercury by ET AAS and CV AAS. The digestion solutions were analyzed by ET AAS with a palladium modifier and by CV AAS using SnCl₂ or NaBH₄, as reducing agents. The detection limits obtained with different procedures were also evaluated. For the soil containing 6.25 g/g of Hg the ET AAS measurements were possible. In the case of lower concentration of mercury the CV AAS determination following the microwave digestion procedure with HCl or aqua regia is recommended. The accuracy of the proposed procedure was confirmed by the determination of total mercury in SRM 2711 Montana Soil.On leave from: Institut für Analytische Chemie, Technische Universitat Wien, Getreidemarkt 9, A-1060 Wien, Austria     

Copper(II)-methylmalonate complexes with unidentate N-donor ligands: Syntheses,structural characterization and magnetic properties

Two new methylmalonate-bridged copper(II) complexes with the formulas [Cu(3-Ipy)(Memal)(H₂O)] (1) and [Cu(2,4′-bpy)(Memal)(H₂O)] · 3H₂O (2) [Memal = methylmalonate dianion, 3-Ipy = 3-iodopyridine, 2,4′-bpy = 2,4′-bipyridine] have been synthesized and characterized by X-ray diffraction. Both compounds crystallize in the monoclinic space group P2₁/n and Z = 4, with unit cell parameters a = 8.5874(13) Å, b = 7.1738(14) Å, c = 19.093(5) Å, β = 99.509(15)° in 1 and a = 17.375(4) Å, b = 7.3305(14) Å, c = 14.247(3) Å, β = 111.409(15)° in 2. The structures of 1 and 2 consist of zigzag chains of anti-syn carboxylate-bridged copper(II) ions running along the b direction. The pyridine-like ligands occupy one equatorial position of the copper environment avoiding the formation of the sheet-like arrangement observed in previously reported Memal complexes. The chains are grouped together in hydrophilic layers through hydrogen bonds and the layers are pillared through the 3-Ipy (1) and 2,4′-bpy (2) ligands which are stacked through π–π interactions involving alternatively aromatic ligands from two adjacent chains. Magnetic susceptibility measurements of both compounds in the temperature range 2–290 K show the occurrence of intrachain ferromagnetic interactions between the copper(II) ions [J = +2.66(2) cm^?1 (1) and J = +2.62(2) cm^?1 (2)].     

Stabiliser distribution and efficiency examined by depth profiling polypropylene using a positron beam

The effectiveness of stabilisers, organic (hindered amine light stabilisers), inorganic (nanoparticulate zinc oxide), and combinations thereof, in preventing the signatures of degradation in polypropylene subjected to accelerated weathering is studied. Not only the type of stabiliser but also its distribution is important for stabiliser efficiency. The spatial effects of stabilization are studied using positron spectroscopy depth profiling.     

The smallest resonance energy transfer acceptor for tryptophan

The utility of diazirine ligands as acceptors in resonance energy transfer (RET) distance measurements with tryptophan or tryptophan analogues as donor is reported. The principle is demonstrated for a diazirine derivative of d-mannitol, 2-azi-2-deoxy-d-arabino-hexitol, and single-tryptophan-containing mutants of the mannitol transporter, EIImtl, from E. coli. The F?rster distance is 10 A for the tryptophan-diazirine donor-acceptor couple, allowing the measurement of distances up to 17 A. The versatility of tryptophan as an intrinsic spectroscopic probe in protein chemistry and the small size of the diazirine group makes this a very attractive donor-acceptor couple for accurate RET distance information in protein chemistry.     

Synthesis of substituted terpyridine ligands for use in protein purification

A number of 4,4″-disubstituted terpyridines bearing a 4′-thioethanamine linker, and regioisomers thereof, have been synthesised from 4-substituted picolinates. The substituted terpyridines were immobilised onto epoxy-activated Sepharose™ FF gel, creating functionalised solid supports for the fractionation of proteins—including antibodies—by mixed mode affinity chromatography. The metal chelating properties of the immobilised ligand render the stationary phase also amenable for use in immobilised metal-ion affinity chromatography (IMAC), and have been demonstrated with the purification of suitably tagged green fluorescent protein (GFP).     

Gyration Waves in Optical Crystals

The optical activity of crystals can be explained by energy transfer from radiation incident on the crystal into the radiation mode (gyration wave) propagating in the incident wave direction but having the polarization plane perpendicular to that of incident radiation.__________Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 6–10, January, 2005.