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1.
The retention of palladium and platinum complexes with nitroso-R-salt on silica gel treated with Aliquat 336 has been investigated. The complexation of platinum with nitroso-R-salt (NRS) requires heating of H2PtCl6 with an excess of NRS at 100°. The affinity of the complexes for an Aliquat 336 stationary phase increases in the following order: PdCl42− ˜ Pt-NRS < PtCl62− Pd-NRS. The complexes of palladium and platinum can be separated by column chromatography on silica treated with Aliquat 336 and eluted with 0.25M perchloric acid (Pt) and 1M perchloric acid (Pd). 相似文献
2.
In order to enhance the shelf-life of edible mature mushrooms Agaricus bisporus, 2 kGy ionising treatments were applied at two different dose rates: 4.5 kGy/h (I−) and 32 kGy/h (I+). Both I+ and I− showed 2 and 4 days shelf-life enhancement compared to the control (C). Before day 9, no significant difference (p>0.05) in L* value was detected in irradiated mushrooms. However, after day 9, the highest observed L* value (whiteness) was obtained for the mushrooms irradiated in I−. Analyses of phenolic compounds revealed that mushrooms in I− contained more phenols than I+ and C, the latter containing the lower level of phenols. The polyphenol oxidase (PPO) activities of irradiated mushrooms, analysed via catechol oxidase and dopa oxidase substrates, resulted in being significantly lowered (p0.05) compared to C, with a further decrease in I+. Analyses of the enzymes indicated that PPO activity was lower in I+, contrasting with its lower phenol concentration. Ionising treatments also increased significantly (p0.05) the phenylalanine ammonia-lyase (PAL) activity. The observation of mushrooms cellular membranes, by electronic microscopy, revealed a better preserved integrity in I− than in I+. It is thus assumed that the browning effect observed in I+ was caused by both the decompartimentation of vacuolar phenol and by the entry of molecular oxygen into the cell cytoplasm. The synergetic effect of the residual active PPO and the molecular oxygen, in contact with the phenols, allowed an increased oxidation rate and, therefore, a more pronounced browning in I+ than in I−. 相似文献
3.
Diphenylthiovioluric acid (DPHTVA) reacts with ruthenium(III) to form a complex which has an absorbance maximum at 520 nm. Effects of pH, heating time, buffer and reagent have been studied. DPHTVA has been found to be a sensitive reagent for ruthenium(III) (sensitivity = 0.0044 μg Ru/cm2 for log I0/I = 0.001), and has been made selective by the use of masking agents. The composition of the complex as revealed by different methods is 1:2 (ruthenium:DPHTVA). 相似文献
4.
Edoardo Cesarotti Maria Grassi Laura Prati
Francesco Demartin
《Journal of organometallic chemistry》1989,370(1-3):407-419The DANTE technique and NOESY two-dimensional method have been employed to observe the isomerization of the chiral cationic complex [Pd(η3-CH2CMeCH2(P-P′)]+ (1a), where P-P′ = the chiral chelating ligand (S)(N-diphenylphosphino)(2-diphenylphosphinoxymethyl)pyrrolidine. The rate constant was found to be 0.5 s−1 in CHCl3 at 295 K and 1.50 s−1 in the presence of added free ligand. In the latter case the epimerization proceeds by a π-σ-π mechanism via the intermediacy of a primary η1-allylpalladium complex. Although the intermediate was not detected, the NMR findings reveal that it has the allylic terminus η1-bonded to palladium. The structure of 1a in its PF6− salt has been determined. The compound crystallizes in the orthorhombic space group P212121 with a 10.029(4) b 19.203(8) c 36.115(6) Å, Z = 8, R = 0.0572 and Rw = 0.0712 for 3716 observed reflections with I > 3σ(I). 相似文献
5.
Spectrophotometric determinations of palladium(II) and tartaric acid were respectively investigated by using the color reactions between 2(5-nitro-2-pyridylazo)-5-(N-propyl-N-3-sulfopropylamino)phenol(5-NO2.PAPS) and palladium(II) in strong acidic media, and between 5-NO2.PAPS, niobium(V) tartaric acid in weak acidic media. The calibration graphs were linear in the range of 0–25 μg/10 ml palladium(II), with an apparent molecular coefficient () of 6.2×104 l mol−1 cm−1 at 612 nm, and 0–23 μg/10 ml tartaric acid with =1.08×106 l mol−1 cm−1 at 612 nm, respectively. The proposed methods were selective and sensitive in comparison with other chelating pyridylazo dyes–palladium(II) or metavanadic acid–tartaric acid method, and the effect of foreign ions such as copper(II) was negligible for the assay of palladium(II) with 5-NO2.PAPS. 相似文献
6.
Judit Masllorens Anna Roglans Enriqueta Antic Cludia Fonts 《Analytica chimica acta》2006,560(1-2):77-83
This work deals with the evaluation of a synthesized 15-membered triolefinic azamacrocycle containing a NH group, (E,E,E)-1,6-bis(p-tolylsulfonyl)-1,6,11-triazacyclopentadeca-3,8,13-triene (R2NH), for the selective extraction of palladium and platinum from aqueous chloride matrices prior their analysis by ICP-AES. The optimal conditions for liquid–liquid experiments have been evaluated, with special emphasis given to the selection of the organic solvent and the optimal aqueous chloride concentration for the extraction of PdCl42− and PtCl62−. The selective transport and separation of palladium(II) from a mixture of Pd(II) and Pt(IV) was accomplished by means of a supported liquid membrane system containing the macrocycle as carrier dissolved in anethol and 0.5 M thyocianate solution as stripping solution. A C18 cartridge has been activated with the reagent R2NH in order to test the feasibility of achieving the preconcentration of palladium solutions. Enrichment factors close to the theoretical ones were obtained with the designed system and using thiourea as eluting solution. 相似文献
7.
Formation constants for the binary and ternary Mn(II)-nitrilotriacetic acid (NTA) and adenosine triphosphate (ATP) which model the action of (Na+ + K+) ATPase have been determined at 25°C and I = 150 mmole dm-3 NaCl. The results are interpreted in terms of the known stabilities of the enzyme complexes and it is concluded that metal-ion chelation of ATP alone is not enough for hydrolysis to occur. A substantial stabilisation of the ternary complex occurs, possibly through bridging sodium ions. 相似文献
8.
II 《Journal of organometallic chemistry》1993,450(1-2):263-267
Treatment of [Pd{CH2C(CH3)CH2}(Ph2PPy)Cl] (Ph2PPy = 2-(diphenylphosphino)pyridine) with cis-[Pd(tBuNC)2Cl2] in dichloromethane affords the mixed isocyanide-tertiary phosphine complex cis-[Pd(tBuNC)Ph2PPy)Cl2], in which the Ph2PPy is a monodentate P-donor, and [{Pd[CH2C(CH3)CH2]Cl}2]. The steric effects of the Ph2PPy bridging ligand in determining the reaction course is discussed. The complex cis-[Pd(tBuNC)(Ph2PPy)Cl2] was crystallographically characterized: P21/n, a = 15.143(2), b = 9.527(1), c = 17.517(4) Å, β = 113.96(1)°, V= 2309.4(7) Å3, Z = 4. The final R value was 0.044, Rw= 0.046 for the 3078 reflections with I > 3σ(I). 相似文献
9.
Fluorimetric determination of aminoglycoside antibiotics using lanthanide probe ion spectroscopy 总被引:9,自引:0,他引:9
The application of probe ion fluorimetry has succeeded in the microdetermination of six aminoglycoside antibiotics: neomycin, streptomycin, gentamicin, tobramycin, amikacin and kanamycin as sulfate salts in pure form and in some pharmaceutical preparations. The method is based on the reaction of Eu3+ ions with aminoglycosides through amino and hydroxy groups. Such interactions enhance the intensity of the 616 nm fluorescence emission of the Eu3+ ion. The fluorescence at 592 nm comes from a non-hypersensitive transition and is not affected by the ligand which is bound to the probe ions. The intensity ratio R, defined as I592/I616 was used to determine the amount of free and bound europium ions. A linear relationship between bound europium ions and aminoglycoside was found within the concentration ranges 20–100 ppm for neomycin, 5–60 ppm for streptomycin, and 10–70 ppm for gentamicin, tobramycin, amikacin, and kanamycin as sulfate salts. The percentage recoveries ranged from 99.22 to 101.07, with standard deviations ranging from ± 1.5 to ± 4.38. The relative stability constants ranged from 5 × 103 to 2 × 104. The optimum reaction conditions were studied and the results obtained compared favourably with the fluorimetric method using fluorescmine reagent. 相似文献
10.
The praseodymium and europium dichloroacetates were obtained in the form of monocrystals. Crystal structures of the Ln(HCl2CCOO)3·2H2O (Ln=Pr, Eu) compounds were determined by X-ray analysis. Both crystals proved to be isomorphous. They are monoclinic, space group P21/n with: a=9.747(6), b=13.857(7), and c=23.595(9) Å, β=95.03(4)°, U=3175(3) Å3, Z=8 for C6H7Cl6O8Pr and a=9.634(7), b=13.757(11), and c=23.524(14) Å, β=94.84(4)°, U=3107(4) Å3, Z=8 for C6H7Cl6O8Eu. There are two symmetry independent lanthanide cations, which adopt a nine-coordinate geometry with seven oxygen atoms from carboxylate groups and two oxygen atoms from water molecules. Absorption (Pr3+, Eu3+), emission and emission excitation (Eu3+) spectra of single crystals of Ln(HCl2CCOO)3·2H2O were recorded at room temperature and low temperatures down to 4.2 K. Spectral intensities of the investigated systems are parametrized in terms of the Judd–Ofelt theory and compared to those of lanthanide trichloroacetates and acetates crystals. The relationship between the hypersensitivity and covalency is discussed. The nephelauxetic ratio β and Sinha's parameter δ are calculated based on the absorption spectra. The variation of these parameters and their correlation with the nature of metal–ligand bond is discussed. The bond polarity and bond strength of coordination complex determine the activity and stereospecifity of the catalyst thus the study of these properties are very important because of the application of lanthanide carboxylates as precursors of catalysts. The spectroscopic results are correlated with those from the crystal structure studies, especially with Ln–O distances and the co-ordinating forms of the carboxylate ions. The vibronic coupling in the f–f transitions were analysed. In order to determine the vibronic coupling quantitatively, calculations of the R=IVIB./I0-phonon rates were performed from the low temperature absorption spectra. The correlation between the vibronic coupling and covalency is analysed. 相似文献
11.
Surface phenomena occurring in the process of palladium hydride formation during the interaction of thin Pd film with molecular hydrogen were studied by means of simultaneous measurements of surface potential and H2 pressure. This allows to differentiate between various states of the adsorbate, and to correlate their behaviour with hydrogen concentration on the surface and in the bulk. Two distinct states of the adsorbate were determined: (i) the negatively polarized, atomic adspecies, stable on the surface, arising at the beginning of the adsorption, referred to as β-, and (ii) the induced, positively polarized, atomic adspecies, incorporating quickly from the surface into the bulk, referred to as β+. The β+ adspecies form a precursor surface state for PdHx creation. It has been found that at low temperature (78K) the β+ adspecies are placed above the surface image plane (SIP). Under these conditions, the maximal hydrogen concentration on the palladium hydride surface approaches 2, while in the bulk the (H/Pd) ratio does not exceed 1. At higher temperatures (120K, 160K), when the β+ adspecies are located below the SIP, hydrogen concentration on the surface and in the bulk is uniform, approaching (H/Pd) ˜ 1. 相似文献
12.
The Schiff base compound, N-N′-bis(4-methoxybenzylidene)ethylenediamine (C18H20N2O2) has been synthesized and its crystal structure has been investigated by X-ray analysis and PM3 method. The compound crystallizes in monoclinic space group P21/n with a=10.190(1), b=7.954(1), c=10.636(1) Å, β=111.68(1)°, V=801.1(1) Å3, Z=2 and Dcal=1.229 Mgm−3. The title structure was solved by direct methods and refined to R=0.056 for 2414 reflections [I>3.0σ(I)] by full-matrix anisotropic least-squares methods. The energy profile of the compound was calculated by PM3 method as a function of θ[N1′–C9′–C9–N1]. The most stable molecular structure of the title compound is the anti conformation, which is different in energy by 5.0 and 1.0 kcal mol−1 from the eclipsed conformation I and gauche conformations, (III and V), respectively. 相似文献
13.
Da-Ming Du Wen-Ting Hua Ling-Ping Zhou Jian-Wu Wang Xiang-Lin Jin 《Journal of Molecular Structure》2001,560(1-3):23-28
The new host 1,4,11,14-tetramethoxy-dibenzo[b,n]tetraphenylene forms a 1:1 inclusion compound with pyridine, in which a pair of centrosymmetrically-related guest species are enclosed in the cage surrounded by six host molecules. C36H28O4·C5H5N, FW=603.68, triclinic, space group P-1, a=11.796(2), b=16.075(3), c=9.004(2) Å; =98.39(3)°, β=90.01(3)°, γ=108.19(3)°, V=1602.8(5) Å3, Z=2, F(000)=636, Dc=1.251 g/cm3, μ=0.080 mm−1. The final R indices [I>2σ(I)] R1=0.0759, wR2=0.1970 for 5623 MoK observed data. 相似文献
14.
Karen V. Baker John M. Brown Neil A. Cooley Gareth D. Hughes Richard J. Taylor 《Journal of organometallic chemistry》1989,370(1-3):397-406
The palladium dibromide complexes of (S,R)-(1,1′-bis-diphenylphosphino)-2-ferrocencylthyldimethylamine and (S,R)-(1-diphenylphosphino)-2-ferrocenylethyldimethylamine have been reduced with dilithiocyclooctatetraene to form the corresponding Pd0 cyclooctatetraene complexes. Their reactions with E-4-methoxy-2′-bromophenylethene, and then benzylmagnesium chloride at −60 to −30°C, provide information on the structure of intermediates in asymmetric cross-coupling. 相似文献
15.
Preparation of novel ion exchange polyurethane foam and its application for separation and determination of palladium in environmental samples 总被引:1,自引:0,他引:1
Moawed EA 《Analytica chimica acta》2006,580(2):263-270
The new strong anion exchanger (PUFIX) from polyurethane foam was prepared by coupling of the primary amine of the foam matrix with ethyl iodide. PUFIX was characterized using different tools (IR spectra, elemental analysis, density and thermal analysis). The sorption properties of the new anion exchanger (PUFIX) and chromatographic behaviour for separation and determination of palladium(II) ions at low concentrations from aqueous iodide or thiocyanate media were investigated by a batch and dynamic processes. The maximum sorption of Pd(II) was in the pH range of 0.3–2. The kinetics of sorption of the Pd(II) by the PUFIX was found to be fast with average values of half-life of sorption (t1/2) of 3.32 min. The variation of the sorption of Pd(II) with temperature gives average values of ΔH, ΔS, ΔG and ΔE to be −38.3 kJ mol−1, −100.7 J K−1 mol−1, −8.3 and 11.8 kJ mol−1, respectively. The sorption capacity of PUFIX was 1.69 mmol g−1 for Pd(II), preconcentration factors of values ≈250 and the recovery 99–100% were achieved (R.S.D. ≈ 1.24%). The lower detection limit, 1.28 ng mL−1 was evaluated using spectrophotometric method (R.S.D. ≈ 2.46%). 相似文献
16.
T. I. Karu O. A. Tiphlova Yu. A. Matveyets A. P. Yartsev V. S. Letokhov 《Journal of photochemistry and photobiology. B, Biology》1991,10(4):339-344
To evaluate the contribution of local pulsed heating of light-absorbing microregions to biochemical activity, irradiation of Escherichia coli was carried out using femtosecond laser pulses (λ = 620 nm, τp=3 × 10−13 s, fp = 0.5 Hz, Ep = 1.1 × 10−3J cm−2, Iav = 5.5 × 10−4 W cm−2, Ip = 109 W cm−2) and continuous wave (CW) laser radiation (λ = 632.8 nm, I = 1.3 W cm−2). The irradiation dose required to produce a similar biological effect (a 160%–190% increase in the clonogenic activity of the irradiated cells compared with the non-irradiated controls) is a factor of about 103 lower for pulsed radiation than for CW radiation (3.3 × 10−1 and 7.8 × 102 J cm−2 respectively). The minimum size of the microregions transiently heated on irradiation with femtosecond laser pulses is estimated to be about 10 Å, which corresponds to the size of the chromophores of hypothetical primary photoacceptors—respiratory chain components. 相似文献
17.
X. Xu P. C. A. M. de Bruyn J. A. de Koeijer H. Logtenberg 《Journal of chromatography. A》1999,830(2):186-451
A method for low-molecular-mass anion screening is described using a buffer composed of 5-sulfosalicylate (SS) as a visualizing ion, hexadimethrine bromide as an electroosmotic flow modifier and Tris as a pH buffer component, at pH 8.6. All ions with effective mobility higher than 2610−9 m2 s−1 V−1 can be separated within 7.5 min under −30 kV. By using the moderately mobile SS (5410−9 m2 s−1 V−1), not only the sensitivity of the detection is improved due to its high UV absorptivity, but also a smaller overall overloading effect is achieved. Meanwhile, the resolution of the high mobility ions, which is normally critical, remains almost the same as compared to a chromate buffer. With an electrokinetic injection, the limit of detection (LOD) of the common ions is 2–13 nM and the detection range is linear up to 0.5–3 μM. With a hydrostatic injection the LOD is 0.15–1 μM and the detection range is linear up to 25–200 μM. The identification of ions is performed by comparing the mobility of the ions with that of standards, taking the apparent and effective mobility of HCO3−, which is normally present in the sample solution, as a reference. 相似文献
18.
Alessandro de Robertis Concetta de Stefano Rosario Scarcella Carmelo Rigano 《Thermochimica Acta》1984,80(2):197-208
The formation constants for the complexes Mg2+ -, Ca2+ -, Sr2+ - and Ba2+ - succinate (succ2−) have been determined by potentiometric measurements, in aqueous solution, at different temperatures and ionic strengths. The species [M(succ)]0 and [M(succ)H]+ were found for all systems. For the stability constant the ionic strength dependence has been found, and general parameters for the relation log β = f(I) have been obtained. From the temperature dependence of stability constants ΔH values have been deduced. The procedure adopted in calculating all the thermodynamic parameters for the systems under study, where weak complexes are formed, is discussed. The stability of the complexes follows the order Mg < Ca Sr ≈ Ba. 相似文献
19.
Jun Wang Xiangdong Zhang Xiao Ling Weiguo Jia Huifang Li 《Journal of Molecular Structure》2002,610(1-3):151-158
The syntheses and structural determination of NdIII and ErIII complexes with nitrilotriacetic acid (nta) were reported in this paper. Their crystal and molecular structures and compositions were determined by single-crystal X-ray structure analyses and elemental analyses, respectively. The crystal of K3[NdIII(nta)2(H2O)]·6H2O complex belongs to monoclinic crystal system and C2/c space group. The crystal data are as follows: a=1.5490(11) nm, b=1.3028(9) nm, c=2.6237(18) nm, β=96.803(10)°, V=5.257(6) nm3, Z=8, M=763.89, Dc=1.930 g cm−3, μ=2.535 mm−1 and F(000)=3048. The final R1 and wR1 are 0.0390 and 0.0703 for 4501 (I>2σ(I)) unique reflections, R2 and wR2 are 0.0758 and 0.0783 for all 10474 reflections, respectively. The NdIIIN2O7 part in the [NdIII(nta)2(H2O)]3− complex anion has a pseudo-monocapped square antiprismatic nine-coordinate structure in which the eight coordinate atoms (two N and six O) are from the two nta ligands and a water molecule coordinate to the central NdIII ion directly. The crystal of the K3[ErIII(nta)2(H2O)]·5H2O complex also belongs to monoclinic crystal system and C2/c space group. The crystal data are as follows: a=1.5343(5) nm, b=1.2880(4) nm, c=2.6154(8) nm, b=96.033(5)°, V=5.140(3) nm3, Z=8, M=768.89, Dc=1.987 g cm−3, μ=3.833 mm−1 and F(000)=3032. The final R1 and wR1 are 0.0321 and 0.0671 for 4445 (I>2σ(I)) unique reflections, R2 and wR2 are 0.0432 and 0.0699 for all 10207 reflections, respectively. The ErIIIN2O7 part in the [ErIII(nta)2(H2O)]3− complex anion has the same structure as NdIIIN2O7 part in which the eight coordinate atoms (two N and six O) are from the two nta ligands and a water molecule coordinate to the central NdIII ion directly. 相似文献
20.
The nucleophile [ArTe−] generated in situ borohydride solution of Ar2Te2, reacts with 2-(chloromethyl) tetrahydrofuran and 2-(2-bromoethyl)-1,3-dioxolane resulting in L1 and L2, respectively. The complexes of palladium(II) and platinum(II) with L1/L2 having stoichiometries [MCl2·L2], [ML2](ClO4)2, [(DPPE)ML2](ClO)4)2, [(PPh3)2ML2](ClO4)2 and [(phen)ML2](ClO4)2 (where L = L1/L2 DPPE = Ph2PC H2CH2PPh2, PHEN = 1,10-phenanthroline and M = Pd/Pt) have been synthesized. IR, 1H, 125Te{1H} and 31P{1H} NMR and UV-vis spectral data of these species in conjunction with their molar conductance and molecular weight data have been used to authenticate the new species. In all complexes (1–20) the ligands L1 and L2 are coordinated through tellurium and in the complexes of formula [ML2](ClO4)2 (M = Pd, Pt) the ligand is bidentate with the oxygen atom used in complexation. In solution, complexes PtCl2L2 exist as a mixture of cis and trans isomers whereas only the trans isomer was observed for the palladium analogues. The [(phen)PdL2](ClO4)2(Q) quenches 1O2 readily. The plot of log [Q] vs time is linear. Mechanism compatible with the experimental observations is proposed. 相似文献