摘要:

The absorbance signal in electrothermal atomic absorption spectrometry is a result of the processes of atom formation and dissipation and first of all depends on the initial generation of atoms from the surface. The rising part of the absorbance time profiles can be used for characterization of the release of the metals like Pd, Ag, Au etc. The method is applied to investigate the palladium release from a pyrocoated graphite support at different initial masses of the Pd. The kinetic parameters are evaluated and conclusions about the distribution of palladium on the graphite surface are made. The estimated values of apparent activation energies depend on the initial mass of analyte. The advantages and limitations of the present approach are discussed.

ISSN:0038-7010    

DOI:10.1080/00387019708006989

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Cephalexin, cefixime, ceftriaxone and cefotaxime were determined spectrophotometrically in the pure form and in pharmaceutical formulations by using ferrihydroxamate method. Reaction optimization with respect to reaction time and temperature has been investigated. Influence of the presence of ester functional group on the determination of cephalosporins as ß-lactams under conditions optimized was evaluated. Using cefotaxime sodiume as model drug with ester functional group, it was shown that proposed method gives equally acurate and precise results even in the presence of ester functional group.

ISSN:0038-7010    

DOI:10.1080/00387019708006990

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The FT-IR and FT-Raman spectra of the tetranuclear Bi(III) complex Bi(C5H5NH)6Bi4Cl18are investigated. The spectroscopic data reflect the non-equivalence of the pyridinium ions and suggest a strong distortion of the octahedral structure for the Bi4Cl18group. The near-infrared data show that like in the fundamental region, protonation of pyridine results in a frequency increase of several combination bands.

ISSN:0038-7010    

DOI:10.1080/00387019708006991

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A rapid and convenient spectrophotometric method is described for the quantitative determination of some of Cephalosporines Cefadroxil, I Cephradine II and Cefaclor III. The proposed method depends upon the conversion of these compounds to the corresponding piperazine-2,5 dione derivatives by heating in an alkaline sorbitol-zinc ion solution for 10—25 minutes at 90°C and subsequent treatment of these derivatives with 0.1 N sodium hydroxide to obtain highly absorbing products with λmaxat 345 nm for I & II and at 334 nm for III using zero order absorption curve. Using first derivative spectrum (D1) for III the λmaxis at 362 nm. The method was found to be free of the interference from polymerization and other degradation products. Its application to assess the stability of the Cephalosporines was demonstrated. Verification of Beer's Law showed lincarity at concentrations of 12.5-87.5 μg ml−1, 12.5-125 μg ml−land 6.7-66.7 μg ml−1for I, II and III respectively with mean accuracies 100.37 ± 0.72%, 100.45 ± 0.87% and 99.63 ± 1.97% when using zero order absorption curve. Using D1 for III gave linearity at concentration range 42-114 μg.ml−1with mean accuracy of 99.54 ± 0.77%.

ISSN:0038-7010    

DOI:10.1080/00387019708006992

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The photoacoustic(PA) studies of the nonradiative processes in dibenzoylmethide(DBM) Sm3+complex:Sm(DBM)3are reported. Compared with the PA spectra of La(DBM)3and Gd(DBM)3, the paramagnetic effect of the 4f-electrons of Sm3+to DBM and the intramolecular energy transfer from DBM to Sm3+is discussed. The excitation spectra of Sm(DBM)3are also reported to study the relaxation properties of Sm3+and the energy transfer between DBM and Sm3+. A model of relaxation and energy transfer processes of Sm(DBM)3is established.

ISSN:0038-7010    

DOI:10.1080/00387019708006993

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

ATLC spectrodensitometric procedure was developed for the determination of methyl paraben, propyl paraben, sorbic acid and benzoic acid as bulk powders or in pharmaceutical dosage forms and foods. The procedure was used for the determination of the two parabens singly or together and also was used for the determination of benzoic and sorbic acids singly because they were found singly in some commercial food and pharmaceutical products. The cited compounds were separated on silica gel with fluorescent indicator in systems, acetone-ethanol-aqueous ammonia 28%-ethyl acetate (84:3:9:9) for the determination of benzoic and sorbic acids and n-hexane-ethyl acetate-acetic acid (80:5:20) for the determination of the two parabens. Absorbance measurement (detection of reflectance) of separated compounds was carried out in situ, at 254 nm for the two parabens, sorbic acid, and at 228 nm for benzoic acid using multilevel calibration curves in the concentration ranges of 0.2—2.5 μg/spot, 0.5—3 μg/spot, and 2.5—12.5 μg/spot for sorbic acid, the two parabens, and benzoic acid, respectively. The results were evaluated by linear regression analysis. The mean % accuracies were found to be, mean ±C.V.(%), 99.65 ±0.963, 99.45±1.02, 99.60±0.825 and 99.34±0.969 for benzoic acid, sorbic acid, methyl paraben and propyl paraben in bulk powders, respectively. While in case of benzoic and sorbic acids in foods the mean % accuracies were found to be: 97.72±1.231 and 98.81±1.296, respectively. The mean % accuracies of methyl paraben, propyl paraben, sorbic acid in pharmaceutical dosage forms were found to be: 98.19±0.874, 97.830±0.799 and 98.36±0.572, respectively.

ISSN:0038-7010    

DOI:10.1080/00387019708006994

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Absorption spectra of Yb(DPA)33-complex (where DPA=dipicolinate) in aqueous solution are studied and all of their spectral peaks are assigned based on Double Sphere Coordination Point Charge Field model(DSCPCF). It is shown that calculated and observed results are agreeable to each other. Meanwhile the coordination structure of the complex reported in aqueous media are also deduced.

ISSN:0038-7010    

DOI:10.1080/00387019708006995

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The vibrational frequencies of several silanes H3SiX (X=BH2, AlH2, PH2and SH) are determined. The infrared and Raman spectra are plotted. Several scale procedures were use to improve the theoretical spectra. The geometric parameters in theplanar, staggeredandeclipsedstructures of these species are fully optimized and compared with ab initio calculations. Basis set effects on the calculated structures are discussed. A few thermodynamic parameters, net atomic charges, dipole moment and energy are also computed.

ISSN:0038-7010    

DOI:10.1080/00387019708006996

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Three one-dimension chain adducts,catena-poly-{bis(dibutyldithiophosphato-K2S,S') nickel(II)-μ-(4,4'-bipyridine)-KN,KN),catena-poly(bis(8-quinolinolato-N1,O8)nickel(II)-μ-(4,4'-bipyridine)-KN,KN} and catena-poly(bis(4,4,4-trifluoro-l-(2-thieny])-l,3-butanedionato-K2O,O') nickel(II)-μ-(4,4'-bipyridine)-KN,KN), hereafter abbreviated to [4,4'-(bipy)-Ni(Bu-dtp)2]n, (4,4'-(bipy)-NiQ2]nand [4,4'-(bipy)-Ni(TTA)2]nhave been synthesized and characterized by elemental analysis, IR, magnetic properties and X-ray photoelectron spectra(XPS). The crystal structure determination of [4,4'-(bipy)-Ni(Bu-dtp)2]nreveals that the local coordination geometry around nickel(II) is a distorted octahedron and the Ni(Bu-dtp)2units are bridged by 4,4'-bipyridine to form an infinite chain. The Ni-S and Ni-N bond lengths are 2.468(6)-2.494(6)Å and 2.10(2)-2.15(2)Å, respectively.

ISSN:0038-7010    

DOI:10.1080/00387019708006997

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The infrared and Raman spectra of 7-methylguanine, 9-methylguanine, 9-ethylguanine, 1,7-dimethylguanine, and 1,9-dimethylguanine in the solid state have been reported and discussed. Hydrogen bonds in these solid guanine derivatives bring about strong perturbations which are discussed in terms of structural data given by X-ray diffraction methods. The spectra of guanine and 9-methylguanine are compared with the spectra of the monomers isolated in low-temperature matrices.

ISSN:0038-7010    

DOI:10.1080/00387019708006998

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor