摘要:

Fluorescence spectra and lifetimes of ovalbumin labeled with a variety of fluorescent reagents have been measured. The peak positions of the emission spectrum and the long wavelength band of the excitation spectrum as well as the fluorescence lifetimes, are tabulated. Heterogeneity of binding sites is shown by the broadness of some emisison spectra and the presence of multiexponential decay. The atlas may serve as a guide to the properties of these dyes attached to proteins in general.

ISSN:0003-2719    

DOI:10.1080/00032718508066142

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The ratio of solid-phase/gas-phase ammonia in ambient air may be of significance in the assessment of acid rain potential. Conventional sampling devices such as chemisorptive traps following a filter stage may give erroneous results and it is desirable that other approaches be found. Diffusive sampling tubes lined with a selective sorbent is one route. This paper reports on a study of the use of ion-exchange membranes for the collection of gas-phase ammonia.

ISSN:0003-2719    

DOI:10.1080/00032718508066143

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The parameters affecting the sampling on passive samplers made of graphitized carbon black, an adsorbent with a low specific area, are investigated.

ISSN:0003-2719    

DOI:10.1080/00032718508066144

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Laboratory robots are being used to perform sample preparation and routine analytical determinations 1,2. In addition to these routine applications, laboratory robots should be able to analyze the analytical procedure itself and select the optimal experimental condition for any analytical method. The application of the fixed-sized SIMPLEX algorithm, the Nelder and Mead variable sized SIMPLEX algorithm and response surface fitting methods in analytical robotics is presented3.

ISSN:0003-2719    

DOI:10.1080/00032718508066145

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Complexation constants of Pb2+and Cd2+nitrates with five crown compounds (18-crown-6, dicyclohexyl-18-crown-6, benzo-15-crown-5, dibenzo-24-crown-8 and 12-crown-4), have been determined by d.c. and a.c. polarographic measurements in aqueous medium using 0.1 M HNO3as supporting electrolyte. The complexes of lead with 18-crown-6 and dicyclohexyl-18-crown-6 are very stable which may be attributed to the partially covalent bonds formed by this metal ion.

ISSN:0003-2719    

DOI:10.1080/00032718508066146

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The tenaammetric behavior of di-(2-ethylhexyl)phosphoric acid (D2KHPA) was investigated by non-phase-selective AC polarography. D2EHPA produces in alkali sulfate supporting electrolytes a decrease of the capacitive current in the region of zero-charge potential, as well as a tensammetric peak located between -1.0 and -1.3 Vvs. SCE. In the same range, the second harmonic has a characteristic maximum. The pH of the solution and the nature of the cation in the supporting electrolyte affect both the height and the position of the tensammetric peaks. The tensammetric method allows determination of D2EHPA at concentrations ranging from 0.5 to 200 mg/1. Maximum sensitivity is obtained by measuring the second harmonic.

ISSN:0003-2719    

DOI:10.1080/00032718508066147

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

A quantitative TLC separation of metal ions using cerium (IV) antimonate as the solid phase are described. Using an acetonitrile- HNO3solvent Pb2+can be separated quantitatively (2–10 μg) from several other ions. A quantitative spectrophotometric assay using p-nitroso-dimethylaniline is proposed.

ISSN:0003-2719    

DOI:10.1080/00032718508066148

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Sensitive colour reactions given by 2-Hydroxy-4-methoxyacetophenone; 4-Benzyloxyresacetophenone; 2′, 4′, 4-Trihydroxychalkone; 2-Hyaroxy-4′, 6′-dimethoxychalkone and 2-Methyl-5,7-dihydroxychromone are reported as chromatographic spray reagents for the detection of a number of metal ions on paper chromatograms. Sensitivity limits for detection of Be(II), Al(III), V(IV), Fe(II), Fe(III) and Th(IV) in relation to 2-Hydroxy-4-methoxyacetophenone; 2′-Hydroxy-4′, 6′-dimethoxychalkone; 2′, 4′, 4-Trihydroxychalkone and 2-Methyl-5, 7-dihydroxychromone are also reported alongwith separation of groups of metal ions by using three new solvent systems.

ISSN:0003-2719    

DOI:10.1080/00032718508066149

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Laser mass spectra (LMS) of triphenylmethane dyes were obtained directly from a thin layer chromatographic (TLC) plate using the LAMMA-1000 laser microprobe. Spectra obtained from TLC plates were very similar to those obtained from standard substrates, the only difference being that at threshold power densities spectra from the TLC plates show greater fragmentation. The region below m/z 100 is mostly obscured by peaks due to the chromatographic support; above this range, peaks can be identified corresponding to the molecular cation and simple neutral losses. The inherent lateral rèsolution of the Instrument (∼5 μm) was used to resolve multiple components in broad chromatographic spots. The TLC-LMS combination has the advantage that components can be identified even if they are not completely resolved chromatographically.

ISSN:0003-2719    

DOI:10.1080/00032718508066150

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Changes in concentration of very dilute solutions of metals, due to adsorption on the walls of the container, are well known. Earlier studies, however, have been confined to follow the changes in trace metal concentration of the solution phase with time. Characterisation of the solid surface is equally important and for such a study are needed reproducible thin layers of the ions under consideration on the particular substrate. Deposition of thin layers of copper on platinum by electrodeposition and solution evaporation of CuCl2on platinum gave comparable results on examination of the Cu 2p peaks by XPS. Solution evaporation was found successfully for the sodium glass substrate as well. However, solution evaporation could not be applied to Teflon or PVC substrates.

ISSN:0003-2719    

DOI:10.1080/00032718508066151

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor