摘要:

A rapid, sensitive and reproducible chronoarnperometric method for the determination of lecithin is described. The method is based on the inhibition of the oxygen reduction process by the adsorption of lecithin at the mercury -solution interface. Current-time curves recorded during the growth of single mercury drops at −0.200 V (vs SCE) in aqueous-ethanolic solutions of lecithin are employed. The adsorption effect may be evaluated by measuring the time necessary for a complete drop surface coverage, “to”, interpolating the descending branch of the i-t curves linearly to zero current. The influence of the variables that affect the inhibition process is studied and a linear relationship between t1/2oand lecithin concentration in the 20–80 μg/ml range is found. The relative standard deviation of the proposed method is 1.3%.

ISSN:0003-2719    

DOI:10.1080/00032717908067923

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

An iodide membrane electrode, in conjunction with rat liver microsomes, is used to measure thyroxine at sub-micromolar levels. The microsomes serve as biocatalytic reagents which selectively remove iodide from the hormone. The amount of iodide liberated, as measured by the electrode, is proportional to the initial thyroxine concentration. The electrode can further be employed to directly monitor the rate of deiodination of the hormone with advantages of speed and convenience over existing techniques.

ISSN:0003-2719    

DOI:10.1080/00032717908067924

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Matrix isolation Fourier transform infrared spectra of isomeric methylnaphthalenes and methylbiphenyls, in N2matrices at 15 K, are compared with each other and with those of the respective parent hydrocarbons. The applicability of matrix isolation Fourier transform infrared spectroscopy to both identification and quantitative analysis of individual alkylated polycyclic aromatic hydrocarbon isomers in mixtures is demonstrated.

ISSN:0003-2719    

DOI:10.1080/00032717908067925

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

A new technique is described for rapid elemental analysis of atmospheric particulates. The basic principle is direct deposition of atmospheric particulate matter in a furnace for electrothermal atomization and analysis by atomic absorption spectrometry. A prototype instrument has been tested by analyzing the lead content in the laboratory atmosphere.

ISSN:0003-2719    

DOI:10.1080/00032717908067926

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Interferences from small amounts of sea salt in the determination of cadmium and lead were investigated. Test samples were made to mimic solutions obtained after extraction of sea water for trace metal analysis. Sea salt concentrations in the range 0–400 mg/l were investigated. Background absorption from this salt was high but easily minimised through the addition of nitric acid (2 % v/v). Sensitivity reductions due to the salt were considerable and varied from one graphite tube to the other. This problem was overcome by the addition of 1000 mg lanthanum per litre of sample. The positive effect of the lanthanum matrix modification is thought to be due to a change of the graphite tube surface.

ISSN:0003-2719    

DOI:10.1080/00032717908067927

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The distribution of zinc was studied between the decaline phase having tri-n-octylphosphine oxide (TOPO) and the methanol-water phase (4:1 in molar ratio) having chloride ion, and the stability constants of zinc with chloride in the methanolic solution were calculated from the extraction experiments (K1= 2.4 × 103, K2= 1.9 × 102at 298°K).

ISSN:0003-2719    

DOI:10.1080/00032717908067928

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

A method is described for the determination of several pesticides containing bromine and chlorine by molecular emission cavity analysis (MECA). The pesticides were decomposed in an oxygen flask and the combustion products dissolved in aqueous ammonia. The ammonium halides were separated by TLC using microcrystalline cellulose adsorbent. After scraping from the TLC plates and dissolving in water the separated components were quantitated by MECA using either the InBr (Λmax= 376 nm) or the InCl (Λmax= 360 nm) emission bands. Recoveries of over 96% were obtained. Soils fortified with l, 2-dibromo-3-chloropropane at levels of 5–25 ppm were extracted using shaking and distillation procedures. Subsequent analysis showed that the shaking extraction gave a recovery of 92% compared to 85% from acid refluxing.

ISSN:0003-2719    

DOI:10.1080/00032717908067929

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0003-2719    

DOI:10.1080/00032717908067922

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor