Analytical Letters

Belcher, R.; Fleet, B.

doi: 10.1080/00032716808051159pmid: N/A

Abstract Preliminary studies on the development of a method for the determination of carbon and hydrogen in 50–100 μg samples of organic compounds are described. The sample is burned over copper oxide in a helium stream and the water formed is converted to acetylene. Separation of CO2 and acetylene on a silica gel column is followed by combustion of acetylene to carbon dioxide; the two peaks remain separate and are measured by a highly sensitive katharometer.

Bowman, John T.; Bard, Allen J.

doi: 10.1080/00032716808051160pmid: N/A

Abstract A technique involving the application of a constant potential step before chronopoteatiometric examination of multicomponant systems is shown to be useful in reducing the effect of more easily electrolyzed components on the following waves. A mathematical treatment of the technique and experimental results are given. A technique involving a constant potential step before reversal chronopotentiometry of a single component system is also discussed.

Moorhead, E. D.; Britton, D.

doi: 10.1080/00032716808051161pmid: N/A

Abstract The direct and alternating current polarography of pyrazine has been re-examined. Evidence shows that the aromatic 1,4-diazine is reduced stepwise from strong acid, and the added resolving power afforded by the a.c. technique indicates that such a mechanism may prevail up to pH 4.5. Controlled potential electrolysis of pyrazine at pH 1 produced an intense violet color whose spectral characteristics and time instability suggest the presence of an acid-stabilized radical.

Guilbault, G. G.; Sadar, M. H.; Arcenaux, D.

doi: 10.1080/00032716808051162pmid: N/A

Abstract The results of a complete study of 12 substrates for lipase indicated 4-methyl umbelliferone heptanoate to be the best substrate for the analysis of this enzyme. Using this ester, from 0.000020 to 0.066 units per ml. of porcine pancreas lipase can be determined with an accuracy and precision of about 1.5%. Analysis is performed by a direct initial reaction rate method in 2–3 minutes.

Ewing, Galen W.; Young, Mahlon G.

doi: 10.1080/00032716808051163pmid: N/A

Abstract A balanced Wheatstone bridge circuit for two photo-conductive cells applied to chemical photometry is analyzed mathematically. The governing relation between the output voltage E and the transmittance T is Minimum relative error occurs at 0.67 absorbance.

Busev, A. I.; Ivanov, V. M.; Größ, V. G.

doi: 10.1080/00032716808051164pmid: N/A

Abstract It has been shown, that depending on the ratio of the concentration of Rh(III) and 1-(2-thiazolylazo)-resorcin and the pH there will be formed in solution at least two substances with different chemical and light absorption properties. The optimum conditions for the existence of each substance have been determined in addition to molar absorbtivities of the colored substances, the equilibrium constants for their formation, and their stability constants.

Sandoval, Maud W.; Sandoval, Antonio A.; Cheng, K. L.

doi: 10.1080/00032716808051165pmid: N/A

Abstract Aqueous solutions of triethylenetetraminehexaacetic acid (TTHA) in the pH range 4 to 11 have been studied by NMR. Chemical shifts as a function of pH are reported and a structure proposed for TTHA on the basis of these data. The influence of complex formation of metal ions with TTHA, in varying ratios, on NMR spectra is discussed.