Chemoselective derivatization of alkaloids in periwinkle

The terpene indole alkaloid biosynthetic pathway can utilize a secologanin substrate analog containing a handle for functionalization, and the resulting non-natural alkaloids can be chemoselectively derivatized in crude extracts of plant tissue.     

The selective determination of halogens and sulphur in solution by atmospheric-pressure helium microwave-induced plasma emission spectrometry coupled to an electrothermal introduction system

Instrumentation is described for the direct determination of Cl, Br, I and S in dissolved samples. A tantalum furnace is coupled directly to a TM₀₁₀ cavity, in which a helium microwave plasma is generated at atmospheric pressure. Samples (20 μl) are dried, ashed and atomized; the free atoms are transported by helium to the cavity, where they are excited. Detection limits are in the sub-mg l^-1 region. The effect of counter cations is removed by the addition of 50 mg l^-1 potassium hydroxide, which also helps to suppress interferences by large amounts of matrix constituents, but the standard addition technique remains necessary to permit determinations that are reliable to within 5%.     

Analytical chemistry in the Netherlands

Summary A general review is given of analytical chemistry in the Netherlands. The following points are discussed: education, professional organisations, research, funding of research, international activities, analytical control in practice.

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Analytische Chemie in den Niederlanden

Zusammenfassung Ein allgemeiner Überblick über die Analytische Chemie in den Niederlanden wird gegeben. Die folgenden Themen werden diskutiert: Ausbildung, Berufsorganisationen, Forschung, Finanzierung der Forschung, internationale Aktivitäten, analytische Kontrolle in der Praxis.

     

The possibility of a truly absolute method of spectrographic analysis

A quantitative expression is given for the relation between the concentration of an element in a sample and the line intensity when a low current d.c. carbon arc with anode excitation is employed. With this equation, the concentration of an element can be determined without previous establishment of a working curve.     

Line profiles emitted by Cu and Ca hollow cathode lamps pulsed to one ampere

Interferometrically measured emission resonance line profiles are presented for commercial copper and calcium hollow cathode lamps, pulsed at frequencies from 10 to 300 Hz with pulses having a constant current-duration product. Pulses ranged from 7.8 mA at 1280 μs to 1000 mA at 10 μs. Time integrated profiles show that self-reversal increases with repetition frequency and that the lines broaden with increased current. Time resolved profiles show that self reversal developes during a pulse. A simple transport model is proposed to account for the observed blue shifts in the emission profile and in the self-reversal dip of the copper resonance line. The analytical significance of the results is briefly discussed.