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PubMed2001

An extraction chromatography method for Hf separation prior to isotopic analysis using multiple collection ICP-mass spectrometry.

A novel method for the single-step separation of Zr + Hf from all matrix elements of geological samples has been developed for Hf isotopic measurements using multiple collector-ICP-mass spectrometry. The method combines an effective sample decomposition by LiBO2 fusion with a selective separation of Hf + Zr by a solid-phase extraction material based on dipentyl pentyl phosphonate, commercially available as U-TEVA.Spec. Using this simple and rapid procedure, Hf and Zr can be isolated in a single separation step with good recoveries (>90%) and satisfactory blank levels (approximately 55 pg of Hf), so that a subsequent isotopic measurement with ICPMS is possible. An excellent separation from rock-forming constituents is achieved, including those elements (Al, P, Ti, Cr, Fe, Mo, etc.) known to interfere in conventional separation methods based on ion-exchange techniques. The potential of this new method for Hf isotopic analysis is demonstrated by replicate MC-ICPMS measurements of 176Hf/177Hf ratios in seven international reference materials of silicate rocks, spanning a range of Hf contents and bulk compositions.

Journal Article↗

PubMed1984

A simple spectrophotometric assay of plasminogen activator: comparison with the fibrinolytic method.

We describe a simple assay of plasminogen activator in which the enzyme reacts with a mixture of plasminogen and H-D-valyl-L-leucyl-L-lysine-p-nitroanilide for 1 h at 37 degrees C after which the absorbance is measured at 405 nm. The method detects as little as 2 CTA milliunits of activator and is linear over a 100-fold range of enzyme concentration. The new procedure has been used successfully for the assay of activator in breast tumor cytosols, cell culture supernatants, and pleural or ascitic fluids. Thirty-two biological samples have been assayed for plasminogen activator activity with both the spectrophotometric method and a classical fibrinolytic technique using radiolabeled fibrin. Although the two series of results are significantly correlated, the activities measured with the former assay are significantly different from those determined with the latter. It is shown that the spectrophotometric method is, in many respects, superior to the fibrinolytic procedure.

Ascitic Fluid↗