Abstract: A method and test for field sample arsenic speciation in aqueous solutions, in particular, arsenic speciation in drinking water, is described. In particular, the method and test uses in series three columns wherein the first column removes interfering cations from water, the second column removes dimethylarsenate (DMA) from the water, and the third column removes As(V) (collectively H3AsO4/H2AsO4?/HAsO42?/AsO43?) and monomethylarsinate (MMA) while As(III) (collectively H3AsO3/H2AsO3?/HAsO32?/AsO33?) remains in the water effluent. The bound arsenic species are separately eluted from the columns in a laboratory and then each of the eluants and the effluent are tested for the arsenic species, preferably using graphite furnace atomic absorption spectroscopy.

Abstract: A centrifuge tube for the separation of liquid phases in a liquid/liquid raction process is provided with a tube reaching below the upper phase and into the lower phase which receives a centrifugally ejectable block. After insertion of the tube and stratification of the liquid phases, the system is again subjected to centrifugation to remove the block and allow the lower phase to be withdrawn, e.g. through a disposable pipette.