Methods for the separation of adrenaline, noradrenaline, hydroxytyramine, and dihydroxyphenylalanine (dopa) by employing starch columns (2, 3), paper chromatography (4-7), or countercurrent extraction (8) have limited usage either because of the length of time required for the fractionation or because of the small amounts of material that can be separated. A procedure is described below in whic...

Countercurrent systems have evolved in a variety of biological systems that allow transfer of heat, gases, and solutes. For example, in the renal medulla, the countercurrent arrangement of vascular and tubular elements facilitates the trapping of urea and other solutes in the inner medulla, which in turn enables the formation of concentrated urine. Arteries and veins in the cortex are also arra...

A physical model was used in a laboratory exercise to teach students about countercurrent exchange mechanisms. Countercurrent exchange is the transport of heat or chemicals between fluids moving in opposite directions separated by a permeable barrier (such as blood within adjacent blood vessels flowing in opposite directions). Greater exchange of heat or chemicals between the fluids occurs when...

The design of mass diffusion columns operated with partition membranes, for the separation of light gaseous isotopes, is discussed. A theoretical analysis of experimental results obtained indicates that a good agreement between experimental results and theory is only obtained at low column pressures and moderate countercurrent flow rates. At fairly low countercurrent flow rates mixing effects d...

The micropuncture evidence relating to the location and the mechanism for concentration and dilution of the urine is reviewed. As required by the countercurrent hypothesis for urine concentration, these data demonstrate that in the presence of antidiuretic hormone, the tubular urine is first concentrated in the descending limb of the loop of Henle and then diluted in the ascending limb of the l...

In this application note the purification of a common light-chain bispecific antibody using Multicolumn countercurrent solvent gradient purification (MCSGP) is described. The KNAUER Contichrom® system that is offered in cooperation of KNAUER and Chromacon is the only system on the market that can be used in MCSGP mode for difficult bioseparations. MCSGP is a countercurrent chromatographic proce...

Germanium recovery from coal fly ash by hydrometallurgical procedures was studied at the pilot scale (5 kg of fly ash/h). Results were used to design the equipment of a demonstration-sized plant (200 kg of fly ash/h). The process is based on hydrometallurgical operations: firstly a germanium extraction from fly ash by leaching and a consequent Ge separation from the other elements present in th...