Eckhard Herrmann

Beitrag zur trennung von seltenerden durch extraktionschromatographie mit di(2-äthylhexyl)phosphorsäure (HDEHP) I. Silicagel als trägermaterial für die stationäre phase

Abstract Hydrophobised silica gel was used as support material for extraction chromatographic separations of rare earths with di(2-ethylhexyl)phosphoric acid (HDEHP). Columns with a capacity of 0.8 mequiv, per ml of column and a “height equivalent of one theoretical plate” of H ≤ 0.1 mm for europium and gadolinium were obtained. H is independent of the type of silica gel when its mean pore diameter is ≥ 35 A, and is also nearly independent of the amount of HDEHP used, as long as the silica gel only absorbs the dialkylphosphoric acid so that a dry powder is produced again after absorption. Examples of separation show the efficiency of the columns obtained.

Beitrag zur trennung von seltenerden durch extraktionschromatographie mit di(2-äthylhexyl)phosphorsäure : II. Verhalten der matrix und ihr einfluss auf die mikrokomponente

Abstract A contribution to the separation of rare earths by extraction chromatography with di(2-ethylhexyl)phosphoric acid. II. The behaviour of the matrix and its influence on the behaviour of microcomponents The use of extraction chromatography with undiluted di(2-ethylhexyl)phosphoric acid as the stationary phase for macro/micro separations of lanthanides has been studied. Macro amounts of a rare earth element are retained on the column bed from weakly acidic solutions in the form of tris(dialkyl phosphates). By elution with diluted mineral acids an asymmetrical peak with a sharp front and a long tail is observed. The position A of the front, normalized to the unity di(2-ethylhexyl)phosphoric acid volume on the column, depends on the loading B (expressed in %) of the column with rare earth ions and on the partition coefficient D for this element in tracer concentration. This dependence can be expressed by the following equation: log A = log D  0.036 B  0.15 The influence of the macro amount of the given rare earth element on the behaviour of the other lanthanides present in tracer concentration has also been investigated. When the micro element has a lower atomic number than the macro element and A macro / D micro ⩾ 1.5, it is possible to isolate the tracer with a yield of more than 80% and with an enrichment factor of about 10 6 . But in this case the loading of the column should be no more than about 50% of the maximum column capacity. In the opposite case, when the tracer has the higher atomic number, the isolation process of micro elements is less sensitive to the macro amount. In some cases even the total column capacity could be used. But as a result of the tailing effects the enrichment factors are usually reduced to values of about 10 3 –10 4 .

On the Reaction of Phosphorous Acid Esters with Nucleophiles in the Presence of Carbon Tetrachloride

Abstract Esters of N-Phosphoryl phosphazenes are prepared by a modified Atherton-Todd reaction from di- and triesters of phosphorous acid, sodium azide, and carbon tetrachloride in high yields. The utilization of the two-component system trialkyl phosphite/ carbon tetrachloride for preparing phosphazenes, (RO)3P[dbnd]NY (Y: PO(OR)2, SO2R, COR, CN), and dialkoxyphosphoryl compounds, (RO)2P(O)X (X: NHR, NR2, OPh, CN, F, NCO), is presented.