Microscale compound preparation

The only other crystallographic result reported for a berkelium chal-cogenide besides those summarized in Table II is a cubic lattice parameter of 0.844 nm for Bk2S3 (155). The microscale synthesis of the brownish-black sesquisulfide was carried out by treatment of berkelium oxide at 1400 K with a mixture of H2S and CS2 vapors. In later work (136,137), the higher chalcogenides were prepared on the 20- to 30-jug scale in quartz capillaries by direct combination of the elements. These were then thermally decomposed in situ to yield the lower chalcogenides. The stoichiometries of these compounds have not been determined directly. 

All these compounds are intermediates in indole-3-acetic acid (auxin) biosynthesis of plants. They have been prepared on microscale with reasonably high yield, high purity... 

Preparation of multi-milligram quantities of compounds as well as microscale synthesis... 

The chemistry required to convert the oxide to other binary compounds is independent of the scale of operation. However, with microscale synthetic methods applied to radioactive materials, successful preparations are achieved more readily by carrying out the chemistry in situ, that is, in such a manner that eliminates, or at least minimizes, the necessity of having to "handle" the sample during or following its synthesis. Thus, actinide compounds are usually prepared in silica capillary tubes which can be flame sealed at the conclusion of a synthesis to provide the desired sample for study in a small volume, quartz container. A special feature of the preparation/vacuum system in the TRL is the capability to interrupt a synthesis, isolate (by means of a stopcock) and remove the sample, examine it in... 

The sample and standards are spotted on a TLC plate and developed with each of the developing solvents, dried, and examined under uv radiation. The / /s are determined, and the solvent providing an between 0.2 and 0.35 is selected. A microscale column is prepared, and the sample added. 15 to 18 fractions are collected and spotted on two TLC plates, dried, examined with uv radiation and stained. The fractions containing the desired compound are combined, the solvent is evaporated and the compounds are collected. 

Microscale decolorization of a solution on a chromatography column requires that a column be prepared in a Pasteur pipette, using either alumina or silica gel as the adsorbent (Section 19.6). The sample to be decolorized is diluted to the point where crystallization within the column will not take place, and it is then passed through the column in the usual manner. The desired compound is collected as it exits the column, and the excess solvent is removed by evaporation (Technique 7, Section 7.10). 

Gas chromatography is one of the most useful instrumental tools for separating and analyzing organic compounds that can be vaporized without decomposition. Common uses include testing the purity of a substance and separating the components of a mixture. The relative amounts of the components in a mixture may also be determined. In some cases, gas chromatography can be used to identify a compound. In microscale work, it can also be used as a preparative method to isolate pure compounds from a small amount of a mixture. 

In most instances, the first solid materials of the actinides that were studied were oxides, not only because the oxides of electropositive metallic elements are primary compounds, but also because oxides may have been the easiest compound to prepare, especially on the microscale. 

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