Elution alpha detector

A flow-through alpha detector in the column effluent line is used to monitor the progress of an elution, and a movable neutron probe is used to determine the location of the 252Cf... 

The separation column effluent is divided into about 15 fractions that are collected in small (250-mL) polyethylene bottles. The volume collected in each bottle is determined by the appearance of the alpha-emitting elements in the column effluent solution as indicated by the response from the flowthrough alpha detector a typical response curve is shown in Fig. 2. Normally/ two einsteinium fractions/ two intermediate fractions/ and three californium fractions are collected. The intermediate fractions are taken when the valley between the einsteinium and californium peaks occurs on the response curve and usually contain less than 5% of each element. Sometimes the alpha trace will show a small fermium peak just ahead of the einsteinium/ but usually there is not enough fermium alpha to make a response and the fermium is assumed to be in one or both of the two fractions taken just prior to the einsteinium. The berkelium is primarily a beta emitter and is not detected by either the alpha or neutron detectors thus, three fractions are usually taken after the californium alpha peak to isolate the berkelium. If there is a significant amount of 244Cm he feed (milligram quantities)/ the alpha trace will show a third major peak when americium and curium are eluted at the end of the run. 

Monitoring of the 232Cf band movement with the neutron probe (Fig. 3) provides advance information on when to expect einsteinium in the eluate and can be used as a backup indicator for changing effluent collection bottles during the einsteinium-californium elution if the alpha detector fails. Also/ the neutron probe can be used to detect problems such as insufficient resin in the columns or incomplete elution from the loading column. 

Radioactivity of uranium can be measured by alpha counters. The metal is digested in nitric acid. Alpha activity is measured by a counting instrument, such as an alpha scintillation counter or gas-flow proportional counter. Uranium may be separated from the other radioactive substances by radiochemical methods. The metal or its compound(s) is first dissolved. Uranium is coprecipitated with ferric hydroxide. Precipitate is dissolved in an acid and the solution passed through an anion exchange column. Uranium is eluted with dilute hydrochloric acid. The solution is evaporated to near dryness. Uranium is converted to its nitrate and alpha activity is counted. Alternatively, uranium is separated and electrodeposited onto a stainless steel disk and alpha particles counted by alpha pulse height analysis using a silicon surface barrier detector, a semiconductor particle-type detector. 

A commercial CE system and a micropacked capillary was used to separate N—, O—, and S-containing heterocyclic compounds. Migration time reproducibility, linearity, and detector response was found to be comparable to HPLC. A study of the heterocyclic compound s elution order followed that predicted by the octanol-water partition coefficients (354). While chiral CEC provides improved resolution and higher efficiencies, additional work is needed since chiral CEC capillaries are not available commercially. The separation principles and chiral recognition mechanism for the separation of enantiomers have been reviewed (355). Furthermore, a comprehensive collection of drug applications and other compounds of interest has been reported (356). Direct enantiomeric separations by CEC were studied using a capillary packed with alpha-1-acid glycoprotein chiral stationary phase (357). Chiral resolution was achieved for enantiomers of benzoin, hexobarbital, pentobarbital, fosfamide, disopyramide, methoprolol, oxprenolol, and propanolol. The effects of pH, electrolyte concentration, and con-... 

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