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Biomedical subjects

E P Horwitz

Publications and source records attributed to E P Horwitz.

6 recordsLinked to original sources
PubMed2006

Automated measurement of 224Ra and 226Ra in water.

We present a new simple approach for automated, non-destructive measurement of the alpha-emitting radium isotopes ((223)Ra, (224)Ra, and (226)Ra) in water based on the emanation of their respective radon daughters ((219)Rn, (220)Rn, and (222)Rn). The method combines the high adsorption uptake of MnO(2) Resin for radium (K(d)=2.4 x 10(4)ml/g) over a wide pH range with the simplicity of the activity registration using a commercial radon-in-air analyzer (RAD7, DURRIDGE Company, Inc). Radium is first adsorbed onto the MnO(2) Resin by passing a water sample through the resin packed in a gas-tight glass cartridge. The same cartridge is then connected to the radon analyzer via a simple tubing system to circulate air through the resin and a drying system. The efficiency of the proposed system is determined by running standards prepared in the same manner. Our results indicate that the efficiency for (226)Ra is >22% if both (218)Po and (214)Po counts are collected. This is comparable with typical efficiencies for alpha spectrometry but with much less sample preparation. We estimate that an MDA of 0.8 pCi/L for (226)Ra may be obtained with this new approach using a 1L water sample and less than 4h of counting.

Automation↗
PubMed2005

A process for the separation of 177Lu from neutron irradiated 176Yb targets.

A conceptual flowsheet has been developed for the separation of (177)Lu from a 300 mg neutron irradiated (176)Yb enriched target. The key component of the process is an extraction chromatographic (EXC) resin containing 2-ethylhexyl 2-ethylhexylphosphonic acid (HEH[EHP]) sorbed onto a 25-53 microm Amberchrom CG-71 substrate. The process is divided into three sections: (1) front-end target removal system, (2) primary separation system and (3) secondary separation system. Each section involves the separation of Yb and Lu using the HEH[EHP] resin followed by concentration and acid adjustment of the Lu-rich eluate using an EXC material containing a diglycolamide extractant. The use of the diglycolamide EXC material is a significant feature of the flowsheet, allowing one to avoid lengthy evaporations and acidity adjustments between successive HEH[EHP] column runs while removing adventitious impurities from the (177)Lu. The overall recovery of (177)Lu is estimated at 73% with an overall decontamination factor from Yb of 10(6). The overall processing time can be as short as 4h.

Journal Article↗
PubMed2004

Radium-228 determination of natural waters via concentration on manganese dioxide and separation using Diphonix ion exchange resin.

The objective of this work was to establish a new procedure for 228Ra determination of natural waters via preconcentration of radium on MnO2 and separation of its daughter, 228Ac, using Diphonix ion exchange resin. Following removal of potential interferences via passage through an initial Diphonix Resin column, the first daughter of 228Ra, 228Ac, is isolated by chromatographic separation via a second Diphonix column. A holding time of > 30 h for 228Ac ingrowth in between the two column separations ensures secular equilibrium. Barium-133 is used as a yield tracer. Actinium-228 is eluted from the second Diphonix Resin with 5 ml 1M 1-Hydroxyethane-1,1-diphosphonic acid (HEDPA) and quantified by addition of scintillation cocktail and LSC counting. Radium (and 133Ba) from the load and rinse solutions from the 2nd Diphonix column may be prepared for alpha spectrometry (for determination of 223Ra, 224Ra, and 226Ra) by BaSO4 microprecipitation and filtration. Decontamination tests indicate that U, Th, and Ra series nuclides do not interfere with these measurements, although high contents of 90Sr (90Y) require additional treatment for accurate measurement of 228Ra. Addition of stable Sr as a "hold back" carrier during the initial MnO2 preconcentration step was shown to remove most 90Sr interference.

Chromatography, Ion Exchange↗
PubMed1991

An improved method for determining 89Sr and 90Sr in urine.

A method has been developed for the rapid isolation and quantitation of 89Sr and 90Sr in urine samples. The radiostrontium is concentrated from the bulk urine sample by coprecipitation with calcium phosphate. The precipitate is then wet ashed with nitric acid, and a solution of the resulting residue in 2 M HNO3-0.5 M Al(NO3)3 is passed through an extraction chromatographic column containing a supported crown ether that preferentially retains strontium. Sorbed strontium may then be eluted from the column with either dilute HNO3 or water and counted via liquid scintillation. A new counting scheme that permits quantitation of both 89Sr and 90Sr on the same day the separation is performed is described.

Humans↗
PubMedDate not supplied

Gross alpha determination in drinking water using a highly specific resin and LSC.

Some results of experiments concerning a new highly specific resin for the extraction of alpha-emitting nuclides from drinking water samples are presented. The product used during these experiments is a new extraction chromatographic resin which consists of a combination of several reagents and extractants supported on inert polymeric substrates, called "Resin" hereafter. It shows strong affinity for Actinides in the tri-, tetra- and hexavalent oxidation state, as well as for radium, even in presence of large amounts of calcium. Gross-alpha activities were determined using alpha-/beta-discrimination liquid scintillation counting (alpha-/beta-LSC) by direct measurement of the dried resin after extraction. Counting conditions were optimised accordingly. A method for the determination of alpha-emitting nuclides in drinking water was developed and tested using intercomparison and spiked drinking water samples.

Alpha Particles↗