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[Value of separation on ion exchange resins of plasma iodine fractions. Comparison with Werner's suppression test].

This was a study of 71 patients suspected of hyperthyroidism who had undergone a tri-iodothyronine suppression test. A study of circulating protein-bound iodine after separation on ion-exchange resins had been carried out before triiodothyronine administration, on the same patients. The results showed that the radioactive hormonal fraction has a better diagnostic value than radioactive serum protein-bound iodine. In 60% of cases, a study of the radioactive hormonal fraction could have permitted to avoid the use of the suppression test.

Evaluation Studies as Topic↗

Monitoring nitrogen deposition in throughfall using ion exchange resin columns: a field test in the San Bernardino Mountains.

Conventional throughfall collection methods are labor intensive and analytically expensive to implement at broad scales. This study was conducted to test an alternative approach requiring infrequent sample collection and a greatly reduced number of chemical analyses. The major objective of the study was to determine the feasibility of using ion exchange resin (IER) to measure N deposition in throughfall with field deployment periods of 3 to 12 mo. Nitrogen deposition measurements in bulk throughfall collected under pine (Pinus sp.) canopies and in forest clearings were compared between co-located conventional throughfall solution collectors and IER throughfall collectors using mixed bed IER columns. Deposition data were collected for 1 yr at a high deposition site (Camp Paivika, CP) and a relatively low one (Barton Flats, BF) in the San Bernardino Mountains in southern California: Annual throughfall deposition values (kg ha(-1) of NH(4)-N + NO(3)-N) under large ponderosa pine trees (Pinus ponderosa Laws.) were 145.8 and 143.9 at CP and 17.0 and 15.0 at BF according to the IER and conventional methods, respectively. Analogous values for bulk deposition in forest clearings were 15.6 and 12.3 at CP and 4.0 and 3.3 at BF. It was concluded that the IER collectors can be used for routine monitoring of deposition in throughfall and bulk deposition, provided that field blanks are used to account for background levels of N in the IER columns, which at times are slightly elevated, possibly from slow release of amine groups from the anion exchange resin during field exposures.

Altitude↗

Effect of temperature and an ion-exchange resin on cation diffusion through silicone polymer tubing.

Permeation of cations through silicone rubber tubing was measured, and the effect of an ion-exchange resin on the cation diffusion was determined. Silicone rubber has been used as a biomedical polymer and shows a very low solubility to ionizable species. Correlations between the calculated diffusion coefficients, with and without the resin, depended on the charge and number of waters of hydration for each cation. These increases ranged from 1.11 for potassium to 3.06 for iron, multiplied by the diffusion coefficient as a result of the resin. Solubilities of each cation in the polymer were temperature dependent. Activation energies were calculated for each cation by measuring the increased permeation with increasing temperature, with and without the resin. Decreasing magnitudes of activation energies ranged from 0.91 for sodium to 0.57 for iron when the resin was present. Correlations were established between the measured activation energies and reported free energy change for the hydration of each cation.

Anion Exchange Resins↗