Process for measuring low cadmium levels in blood and other biological specimens

Abstract

A process for measuring low levels of cadmium in blood and other biological specimens is provided without interference from high levels of alkali metal contaminants by forming an aqueous solution and without contamination by environmental cadmium absent the proteins from the specimen, selectively removing cadmium from the aqueous solution on an anion exchange resin, thereby removing the alkali metal contaminants, resolubilizing cadmium from the resin to form a second solution and analyzing the second solution for cadmium, the process being carried out in a cadmium-free environment.

The embodiments of this invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. A process for measuring half microgram levels of cadmium in biological fluids containing at least one alkali metal contaminant, comprising the steps of forming an aqueous solution of cadmium and the contaminant from a sample of the fluid converting the cadmium to anionic cadmium chloride selectively removing cadmium apart from a substantial portion of the contaminant from the aqueous solution on an anion exchange resin, resolubilizing cadmium from the resin to form a second solution, and analyzing for cadmium in the second solution, the process being carried out in an essentially cadmium-free environment.   
     
     
       2. The process of claim 1 wherein the analysis for cadmium is carried out by electrothermal atomic absorption. 
     
     
       3. The process of claim 1 including the step of increasing the cadmium content of the second solution by increasing the volume of the aqueous solution compared to the volume of the second solution. 
     
     
       4. The process of claim 1 wherein the fluid is blood, plasma or urine. 
     
     
       5. The process of claim 1 wherein the sample contains zinc and the process includes the step of increasing the analyzed value by a predetermined amount to correct for the limiting effect of Zn on the analyzed value for cadmium. 
     
     
       6. The process of claim 1 including the steps of adding a predetermined amount of  109  Cd to the sample before resolubilizing the sample cadmium from the resin and analyzing for  109  Cd as well as sample cadmium to provide a correlation between the analyzed sample cadmium with sample cadmium in the second solution. 
     
     
       7. The process of claim 1 including the step of selecting respective volumes of the aqueous and second solutions and the number of samples to provide a measure of cadmium content in the fluid with a coefficient of variation less than about 25%. 
     
     
       8. The process of claim 1 including the step of analyzing for blood and plasma to form a ratio separately for cadmium a patient useful in detecting recent exposure to harmful levels of cadmium. 
     
     
       9. A process for measuring half microgram levels of cadmium in biological fluids containing at least one alkali metal contaminant, comprising the steps of forming an aqueous solution of cadmium and the contaminant from a sample of the fluid, selectively removing cadmium apart from a substantial portion of the contaminant from the aqueous solution on an anion exchange resin, resolubilizing cadmium from the resin to form a second solution, and analyzing for cadmium in the second solution, the process being carried out in an essentially cadmium-free environment,   the cadmium content of the second solution being increased by increasing the volume of the aqueous solution compared to the volume of the second solution, and a corrective factor for Zn being applied to correct for the limiting value of Zn on the analyzed value for cadmium.