Spectrophotometric measurements of serum nickel.

An ultraviolet spectrophotometric procedure has been developed for the measurement of serum nickel. Samples of serum are lyophilized and the dry residues are subjected to acid digestion. Nickel is separated from interfering elements by chloroform extraction of nickel dimethylglyoximate at alkaline pH. Nickel is converted to the diethyldithiocarbamate complex and is extracted with isoamyl alcohol. The absorbance of nickel bisdiethyldithiocarbamate is measured as the difference between the absorbance maximum (325 m) and the absorbances at 2 background wave lengths (295 and 355 m). The concentrations and volumes of the reagents have been adjusted in order to achieve a sensitivity of 0.002 ppm (2 &g./L.). The recovery of 2.5 pg. of nickel added to 8 samples of serum averaged 104% (S.D. ± 8), with a range from 91 to 115%. The mean concentration of nickel in serum from 23 normal subjects was 2.2 p.g./100 ml. (S.D. ± 1.8), with a range from 0.1 to 7.7 pg./100 ml. The median concentration of serum nickel was 1.7 i.g./100 ml.