Abstract
A selective determination method for palladium (Pd) ion in river water by reversed‐phase HPLC has been developed. The Pd ion was quantitatively extracted into 4‐methyl‐2‐pentanone over the pH range of 0.5 to 4 as 5‐chloro‐2‐mercaptobenzothiazole (CMBT) chelate. Job's method indicated that the Pd‐CMBT chelate composition was Pd(CMBT)2. The molar absorptivity of the Pd chelate was determined as 1.58×103 at 440 nm. The extracted Pd‐CMBT chelate was then separated on a phenyl column with an eluent of methanol/2‐propanol/1‐hexanol/0.1 mol/L CMBT (40∶50∶9∶1, v/v) and detected at 440 nm. The correlation coefficients of the calibration curves obtained with 5 mL Pd standards were more than 0.999 over the range of 10 ng/mL (ppb) to 10 µg/mL (ppm). The detection limit of the Pd ion in 5 mL water was estimated as 5 ppb by a signal to noise ratio of 3. Relative standard deviations of peak areas (N=6) for 1 and 0.1 ppm Pd standards were 0.8 and 1.1%, respectively. The recoveries with a spiked river water sample for 5, 0.5, and 0.05 ppm Pd ion (N=5) were 100±1%, 98±1%, and 98±4%. Effects of foreign ions on the method were investigated with 57 metal ions. Almost none of the ions interfered except for Hg(II), Ag(I), and Cu(II).