Polyurethane foam (PUF) mini-column was used to eliminate copper and iron for the determination of
nickel in pierced rings. The PUF mini-column was connected to FIA system for on-line sorption of copper
and iron in complexes form of CuSCN
þ
and FeSCN
2
þ
. For this season, the acid solution containing a
mixture of Ni(II), Fe(III), Cu(II) and SCN
ions was
fi
rstly
fl
ew into the PUF column. Then, the percolated
solution which Fe(III) and Cu(II) ions is separated from analysis was injected into FIA system to react
with 4-(2-pyridylazo) resorcinol (PAR) reagent in basic condition which this method is called pH
gradient technique. The Ni
–
PAR complexes obtained were measured theirs absorbance at 500 nm by UV
visible spectrophotometer. In this study, it was found that Cu(II) and Fe(III) were completely to form
complexes with 400 mmol/L KSCN and entirely to eliminate in acidic condition at pH 3.0. In the
optimum condition of these experiments, the method provided the linear relationship between
absorbance and the concentration of Ni(II) in the range from 5.00 to 30.00 mg/L. Linear equation is
y
¼
0.0134
x
þ
0.0033 (
R
2
¼
0.9948). Precision, assessed in the term of the relative standard deviation, RSD,
and accuracy for multiple determinations obtained in values of 0.77
–
1.73% and 97.4%, respectively. The
level of an average amount of Ni(II) in six piercing rings was evaluated to be 14.78 mg/g.