2.5. General procedure
A portion of aqueous sample solution containing Tl(I) was
prepared and the pH value was adjusted to desired value with
0.1 M HCl and NaOH. The solution was passed through the
column by using a peristaltic pump adjusted to the desired flow
rate. As the preconcentration was completed, the retained metal
ions on the microcolumn were eluted with 1.0 mL of 1.0 M
HCl solution. The analytes in the effluents were determined by
GFAAS. The column could be used repeatedly after regeneration
with 1.0 M HCl or HNO3 solution followed by distilled
water. Between the extractions, the minicolumn was dried by
passing the air through it for 30 min.