Determination of Impurity Anions in High Pure Fluoride Reagents by Ion Chromatography with Column-Switching
A method was developed for the determination of trace anions(Cl~-,NO_3~-,PO_4~(3-) and SO_4~(2-) ) in high pure fluoride reagents by ion chromatography(IC) with column-switching.Ion excluding column IonPac ICE-AS6 was used in the first step to separate the trace anion analytes from the high concentrated fluoride using deionized water as the mobile phase,separated analytes were enriched in the pre-concentration column IonPac TAC-ULP1 at the same time.By using a mixture of 4.5 mmol/L Na_2CO_3-0.8 mmol/L NaHCO_3 as the eluent at a flow rate of 1.2 mL/min,the analytes were eluted from the pre-concentrated column after switching the pre-concentrated column into the analytical system.The separation of the analytes was performed with IonPac AG23(50 mm×4 mm) as guard column and IonPac AS23(250 mm×4 mm) as analytical column,and the detection was performed by suppressed conductivity detector.As a result,the linear ranges of the method for Cl~-,NO_3~-,PO_4~(3-)and SO_4~(2-) were 0.02-5.0 mg/L(r= 0.9996),0.02 - 5.0 mg/L(r=0.9999),0.05- 10.0 mg/L(r = 0.9998), 0.02—5.0 mg/L(r = 0.9997) respectively.The average recoveries were 92.0%—103.5%with the relative standard deviations(RSD,n = 7) less than 3.0%.The detection limits(S/N = 3) were 0.2, 0.6,3.0 and 0.5 mg/kg for Cl~-,NO_3~-,PO_4~(3-)and SO_4~(2-),respectively.