Determination of Aluminum Extracted from Soils by ion Chromatography

Abstract

Abstract A fully automated ion chromatographic (IC) method for the determination of Al extracted with 1 M KCl, 1 M NH 4 Cl and 0.2 M NH 4 ‐oxalate was evaluated utilizing a Dionex 2020i ion chromatograph. For Al in the KCl and NH 4 Cl extracts, the method involved direct injection of the extract onto a Dionex CG‐3 column, post column reaction and complexation of the Al in a Dionex reagent delivery module, and detection on a Dionex UV/Vis detector. The eluant consisted of 0.4 M NH 4 Cl acidified to pH 3.1. Standard curves were prepared by plotting the integrated peak intensities of the chromatograms against concentration of standard Al solutions. The standard curve has a very large dynamic linear range (0.05 to 15 mg L −1 ). The detection limits of the technique are 50 and 20 µg L −1 when utilizing a 50 and 100‐µL injection loop, respectively. The NH 4 ‐oxalate extractable Al was determined by ashing a sample aliquot, redissolution in HNO 3 , and then direct injection onto the CG‐3 column. In this application, Fe in the NH 4 Ox extract injected onto the CG‐3 column can also be quantitatively determined without further sample preparation.