Discrimination between aluminium held within vegetation and that contributed by soil contamination using a combination of Electron Probe Micro Analysis (EPMA) and Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES)

Aluminium concentrations in NIST (formally NBS) Standard Reference Material Tomato Leaves and Citrus Leaves were determined by ICP-AES after acid digestion. The normal total acid attack (nitric and perchloric acids) gave very low recovery (40%) of Al in NIST tomato leaves, but not for citrus leaves. The contribution of Al from Al-rich soil particles in both tomato leaves and citrus leaves was estimated semi-quantitatively by computer-controlled EPMA. The Al held in these particles corresponded in approximate concentration to the shortfall between the acid soluble component determined in this study and the certified value. Analysis by EPMA can provide, therefore, a method of estimating Al contributed by soil contamination to plant materials. The limitations of the NIST tomato and citrus leaf reference material for the validation of methods for the determination of Al in vegetation are demonstrated.