Portable X-ray fluorescence spectrometry: a tool for rapid measurement of nutrients in plants

Abstract

To get spatialized and temporal data is an important need about the multi-element composition of plants in the agrosystems. The emergence of portable analytical devices allows nowadays getting practical and easy tools that give indicators in real time of productive and quality performances of cultivated species. In this scope, the direct analysis of plants by a portable spectrometer of X-rays fluorescence (pXRF) has been evaluated. The instrument has an irradiation window of an 8 mm diameter and a measure time of 60 seconds. Its analytical performance was first estimated to determine simultaneously P, K, Ca, Mg, S, Al, Fe, Mn, Cu and Zn on dry plant powders with well known compositions. Some relevant linear relationships were found for all elements between measured concentrations and reference values. Correlation coefficients (r2 ) up to 0.92 were obtained excepted for Cu. The instrument lacks of sensibility for this element that is present in low concentrations (= 10 mg/kg). The measure dispersion was bounded between 6 % (Ca) and 19 % (Mg). The pXRF capacity to measure concentrations of grape leaves was also studied. The sample leaves were analysed by a reference method with acid digestion and measure with atomic emission by ICP-OES. On the grinded and dry samples, the pXRF accuracy was confirmed excepted for Mg. On fresh leaves, the accuracy of the determinations can be affected by the lack of homogeneity of samples, water presence and sample thickness. These results show that the portable XRF spectrometry frames an attractive strategy for a direct, cheap and rapid analysis in the domain of agronomy reinforcing the implementation of precision agricultural concepts and green analytical chemistry.