Phosphorus Quantification in Sugar Cane (Saccharum officinarum) Leaves In Vivo by Portable X-ray Fluorescence Spectroscopy

This study aimed to evaluate the potential of portable X-ray fluorescence (pXRF) equipment to quantify P in sugar cane leaves in vivo. Therefore, sugar cane seedlings were grown in soil fertilized with increasing doses of P, and the leaf P content was measured by pXRF and by induced coupled plasma optical emission spectrometry (ICP OES). This investigation included examination of the X-ray tube operational condition, analysis under vacuum or air, assessment of the number of spots measured per leaf, determination of the acquisition time per spot, and the best quantitative strategy for determining the P content in leaves. Using three points per leaf, an acquisition time of 60 s per point, a voltage of 40 kV, a current of 30 μA, analysis under vacuum, and an external calibration curve considering the densities of standards and leaves, we found a high correlation between the P content in sugar cane leaves by pXRF and ICP OES. A cross-calibration curve can be equally useful.