A rapid and multi-element method for the analysis of major nutrients in grass (Lolium perenne) using energy-dispersive X-ray fluorescence spectroscopy

Abstract

Elemental analysis of grass (Lolium perenne) is essential in agriculture to ensure grass quality and animal health. Energy-dispersive X-ray fluorescence (EDXRF) spectroscopy is a rapid, multi-element alternative to current methods using acid digestion and inductively coupled plasma optical emission spectrometry (ICP-OES). Percentage phosphorus (P), potassium (K), magnesium (Mg) and calcium (Ca), determined from grass samples using EDXRF, were within 0.035, 0.319, 0.025 and 0.061, respectively, of ICP-OES values. Concordance correlation coefficients computed using agreement statistics ranged from 0.4379 to 0.9669 (values close to one indicate excellent agreement); however, the level of agreement for each element depended on the calibrations used in EDXRF. Empirical calibrations gave excellent agreement for percentage P, K and Ca, but moderate agreement for percentage Mg due to a weaker correlation between standards and intensities. Standardless calibration using the fundamental parameters (FP) approach exhibited bias, with consistently lower values reported for percentage P and Mg, when compared with ICP-OES methods. The relationship between the methods was plotted as scatter plots with the line of equality included, and although correlation coefficients indicated strong relationships, these statistics masked the effects of consistent bias in the data for percentage P and Mg. These results highlight the importance of distinguishing agreement from correlation when using statistical methods to compare methods of analysis. Agreement estimates improved when a matching library of grass samples was added to the FP method. EDXRF is a comparable alternative to conventional methods for grass analysis when samples of similar matrix type are used as empirical standards or as a matching library.

Energy‐dispersive X‐ray fluorescence spectrometry as a tool for the rapid determination of the five major minerals (Na, Mg, K, P and Ca) in skim milk powder

“…These matching libraries are used to alter the calibration of the method and account for matrix effects and can significantly improve the accuracy of results (Daly and Fenelon ). A third calibration option, known as the empirical method (EM), involves the establishment of an empirical ‘calibration curve’ using samples of a similar matrix whose elemental composition span an extensive range of values (Daly and Fenelon ).…”

The importance of nutrient hotspots for grazing ungulates in a Miombo ecosystem, Tanzania

“…Samples were air dried [43,44] and transported to the Core Facility Centre, Hohenheim University, Germany. Soil samples were ground using mortar and pestle, while grass samples were ground using Fritsch'smill with a sieving ring of 0.5 mm, digested under a microwave ultra clave [45] and introduced into ICP-OES (Vista Pro) [46][47][48] to determine total N and P contents. We analyzed a total of 101 grass and 24 soil composite samples from 332 samples in total from 122 plots ( Table 1).…”

Application of Energy Dispersive X-ray Fluorescence Spectrometry to the Determination of Copper, Manganese, Zinc, and Sulfur in Grass (Lolium perenne) in Grazed Agricultural Systems

“…For environmental samples, this approach often improves the accuracy of concentrations determined by EDXRF given the complex matrix and sample heterogeneity. 11–13…”

“…Energy dispersive X-ray fluorescence is a spectroscopic technique used to determine total elemental concentrations in a range of material types (solids, powders, liquids, and gels) with the ability to capture elements from 11 Na to 92 U. 5,6 In this technique, X-ray radiation excites the inner orbital electrons within the sample and a fluorescent energy is emitted when these electrons relax to the ground state, resulting in measurable intensities and spectral lines specific to each element present in the sample.…”

“…For environmental samples, this approach often improves the accuracy of concentrations determined by EDXRF given the complex matrix and sample heterogeneity. [11][12][13] The empirical approach to calibrating spectroscopic intensities with sample concentrations requires a set of empirical standards derived from a similar sample and matrix type with a range of known concentrations. This provides an advantage over theoretical calibrations, which cannot account for matrix effects in heterogeneous samples such as soils, plants, and crops.…”