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Quantitation of metals in vegetal material by X-ray fluorescence spectrometry (XFS) (CAT#: STEM-ST-0187-WXH)

Introduction

Because of their capacity to act as efficient interceptors and accumulators of chemicals, vegetal species are widely employed as passive monitors in areas contaminated by heavy metals. However, plants are extensively used in food, beverages, medicinal preparations and recreational products (e.g., tobacco) and the concentration of some elements is one of the criteria that make raw plants admissible for human consumption. There has therefore been increasing need for suitable analytical tools to determine the chemical composition of vegetal matrices.




Principle

XRF describes the process where some high-energy radiation excites atoms by shooting out electrons from the innermost orbitals. When the atom relaxes, that is, when outer electrons fill inner shells, X-Ray fluorescence radiation is emitted.

Applications

XRF is widely used as a fast characterization tool in many analytical labs across the world, for applications as diverse as metallurgy, forensics, polymers, electronics, archaeology, environmental analysis, geology and mining.

Procedure

1. Primary X-rays knock out an electron from one of the orbitals surrounding the nucleus within an atom of the material.
2. A hole is produced in the orbital, resulting in a high energy, unstable configuration for the atom.
3. To restore equilibrium, an electron from a higher energy, outer orbital falls into the hole. Since this is a lower energy position, the excess energy is emitted in the form of fluorescent X-rays.
The energy difference between the expelled and replacement electrons is characteristic of the element atom in which the fluorescence process is occurring – thus, the energy of the emitted fluorescent X-ray is directly linked to a specific element being analyzed.

Materials

XRF spectrometer (including X-ray source, sample chamber, analysing crystal, detector and signal processing computer)