Читать книгу X-Ray Fluorescence in Biological Sciences - Группа авторов - Страница 19

ICP‐AES is an analytical technique that allows researchers to ascertain the quantitative bulk elemental composition of samples in solid, liquid, powder, and suspension forms [3, 4]. In this method, samples are digested using a mixture of acids in a closed microwave system and retains potentially volatile analyte species. The prepared solution is then nebulized into the core of IC argon plasma, and a temperature of nearly 9000 K is established. At this high temperature, the nebulized solution is vaporized and the analyte species are atomized, ionized, and thermally excited. After that, the analyte species are detected using an optical emission spectrometer. The AES spectrometer measures the intensity of radiation emitted by the specific element present in the sample which is proportional to the concentration of that element. Finally, the concentrations of the elements are determined using the standard calibration curve method, which is mostly used in cases where standards are unavailable.

The ICP‐AES method is also used to determine the content of metals in wines and alcoholic beverages, heavy metals such as arsenic (As) in food stuffs, and trace elements in complex biomolecules such as proteins. It is capable to determine traces of oil additives which further indicate the service life left for the motor oil. It is capable to detect Li (Z = 3) to U (Z = 92) except gases, halogens, low contents of P and S. However in XRF, P and S can be easily determined and quantified. The combined use of ICP‐AES and ICP‐MS is very powerful and gives highly accurate and precise results for a broad range of elements from the major (percentage, %) to trace levels (typically sub ppb) [3].

The disadvantage of this technique is that the emission spectra are complex and subject to spectral interferences for some elements. Matrix effects also create many challenges to quantifying the elements of interest. Some of the lither elements such as C, H, N, O, and halogens cannot be determined using this technique. Some elements cannot be detected by ICPs but often are subject to be analyzed exclusively by XRF such as S, Br, and Cl.

In case of the limits of quantification equal to or above 1 ppm (μg/g), or where non‐destructive analysis is required, XRF is the most popular and attractive technique to analyze the solid samples, powders, oils, and slurry samples. As opposed to ICP‐AES, ICP‐MS, and AAS, it does not require sample dissolution or digestion and allows essentially non‐destructive analysis. In that case, XRF ensures accurate and reliable results by avoiding the potential for inaccuracies caused by incomplete dissolution and large dilutions.