Determination of Rare Earth Elements in Synthetic Calcium Phosphates Using Continuum Source Electrothermal Atomic Absorption Spectrometry

Hydroxyapatites (HA) and tricalcium phosphates (TCP) (analogs of the mineral component of bone tissue in phase and dynamic composition) serve as the basis for the creation of ceramic, cement, and composite biomaterials. Since the crystallographic structures of HA and TCP are prone to isomorphous substitution, their modification with ions of various metals including rare earth elements (REEs) to obtain materials with the properties required for medical use is a relevant field of research. To obtain the specified properties, it is necessary to control not only the structure, but also the chemical elemental composition of the material. The analytical capabilities of the continuum source electrothermal atomic absorption spectrometry (CS-ETAAS) are studied in relation to the determination of europium and ytterbium in hydroxyapatites and tricalcium phosphates including the choice of conditions and modes of analysis (temperature–time program, use of modifiers, plotting of a calibration dependence, etc.) to obtain accurate results. It is found that the use of magnesium nitrite and EDTA as matrix modifiers makes it possible to increase the absorption of analytes by almost 1.5 times and by 10–30%, respectively. The possibility of simultaneous determination of Eu and Yb in the range of contents from 0.09 to 2 wt % with a relative standard deviation of no more than 6 rel % is demonstrated. The trueness of the determination of europium and ytterbium in HA and TCP samples doped with each or both REEs is confirmed by varying the sample weight and comparing with the results of the ICP-AES reference method.