Exploratory investigations on the potential of radiofrequency glow discharge-optical emission spectrometry for the direct elemental analysis of bone

A radiofrequency glow discharge (rf-GD) coupled to optical emission spectrometry (OES) has been tested for the analysis of the elemental composition of bones. To achieve this goal, three sample preparation strategies were investigated: (i) utilization of a metallic holder for samples 1 mm thick; (ii) embedding the samples (0.5 or 1 mm thick) in a conducting resin; and (iii) encapsulation of thin layer (8-20 mum thick) bone samples in poly(methylmethacrylate) and final pasting over a flat support (copper and glass were studied as supports). From a medical point of view, this third approach can be considered as the more practical one since it requires a smaller amount of patients' bone and also this particular sample preparation follows an already well-established procedure for bone analysis in clinical laboratories. Optimisation of the discharge parameters, including rf delivered power, plasma pressure, anode orifice diameter and the effect of cooling the discharge, has been investigated for the analysis of bones for each of the three sample preparation methodologies. The spectral region from 190 to 600 nm was scanned and results showed that best analytical sensitivity is obtained using approach "iii" with samples pasted over a flat copper support. At the selected conditions of 6 Torr, 35 W of rf delivered power and 6 mm internal diameter of the anode orifice, intense emission lines for Ca, Na, Mg, P and C were observed for the thin layer bone.