Ion microprobe determination of ex vivo trace element molarities: The LINAEUS code suite †

Abstract

MeV-ion based analytical methods such as Particle induced X-ray Emission (PIXE) using a MeV ion microprobe in conjunction with analysis codes such as GeoPIXE represent powerful methods for analysis of trace elements in biomedical samples. In order to make the method truly quantitative for thin biological samples, knowledge of the local composition and thickness is required. Here the development and application of the LINAEUS code package, a complementary companion code to GeoPIXE code is described. This provides regional major element (C, H, N and O) composition and thickness data from Elastic Backscattering Spectrometry (EBS) and Off-Axis Scanning Transmission Ion Microscopy (OA-STIM) measurements. The program suite employs the same Dynamic Analysis method as used in GeoPIXE. LINAEUS incorporates a tissue region detection procedure based on spatial correlation to mitigate bias due to void regions without tissue corresponding to blood vessels etc. The results for healthy murine small-intestine tissue showed no differences in the C, H, N and O contents but did show differences in thickness that were attributed to morphological distortion during drying of the tissue section. The molarity of trace elements (S, Cl, K, Ca and Fe) exhibited differences between tissue regions. Ca "hot-spots" (10-30 µm regions with much enhanced Ca levels) reported in other simian tissue samples were observed. These could not be attributed to mineralisation and their origin remains unclear.