Protocol for production of matrix-matched brain tissue standards for imaging by laser ablation-inductively coupled plasma-mass spectrometry

Calibration with matrix-matched standards remains the most practical means for producing quantitative images of trace metal distribution in tissue sections by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). A general guide for producing matrix-matched standards for assay of trace metals in brain tissue is presented. Cortical tissue was taken from pooled sheep brains and spiked with varying approximate concentrations of standard solutions of Co, Cu, Fe, Mg, Mn, Sr, Se and Zn. The tissue was homogenised and the total analyte amount accurately determined by solution nebulisation ICP-MS. The analytical figures of merit for LA-ICP-MS imaging were determined from these tissue standards cryosectioned at 30 mu m. Repeated 8-point calibration curves were reproducibly linear, with correlation coefficients ranging from 0.9874 (Mg) to 0.9991 (Sr). Limits of analysis were suitable for quantifying most analytes in a sample mouse brain, with the exception of Co and Se.