Determination of strontium and its relation to other alkaline earth elements in human brain samples

Strontium content of five brain regions of five control and five Alzheimer's diseased (AD) patients and eight brain regions of three Hungarian control patients was determined. Microwave-assisted and high-pressure Parr-bomb digestions were used for sample dissolution. Strontium content of the digested samples was measured by ETAAS. The optimized parameters for digested human brain samples are: T_{pyrolysis, max}: 1500 °C, T_atomization: 2500 °C, 0.4% La(NO₃)₃ as a chemical modifier. The detection limit is 0.057 ng/ml and the characteristic mass is 1.0 pg. Calcium and magnesium content of the same digested samples were measured by ICP-OES. Accuracy of the applied methods was tested by analyzing NBS SRM1577 Bovine liver reference material, digested and measured with the samples together. Recovery measurements were done to eliminate the disturbing effect of the matrix. Strontium concentrations show great individual differences (20–450 ng/g, dry weight) independent of being either control or AD values, in contrast to the Mg (c_{control,Hungarian}: 590–675 μg/g, c_{control,German}: 620–675 μg/g, c_AD,German: 640–695 μg/g) and Ca (c_{control,Hungarian}: 270–390 μg/g, c_{control,German}: 310–400 μg/g, c_AD,German: 435–515 μg/g) concentrations.