SEM/EDX analysis of inorganic elements in human scalp hairs with special reference to the variation with different locations on the head.

In order to obtain additional data for individualizing hair samples collected from the scene of crime, the authors attempted to analyze the inorganic elements in scalp hairs such as sodium, phosphorus, potassium and calcium by a SEM/EDX method. For the purpose of detecting such elements from scalp hairs efficiently, the samples were ashed on a carbon specimen mount for 60 minutes by an oxygen plasma microincineration technique. The characteristic X-ray counts of the elements were investigated as functions of hair location, viz., the frontal, the vertex, the nape, the left and the right lateral, on the head of the same person. The oxygen plasma microincineration method was very efficient in detecting sodium, phosphorus, potassium and calcium from scalp hairs. The characteristic X-ray counts of the elements, especially potassium and calcium, varied from person to person. Within the same location, the variation of X-ray counts was relatively low, with a standard deviation of less than 20%. It was observed that hairs from the frontal and the vertex locations, in general, showed lower X-ray counts for potassium than did those from the nape, the left and the right lateral locations. The calcium X-ray counts varied considerably from person to person but generally tended to give the highest value at the vertex location. The EDX spectrum pattern associated with such elements could be helpful in individualizing hair samples collected as forensic evidence.