Abstract

Laser ablation combined with inductively coupled plasma mass spectrometry has been applied to the spatially resolved determination of mercury concentrations in human teeth. In addition, the concentrations of silver and copper, which are also major components in dental amalgam, have been determined for comparison purposes. The fundamental wavelength of 1064 nm of an Nd∶YAG laser was used for the analysis. Crater diameters down to 1 × 10⁻⁴ cm were obtained at a pulse energy of 5 × 10⁻² J and at a pulse number of 200 (10 Hz). The ablated sample mass was 2 × 10⁻⁴ g. Sample preparation was simple as only ultrasonic purification of the surface in sub-boiling distilled water was necessary. The isotopes ²⁰⁰Hg, ²⁰¹Hg, ²⁰²Hg, ¹⁰⁷Ag, ¹⁰⁹Ag, ⁶³Cu and ⁶⁵Cu were used for the measurements. ⁴⁴Ca was chosen for internal standardization. The calibration samples were prepared with CaSO₄ powder, which was doped with standard solutions, dried and pressed to pellets. Because the matrix material of the calibration standards differs from the matrix material of the samples a correction of the calibration constant of mercury has to be taken into account. To verify the analytical method mercury was determined in a sample using both solution ICP-MS and laser ablation-ICP-MS. The following relative standard deviations were obtained: for mercury between 4 and 10% depending on the concentration range, for silver and copper 5 and 4%, respectively. Detection limits of 6 × 10⁻⁶ g g⁻¹ for mercury, 7 × 10⁻⁶ g g⁻¹ for silver and 6 × 10⁻⁶ g g⁻¹ for copper were determined. A diffusion coefficient of 2.7 × 10⁻¹⁰ s⁻¹ cm⁻² was obtained for mercury. The values obtained for silver and copper were 2.0 × 10⁻¹¹ s⁻¹ cm⁻² and 1.9 × 10⁻¹¹ s⁻¹ cm⁻², respectively.