Characterization of hyperbolic calibration curves for continuum source atomic absorption spectrometry with array detection

Abstract

The suitability of a hyperbolic calibration curve for continuum source atomic absorption spectrometry (CS-AAS) using electrothermal atomization and array detection was critically examined for Ag (328.1 nm), Cd (228.8 nm) and Pb (283.3 nm). For each element, 20-25 calibration standards were used to cover six orders of magnitude of concentration. The same hyperbolic shape, with appropriate offsets of the X and Y  axes, was found to be suitable for fitting each series of standards. The inflection point of the hyperbolic calibration curve, and hence the X and Y  offsets, were dependent on the element and atomization temperature. These shifts arose from fundamental differences in the shape of the absorbance profile due to the ratio of Doppler and collisional broadening. As few as two standards (one above and one below the inflection point) were used to construct calibration curves covering six orders of magnitude of concentration. The use of four standards (two above and two below the inflection point) reduced the recalibration precision by a factor of two and, in general, introduced less uncertainty into the quantification of an unknown than the absorbance noise associated with the analytical measurement.