Application of experimental design for optimization of erbium determination by high-resolution continuum source electrothermal atomic absorption spectrometry using lanthanum as a chemical modifier

ABSTRACT

In this paper, lanthanum was used as a chemical modifier for the direct determination of erbium by high-resolution continuum source electrothermal atomic absorption spectrometry. A two-step experimental design was used for optimization, first a full factorial design was conducted for identification of significant factors, and then a central composite design was carried out for final optimization of the significant factors. The optimum parameters were obtained as follows: atomization temperature of 2500°C, pyrolysis temperature of 1600°C, and pyrolysis time of 10 s in the presence of lanthanum as a chemical modifier. Under optimum conditions, the characteristic mass, limit of detection, and limit of quantification were 29 pg, 0.71, and 2.4 µg L⁻¹, respectively. The precision of the method, estimated as the relative standard deviation for 10 replicate measurements of 50 µg L⁻¹ of erbium, was 1.8%. The optimized method was applied to determine erbium content in sediments and rock samples. The determined values of erbium in sediment certified reference materials were in satisfactory agreement with the certified values according to the t-test for a 95% confidence level.

KEYWORDS:

• Chemical modifier
• electrothermal atomization
• erbium
• experimental design
• high-resolution continuum source atomic absorption spectrometry