Solid sampling analysis of a Mg alloy using electrothermal vaporization inductively coupled plasma optical emission spectrometry

Abstract

Electrothermal vaporization hyphenated with inductively coupled plasma optical emission spectrometry (ETV-ICPOES) was applied to the analysis of the AZ31 Mg alloy in an attempt to quantify Al, Cu, Mn, Ni and Zn. Small pieces of the alloy were simply placed in graphite boats for automated insertion into the ETV graphite furnace. The optimized ETV conditions included a carrier gas flow rate of 0.15 L min⁻¹ and an argon by-pass flow rate of 0.50 L min⁻¹, along with 8 mL min⁻¹ Freon 23 (CHF₃, trifluoromethane) as the reaction gas. The heating program included pyrolysis (400 °C for 20 s), cooling (20 °C for 15 s), atomization (2200 °C for 30 s) and cooling (20 °C for 20 s) steps. The peak area of each transient signal was integrated (over 50 s) after point-by-point internal standardization with Ar emission (at 415.859 nm) to compensate for loading effects. To build calibration curves, 1 to 6 mg of certified reference material NIST 1648a (Urban Particulate Matter) was weighed into graphite boats. The limits of quantification based on 10 times the standard deviation of the blank (using empty graphite boats and based on 3 mg sample) ranged from 0.2 mg kg⁻¹ (Cu) to 400 mg kg⁻¹ (Ca). The analytes' concentrations obtained were in reasonable agreement with both the reported values and those found after digestion by ICPOES or ICP mass spectrometry. Hence, ETV-ICPOES shows great potential for fast screening of minor and trace elements in Mg alloys.