Novel strategies for rapid trace element analysis of polyamide by graphite furnace atomic absorption spectrometry and inductively coupled plasma mass spectrometry. Dissolution in an organic solventversus direct solid sampling approaches.

Abstract

Titanium dioxide is added to polyamide since it efficiently scatters visible light and imparts whiteness, brightness and high opacity. TiO₂, however, can degrade easily and to counteract this, it is coated with a layer of inorganic material, containing Al, Mn and Si. For quality control, it is important to develop fast and reliable methods for the determination of these elements. Due to the fact that acid digestion techniques are labor-intensive, time-consuming and bring about the risk of contamination, an alternative dissolution procedure has been developed using formic acid to dissolve polyamide. The solutions thus obtained were measured by means of graphite furnace atomic absorption spectrometry (GFAAS) and inductively coupled plasma mass spectrometry (ICPMS). For the latter technique, sample introduction was performed using a pneumatic nebulization system, containing a membrane desolvating unit to remove the organic solvent. This approach provided satisfactory results in terms of precision (6–10% RSD) and limits of detection (0.1–0.6 μg g⁻¹, except for Si when using ICPMS). Addition of formic acid to the calibration standards was demonstrated to be required. To enhance the sensitivity, increase the sample throughput and reduce the risk of contamination and/or analyte losses, the direct solid sampling methods solid sampling GFAAS and electrothermal vaporization (ETV)-ICPMS were also evaluated. Both techniques provided accurate results using calibration versus aqueous standards, with RSD values of ∼10%. Limits of detection were improved considerably compared to those attainable after dissolution. In contrast to GFAAS, ETV-ICPMS allows the simultaneous determination of all of the analytes.