Discrimination between ionic silver and silver nanoparticles in consumer products using graphite furnace atomic absorption spectrometry

In this work, a rapid method for discrimination between trace amounts of ionic silver and silver nanoparticles (AgNPs) using graphite furnace atomic absorption spectrometry (GFAAS) was developed. Systematic studies of the influence of stabilizing agents (Triton X-100, Tween 80, sodium dodecyl sulfate, tetrabutylammonium hydroxide (TBAH), tetramethylammonium hydroxide (TMAH), gelatine, and sodium citrate) on the determination of Ag+ and AgNPs of diameter 10–100 nm were undertaken. Careful optimization of atomization conditions (wall or platform atomization, heating rate, atomization temperature) was also completed. The atomization delay time (tad) was used to compare the atomization profiles of different silver species. The best resolution of signals was obtained for silver atomization from the graphite platform at 975 °C using 2 × 10−3 mol L−1 of sodium citrate as a stabilizer. The linear relationship between tad and AgNP size was applied to estimate NP diameter. The within-day repeatability of the method was 1.1–2.3% for 2.5 μg L−1 of AgNPs. The accuracy of the method was shown by the analysis of the reference material of AgNPs (RM 8017). To evaluate the utility of the proposed method for simultaneous qualitative and quantitative determination of silver forms, the analysis of model mixtures containing Ag+ and AgNPs of different sizes was done. The benefits and restrictions of the developed method are discussed in this context. Finally, the method was used for assessment of silver migration from fabrics and hygiene products.