Speciation and Determination of Ionic and Trace-Level Colloidal Silver in Selected Personal Care Products by Thermal Lens Spectrometry

The collinear dual beam thermal lens spectrometric (TLS) detection in batch mode (BM), as well as combined with the flow injection analysis (FIA), was applied to determine the colloidal silver in personal care products available in the public pharmacies and declared by producers to contain nanosilver at the level of 5-30 μg ml-1. It was found, that the examined samples contain mainly ionic silver (99% or more), whereas the colloidal form of silver is at the level of less than 1 μg ml-1. The TLS methods were confirmed to be fast, precise, highly accurate and highly sensitive with limits of quantitation of 0.30 ng ml-1 and 1.50 ng ml-1 and relative standard deviations not higher than 1.2% and 6.0% for BM- and FIA-TLS configuration, respectively. The developed TLS methods have nearly 60 times lower LOQ values concerning the colloidal silver determination than the classical spectrophotometric method. To verify the obtained results of the real sample analysis the total amount of ionic silver was determined by the use of ICP-OES technique.