Analysis of trace lead in TiO₂ powders used in cosmetics

Due to the hazards of trace heavy metals on the environment, many regulations have been established to lower the limits of these components drastically from previous acceptable levels in various products.

X-ray fluorescence analysis is widely used in process control, quality control and other fields because it can perform qualitative and quantitative analyses quickly and non-destructively. Advances in fundamental parameter methods and the use of the SQX analysis programs to calculate semi-quantitative values from qualitative analysis results without the need for standards are becoming more prevalent.

As an example consider the determination of trace Pb in TiO₂ powder, a pigment widely used in cosmetics to obtain a desired color. Three different cosmetic samples were pressed at 20 tons of pressure using an Al ring to form a pellet and run on the Rigaku ZSX Primus II XRF spectrometer. The measurements conditions are listed in table 1. 

A scan of the Pb-Lα1 line was performed using a Cu primary beam filter to enhance the Pb signal relative to background. The scan is shown in figure 1.

Figure 1

Table 2 shows the full SQX analysis for the three samples. It is clear from the results that trace analysis of Pb in this material is obtained quickly and easily without the need for standards.

Table 2: SQX results

Tags: XRF, Primus, WDXRF, standardless, failure, analysis