Overview
This MethodsX paper describes preparation of low-cost homemade thin standards for calibrating an energy-dispersive X-ray fluorescence (EDXRF) portable system, proposed as an undergraduate or postgraduate laboratory activity. The calibration procedure is then demonstrated by measuring elemental concentrations in commercial lipstick samples. The paper is primarily a methodology and educational protocol; it provides indicative detection limits and calibration performance data, but does not report systematic concentration data for a defined sample population. The lipstick measurements are illustrative and not suitable as occurrence evidence for population-level contamination profiling.
Key numbers
This source is classified evidence tier B because (a) the sample n is not stated, (b) the sampling design and market of origin are not described, and (c) the paper does not distinguish between above-LOD concentration values and LOD/LOQ bounds in reported lipstick results. The following data are from the methods-development work, not from a systematic occurrence study.
Calibration-derived detection limits in lipstick matrix (ppm)
The following indicative detection limits (IDL) for a portable EDXRF system applied to lipstick thin-film samples were reported:
| Element | IDL (ppm) |
|---|---|
| K | 600 |
| Ti | 150 |
| Cu | 150 |
| Fe | 100 |
| Zn | 100 |
| Br | 10 |
| Rb | 10 |
| lead (Pb) | 30 |
Calibration performance
Calibration standards prepared as thin films from water solutions of K, Fe, Cu, Br, tin (Sn), I, and lead (Pb) at several concentrations from 0.5 to 5 times 10 to the negative 3 mol/L. Commercial micromatter thin-film standards used for Cu, Ga, Br, Sb, and Pb verification. Sensitivity factors (SF) extracted from calibration curves.
Methods (brief)
System. Portable EDXRF system (make not specified in available text). Thin-sample geometry; sample self-absorption assumed negligible.
Standard preparation. Monoelemental solutions of compounds at 99% initial purity prepared as thin films deposited on membrane supports. Procedure proposed as a laboratory exercise.
Sample preparation. Lipstick samples prepared as thin films for EDXRF analysis; preparation details not fully described in available text.
Speciation. Total elemental X-ray fluorescence; no speciation of chromium, arsenic, or other elements capable of multiple oxidation states.
Limitations for occurrence profiling
This paper should not be used as evidence for lipstick metal concentrations without verification against a systematic occurrence study. The sample population is undefined, the n is unstated, and the lipstick results function as method demonstration rather than contamination characterization. It is included in this deposit because the deposit conduct selected it, but its contribution to the childrens-makeup product page is as broad methodological context only.
Implications
Courses. Useful as a teaching case for EDXRF calibration methodology, thin-sample geometry, and the trade-offs between portable XRF sensitivity and laboratory ICP-MS sensitivity for cosmetic matrices. The IDL table provides a useful calibration-performance benchmark.
Related evidence
Update history
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