Written by Iacopo Avolio, Application Specialist | 5 March 2024

Direct mercury analysis in cosmetics sample in compliance with ISO 23674

Direct Hg analysis in cosmetics sample in compliance with ISO 23674 using Milestone DMA-80 evo

INTRODUCTION

Mercury and harmful substances have been found in cosmetics, often without proper labelling. Some creams claim to remove blemishes and lighten the skin using mercury's low cost and preservative properties. Because of these properties, mercury in its toxic form, methylmercury, can be added later to already manufactured products.
Despite its uses in cosmetic applications, mercury is highly toxic for human health, even at low concentration. Long-term exposure can cause damage to the kidneys, liver and nervous system, leading to personality changes and loss of vision.
Due to its high toxicity, FDA and other regulatory bodies banned mercury in cosmetics products.
The International Organisation for Standardisation (ISO) has developed a method for detecting trace amounts of mercury in cosmetic. This method involves the direct analysis of cosmetic samples without the need for sample preparation. It allows the direct quantification of the total amount mercury in both solid and liquid cosmetic samples. This has led to the introduction of ISO 23674, which focuses on direct mercury analysis techniques. In this application report we demonstrate how Milestone DMA-80 evo responds to the requirements of the ISO 23674.

EXPERIMENTAL

Milestone's DMA-80 evo Direct Mercury Analyzer is the instrument used to perform the analysis, with the configuration Tricell Double-Beam, that is in fully compliance with ISO 23674 requirements.
Liquid calibration standards can be prepared by using a commercially available solution of 1000 mg/L Hg, which is preserved in 5% HNO3. Working standards from 1 to 1000 ppb were prepared and preserved in 2% HCl, then stored in amber glass vials. Calibration curves were created by injecting increasing volumes of standards (from 1ppb to 1000ppb) directly into the quartz sample boats, thus covering the range of 0-500 ng of mercury. As the technique is matrix independent, calibration standards can be either liquid or solid.

RESULTS AND DISCUSSION

ANALYTICAL PROCEDURE
This application report validates DMA 80-evo's compliance with ISO 23674 through a recovery study. Samples were homogenized and introduced into quartz boats for analysis using the DMA-80. The focus is on testing the ISO 23674 method at lower concentrations to achieve a relative standard deviation within the range specified by the International Standards Organization.
Samples are thermally decomposed in the oxygen/air flow of the instrument at temperatures between 650 °C to 900 °C. Combustion gases pass through a catalyst tube set at ~615 °C. The result of this step is the conversion of all mercury in its atomic form (Hg0), while interferences are flushed out. Mercury atomic vapours are then enriched on a gold amalgamator and thermically released at 800°-900°C. Finally, the atomic vapours pass through a UV measuring cuvette system at the wavelength of 253.7 nm. The whole process.

TESTS AND RESULTS
Foundation, Body Lotion and Shampoo samples underwent analysis in our internal lab, using the ISO 23674 method and adding 0.1mL of a 100ppb (10ng Hg) standard as a recovery control spike. At first, these samples were analysed to measure the mercury content in the commercial products.

ISO enabled to validate the analytical methodology described in this standard for the ranges 0.15 mg/kg (ppm) to 1 mg/kg (ppm) (second ring test) and 0.5 mg/kg (ppm) to 2.5 mg/kg (ppm) (first ring test) with an acceptance limit of ±30 %. Our study highlighted how it’s possible to achieve even better results on cosmetics samples, respectively with an RSD% of 2.18%, 0.16% and 1.02% on spiked samples, adhering to ISO requirements and using the method detailed in the standard.

CONCLUSION

The results shown in Table 3 indicate that direct mercury analysis is an effective technique for the determination of mercury in cosmetics and similar products. Additionally, the results demonstrate the DMA-80 evo's capability to analyse samples with exceptionally low levels of mercury while maintaining superior precision. Our experiments yielded RSD% safely adhere to the ISO standard boundary of a maximum of 20% RSD%. These findings increase our confidence in the instrument's accuracy and precision. The DMA-80 evo doesn't require sample preparation, resulting in lower detection levels than traditional techniques. This further emphasize its proficiency when dealing with cosmetic samples, notoriously of varying forms.

DMA-80 evo

Direct Mercury Analyzer

The DMA-80 mercury determination system can analyze any matrix (solid, liquid or gas) without any pre-treatment or chemical additions in as few as 6 minutes in full compliance with EPA method 7473.

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