Although there are currently a number of published extraction techniques in place, this new method focuses on removing the lipophilic musks from other lipophilic components present in cosmetic creams, like paraffin, stearic acid and long-chain alcohols.
To date, most regulatory bodies have either banned or limited the cosmetic content of a key group of seven musks, so analytical methods are already in place to allow for safety testing.
However, various environmental groups are still concerned that musks can induce conditions like dermatitis, endocrine disorders and cancer.
In this instance, researchers at the Beijing University of Technology and the National Institute of Metrology focused in on musk amberette, xylene, moskene, tibetene, ketone, phantolide and musk tonalide.
The process was subsequently applied to 4 baby creams and 24 adult cosmetic creams.
SLE and SPE
SLE is a common technique that eliminates the need for conditioning and washing steps and is easy to automate. It takes place in a cartridge, like SPE, and the conventional "support" is a filler of diatomaceous earth.
In this case, samples of commercial cosmetics were spiked with the seven synthetic musks before being vigorously mixed with an aqueous solution of isopropanol.
The resulting upper layer was added to the SLE cartridge and left for a few minutes to seep into the filler. The water in the extractant solution was absorbed into the diatomaceous earth, along with some of the hydrophilic and lipophilic components.
However, this process is not perfect, so the second step of SPE is required to improve the purification.
The SLE cartridge was positioned above an alumina SPE cartridge and dichloromethane was used to elute the musks and trap any remaining lipophilic compounds in the SPE column. The final step involved transfer to isooctane for the GC/MS analysis. With the optimum extraction conditions, all seven musks were extracted with recoveries higher than 86%.
Safe cosmetics
Although the combined SLE-SPE process removes many of the components of the creams which could cause interferences during mass spectrometry, it did not remove them all.
So, the researchers added isotope-labelled internal standards which were added to the creams before extraction began to overcome any interferences.
Musk tibetene was detected in one adult cream but it was at a very low level, below the limit of quantitation.
The remaining six synthetic musks, consisting of the two banned compounds and four restricted ones, were all present in some of the creams, with tonalide and musk ketone found in all the adult cosmetics tested.
None of the three banned musks, musk amberette, musk moskene and musk tibetene, were found in the baby products.
The scientists conclude that all of their levels were below the maximum residue levels set by the authorities.