Beauty and the beast: Simple test detects cosmetic genotoxin

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  • Published: Aug 1, 2016
  • Author: Ryan De Vooght-Johnson
  • Channels: Gas Chromatography
thumbnail image: Beauty and the beast: Simple test detects cosmetic genotoxin

Eternal beauty

Amongst the plethora of beauty products lurks a supposedly genotoxic beast. Spurred on by the lack of suitable detection tests, researchers from the Malaysian Palm Oil Board, the National University of Malaysia and the University of Malaysia collaborated to plug the void.

The Philosopher’s stone was highly sought after. Legend boasts of its ability to transmute common metals into gold. Others believed it to be the Elixir of Life – the potion of rejuvenation and the embodiment of eternal immortality. In pursuit of this mercurial and supposedly red compound, in the past Alchemists toiled away by candle light, tinkering with their master formula, concocting chemicals here and there, but their pursuits were never fruitful.

Fast forward to the twenty-first century. Whilst immortality still remains elusive, lead can be transmuted into gold, and cosmetics can, they claim, combat the wears and tears of modern life. These modern-day cosmetics, just like folklore predicted, are blends of a vast array of chemicals. However, unlike in Renaissance times, these blended chemicals are meticulously researched and highly regulated.

Take isopropyl palmitate (IPP) and isopropyl myristate (IPM), for example. Known to enhance the permeability of skin, they are added to a range of creams, lotions, moisturisers, sticks, balms and oils. These perfectly complement the delivery of active, beautifying chemicals across the otherwise unbreachable dermis, but amongst all this beauty there lurks a beast: isopropyl p-toluenesfulfonate – or IPTS.

Tribulations and regulations

Formed during the synthesis of IPP and IP, IPTS is a by-product of the esterification of palmitic and myristic acids – two components of palm oil. Recently, it has kicked up somewhat of a storm. ‘IPTS,’ Tay and his colleagues reported to the International Journal of Cosmetic Science, ‘…has been demonstrated to exhibit genotoxic activity.’ If these findings are proven to be true, IPTS could effectively piggyback across our dermal defences on the shoulders of IPP and IPM, amplifying its toxicity.

Whilst the International Cooperation on Cosmetics Regulations ponders their next steps and potential regulation, scientists based in Malaysia were quick to react to more generic guidelines. The European Medicines Agency (EMEA) and the US Food and Drug Administration (FDA), for example, have proposed a ‘threshold of toxicological concern’ covering all genotoxins, advising exposure to less than 1.5 μg per day. So far ‘no method,’ the authors explain, ‘has been reported for the analysis of IPTS in cosmetic products.’

Galvanised by necessity, the authors set out to devise a straightforward method capable of determining the presence of IPTS in cosmetic and personal-care products. They settled on two complementary approaches: the first, HPLC coupled to a quantitative diode array detector (DAD); and the second, a GC-MS assay used for structure confirmation.

Plugging the void

Keeping to their promise of straightforward testing, the authors designed a quick, three-step sample preparation involving extraction with acetonitrile and ultrasonication, followed by filtration through a membrane. Next, components were loaded onto a C8 column, from which IPTS was eluted isocratically and detected at 230 nm with a DAD.

This HPLC-DAD method demonstrated strong linearity in its response to spiked cosmetic samples, being able detect down to 0.5 μg and quantitate upwards of 1.6 μg of IPTS per 1 mL of cosmetic product. What’s more, determination of 25–750 μg of IPTS fortified into 1 g of lotions, creams and cleansing milks was achieved with 94.0–101.1% accuracy. The precision in determining samples of 1–30 μg/mL IPTS was less than 2% RSD over the course of one day, and below 5% over four days.

The authors originally toiled with a quantitative GC-MS method, but eventually yielded to the insurmountable matrix influences of cosmetic products. This misfortune, however, turned serendipitous, particularly in in the absence of suitable tools to verify their findings. They therefore used their GC-MS assay to scan for the IBPTS ion theorised from a mass spectral library and found an ion eluted at 15.2 minutes with a molecular weight identical to that of IPTS.

Having devised, for the first time, an assay capable of quantitating IPTS in cosmetics, as well as a complementary confirmation tool, the scientists analysed off-the-shelf products. ‘Monitoring of 83 types of commercially available cosmetics containing either IPP or IPM,’ the study writes, ‘showed that no ITPS was present’.

Related Links

International Journal of Cosmetic Science. 2016, Early View paper. Tay et al. Determination and confirmation of isopropyl p-toluenesulfonate in cosmetics by HPLC-diode array detector method and GC–MS.

Article by Ryan De Vooght-Johnson

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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