Chromatography Finds Viagra in Dietary Supplements

The market in the UK for supplements and vitamins is growing year-on-year with sales of over £400 million — and it is estimated that around half of us take some form of supplement every day. But can we always be sure that we are taking has not been adulterated?

Regulating supplements in the EU

In the UK and Europe, food supplements are regulated by an EU directive which says what a supplement is — or is not. Directive 20023/46/EU says food supplements:

‘means foodstuffs the purpose of which is to supplement the normal diet and which are concentrated sources of nutrients or other substances with a nutritional or physiological effect, alone or in combination, marketed in dose form, namely forms such as capsules, pastilles, tablets, pills and other similar forms, sachets of powder, ampoules of liquids, drop dispensing bottles, and other similar forms of liquids and powders designed to be taken in measured small unit quantities’

But any online search turns up numerous news stories of supplements being adulterated — including some by pharmaceutical medicines. The use of additional medicines can make supplements work faster or better — for example, a diuretic added to a weight loss supplement could help reduce water retention and thus help in the illusion of weight loss.

No hiding the viagra

Viagra — or to use its proper name, sildenafil — has been turning up in supplements for years. One reason is the addition of sildenafil to products that claim to boost sexual performance — something Viagra was has been doing for years. But adding adulterants to supplements is extremely risky.

Consequently, chemists are always searching for new or improved analytical techniques to identify adulterants in supplements. A recent paper in the Journal of Separation Science reports on a new method that has been developed by Korean scientists to determine Viagra and its analogues in dietary supplements.

A simpler method of detection

There are already analytical methods to determine Viagra in supplements involving liquid chromatography and mass spectrometry — LC-MS. But the Korean scientists wanted to find a method using liquid chromatography and UV detectors. UV detectors are less sensitive than MS, but they can be used with many more mobile phases and are much easier to use and are available to more chemists — thus increasing the potential power of the method.

But since UV is less sensitive than MS, the team needed to ensure that they could extract all the Viagra from the sample. They developed a method using solid phase extraction, a technique discussed in the article, PAL SPME Arrow: An Evolutionary Step Forward for Solid-phase Microextraction (SPME).

The method the team developed has been shown to be very sensitive, capable of determining Viagra at nanogram levels like the more sophisticated LC-MS methods. The extraction processes they developed can recover between 76% - 114% of the Viagra in doped samples.

Be careful what you take and where you buy it.