Chemical molecules have an orientation in space: they can be directed to the left or the right, taking on two opposite forms from one another. In the majority of cases these two forms are both present and, often, have different chemical and physical forms. The different orientation is very important in pharmacology, because at times only one of the two forms (left or right) is active, from a biological point of view. In several cases, in fact, one of the two is toxic. This very rare occurrence was the case, for example, with thalidomide, an anti-nausea drug administered in the 1960s to pregnant women, which caused thousands of cases of deformations in new-borns, because it was unknown that only one of the two chemical forms was effective against nausea (the right one), whereas the other had a potent anti-angiogenetic effect (i.e. one that inhibited the formation of blood veins), causing very serious damage in growing foetuses. This also happened because the rules on the experiments, at that time, compared to current rules, were very lenient and not well defined.

In any case, separating the two chemical forms, left and right, (in technical terms: the two enantiomers) has always been a complicated and costly process that is to be applied to each molecule. This process has not always been followed, despite the recommendations of the American Food and Drug Administration (FDA) and other supervisory authorities, which have requested the proposal of only one of the two forms, the left or the right, for some time. However, this problem also presents itself in other sectors, beyond the field of pharmaceuticals: for example, in the agrochemical sector, where it is very difficult to separate molecules, even if it is known that only one of the two forms of a substance, for example, acts against weeds or insects.

Now, however, two groups of Israeli researchers, one from the Weizmann Institute of Science in Rehovot, and one from the Jewish University of Jerusalem, have developed a technique that could considerably make things easier, starting with a known physical property: each enantiomer interacts with a different magnetic pole. The method, described in the journal Science, enables the two forms to be separated based on this property in an cheap, simple and universal way, because it can be applied to any substance.