Scientists have discovered a simple method to extract gold from old mobile phones.

The research team believes the new technique could help safely salvage hundreds of tonnes of the precious metal from electronic scrap.

Electrical waste, such as old mobile phones, televisions and computers, is thought to contain as much as seven per cent of all the world's gold, which is used in circuit boards.

Current ways of extracting gold from unused gadgets often use toxic chemicals such as cyanide but scientists have now developed a simple extraction method using a non-toxic chemical compound, which they claim yields more efficient results.

The technique involves submerging printed circuit boards in a mild acid to dissolve the metal parts, before adding an oily liquid containing the team's chemical compound.

The compound isolates gold from the complex mixture of other metals, enabling extraction.

Study leader Professor Jason Love, of Edinburgh University, said: "We are very excited about this discovery, especially as we have shown that our fundamental chemical studies on the recovery of valuable metals from electronic waste could have potential economic and societal benefits."

The research team believes their discovery could help salvage some of the estimated 300 tonnes of gold used in electronics each year.

The study, published in the journal Angewandte Chemie, was funded by the Engineering and Physical Sciences Research Council.