On New Year’s Eve, millions around the world sing, “Should auld acquaintance be forgot, and auld lang syne!” Scottish poet Robert Burns, who wrote those lyrics in his adaptation of a folk song, is so famous that his original letters or poems can fetch up to $100,000 in auction.
But some collections of his work are littered with forgeries. To help authenticate Burns’s manuscripts, researchers in Scotland have now developed a mass spectrometry technique that can spot the differences between the genuine documents and the fakes (Sci. Rep. 2018, DOI: 10.1038/s41598-018-28810-2). The method could offer a nondestructive means of testing the authenticity of other historical documents.
Burns lived in the latter half of the 18th century, writing poems in a Scottish dialect that appealed to national sentiment. People around the world still celebrate Scottish culture on his birthday, Jan. 25, with a “Burns supper” of haggis. (“Great chieftain o’ the puddin’-race!” wrote Burns of the dish.) As his popularity grew, though, forgers began to generate bogus manuscripts—the most notorious, Alexander Smith, was jailed in the 1890s for his efforts.
Karl Burgess, a mass spectrometry expert at the University of Glasgow, realized that a technique called direct infusion nanospray mass spectrometry, typically used in proteomics, could produce detailed chemical fingerprints of the manuscripts’ inks. Since Burns wrote with different inks than the forgers, the technique would allow Burgess’ team and others to weed out the impostors.
The researchers tested the technique on three authentic Burns manuscripts and seven of Smith’s forgeries. Using a pipette containing just 2 µL of methanol and water, the team gently allowed the solvent to contact ink on a manuscript to extract its compounds. Then the scientists used a commercial microfluidic system to spray nanoliters of each sample into their mass spectrometer, a tactic that improves its sensitivity to the dissolved molecules.
A machine-learning algorithm helped to find 94 features in the mass spectra of the ink samples that were unique to either Burns’s and Smith’s manuscripts, enough to reliably distinguish between them. “I think it’s a really interesting new technique that hasn’t been applied to manuscripts before,” says Matija Strlic, who develops methods for heritage science at University College London.
Although mass spectrometry has been used in forensic investigations of modern inks, Burgess suggests that conservators have been wary of subjecting historical manuscripts to potentially destructive techniques, such as one that involves firing charged solvent droplets at a page to free ionized sample molecules. “So we spent a lot of time and effort making sure that our method was nondestructive”, Burgess says. The new method also offers a more detailed chemical profile of inks than Raman spectroscopy or X-ray fluorescence spectroscopy, which are more commonly used to study old inks.
While the Glasgow group was developing the method, Burgess’ student James Newton spent the first year of his Ph.D. creating his own Burns forgeries to practice on. Newton mixed up different types of black ink using centuries-old recipes that sometimes included lard, treacle, and stale beer. “It was essential to have something similar enough to the real documents,” Burgess says.
Although he generally uses mass spectrometry in biomedical research, Burgess is no stranger to such unusual diversions. “This is just one of a long line of off-the-wall projects,” he says. “I’ve worked on everything from martian meteorites to wildebeest hair.”
The researchers now hope to test their method on a wider range of historical documents, building up a database of ink profiles that could be used by auction houses, for example, to help assess the authenticity of manuscripts.