A 60-year-old scientific method of analysing the chemical composition of materials has been revealed as giving incorrect results in many cases. X-ray photoelectron spectroscopy (XPS) was developed in the 1960s and has been the mainstay of scientific research since, but recent research has revealed that it has been incorrectly applied in many cases and the resulting inaccuracies could mean more than 12,000 scientific papers produced every year over recent decades should be re-investigated.
As technology improves the standard of scientific equipment, we can be forgiven for thinking accuracy will also increase.
But not so with XPS because technicians have been calibrating the increasingly precise equipment using old, and increasingly imprecise, methods.
Grzegorz Greczynski and Lars Hultman from Linköping University in Sweden have demonstrated that an underlying error in the 54-year-old method of calibrating equipment for XPS analyses that was relatively accurate at the start, has now become sometimes wildly inaccurate due to the precision of modern equipment magnifying the error.
This calibration standard was set in 1967 when Kai Siegbahn from Sweden’s Uppsala University published his study of XPS setting of world-wide improvements in analysing materials in laboratories. Greczynski points out that Siegbahn’s ground-breaking methods are still completely valid, but the accuracy of subsequent research could be impaired by the problem he has exposed.
He said: “It is, of course, an ideal in research that the methods used are critically examined, but it seems that a couple of generations of researchers have failed to take seriously early signals that the calibration method was deficient.” He added: “This was the case also for a long time in our own research group. Now, however, we hope that XPS will be used with greater care.”
The problem he revealed was that calibration of equipment for a new experiment is usually performed by sampling carbon from the surface of the material to be tested.
But the carbon-based compounds can be a result of condensation on the sample that introduces errors by incorporating signals from surrounding materials that could be the material to be tested itself – meaning the test process could be based on arbitrary and inaccurate settings.
Hultman believes the error could affect research from the last 40 years due to a lack of critical thinking in the scientific and publishing communities.
He said: “Not only has a rapidly growing number of scientists failed to be critical, it seems that there is a form of carelessness among editors and reviewers for the scientific papers.
“This has led to the publishing of interpretations of data that are clearly in conflict with basic physics. “You could call it a perfect storm.”
The research was published by Scientific Reports in May.
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