A new non-invasive technique makes it possible to assess the antiquity of pieces from historical collections

Collaborative research between the Museu de Ciències Naturals de Barcelona, the Universitat Rovira i Virgili (URV) and the Università degli studi dell’Insubria (Como, Itàlia) has successfully applied near-infrared (NIR) spectroscopy to classify bones according to their age without damaging the pieces. The results have been published in the journal Analytical Chemistry.

Ancient specimens from zoological collections are critical to understanding numerous biological processes, as they offer a ‘historical snapshot’ of the diversity of the natural world in the recent past. Unfortunately, it is estimated that there are 120 million specimens in the world in natural science collections that have a very limited usefulness in research due to a lack of information on when they were collected. Until now, to date these pieces without documentation, it was necessary to resort to techniques that require extracting a sample of the bone and can compromise its condition, or to resort to very slow and not always successful historical archaeology research.

To address this challenge, the Museum of Natural Sciences of Barcelona has partnered with specialists from the Rovira i Virgili University (URV) and the Università degli studi dell’Insubria (UniInsubria) to develop and validate a method that combines NIR spectroscopy with chemometric tools, a branch of analytical chemistry that incorporates mathematical and statistical methods. The NIR technique involves irradiating bone pieces with infrared light and analyzing the resulting spectrum, which reflects how the radiation interacts with the composition of the bone, especially collagen and moisture, which vary with the age of the sample. All this allows specimens to be classified as historical or modern in less than a minute and without any damage. The results of this research have been published in the journal Analytical Chemistry.

“In scientific collections we often say that 50% of the value of a specimen is the label. Knowing when and where it was collected is just as important as the piece itself. When we do not have this information, the specimen loses much of its potential for research,” explains Javier Quesada, curator of vertebrates at the Museum. He adds: “Obtaining information without compromising the integrity of the pieces is a challenge since in some cases the samples are very small or the specimens have a great heritage value, and having a fast and non-destructive technique is especially valuable.”

The study has tested the technique by analysing the skulls of 59 specimens of red squirrel (Sciurus vulgaris) from the Museum’s collection divided into two known age groups: historical individuals, collected between 1916 and 1923, and modern individuals, collected between 2005 and 2021. The results have achieved a classification reliability of 100% in the skulls and between 87% and 95% in the jaws. “One of the main innovations is that we have also applied a chemometric method that allows us to know which parts of this spectrum may have the most error and thus identify which are more reliable,” says Jordi Riu, a researcher at the URV.

The origin of the project combines scientific curiosity and opportunity. Javier Quesada explains how the idea came about: “Seeing how, in a crime series, forensics managed to determine the date of death in humans, I studied whether similar techniques could be applied to date pieces of the vertebrate collection from which we lacked that information. As NIR spectrometry was the best candidate, I contacted Jordi Riu, from the URV, and Bárbara Giussani, from UniInsubria, who were immediately enthusiastic about the idea.”

With the results obtained, new perspectives are opened up for museums and laboratories around the world. The methodology could be extended to other species and materials, such as birds or naturalized skins. “Museums often preserve material that cannot be used in research at the moment, but we do so in the hope that technological innovations will make it possible in the future. This is exactly one such case,” concludes Marc Campeny, director of the Museum’s Scientific Area, who also participated in the study.

Reference article:

Riu, J., Giussani, B., Monti, M., Baruffaldi, L., Campeny, M., Quesada, J. (2026). Shedding Light on the Past: Temporal Classification of Zoological Specimens from Museum Collections with Portable NIR Sensors and Multivariate Error Modeling. Analytical Chemistry, 98(13), 9658–9671. https://doi.org/10.1021/acs.analchem.5c06767