Applicability of a Diffuse Reflectance Infrared Fourier Transform handheld spectrometer to perform in situ analyses on Cultural Heritage materials

•Applicability of a Diffuse Reflectance Infrared Fourier Transform handheld device.•Reststrahlen distortions in the diffuse reflectance spectra obtained in situ.•This work proposes a few guidelines to acquire good spectra and resolve them easily.•DRIFT handheld device a real alternative to the Raman spectroscopy.

This work studies the applicability of a Diffuse Reflectance Infrared Fourier Transform handheld device to perform in situ analyses on Cultural Heritage assets. This portable diffuse reflectance spectrometer has been used to characterise and diagnose the conservation state of (a) building materials of the Guevara Palace (15th century, Segura, Basque Country, Spain) and (b) different 19th century wallpapers manufactured by the Santa Isabel factory (Vitoria-Gasteiz, Basque Country, Spain) and by the well known Dufour and Leroy manufacturers (Paris, France), all of them belonging to the Torre de los Varona Castle (Villanañe, Basque Country, Spain). In all cases, in situ measurements were carried out and also a few samples were collected and measured in the laboratory by diffuse reflectance spectroscopy (DRIFT) in order to validate the information obtained by the handheld instrument. In the analyses performed in situ, distortions in the diffuse reflectance spectra can be observed due to the presence of specular reflection, showing the inverted bands caused by the Reststrahlen effect, in particular on those IR bands with the highest absorption coefficients. This paper concludes that the results obtained in situ by a diffuse reflectance handheld device are comparable to those obtained with laboratory diffuse reflectance spectroscopy equipment and proposes a few guidelines to acquire good spectra in the field, minimising the influence caused by the specular reflection.

Graphical abstractThis paper studies the applicability of a different optical configuration implemented on a diffuse reflectance handheld device to perform in situ analyses of several samples belonging to Cultural Heritage and also tries to solve the problems that may arise during the interpretation of the spectra, such as, how to prepare the standards, where to measure the standards, how to correct the distortions or in which cases it is possible to correct the distortions. Finally this work proposes a few guidelines to acquire good spectra and resolve them easily.Figure optionsDownload full-size imageDownload as PowerPoint slide