FT‐Raman spectroscopy for quantitative analysis of salt efflorescences

Abstract

Salt crystallization in porous materials constitutes one of the major causes of decay of buildings and archeological sites. Depending on the environmental conditions, salts can crystallize inside the porous network (subflorescence or cryptoefflorescence) on the material surface (efflorescence or compact crust). Generally speaking, the salt deposits may comprise different inorganic ions (i.e. sodium or potassium sulphates, nitrates or chlorides), and they cause several damages, i.e. flaking, alveolar weathering, crumbling, loss of material or dissolution. In order to determine the nature and the concentration of salts, ionic chromatography (IC) is generally used. Although valuable, the IC analytical method presents a number of drawbacks, i.e. requires long sample preparation times, different sample dilutions, and the determined values are referred only to the ionic species (cations or anions). For a quick quantitative identification, the Raman spectroscopy appears more suitable, but a calibration of such analytical method is necessary. The present paper deals with the application of Fourier transform (FT)-Raman spectroscopy to the study of soluble salts constituting the most diffuse efflorescences in monuments and archeological sites. The FT-Raman calibration was set up by measuring the band integration area of each standard salt solution at the more intense and/or well-resolved band. Twelve control mixtures were tested, and the calibration curve fitting was evaluated. The obtained results were compared with IC determinations performed on the same salt mixtures.The FT-Raman spectroscopy demonstrated to be an easy approach to salt quantitative analyses, that in addition enables the direct identification of the nature of the analyzed samples.

Raman spectroscopic study of the degradation of a middle age mural painting: the role of agricultural activities

“…In this case, Raman spectroscopy confirmed the presence of the same compounds mentioned before but with a different ratio between the intensities of their main peaks, thus, with different concentrations. Studies found in bibliography demonstrated the direct proportionality between the intensity of the main peaks of salts with their concentration . In the present case, several calibration curves for Na 2 SO 4 , KNO 3 , and NaNO 3 were prepared.…”

Determination of Lactose in Milk by Raman Spectroscopy

“…The most common solution to these problems is to use an internal standard (Bell and Sirimuthu 2008;Broggi et al 2012). Carbon tetrachloride (459 per centimeter) is commonly used as an internal standard of non-aqueous solutions, while nitrate ion (1050 per centimeter) and perchlorate ion (930 per centimeter) are commonly used in aqueous solution.…”

A combined analytical approach applied to Medieval wall paintings from Puglia (Italy): The study of painting techniques and its conservation state

“…S2a, Supporting Information). Nitrates were also detected spectroscopically thank to the sharp peak at 1384 cm −1 and in the region of 1040–1055 cm −1 in the infrared and Raman spectra, respectively …”