Feasibility of FT-IR spectroscopy as a supporting tool for radiocarbon dating of restored samples

In this thesis, I have discussed the feasibility to use the Fourier Transform Infrared techniques (FT-IR) as supporting tool during the pre-treatment phases of restored samples for radiocarbon dating by Accelerator Mass Spectrometry (AMS). The pre-treatment is a crucial step for the removal of possible contaminations due to exogenous carbon present in the material that causes an alteration of original 14C concentration. In particular, if the contaminations are due to material rich in fossil carbon, they produce an apparent aging of the dated sample. The fossil contamination can be due to the typical synthetic product used to restore materials in the Cultural Heritage field since the 1960s. One of the most widespread products is the acrylic resin Paraloid B72. The removal of this substance is generally complicated by the fact that the resin, subjected to the photochemical action and time aging effects, undergoes transformations in the molecular structure that cause a remarkable decrease of solubility in common organic solvents. My PhD activity has especially focused to all the phases involving the preparation and the pre-treatment of samples to be dated. The mechanical cleaning and the simple pretreatment Acid-Base-Acid (ABA), usually applied to clean the samples from naturally occurring pollutants, are not sufficient to eliminate this kind of contamination. A procedure based on chloroform (CHCl3) as the key solvent is proposed. The effectiveness of chloroform as a solvent for the removal of Paraloid B72 was the first step to be checked. The second step was test the Fourier Transform Infrared Spectroscopy (FT-IR) technique as a supporting tool to answer to basic questions: whether estimate if Paraloid B72 is present on the sample to be dated is possible and whether we can discriminate if our sample pre-treatment has been successful in the removal the possible contaminants. FT-IR has been chosen thanks to its great sensitivity to detect the functional groups of organic molecules. In addition, FT-IR technique requires small samples to acquire a spectrum. This is indispensable key points when dealing with samples in the field of Cultural Heritage. The samples principally investigates were wood and bone samples. These materials were chosen because they represent very usual samples in radiocarbon dating. Wood is one of the most common materials in the Cultural Heritage field and bones are the typical findings in an archaeological context. The problem of interfering bands, added to the great difficulty to prepare homogenous KBr pellets when dealing those samples, has headed the use of FT-IR as monitoring tool of liquid extracts, performed during the chloroform-based procedure. Definitely, the FT-IR technique is proved to be a great helpful tool in the case of spectra acquired on extracts, since it can verify whether the sample pretreatment has been successful or not. This allows us to decide how many extractions are needed during the pre-treatment process. Considering this powerful aspect, the use of FT-IT could be regularly introduced to monitor sample preparation for those restored sample to be radiocarbon dated.