## 3 Results and Discussion
### MALDI-TOF MS  
The samples were extracted and analyzed by MALDI-TOF MS technique. In order to tentatively identify the possible oligomers, a homemade database with the common starting monomers used in the formulations of polyester coatings was developed. The homemade database was created considering nineteen polyols (one monoid, seventeen diols, and one trioi) and six polyacids (five diacids and one triacid) known to be potentially used as monomers in polyester formulations intended for food-contact coatings, according to the literature. For each combination, the linear and fully cyclized forms (depending on the number of H\({}_{2}\)O losses) were considered, resulting in a high number of oligomer structures.  
Observing the mass spectra obtained with MALDI-TOF MS, it was possible to notice that samples CM2 and CM3 presented a similar pattern, different from sample CM1. All of them presented series of signals appearing at intervals of 234.1 Da, which corresponds to a phthalic/isophthalic/terephthalatic acid (PA) with neopentyl glycol (NFG), as reported in the study of [PERSON] et al. [64].  
In sample CM1, adjacent mass groups were observed, separated by 14 Da intervals. Exchanging neopentyl glycol with 1,6-hexanediol (HD) increased the mass by 14 Da, while exchanging neopentyl glycol with 1,3-butanediol, 1,4-butanediol (BD), or 2-methyl-1,3-propanediol (MPO) reduced the mass by 14 Da. Taking into account the intensity of the masses, it can be concluded that the alcohol used in the highest proportion was  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline
**TR (min)** & **CAS N\({}^{*}\)** & **Compound** & **m/z** & **SI** & **RSI** & **CM1** & **CM2** & **CM3** \\ \hline
18.5 & & Unknown (alcohol structure) & 43,55,69,83 & 915 & 936 & X & X & X \\
18.7 & 24157.81-1 & 2,6-diisopropylnaphthalene & 197,155,212 & 737 & 877 & X & X & X \\
18.8 & 629-78-7 & Heptadecane & 57,43,71,85 & 757 & 885 & X & X & X \\
20.04 & & Unknown (alkane structure) & 43, 57, 71, 85 & & & X & X & X \\
20.18 & 118-60-5 & 2-ethylhexyl salicate & 120, 138, 250 & 738 & 890 & X & X & \\
20.3 & 110-27-0 & Isopropyl myristate & 102, 228, 129, 185 & 720 & 758 & & X \\
20.8 & & Unknown (phthalate structure) & 149, 223, 167 & & & X & X & X \\
20.9 & & Unknown (alcohol structure) & 69, 97, 55 & 789 & 847 & & & X \\
21.46 & 82304-66-3 & 7,9-di-tert-butyl-1-oxaspiro[4;5]deca-6.9- & 205, 175, 189 & 843 & 858 & X & X & X \\ \hline \end{tabular} SI: direct matching factor; RSI: reverse search matching factor.  
\end{table}
Table 3: _Cont._NPG, followed by HD and BD/MPO. Within the first group of masses detected, it was possible to tentatively identify the adduct of the cyclic oligomer 2 PA+2 NPG with sodium (491.2), the adduct of the cyclic oligomer 2 PA+NPG+HD with sodium (505.2), and the adduct of the cyclic oligomer 2 PA+2 HD with sodium (519.2). In addition, another series of signals appeared with intervals of 114.1 Da and were identified in this sample, which were assigned to the adduct of caprolactone cyclic oligomers with sodium. Caprolactone is used as an additive in polyester lacquers [38]. For illustration, as an example, the masses corresponding to 593.4, 707.5, and 821.6 were assigned to caprolactam cyclic pentamer, hexamer, and heptamer. Figure 4 shows the MALDI mass spectrum of the acetonitrile extract of this sample.  
Regarding samples CM2 and CM3, adjacent mass groups were observed, separated by increments of 40 Da or reductions of 42 Da. Exchanging neopentyl glycol with 1,4-bis(hydroxymethyl)cyclohexane (CHDM) increased the mass by 40 Da, while exchanging neopentyl glycol with ethylene glycol (EG) reduced the mass by 42 Da. Taking into account the intensity of the masses, it can be concluded that the alcohol used in the highest proportion was NPG, followed by CHDM and EG in a lesser proportion. Within the first group of masses detected, the mass of greater intensity could be tentatively identified as the adduct of the cyclic oligomer 2 PA+2 NPG with a proton (469.2), as in the study of [PERSON] et al. [65].