# Microplastics' Detection in Honey: Development of Protocols in a Simulation
## 3 Results and Discussion
### Contamination Check  
#### 3.4.1 Reference Spectra and Assignments  
Raman spectra of both PET MPs (Figure 9a) and honey (Figure 9b) are presented, to verify that there are no overlaps that could mislead this research (shown in Figure 9c). As is evident, between the two spectra, there are only three small peaks that belong to the same wavenumber, which are depicted with blue lines in Figure 9c and with bold in Table 1. The remaining ten Raman lines (in green colour), including the strongest PET Raman peaks centered at 1613 cm\({}^{-1}\) and 1726 cm\({}^{-1}\), do not exist in the honey spectrum. As a result, the PET characterization and identification in this work will be based only on the ten remaining Raman spectral features as depicted in green color in Figure 9c. Table 1 presents the Raman peak assignments found in honey and PET [41; 42; 43].  
Figure 8: Raman maps comparison between different organic solvents and their aqueous phases: (a) Raman map of S1, toluene sample; (b) Raman map of the aqueous phase of S1; (c) Raman map of S2, petroleum ether sample; (d) Raman map of the aqueous phase of S2; (e) Raman map of S3; (f) Raman map of S4, pentane sample, (g) Raman map of the aqueous phase of S4.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Peak** & \multicolumn{2}{c}{**Raman Shift**} & \multicolumn{2}{c}{**Assignments**} & \multicolumn{2}{c}{**Peak Strength**} \\
**Number** & \multicolumn{2}{c}{**(cm\({}^{-1}\))**} & \multicolumn{2}{c}{**Honey**} & **PET** & **Honey** & **PET** \\ \hline
1 & & 277 & & C-C stretching (ring), CCC bending (ring) [41] & Weak \\ \hline
2 & 420 & - & C-C-O and C-C-C bending of major Frucucuc or minor Glucose [42] & - & Strong \\ \hline
3 & 518 & - & C-C-O and C-C-C deformation of minor Frucucuc or major Glucose [42] & - & Strong \\ \hline
**4** & **628** & **630** & **Ring deformation of major Frucucuc or minor Sucrose [42]** & **CCC in-plane bending (ring) [41]** & **Common (strong)** \\ \hline
**5** & **706** & **700** & **C-O and C-C-O stretching, O-C-O bending of Frucuc [42]** & - & **Common (weak)** \\ \hline
6 & - & 792 & - & C-CH out of plane bending (ring) [41] & Weak \\ \hline
7 & 820 & - & C-OH bending of Frucucuc [42] & - & Medium \\ \hline
8 & - & 857 & - & C-C stretching (ring breathing), C-O stretching [41] & Strong \\ \hline
9 & 869 & - & C-O-C Cyclic alkyl ethers of major Frucuc or minor Glucose [42] & - & Medium weak \\ \hline
10 & 916 & - & CH, COH bending of major Glucose or minor Maltose [42] & - & Weak \\ \hline
11 & 980 & - & Ring breathing of Frucucuc [42] & - & Weak \\ \hline
12 & 1075 & - & C-O-C stretching, C-N vibration of proteins in major Frucucuc or minor & - & Medium \\  & & & Glucose [42] & - & \\ \hline
13 & - & 1095 & - & Ring C-C, ester C(O)-O, ethylene glycol C-C (trans) & Weak \\  & & & [43] & - & Weak \\ \hline
14 & - & 1115 & - & CH in-plane bending (ring), C-O stretching [41] & Weak \\ \hline
15 & 1127 & - & C-OH deformation of major Glucose or minor Maltose [42] & & Medium \\ \hline
16 & - & 1174 & - & CH in-plane bending (ring) [41] & Weak \\ \hline
17 & 1264 & - & C-O-C Cyclic alkyl ethers of Frucuc [42] & & Medium \\ \hline
18 & - & 1285 & - & C-C stretching (ring), C-O stretching [41] & Strong \\ \hline
19 & - & 1411 & - & C-C stretching (ring) [41] & Weak \\ \hline
**20** & **1457** & **1455** & **CH2 bending of Frucucuc or minor Glucose [42]** & **CH deformation [41]** & **Common (weak)** \\ \hline
21 & - & 1613 & - & C-C stretching (ring) [41] & Very Strong \\ \hline
22 & - & 1726 & - & C-O stretching [41] & Strong \\ \hline \hline \end{tabular}
\end{table}
Table 1: List of the major Raman peak assignments commonly found in honey and PET [41, 42, 43].  
The mass spectrometry analysis was based on the literature [30], where the fragments with \(m/z\) 167 MH\({}^{+}\) and 211 MH\({}^{+}\) belong to PET monomers/oligomers. The fragment 167 is assigned to terephthalatic acid H-T[TG]\({}_{0}\)-OH (TPA), and the fragment 211 is referred to as monohydroxyethyl terephthalate H-[TG]\({}_{1}\)-OH (MHET) [30].