# Evaluation of the Occurrence of Phthalates in Plastic Materials Used in Food Packaging
## 3 Results and Discussion
### Method Validation  
The performance of the analytical method was assessed based on linearity, sensitivity, selectivity, precision (intra- and inter-days), and recovery (accuracy). The chromatogram profile of the optimized analytical method is depicted Figure 2, and phthalates (60 \(\upmu\)g/L) were totally separated in less than 28 min.  
Figure 1: Multivariate analysis for HS-SPME optimization of phthalates target. Conditions: sample volume: 2 mL; concentration of phthalates: 60 \(\upmu\)g/L; NaCl amount: 0.2 g; extraction time: 15, 30, and 45 min; extraction temperature: 60, 70, and 80 \({}^{\circ}\)C; desorption time and temperature: 6 min and 250 \({}^{\circ}\)C.  
To build the calibration curves for the phthalates, mixed working solutions were prepared in the concentration range 0.5 to 60 \(\upmu\)g/L and plotted using their GC peak area. For all targets under study, a good linearity (R\({}^{2}\geq\) 0.995) with residuals not exceeding \(\pm\)10% was achieved over the whole range of concentrations tested. The LODs ranged from 0.03 (BBP) to 0.08 (BDE) \(\upmu\)g/L, while LOQs ranged from 0.10 (BBP) to 0.24 (BDE) \(\upmu\)g/L. Regarding DIBP, the LOD and LOQ obtained were lower than the default maximum residue limit (MRL, 300 \(\upmu\)g/L) established by many government agencies worldwide, including the European Environment Agency, the USEPA, and the Chinese Ministry of Health [23].  
The precision of the method was assessed by intra- (repeatability) and inter-day (reproducibility) precisions. The intra-day precision varied from 0.65 to 7.93%, whereas the inter-day precision ranged from 1.65 to 12.68%. The recovery was performed by spiking the phthalates in the food package solution at three levels of concentration (low, medium, and high), which ranged from 90.2 to 111% (Table 2). The literature has reported that a quantitative method should be demonstrated as being able to provide mean recoveries within the range of 70-120% and precision with % RSD values lower than 20%. Similar precisions and recoveries for phthalates were obtained in different matrices using HS-SPME/GC-MS [20,24,25].  
In addition, the LODs and LOQs obtained in this work (Table 1) are slightly betterthan those obtained by other authors employing HS-SPME/GC-MS to determine phthalates in plastic containers [24], milk [25], and beers [20].  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**RT (min)** & **PAEs** & **Linear Range (\(\upmu\)g/L)** & **Equation** & **R\({}^{2}\)** & **LOD (\(\upmu\)g/L)** & **LOQ (\(\upmu\)g/L)** \\ \hline
13.18 & DIBP & 0.5–60 & y = 817,649x + 10\({}^{6}\) & 0.996 & 0.06 & 0.21 \\
22.55 & BBP & 0.5–60 & y = 66,577x + 116,115 & 0.999 & 0.03 & 0.10 \\
26.49 & BDE & 1–60 & y = 124,317x + 755,468 & 0.995 & 0.08 & 0.24 \\
27.77 & DOP & 1–60 & y = 44,993x \(-\)100,807 & 0.999 & 0.07 & 0.23 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Figures of merit of the phthalates HS-SPME/GC-qMS methodology.  
Figure 2: HS-SPME/GC-MS chromatograms of phthalates at 60 \(\upmu\)g/L using PDMS/DVB fiber at 80 \({}^{\circ}\)C for 30 min.  
However, a higher LOD (from 0.12 to 0.50 \(\upmu\)g/L) was achieved previously to quantify six phthalates in environmental waters using liquid-liquid extraction (LLE) followed by GC-MS [26]. A summary of the different analytical methods, used for phthalates determination in plastic packaging, is presented in Table 3[20,21,24,27,28,29,30,31,32,33,34,35,36].