A. Kourkopoulos et al.
4
Table 2. Overview of analytical parameters
Radio-frequency (RF) power (W)
Nebulizer gas flow (L/min)
Plasma gas flow (L/min)
Auxiliary gas flow (L/min)
Nebulizer
Spray chamber Cyclonic (quartz)
Interface cones
Mass resolution
0.7 amu
Nickel (sampler and skimmer) and aluminum (hyper skimmer)
1450
0.98
15
1.2
PFA-ST (Thermo Fisher Scientific, Waltham, MA, USA)
incubation, was carefully recovered post-incubation. The powder was subjected to Soxhlet extraction, which involved using a methanol and acetone (1:1, volume ratio) mixture as the solvent. Soxhlet extraction was performed for four full reflux cycles to ensure the thorough removal of any absorbed elements from the Tenax powder. Following the extraction process, the solvent mixture containing the extracts was col- lected. The collected extracts were then immediately stored at −80 °C to preserve their integrity and prevent any degrad- ation or evaporation of volatile components. In addition, coupons of the same FCMs were used for an exhaustive Soxhlet extraction process. This involved placing the FCM coupons (0.5 cm×0.5 cm) in the Soxhlet extractor and subjecting them to extraction using a methanol and acetone (1:1, volume ratio) mixture. The extraction process was carried out for four full cycles to ensure the complete ex- traction of chemicals from the FCM coupons. The resulting extracts from this exhaustive extraction were also collected and stored at −80 °C to maintain their stability and prevent any loss of analytes. Sample preparation for inductively coupled plasma mass spectrometry The high organic content of the migration samples and ex- tracts poses a challenge for accurate elemental analysis using inductively coupled plasma mass spectrometry (ICP-MS). Therefore, two sample preparation approaches were per- formed for the reduction of the organic concentration of the samples. In the first approach, the migration samples and extracts were diluted in deionized water and nitric acid to reach a final organic concentration below 2%. In this regard, the AFM and LFM samples were diluted five times, the FFM sample was diluted 25 times, and the DFM, DE, LAE, and FE samples were diluted 50 times. The final volume of each sample prepared for the analysis was 10 mL, and the final nitric acid concentration was 2% (volume fraction). In the second approach, 12 mL of each sample was completely dried in glass tubes under nitrogen gas. The subsequent dry pellet was dissolved with 10 mL of 2% (volume fraction) nitric acid in deionized water. The reconstituted LFM, FFM, DE, LAE, and FE samples were filtered through 0.4 μ m filters for the removal of any insoluble particles. Elemental analysis The concentrations of 54 elements in the migration samples and extracts were determined via ICP-MS. A 10-mL aliquot of each sample was introduced into the ICP-MS (NexION 2000, PerkinElmer, Waltham, MA, USA). The elemental ana- lysis was conducted under the conditions specified in Table 2. External calibration curves were used for the quantification of the elemental levels in the samples, for which the 7 Li, 9 Be, 23 Na, 26 Mg, 27 Al, 31 P, 43 Ca, 45 Sc, 47 Ti, 51 V, 52 Cr, 55 Mn, 56 Fe, 59 Co,
60 Ni, 65 Cu, 66 Zn, 71 Ga, 74 Ge, 75 As, 78 Se, 85 Rb, 88 Sr, 89 Y, 91 Zr, 93 Nb, 98 Mo, 111 Cd, 115 In, 118 Sn, 121 Sb, 128 Te, 133 Cs, 138 Ba, 139 La, 140 Ce, 141 Pr, 144 Nd, 152 Sm, 153 Eu, 159 Tb, 164 Dy, 165 Ho, 166 Er, 169 Tm, 174 Yb, 175 Lu, 180 Hf, 184 W, 201 Hg, 205 Tl, 208 Pb, 209 Bi, 232 Th, and 238 U were used as external calibration standards. In addition, blank solution of 3% (volume fraction) acetic acid, 10% (volume fraction) ethanol in deionized water, and methanol/ acetone of 1:1 (volume ratio) was analyzed for the determin- ation of background levels of elements in the solvents. The limits of reporting (LORs) for all the elements involved in the detection are provided as Supplementary Information. Calculation of reference tolerable intake values The calculated tolerable daily intake (cTDI) values were calculated using points of departure based on no-observed- adverse-effect-level (NOAEL), lowest-observed-adverse- effect-level (LOAEL), and benchmark dose lower confidence limit (BMDL) found in the OpenFoodTox database (https:// www.efsa.europa.eu/en/discover/infographics/openfoodtox- chemical-hazards-database) for various toxicological endpoints. These threshold values serve as starting points for calculating tolerable intake values by dividing them by an un- certainty factor (UF) of 100. The equation is as follows:
NOAEL, LOAEL, or BDML UF
cTDI =
The units of NOAEL, LOAEL, and BMDL are expressed as the mass of a substance consumed per kilogram of body weight (bw) per day or as the mass of substance consumed per day depending on the available threshold value; UF has no unit. By dividing the threshold values (NOAEL, LOAEL, or BMDL) by the uncertainty factor, the cTDI, which is equal to the tolerable daily intake, represents the maximum amount of a substance that can be consumed daily over a lifetime without posing a significant risk to health. Results Effects of the sample preparation procedure on the detected elements Table 3 presents a heatmap of the elemental concentrations in the AFM and LFM samples and their corresponding extracts (LAEs) for P1, P2, and P3 FCMs. The detected elemental con- centrations in the migration samples and extracts of P2 (FFM and FE) and P3 (DFM and DE) recycled paper samples are also included in this heatmap. The heatmap is shown in gray if the concentration of the elements was below the LOR and on a color scale from yellow to red according to the increase in elemental concentration. Table 3 illustrates that a greater number of elements were detected in the AFM samples, both in solution (19 elements)
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