As mentioned in the “Introduction” section, UAE with a mixture of organic solvents has been widely employed for extracting plasticizers from face masks and QFFs. While its application in foodstuffs is less frequent, the promising outcomes observed in the specific OPE analysis of fish samples [65], coupled with its agility and reduced extraction of interfering compounds, render it a compromise election. Hence, this previously established OPE method [65] was modified for the inclusion of a larger number of plasticizer classes and diverse matrices. Few modifications have been made to adapt it for phthalates and alternative plasticizers extraction in foodstuffs. Considering the anticipated low OPE concentrations in food samples and the unknown plasticizer levels, a larger dried sample amount of 1 g was selected. However, employing a final volume of 5 mL may lead to analyte dilution, potentially resulting in false negative samples. Due to the increased number of analytes targeted, and therefore improving signal intensity, two different final volumes (1 and 2 mL) were assessed. It is well-known that the presence of matrix effects may lead to ion suppression, particularly in samples with higher fat content, such as meat or fish foodstuffs. With a final reconstitution volume of 1 mL, instrumental noise levels increased, and S/N ratios for several plasticizers were below 3. Conversely, acceptable S/N ratios were achieved with 2 mL of final volume. Furthermore, no significant differences in signal were observed between centrifugation times of 10 min and 5 min. Therefore, 5 min was chosen as the optimal time in order to shorten the extraction procedure. With respect to face masks, a reduced volume of hexane:acetone (1:1) amounting to 30 mL was employed, with equivalent results as the original method [24]. Concerning QFFs, the extraction protocol remained unaltered [64].

The primary aim of this study is to leverage the extensively validated TurboFlow™ methodology in OPE analysis [65] for other plasticizers. To achieve this goal, a mixture of standards was injected directly into the LC column, both with and without the preceding purification step involving TFC columns. This approach allowed an assessment of analyte separation and the influence of the on-line purification step. Notably, no discernible differences in analytical response were observed between the direct injection into the LC column and the use of the TurboFlow™ purification. Consequently, the on-line purification method proved suitable, as it contributed to obtaining clean extracts free from interfering compounds.

TurboFlow™ offers two operational modes: Quick Elute and Focus modes. Both modes begin with an initial purification step where analytes diffuse into particle pores, while high molecular weight matrix components are separated. In the second step, the flow direction is reversed, transferring the analytes to the elution column for chromatographic resolution. The main difference lies in the pre-concentration at the column head in Focus mode, assisted by a loop filled with mobile phase. This pre-concentration dilutes the sample and retains analytes at the column head, thereby enhancing sensitivity. Consequently, Focus mode was selected for the method optimization. Furthermore, it has been noted that molecules of high weight can be lost during purification step. Thus, the combination of Cyclone™-P and C18-XL purification columns improves recovery rates, in addition to the fact that effectively reduces matrix content due to the diverse polarity range of the stationary phases. Moreover, optimal flow rates in TurboFlow™ columns are critical for efficient matrix removal, but higher flow rates can lead to overpressure drawbacks, analyte loss, and increased solvent consumption. A flow rate of 0.75 mL min−1 was determined to be a suitable compromise to establish a turbulent regime. Meanwhile, the transfer time of 2 min (Table S2) was chosen to balance high recovery rates with minimal matrix interferences.

Optimized instrumental parameters and selected transitions are provided in Table 1. Obtained DPs were compatible with the pre-established conditions of spray voltage and mobile phase. After selecting precursor ions for each compound, the three most intense transitions with optimized CEs were identified, and two were chosen based on sensitivity and absence of matrix co-elution. The obtained fragments matched the targeted molecular structures, and no adducts were created. Initially, all transitions were acquired throughout the entire chromatogram with a cycle time of 1 s. However, the inclusion of numerous new transitions of native and IS plasticizers decreased the signal of all compounds, thereby compromising the viability of the method. For enhanced sensitivity, three MS acquisition windows were established between 0.0 and 7.0 min (with 6 compounds, among plasticizers and their ISs), 7.0–21 min (with 36 compounds), and 21–36 (with 11 compounds), employing a cycle time of 0.6 s. Compounds lacking an IS were assigned one within the same window for accurate quantification, considering their similarity in retention time and chemical structure. Linearity was observed within the concentration range of 1 to 2000 ng mL−1 for OPEs and most of the newly incorporated compounds, with the exception of di-n-octyl phthalate (DnOP), diisononyl adipate (DINA), and DINCH, which exhibited a range of 10–2000 ng mL−1, and DiNP and diisodecyl phthalate (DiDP), with a range of 50–2000 ng mL−1. All determination coefficients (R2) were higher than 0.99. As for repeatability, RSD values were below 20% for both intra-day and inter-day assays. The iLODs for phthalates and alternative plasticizers were in the range from 0.02 to 18.5 injected pg, while the iLOQs ranged from 0.05 to 61.7 injected pg. Available iLODs for these compounds are scarce, and generally higher than values obtained in our study. A GC–MS method applied to PVC medical devices yielded iLODs within the range of 10–60 pg for most of the phthalates, ATBC, and DEHA, and 70–250 pg for DINCH, DiNP, and DiDP [2]. Meanwhile, a LC–MS/MS method targeting phthalates in water showed iLODs ranging from 0.2 to 28.7 pg [66]. Referred to OPEs, the sensitivity (iLODs, 0.01–1.36 pg; iLOQs, 0.03–4.55 pg) remains equal or slightly higher than the previously established by Giulivo et al. [65] in their methodology only focused on OPE analysis. Thus, the expanded range of analytes in the new methodology did not compromise their sensitivity. This outcome has been facilitated through the implementation of MS time windows, improving the sensitivity in T2IPP (0.08 pg of new iLOD versus 1.56 pg), trihexyl phosphate (THP) (0.06 pg versus 0.24 pg), and tris(2-ethylhexyl) phosphate (TEHP) (0.21 pg versus 0.41 pg). Moreover, iLODs were within the same order of magnitude as those observed in OPE methods applied to foodstuffs through LC–MS/MS (iLODs, 0.08–0.48 pg) [34] and GC–MS (iLODs, 0.27–1.04 pg) [38], where a lower number of analytes were targeted. Hence, the characteristics of the methodology made it suitable for application in routine analysis.

A summary of quality parameters related to foodstuffs analysis is presented in Table S3. Due to the influence of the food matrices, chromatographic resolution concerning the two dibutyl phthalate isomers, diisobutyl phthalate (DiBP) and di-n-butyl phthalate (DnBP), was found to be diminished. Consequently, both isomers were quantified as a combined sum. Each category of food was assessed at two concentration levels (Fig. 2). For low-fat food items, recoveries of phthalates and alternative plasticizers exhibited a range of 63–96% for low-spiked level and 66–98% for high-spiked level. Meanwhile, high-fat foodstuff recoveries ranged between 58 and 99% and 56 and 93% for low- and high-spiked levels, respectively. In all instances, RSD values remained consistently below 15%. Regarding sensitivity, mLODs fell within the range of 0.02 to 2.08 ng g−1 wet weight (ww) for low-fat foodstuffs and 0.01 to 1.55 ng g−1 ww for high-fat foodstuffs. Limited studies have performed analysis with LC–MS/MS (Table S4). Phthalates in fatty food packaged were analyzed with comparable mLODs ranging from 0.02 to 1.60 ng g−1 ww [28]. Another validation of five phthalates, ATBC, and DEHA in cereal-based products provided higher mLODs, which ranged 1.00–50.0 ng g−1 ww [11]. More recently, an investigation involving different food composites reported lower mLODs for DEHP, DiNP, and DEHA at 0.10 ng g−1 ww each, while diethyl phthalate (DEP) (0.20 ng g−1 ww), DnBP (0.10 ng g−1 ww), and DINCH (0.30 ng g−1 ww) exhibited lower sensitivity than our methodology [40]. In the context of alternative plasticizers, a study of CAEs encompassing various Chinese foodstuffs displayed a higher mLOD for ATBC (0.42 ng g−1 ww) compared to the levels obtained in both low-fat (0.03 ng g−1 ww) and high-fat foods (0.01 ng g−1 ww) [12].

Recoveries of selected plasticizers in foodstuffs analysis (PAEs, phthalates; ALTs, alternative plasticizers; OPEs, organophosphate esters)

Nonetheless, the prevailing methods for the measurement of phthalates and certain substitutes such as DEHA or DINCH in foodstuffs are based on GC–MS (Table S4). This approach has been coupled with gel permeation chromatography (GPC) as a purification step for the analysis of eight phthalates in food products from Belgium [27]. mLOQs similarities were observed in dimethyl phthalate (DMP) (0.20 compared to 0.28 ng g−1 ww of our method), greater sensitivity was noted for DnOP (0.50 versus 0.99 ng g−1 ww), and higher values were reported for DEP, butyl benzyl phthalate (BBzP), DiBP, DnBP, dicyclohexyl phthalate (DCHP), and DEHP (1.00–8.00 ng g−1 ww) in contrast to our methodology (0.07–3.81 ng g−1 ww). In addition, an assay of meat roasted in plastic bags was measured by coupling GC–MS to solid-phase microextraction (SPME), providing mLODs for phthalates and DEHA between 0.01 and 0.18 ng g−1 ww [67]. Similarly, a study of dietary exposure to phthalates was performed with gas purge microsyringe extraction (GP-MSE) demonstrating mLODs between 0.14 and 0.38 ng g−1 ww [30]. Another diet assessment conducted in Canada brought mLODs for phthalates in the range of 0.99–39.0 ng g−1 ww, and a mLOD for DEHA (3.16 ng g−1 ww) higher than the mLOQ of our method (2.01 ng g−1 ww) [29]. In more recent studies, fish and squid [39] and fast-food items [4] were subjected to extraction for phthalates and DEHA analysis, resulting in method limits ranging 0.50–5.00 ng g−1 ww and 1.00–14.0 ng g−1 ww, respectively. In the case of fast-food analysis, recoveries were below 30% for DiNP and DINCH, with mLODs (5 ng g−1 ww and 10 ng g−1 ww, respectively) higher than TurboFlow™ methodology. In recent total diet studies on phthalates conducted in China, two key studies were identified. In one study, 22 phthalates were analyzed, with recoveries ranging from 45 to 136% [68], which is broader than the recovery range obtained in our study (56–99%). In a separate study, six phthalates were examined, with higher LOQs reported (4.3–11.0 ng g−1 ww) [69] compared to those achieved in our study (0.04–2.01 ng g−1 ww). As regards GC–MS/MS methods, an application to baby foods provided mLOQs ranging 0.03–1.08 ng g−1 ww [35], and mLODs of 0.01–5.17 ng g−1 ww in edible oils [41]. It is noteworthy that these approaches exhibited sensitivity comparable to our developed method. However, the simplicity, efficiency, and automation offered by the TurboFlow™ technology render it a preferred choice for food analysis.

Regarding OPE quality parameters obtained with our methodology, recovery percentages spanned from 67 to 99% for low-fat foodstuffs and from 50 to 96% for high-fat foodstuffs, all while maintaining RSD values below 13%. Additionally, mLODs ranged between 0.01 and 0.16 ng g−1 ww for low-fat foods and between 0.001 and 0.21 ng g−1 ww for high-fat food items. Dietary exposure investigations concerning OPEs were carried out predominantly by LC–MS/MS and GC–MS/MS (Table S4). Certain studies only provided information about mLOQs, which fell within the ranges of 0.07–0.42 ng g−1 ww [34] and 0.002–62.0 ng g−1 ww [32]. These ranges were aligned to the mLOQ values determined in our method (0.004–0.69 ng g−1 ww) and in an alternative GC–MS/MS approach (0.07–0.69 ng g−1 ww) [38]. Other studies were conducted with methodologies encompassing mLOD ranges of 0.02–0.17 ng g−1 ww [33], 0.004–3.30 ng g−1 ww [31], and 0.003–0.107 ng g−1 ww [36]. Furthermore, a recent advancement by LC-HRMS provided sensitivity values between 0.001 and 0.058 ng g−1 ww [42]. Overall, limits derived from those studies resemble our results. Nevertheless, it should be noted that only a limited number of OPEs were targeted in those investigations, whereas our method encompasses an analysis of 34 plastic-related compounds. In addition, reported recovery rates varied across studies. Some, like the methodologies applied in total diet studies from Australia (60–96%) [31], showed ranges similar to those obtained with our method (50–99%). However, other studies have reported different rates, including studies from the USA (32–140%) [33], China (41–136%) [36], (61–136%) [70], and recent studies on take-away foodstuffs (39–121%) [71], all of which exceeded the range observed in our method.

The wide variety of available foodstuffs poses a challenge for the application of the analytical methodology, particularly due to matrix effects. Therefore, an assessment of the IS sensitivity in food matrices was conducted to ensure quality control (Table S5). Recoveries ranged from 60 to 97% across all types of matrices, confirming the robustness of the methodology and highlighting the purification capabilities of TurboFlow™ technology. This approach enabled the simultaneous analysis of diverse compounds, such as citrates, adipates, phthalates, and OPEs, which previously could not be analyzed together in foodstuffs using LC due to their differing chemical nature.

Face mask quality results are summarized in Table S6. Extraction of plastic additives from face masks resulted in recovery percentages between 52 and 110% for the low-spiked level and between 51 and 120% for the high-spiked level (Fig. 3), with RSD values below 20%, for 29 of the targeted compounds. DMP, triethyl phosphate (TEP), and TEHP exhibited recoveries around 40% at one of the spiked levels. Such recoveries were deemed acceptable, given the inclusion of deuterated ISs in the method for quantification through isotopic dilution, and those compounds had their own deuterated compound. DEP, tris(2-butoxyethyl) phosphate (TBOEP), resorcinol bis(diphenyl phosphate) (RDP), 4-isopropylphenyl diphenyl phosphate (4IPPDPP), and EHDPP were discarded of the methodology due to unacceptable recoveries. mLODs encompass a range of 0.002–0.23 ng g−1, while mLOQs ranged from 0.01 to 0.99 ng g−1. Given the recent nature of research concerning the environmental and human health implications of the use of face masks, only a limited number of studies have been conducted in this area (Table S4). A single study to date has employed LC-HRMS for the simultaneous analysis of six phthalates and ten OPEs in this context [43], with mLOQs between 0.01 and 0.07 ng g−1. Notably, GC–MS was the preferred technique for phthalates analysis, with disparate mLODs ranges: 5.10–26.5 ng g−1 [45], 1.10–3.54 ng g−1 [72], 10.0–30.0 ng g−1 [46], and 0.073–3.41 ng g−1 [73]. Additionally, there is a GC-HRMS approach [74] with a wider mLODs range (0.016–10.0 ng sample−1) than the one obtained in our developed method (0.003–0.153 ng sample−1). To our knowledge, no comprehensive methodologies targeting alternative plasticizers such as ATBC, DEHA, DINA, or DINCH have been reported. Consequently, this method stands as a pioneering approach in the integration of these analytes alongside other plasticizers within the analysis of face masks.

Recoveries of selected plasticizers in face masks and QFFs (PAEs, phthalates; ALTs, alternative plasticizers; OPEs, organophosphate esters)

QFFs quality results are summarized in Table S6. Similar to the strategy implemented for foodstuffs analysis, DiBP and DnBP isomers were quantified as an aggregated sum in the QFFs methodology. Recovery rates were determined for 27 compounds, spanning from 49 to 125% for the low-spiked level and 55 to 117% for the high-spiked level (Fig. 3), with RSD values remaining below 20%. In this case, 7 compounds (DMP, DCHP, DiDP, DINCH, TEP, tripropyl phosphate (TPP), and isodecyl diphenyl phosphate (IDPP)) were excluded due to low recovery values. DEHP recoveries were considered permissible in this method due to the use of their own deuterated compound, which relies on quantification by isotopic dilution. mLODs for the extraction method ranged from 0.001 to 0.93 ng m−3, while mLOQs spanned from 0.004 to 3.10 ng m−3. Those levels are compared to recent research that combined the analysis of different additives (Table S4). A GC–MS method developed for outdoor air sampling [75] revealed recovery rates in the range of 45–119% and mLODs between 0.001 and 0.014 ng m−3. Moreover, a GC–MS/MS methodology designed for atmospheric particulate matter analysis [76] reported mLODs between 0.003 and 1.13 ng m−3 for phthalates, and between 0.003 and 0.16 ng m−3 for OPEs. More recent studies based on GC–MS yielded limits in the range of 0.007–0.268 ng m−3 for phthalates and 0.003–0.012 ng m−3 for OPEs [44], as well as 0.007–0.13 ng m−3 for phthalates [48]. Another recent method combined the analysis of phthalates (mLODs, 0.020–13.0 ng m−3) with ATBC, DEHA, DINA, and DINCH (mLODs, 0.014–4.6 ng m−3) [13]. Additionally, an LC–MS/MS-based approach targeting phthalates and DEHA [47] reported mLODs from 0.03 to 1.15 ng m−3. In summary, available methods consistently provided comparable outcomes to our developed methodology, which encompassed a larger number of analytes than most studies. Furthermore, it provides a new methodology for monitoring alternative additives, which study will be under scrutiny.

Samples corresponding to the different matrices for which the methods have been developed were subjected to analysis of plastic additives. Figure 4 presents the plasticizer levels in three low-fat foodstuffs, three high-fat foodstuffs, three face masks, and three indoor air environments (individual results are provided in Table S7). Exemplified in Fig. 5 is the chromatographic profile of the sweetener sample, where 5 plasticizers were detected and quantified.

Plasticizer levels found in low-fat foodstuffs (a, b, c), high-fat foodstuffs (d, e, f), face masks (g, h, i), and QFFs (j, k, l) (DBP = sum of both isomers, DiBP and DnBP levels)

Chromatograms of 5 plasticizers found in a sweetener sample

Concerning foodstuff samples, 16 out of the 34 targeted plasticizers were identified. Notably, results revealed that low-fat food items exhibit major additive levels compared to those with higher fat content. In specific terms, phthalate concentrations spanned from 1.3 to 49% of total additives in low-fat samples, a range that expanded to 25–87% in high-fat items. In the case of alternative plasticizers and OPEs, the observed ranges were 44–98% and 0.5–6.5%, respectively, for low-fat foodstuffs. These percentages changed to 10–37% for alternatives and 0.5–65% for OPEs in high-fat samples. DiNP predominantly appears in breakfast cereals, rice, and sweetener (Fig. 4a), with concentrations ranging from 205 to 459 ng g−1 ww. Particularly significant is the presence of ATBC (21.6 μg g−1 ww, Fig. 4b) in the sweetener sample (Fig. 5), highlighting the increasing use of alternative plasticizers. Moreover, the sweetener sample stands out due to its dominant TNBP content compared to breakfast cereals and rice (Fig. 4c), where EHDPP was detected at 19.9 and 38.1 ng g−1 ww, respectively. With regard to high-fat foods, beef showed noteworthy levels of DEP (114 ng g−1 ww), and yogurt presented high DiNP levels (147 ng g−1 ww, Fig. 4d), while DEHA is also detected in both samples (81.9 and 20.7 ng g−1 ww, respectively, Fig. 4e). The salmon sample was particularly high in OPE levels (Fig. 4f), with the main contributor being triphenylphosphine oxide (TPPO) (20.0 ng g−1 ww) and TCIPP (2.59 ng g−1 ww).

As regards face masks, 20 out of 29 compounds were detected. The relative contribution of phthalates to total additives was in the range between 59 and 84%. In contrast, alternative additives and OPEs exhibited 0.5–12% and 6.1–40%, respectively. The FFP2 sample exhibited the highest levels of phthalates (Fig. 4g) and alternative plasticizers (Fig. 4h), with remarkable concentrations of DiNP (2094 ng g−1), DEHP (1766 ng g−1), DINA (391 ng g−1), and ATBC (304 ng g−1). In contrast, the FFP3 sample notably presented heightened levels of DiDP (2933 ng g−1) and TEHP (2938 ng g−1, Fig. 4i), while reusable masks demonstrated the lowest levels of plasticizers across each group.

The analysis of indoor air samples provided insight into the exposure to plasticizers over different commercial locations, with the detection of 22 out of 27 targeted additives, and contribution ranges of 83–87%, 2.3–4.6%, and 10–13% for phthalates, alternatives, and OPEs, respectively. DEP and DBP (sum of isomers) emerged as the most prevalent phthalate contributors in the selected spots (Fig. 4j), with levels ranging from 22.1 to 385 ng m−3. The disparity is evident when considering alternative plasticizers (Fig. 4k), where the levels reached a maximum of 14.3 ng m−3. This observation underscores the prevailing presence of conventional plasticizers in these work environments. Notably, OPEs (Fig. 4l) exhibited the widest variety of identified compounds, with levels ranging from 36.9 to 58.6 ng m−3. Among these, tris(2-chloroethyl) phosphate (TCEP), TCIPP, and TNBP emerged as remarkable contributors.

The obtained results demonstrated the presence of alternative plasticizers across different exposure sources, including ingestion (foodstuffs), dermal contact (face masks), and inhalation (ambient air). In fact, the presence of alternative plasticizers such as ATBC in a sweetener sample emphasizes the ubiquity of this compound in the environment. Moreover, the detection of traditional phthalates in indoor air and certain OPEs in face masks is a growing concern due to their potential long-term health effects. The American Environmental Protection Agency (USEPA) [77] and the European Union [78] have established criteria for the maximum tolerable levels of some compounds. Although individual samples did not exceed these thresholds, the cumulative exposure might reach those levels.