Simultaneous analysis of trace polymer additives in plastic beverage packaging by solvent sublation followed by high-performance liquid chromatography

Multi-Residue Analysis of Chemical Additives in Edible Vegetable Oils Using QuEChERS Extraction Method Followed by Supercritical Fluid Chromatography

Since the quality and safety of food highly depend on its preservation and protection, the use of food packaging materials increases the risk of chemical contamination of the packaged food by migration. Herein, we focused on antioxidants, photoinitiators, UV absorbers and plasticizers which are extensive additives used in food packaging materials. In the present study, a rapid, simple, green and reliable method was developed and validated for the determination of twelve chemical additives in edible vegetable oils using SFC together with a modified QuEChERS procedure. Under the optimum conditions, twelve additives were separated within 10 min, and the consumption of the organic solvent was significantly reduced, which improved the environmentally friendliness. The performance of the developed method was evaluated. Good linearity (r > 0.999) was obtained in the range of 0.20−20.0 µg/mL and 0.50−20.0 µg/mL, respectively. The limits of detection and limits of quantification of the twelve additives in vegetable oils were 0.05−0.15 µg/mL and 0.15−0.50 µg/mL, respectively. Recoveries of all the chemical additives for the spiked samples were between 60.9% and 106.4%, with relative standard deviations (RSD) lower than 9.9%. The results demonstrated that the proposed method was efficient, reliable and robust for the routine analysis of additives in edible vegetable oils and can be an alternative to the multi-residue analysis of chemical additives for other packaged foods.

Hollow tube covalent organic framework for syringe filter-based extraction of ultraviolet stabilizer in food contact materials

In this work, a novel hollow tube covalent organic framework constructed by cyclotricatechylene and tetrafluoroterephthalonitrile (CTC-TFPN-COF) with polyether bond was synthesized, and it was coated on filter membrane for extraction of ultraviolet stabilizer in migration from food contact materials. Since the monomers of the polymer were linked by polyether bond, the CTC-TFPN-COF exhibited strong chemical stability in severe conditions such as acid, alkali and various organic solvent. The excellent features of high porosity and robust structure endowed the CTC-TFPN-COF good candidate as adsorbent for extraction of ultraviolet stabilizer. Moreover, the CTC-TFPN-COF coated membranes were immobilized on syringe filter and coupled with multiple channel injection pump to realize high throughput sample pretreatment strategy. Subsequently, a sensitive analytical method for ultraviolet stabilizer was established followed by ultra-high performance liquid chromatography-tandem mass spectrometry. The flow rate of extraction and desorption, elution solvent and the volume of desorption solvent were optimized. The method was assessed, which showed wide linear ranges with R2 greater than 0.99, low limits of detection (0.9-91 ng L^-1) and low limits of quantification (3-300 ng L^-1). The developed method was successfully applied to determine trace ultraviolet stabilizer in the migration of food contact materials with different simulated solution, which demonstrated its promising potential in practical analysis.

Photo aging and fragmentation of polypropylene food packaging materials in artificial seawater

Plastic litters in marine environment usually contain varied types and contents of additives that can significantly affect the photochemical aging and fragmentation process of microplastics (MPs). This study investigated the photo aging process of two common polypropylene (PP) food packaging materials (i.e., meal box and tea cup) in artificial seawater within 12 d of ultraviolet (UV) irradiation. Results revealed that the aging of both plastic materials were critically inhibited compared with pure PP, indicating that PP food packaging materials in natural seawater may share longer aging time than pure ones. GC-MS analysis revealed that antioxidant Irgafos 168 (tris (2,4-di-tert-butylphenyl) phosphite) was the dominant additive in these plastic materials. Photo reaction between Irgafos 168 and hydroperoxide species on the surface of MPs to prevent the formation of hydroxyl radical was the possible mechanism for the inhibiting effects. After antioxidant was exhausted, its photo degradation products could become the dominant contributor to influence the aging process of MPs. This is the first work exploring the role of antioxidant on the aging process of PP MPs in simulated ocean environment. The findings could be of great help for unraveling the effect of antioxidants on the aging-related environmental risk of hydrocarbon plastics in ocean environment.

Identification of Additives in Polypropylene and Their Degradation under Solar Exposure Studied by Gas Chromatography-Mass Spectrometry

Additives are absolutely essential in the development of commercial polymeric materials. Accordingly, an exhaustive control of composition and evolution in these additives over time is necessary to validate their performance and safety during their shelf life and, consequently, their ultimate applications. Gas chromatography coupled with mass spectrometry, GC-MS, is described in the present work to identify and analyze the content of a wide variety of additives, commonly used in industrial polymeric materials. First, the identification under the present experimental protocol of additives with a relatively high molecular weight (Irganox 1330 and Irganox 1010) has been successfully attained. Second, the evolution under solar exposure over time has been analyzed by GC-MS for 11 additives and derived substances, which have been identified in a commercial polypropylene sample, estimating the corresponding depletion times. In addition, the resultant increase of carbonyl groups in the polymeric macrochains along the photo-oxidation has been also determined by infrared spectroscopy. Therefore, GC-MS is found to be a reliable tool for the analysis of the evolution of commonly used polymer additives under specific degradation conditions, which can be very useful in the formulation of improved future additivations.

A general gas-assisted three-liquid-phase extraction method for separation and concentration of puerarin, 3'-methoxydaidzin, puerarinxyloside, daidzin and daidzein from puerariae extract

In this work, a general and novel separation technique gas-assisted three-liquid-phase extraction was established and applied in separating and concentrating isoflavonoids from the actual sample of puerariae extract by one step. For the gas-assisted three-liquid-phase extraction method, optimal conditions were selected: polyethylene glycol 2000 and ethyl acetate as the flotation solvent, pH 5, (NH₄ )₂ SO₄ concentration 350 g/L in aqueous phase, N₂ flow rate 30 mL/min, flotation time 50 min, and flotation twice. Five isoflavonoids compounds puerarin, 3'-methoxydaidzin, puerarinxyloside, daidzin and daidzein were separated with recoveries of 82, 84, 80, 88 and 89%, respectively. The separated products were purified by preparative high-performance liquid chromatography, and the purity of the final products was >96%. The established general gas-assisted three-liquid-phase extraction was used to separate anthraquinones from Cassiae Semen under the optimal conditions, and the recoveries were >75%. The experimental results showed that the established gas-assisted three-liquid-phase extraction method is a general technique for separating active compounds from herb extract.

Benzotriazole-type ultraviolet stabilizers and antioxidants in plastic marine debris and their new products

Ultraviolet stabilizers (UVSs) and antioxidants are the most widely used additives in plastics to enhance the lifetime of polymeric materials. There is growing interest in the roles of plastic marine debris and microplastics as source or vector of toxic substances to marine environment and organisms. However, there is limited information available on plastic associated chemicals, particularly additive chemicals. Therefore, to evaluate their extent of exposure from plastics to the marine environment, we determined UVSs and antioxidants in plastic debris (n=29) collected from beaches along with their corresponding new plastic products in markets (n=27) belonging to food, fisheries, and general use. Antioxidants were present at higher concentrations than UVSs in both plastic debris and new plastics, indicative of their high use over UVSs. Irganox 1076 and Irganox 1010 were more commonly used than other chemicals investigated. The irregular use with high concentration of additive chemicals was observed in short-term use plastic products. Except for Irganox 1076 and UV 326, most antioxidants and UVSs were relatively high in new plastics compared to corresponding plastic marine debris, implying their potential leaching or degradation during use or after disposal. The present study provides quantitative information about additive chemicals contained in plastic marine debris and their new products. These results could be useful for better understanding of environmental exposure to hazardous chemicals through plastic pollution.

Study of the Migration of Stabilizer and Plasticizer from Polyethylene Terephthalate into Food Simulants

This study investigates the determination and migration of stabilizers and plasticizers from polyethylene terephthalate (PET). Two methods [ultrasonic extraction with dichloromethane or methanol and total dissolution with phenol/tetrachloroethane (m:m/1:1)] for pre-concentration of additives in PET material were performed. The diffusion of these additives from PET was evaluated by immersing in deionized water, acetic acid 3% (w/v), ethanol 20% (v/v), ethanol 50% (v/v) and isooctane at 20, 40, 55 and 70°C, respectively. The amount of additives in PET and food simulants was quantified by high-performance liquid chromatography-photodiode array detector (HPLC-PDA). The optimized HPLC method showed high correlation coefficients (R ≥ 0.9993), good precision, accuracy and reproducibility. Experimental diffusion coefficients (DP) were calculated according to a mathematical model based on Fick's second law, and the DP values of considered compounds ranged from 9.8 × 10(-15) to 1.4 × 10(-8) cm(2) s(-1) The experimental DP values were also compared with that predicted by currently used diffusion models. In addition, the effect of temperature on the diffusion rate was assessed. The effect of temperature on the diffusion coefficients followed an Arrhenius-type model with active energies ranged from 40.4 to 113.8 kJ mol(-1) for the target compounds.

Identification and quantification of unknown antioxidants in plastic materials by ultrasonic extraction and ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry

Mass spectrometry has been applied to the targeted analysis of commonly used additives (such as Irganox 1010, Irganox 1076, Irgafos 168, etc.) in plastic materials, but a fast and straightforward method for the non-targeted identification and quantification of unusual or potentially new antioxidant additives is still unavailable. In this study, a novel and simple method for the identification and quantification of unknown antioxidant additives in plastic food packaging using ultrasonic extraction and ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry has been developed. A method for the Irganox series analyzed here has not been reported previously. Unknown antioxidant additives have been identified by accurate m/z determination, MS(2) fragments and comparison with synthesized standards. The mass fragmentation patterns and structural assignments of these antioxidants have been studied. Parameters affecting the efficiency of the process, such as extraction solvents, extraction volume, extraction time and chromatographic conditions, have been studied and optimized. Ultrasonic extraction of plastic materials (40 mg) with dichloromethane (0.5 mL) at 25 °C was applied as optimal. Limits of detection of the target additives ranged from 0.5 ng g(-1) to 1.5 ng g(-1), and the detection was linear over the range studied (0.01-1.5 µg mg(-1), r(2)>0.99). The accuracy of the method has been tested by relative recovery experiments with spiked samples, with results ranging from 94.3% to 104.8%, and the precision (relative standard deviation) was within 11.0% (n=3). Finally, the method has been successfully applied to the determination of antioxidants in several real plastic samples.

Qualitative Analysis of Additives in Plastic Marine Debris and Its New Products

Due to their formulation and/or processing, plastics contain additives and impurities that may leach out under conditions of use and accumulate in the environment. To evaluate their role as vectors of chemical contaminants in marine environment, plastic debris (n = 19) collected from coastal beaches along with new plastics (n = 25; same or same brand) bought from local markets were screened by gas chromatography-mass spectrometry in full scan mode. Detected peaks were identified using NIST library in different polymers (polypropylene (PP) > polyethylene (PE) > PP + PE > polyethyl terephthalate > poly(acylene:styrene) with different use (food, fishery, and general use). A database on the presence of 231 different chemicals were grouped into hydrocarbons, ultra-violet (UV)-stabilizers, antioxidants, plasticizers, lubricants, intermediates, compounds for dyes and inks, flame retardants, etc. The UV326, UV327, UV328, UV320, UvinualMC80, irganox 1076, DEHP, antioxidant no 33, di-n-octylisophthalate, diisooctyl phthalate, hexanoic acid 2-ethyl-hexadecyl ester, and hydrocarbons were most frequently detected. Finding of toxic phthalates and UV stabilizers in those products having moisture contact (like bottles with short use) raised concern to humans and indicated their irregular use. The comparison between new and debris plastics clearly indicated the leaching and absorption of chemicals and supports our assumption of plastic as media for transferring these additives in marine environment.