Valoration of the Synthetic Antioxidant Tris-(Diterbutyl-Phenol)-Phosphite (Irgafos P-168) from Industrial Wastewater and Application in Polypropylene Matrices to Minimize Its Thermal Degradation

Aquatic toxicity of UV-irradiated commercial polypropylene plastic particles and associated chemicals

Plastics often contain non-polar chemical additives, such as antioxidants, flame retardants, plasticizers, and UV stabilizers, which improve performance but have poorly understood environmental risks. This study assessed the aquatic toxicity of polypropylene (PP) containing the antioxidant Irgafos 168 (IRG) to the crustacean Daphnia magna and the green alga Raphidocelis subcapitata. Commercial PP containing IRG (PPc) and additive- and oligomer-free PP (PPd) were irradiated at 254 nm using germicidal light, both with and without H2O2. The tested particles included microplastics (MPs, 1-50 μm and 50-500 μm) and nanoplastics (NPs, < 1 μm). The results showed that the toxicity was influenced by particle size, concentration, and the presence of the antioxidant additive. Smaller particles, along with the presence of IRG and its degradation products, tris(2,4-di-tert-butylphenyl) phosphate, bis(2,4-di-tert-butylphenyl) phosphate, and 2,4-di-tert-butylphenol, contributed to higher toxicity in both D. magna and R. subcapitata. The highest toxicity was observed for NPs containing IRG (PPc), which resulted in an EC20 for D. magna immobilization of 7.2 ± 0.1 mg/L, compared to the less toxic NPs free of IRG (EC20 28.7 ± 4.2 mg/L). The growth rate of R. subcapitata was also more affected by NPs generated from PPc (EC20 0.2 ± 1.2 mg/L) than by the corresponding NPs free of IRG (LOEC 3 mg/L). Our findings showed that the main toxicity was driver was an increase of intracellular reactive oxygen species, lipid peroxidation (LPO), damage to cell membrane integrity and impairment of esterase activity. The results demonstrated that irradiated plastic particles act as carriers for toxic non-polar compounds, enhancing negative effects on aquatic organisms, with particle size being a key factor. This study highlights the complex toxicological impacts of micro- and nano-plastics containing additives on aquatic biota.

Use of a nanoplastic carrier for assessing the aquatic toxicity of an organo-phosphite polymer additive

This work reports the production of nanoplastics (NPs) from polypropylene (PP) free of the antioxidant Irgafos® 168 (IRG) and alkane oligomers (ALK). PP pellets were milled into a powder with particle sizes in the 100-500 μm range. Additives and oligomers were removed using dichloromethane, and the powder exposed to UV irradiation, followed by filtration through 1 μm filters. PP suspensions, free of antioxidant and oligomers, were reloaded with IRG and ALK to their original commercial concentrations. This approach allowed testing the aquatic toxicity of IRG at concentrations compromised by water solubility limits. Toxicity assays using the cladoceran Daphnia magna with 24-48 h immobilization of neonates as endpoint showed toxicity for NPs containing IRG, with EC20 (48 h) in the 1.8-3.5 mg/L range, that corresponded to IRG exposure <1.2 μg/L. Suspensions of PP containing ALK, but not IRG, exhibited low toxicity (EC20 > 20 mg/L). The results allowed estimating the toxicity of IRG with a EC50 value of 3.3 ± 1.1 μg/L. Assays with different proportions of IRG and its oxidized form showed no differences. This work demonstrated the aquatic toxicity of IRG, for which there were no previous data, and developed a method for testing the toxicity of non-polar additives without being limited by their solubility.

Chemical Exposomics in Human Plasma by Lipid Removal and Large-Volume Injection Gas Chromatography-High-Resolution Mass Spectrometry

For comprehensive chemical exposomics in blood, analytical workflows are evolving through advances in sample preparation and instrumental methods. We hypothesized that gas chromatography-high-resolution mass spectrometry (GC-HRMS) workflows could be enhanced by minimizing lipid coextractives, thereby enabling larger injection volumes and lower matrix interference for improved target sensitivity and nontarget molecular discovery. A simple protocol was developed for small plasma volumes (100-200 μL) by using isohexane (H) to extract supernatants of acetonitrile-plasma (A-P). The HA-P method was quantitative for a wide range of hydrophobic multiclass target analytes (i.e., log Kow > 3.0), and the extracts were free of major lipids, thereby enabling robust large-volume injections (LVIs; 25 μL) in long sequences (60-70 h, 70-80 injections) to a GC-Orbitrap HRMS. Without lipid removal, LVI was counterproductive because method sensitivity suffered from the abundant matrix signal, resulting in low ion injection times to the Orbitrap. The median method quantification limit was 0.09 ng/mL (range 0.005-4.83 ng/mL), and good accuracy was shown for a certified reference serum. Applying the method to plasma from a Swedish cohort (n = 32; 100 μL), 51 of 103 target analytes were detected. Simultaneous nontarget analysis resulted in 112 structural annotations (12.8% annotation rate), and Level 1 identification was achieved for 7 of 8 substances in follow-up confirmations. The HA-P method is potentially scalable for application in cohort studies and is also compatible with many liquid-chromatography-based exposomics workflows.

Development of a dispersive liquid-liquid microextraction method for the determination of plastic additives in seawater

A method using dispersive liquid-liquid microextraction (DLLME) prior to high performance liquid chromatography-diode array detection (HPLC-DAD) was developed to determine seven additives from the plastics industry (butylated hydroxytoluene, diisodecyl phthalate, irgafos 168, lawsone, quercetin, triclosan and vitamin E) in seawater samples. These compounds can reach seawater due to direct discharge from wastewater treatment plants and leaching from plastics and microplastics. The extraction was performed using 25 mL of seawater, 500 μL of 1-octanol (extraction solvent) and a stirring step instead of dispersive solvent. Additive concentrations were determined by LC-DAD on a C18 column with a mobile phase of acetonitrile and phosphoric acid aqueous solution (pH 3.5) by gradient elution. The analytical recoveries ranged from 82 to 93% for all compounds, except for lawsone (60%). Repeatability and intermediate precision were adequate with RSD < calculated values following the Horwitz equation at the concentration levels evaluated (0.06 and 0.24 mg L-1). All additives exhibited linear matrix calibration curves (R2 > 0.99). Detection limits ranged from 0.009 to 0.028 mg L-1 and quantification limits ranged from 0.027 to 0.084 mg L-1. Finally, the application of the method to real samples verified the method as accurate and applicable to seawater.