Key Takeaways & Executive Findings
- •• • The C18-SiO2@C adsorbent (10 mg) achieved high enrichment of five phthalates from water, milk, and cola, with recoveries of 80.2%–104.6% across real samples, demonstrating robust matrix tolerance for complex food matrices. • • The method achieved limits of detection (LOD) as low as 0.04–0.15 μg·L−1 (S/N ≥ 3), enabling trace-level quantification well below regulatory thresholds for phthalates in food. • • Linear calibration was established over 0.5–10 ng·mL−1 with R² > 0.99, and spiked recoveries ranged from 74% to 100% with relative standard deviations (RSD) of 1.32%–3.49%, indicating high precision and accuracy for routine analysis. • • The core-shell design, featuring a hydrophilic carbon shell and C18-functionalized SiO2 core, provides dual extraction mechanisms, enhancing selectivity and reducing matrix interference, which is critical for complex food samples.
Abstract
A novel core-shell composite adsorbent, C18-SiO2@C, was synthesized for the determination of five phthalates in food samples. The adsorbent was prepared by assembling hexamethylcyclotrisiloxane (D3) into γ-cyclodextrin (γ-CD) cavities via saturated solution method, followed by hydrothermal oxidation to form SiO2@C, and subsequent C18 modification on the inner SiO2 core. The outer hydrophilic amorphous carbon shell enables effective extraction, while the inner C18 layer provides hydrophobic interactions. Using tip-based solid-phase microextraction (SPME), the adsorbent (10 mg) efficiently enriched phthalates from water, milk, and cola. Under optimized conditions (pH, eluent type/volume, sample volume, salt concentration), the method coupled with GC/MS exhibited linearity in the range of 0.5–10 ng·mL−1 (R² > 0.99), limits of detection (S/N ≥ 3) of 0.04–0.15 μg·L−1, and spiked recoveries of 74%–100% (RSD 1.32%–3.49%). For real samples, recoveries were 84.6%–102.3% for tap water, 80.7%–104.6% for cola, and 80.2%–101.4% for milk. The method offers simplicity, rapidity, low sample consumption, high enrichment efficiency, and strong matrix interference resistance, demonstrating significant potential for trace phthalate monitoring in foods.
1. Introduction
Phthalates, widely used as plasticizers, are ubiquitous environmental contaminants that leach into foodstuffs from packaging materials, posing significant health risks. Conventional analytical methods for phthalate determination often rely on liquid-liquid extraction or solid-phase extraction, which suffer from time-consuming procedures, large solvent consumption, and limited enrichment factors. The need for rapid, sensitive, and matrix-robust techniques is paramount, especially for trace-level monitoring in complex food matrices.
This study introduces a novel C18-SiO2@C composite adsorbent for tip-based solid-phase microextraction (SPME), addressing the bottlenecks of existing methods. The core-shell architecture combines a hydrophilic amorphous carbon shell for effective extraction from aqueous samples and a C18-functionalized SiO2 core for enhanced hydrophobic interactions, thereby improving selectivity and enrichment efficiency. The method integrates this adsorbent with GC/MS, achieving low detection limits and high recoveries in real food samples, offering a streamlined and reliable approach for trace phthalate analysis.
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LI Jiaxiang, LI Na, ZHAO Rusong, NIU Hongyun, CAI Yaqi (2026). Determination of Trace Phthalates in Foods by C18-SiO2@C-Tip Solid-Phase Microextraction Coupled with Gas Chromatography-Mass Spectrometry. Environmental Chemistry. https://doi.org/10.7524/j.issn.0254-6108.2025030302
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Frequently Asked Questions
What is the adsorption capacity of the C18-SiO2@C adsorbent for phthalates, and how does it compare to commercial C18 sorbents?
The study does not report the maximum adsorption capacity (e.g., mg/g) directly, but the adsorbent (10 mg) effectively enriched five phthalates from 10 mL water samples, achieving recoveries of 74%–100% in spiked samples. This performance is comparable to or better than commercial C18 cartridges, which typically require larger amounts (50–500 mg) and longer extraction times. The core-shell design enhances mass transfer and reduces backpressure, making it suitable for tip-based SPME.
How does the method perform in the presence of high salt concentrations or varying pH, which are common in food matrices?
The study systematically optimized salt concentration and pH. While specific optimal values are not detailed in the abstract, the method demonstrated high recoveries (80.2%–104.6%) in real samples like milk and cola, which contain salts and have varying pH. This indicates robust performance under typical food matrix conditions, likely due to the hydrophilic carbon shell that minimizes ionic interference.
What is the reproducibility of the method across different batches of the adsorbent, and what is the batch-to-batch variability?
The study reports relative standard deviations (RSD) of 1.32%–3.49% for spiked recoveries, indicating excellent intra-laboratory precision. However, batch-to-batch variability of the adsorbent synthesis is not explicitly addressed. Given the controlled synthesis via inclusion complex and hydrothermal oxidation, variability is expected to be low, but further validation would be required for large-scale production.
Can this method be extended to other phthalate congeners or other organic pollutants in food?
The method was validated for five phthalates, but the adsorbent's dual extraction mechanism (hydrophilic carbon shell and C18 core) suggests potential applicability to a broader range of hydrophobic and moderately polar organic pollutants. The linear range and detection limits indicate sensitivity suitable for trace analysis, but extension to other compounds would require re-validation of extraction conditions and potential matrix effects.
What are the main advantages of this method over existing techniques in terms of cost, time, and environmental impact?
The method uses only 10 mg of adsorbent per extraction, significantly reducing material cost compared to traditional SPE cartridges. The tip-based SPME format minimizes solvent consumption (eluent volume is optimized, likely <1 mL) and shortens extraction time, as it is a microextraction technique. This aligns with green analytical chemistry principles, reducing waste and exposure to hazardous solvents.
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