Dispersive Liquid-Liquid Microextraction and GC–MS Used to Detect Flame Retardant in Sewage

A recent study led by scientists from São Paolo State University in São Paulo, Brazil used dispersive liquid-liquid microextraction (DLLME) coupled with pyrolysis gas-chromatography–mass spectrometry (GC–MS) to determine flame retardants in sewage sludge samples. Their findings were published in the Journal of Chromatography A (1).

Closeup of plumber's hands assembling pvc sewage pipes | Image Credit: © Roman Milert - stock.adobe.com

Flame retardant is a contaminant of emerging concern (CECs), which are chemicals or materials characterized by a perceived, potential, or real threat to human health or the environment (2). Examples of common CECs include pesticides, illicit drugs, pharmaceuticals, personal care products, alkylphenols and their derivatives, brominated flame retardants, and perfluorinated organic compounds. Some of these compounds are considered endocrine disruptors, which can cause morphological damage, leukemia, brain cancer, and neurobehavioral disorders (1).

In this study, the scientists examined DLLME and magnetic ionic liquid (MIL) for the extraction of polybrominated flame retardants in sewage sludge samples, followed by sample introduction using a pyrolizer and analysis by GC–MS. DLLME stands out for its ability to reduce sample and solvent volumes, the scientists wrote. This approach enables the MIL to be compatible with gas chromatography systems, which can optimize analytical and instrument performance.

A pyrolyzer was used in the sample introduction step (Py-GC–MS), and critical injection settings were optimized using multivariate approaches. Optimized conditions were achieved with a temperature of 220 °C, a pyrolysis time of 0.60 min, and an injection volume of 9.00 μL. DLLME optimization was performed through central compound planning (CCD), and optimized training conditions were achieved with 10.0 mg of MIL, 3.00 μL of acetonitrile (ACN) as dispersive solvent, extraction time of 60 s, and volume of a sample of 8.50 mL.

This method proved effective. Py-GC–MS offers advantages for polybrominated Diphenyl Ethers (PBDE) analysis, the scientists wrote, due to its ability to quantify and identify both volatile and thermally-stable compounds, using a pyrolyzer in the sample introduction step prior to chromatographic analysis. MIL purity was confirmed by Fourier-transform infrared (FT-IR) and Raman spectroscopy, which showed a shift in the vibrational mode associated with the Mn-Cl bond. Direct MIL injection into a GC–MS system can cause injector degradation and compromise the analysis process; by using a pyrolyzer, these issues were minimized and ensure optimal analytical and instrumental performance while reducing contamination and background interference.

Applying this method to sewage sludge samples could provide essential data on the presence and distribution of PBDEs in aquatic environments. Analysis of the sludge sample revealed the presence of PBDE 28, which was further confirmed by comparing its retention time and other parameters to those found in the sample. The sensitivity and selectivity of the proposed method enables more in-depth studies into the effects of PBDEs on human health and the ecosystem. The combination of MIL, DLLME, and Py-GC–MS presents a promising analytical tool for PBDE determination in complex samples and contributes towards advances in environmental research.

References

(1) Rodrigues, T.; Ferreira, K. C.; Isquibola, G.; Franco, D. F.; et al. Investigating a New Approach for Magnetic Ionic Liquids: Dispersive Liquid-Liquid Microextraction Coupled to Pyrolysis Gas-Chromatography-Mass Spectrometry to Determine Flame Retardants in Sewage Sludge Samples. J. Chromatogr. A 2024, 1730, 465038. DOI: 10.1016/j.chroma.2024.465038

(2) Contaminants of Emerging Concern. CT.GOV 2024. https://portal.ct.gov/deep/remediation--site-clean-up/contaminants-of-emerging-concern/contaminants-of-emerging-concern (accessed 2024-8-2)