Determination of trace polychlorinated biphenyls in environmental water samples by solid-phase microextraction-gas chromatography-tandem mass spectrometry using carbon nanotube composite microspheres materials

Polychlorinated biphenyls （PCBs） pose serious threats to the environment and human health because they are among the most common and persistent organic pollutants globally. In this study， six PCBs were extracted from environmental water samples using multiwalled carbon nanotubes （MWCNTs） on polystyrene （PS） microspheres as the solid-phase microextraction （SPME） coating material for gas chromatography-tandem mass spectrometry （GC-MS/MS）. This coating material is highly stable and exhibited a high extraction efficiency. 2，2'，5，5'-Tetrachlorobiphenyl （PCB-52）， 2，2'，4，5，5'-pentachlorobiphenyl （PCB-101）， 2，3'，4， 4'，5-pentachlorobiphenyl （PCB-118）， 2，2'，3，4，4'，5'-hexachlorobiphenyl （PCB-138）， 2，2'，4，4'，5，5'-hexachlorobiphenyl （PCB-153） and 2，2'，3，4，4'，5，5'-heptachlorobiphenyl （PCB-180） were chosen as target analytes. The main extraction factors were optimized using a single-factor optimization method， which led to the following optimum extraction conditions： adsorption time， 50 min； agitation speed， 600 r/min； pH， 6； NaCl concentration， 1.5 mol/L； desorption temperature， 280 °C； and desorption time， 4 min. GC coupled with triple quadrupole mass spectrometry was used to quantify PCBs in water samples. The chromatographic separation system was equipped with a TG-5 SILMS column （30 m×0.25 mm×0.25 μm）， with electron impact ionization and multi-reaction monitoring modes used during mass spectrometry. Five batches of MWCNT@PS were used as SPME coating materials， which were determined to have relative standard deviations （RSD） of less than 8.8% for the six PCBs. The reusability of the MWCNT@PS coating was also investigated； RSD of the recoveries of 2.8%-9.3% were obtained after ten SPME cycles with the same coating. These results reveal that the MWCNT@PS coating materials are highly stable and reusable in SPME applications， with good results obtained under the optimal conditions. The established method exhibited linearity in the range of 0.03-1 000 ng/L for PCB-52 and PCB101， 0.07-1 000 ng/L for PCB118， PCB138， and PCB 153， and 0.10-1 000 ng/L for PCB-180， with correlation coefficients of 0.993-0.998. Limits of detection and quantification （LODs and LOQs， respectively） of 0.01-0.03 and 0.03-0.10 ng/L were determined for the developed method. The intra- and inter-day precisions exhibited RSDs of 1.64%-8.16% and 2.83%-8.41%， respectively， at 2 ng/L， 3.31%-7.19% and 3.79%-9.12%， respectively， at 10 ng/L， and 2.70%-9.38% and 4.04%-8.56%， respectively， at 100 ng/L. The established method was used to determine six PCBs in barreled drinking water， rainwater， and three environmental river water samples. No PCBs were found in barreled drinking water， rain water and river water. Satisfactory recoveries of 82.4%-113.2% were achieved at low， medium， and high levels. Accordingly， the MWCNT@PS-composite-coating-material-based SPME-GC-MS/MS method is accurate and effective. This study revealed that MWCNT@PS composites provide a good avenue for the rapid and sensitive detection of PCBs in water samples.