Investigation of the applicability of highly ordered TiO2 nanotube array for enrichment and determination of polychlorinated biphenyls at trace level in environmental water samples

Fully automated graphitic carbon nitride-based disposable pipette extraction-gas chromatography-mass spectrometric analysis of six polychlorinated biphenyls in environmental waters

A fully automated online emulsification-enhanced disposable pipette extraction-gas chromatography-mass spectrometry (EE-DPX-GC-MS) method has been developed for the extraction of six polychlorinated biphenyls (PCBs) from environmental waters. An in-house prepared material, graphitic carbon nitride (g-C₃N₄), was used as sorbent in a home-packed DPX device. The six PCBs studied include PCB 10, 28, 52, 153, 138 and 180. g-C₃N₄ was characterized successfully by X-ray diffraction, elemental analysis, scanning electron microscopy, Fourier-transform infrared and Raman spectroscopy. As a C-N analogue of graphite, the two-dimensional structure of g-C₃N₄ allows rapid analyte adsorption and desorption to take place. With a significant number of nitrogen functionalities in g-C₃N₄, the material dispersed well in aqueous sample, increasing the active surface area of contact between the sorbent and the sample. When coupled with a pre-emulsification step, PCBs in each portion of sample could be efficiently extracted by g-C₃N₄ within 20 s of gentle turbulence. Under the most favorable conditions, the automated online EE-DPX-GC-MS method achieved wide dynamic working ranges with good linearity (r² ≥ 0.998) for all analytes. Limits of detection ranging between 4.35 and 7.82 ng L^-1 were attained, with enrichment factors of between 34 and 57 and relative standard deviations (RSDs) for intra- and inter-day precision of ≤ 8.95% and ≤ 12.6%, respectively. Absolute recoveries were between 69.3% and 109%. The fully automated online EE-DPX-GC-MS approach was applied to industrial wastewaters and reservoir waters where good relative recoveries of PCBs of between 89.3% and 105% were obtained, with RSDs ≤ 11.6%.

Nano-Al2O3-based micro solid-phase filter membrane extraction for simultaneous determination of tartrazine and sunset yellow in food

A new micro-solid-phase extraction method based on a prestructured filter membrane was developed to facilitate simultaneous analysis of tartrazine (TA) and sunset yellow (SY) with high performance liquid chromatography (HPLC).