Development of an Effective Method for the Determination of p-Hydroxybenzoic Acid Esters (Parabens) in Sediment

This study developed a method for the simultaneous determination of seven paraben compounds in sediment samples using liquid chromatography-tandem mass spectrometry (LC-MS/MS) combined with solid-phase extraction (SPE). Parabens were separated on a C18-column (Kinetex: 150 mm x 2.1 mm, 2.6 µm), with mobile phases (A): 0.05% acetic acid and (B): methanol. One hundred nanograms of each surrogate standard (13C-MeP and 13C-BuP) were added to 500 mg of dried sediment sample. Parabens were then ultrasonically extracted for 10 min with 5 mL of methanol/acetonitrile (1/1, v/v) acidified to pH~3 with formic acid. The sample was centrifuged at 4500 rpm for 5 min, and the supernatant was transferred to a glass tube. The extraction procedure was repeated twice. The extracted solution were then concentrated to ~1.5 mL under a gentle stream of nitrogen. The sample was then added with 10 mL of ultrapure water and passed through an SPE column (Oasis HLB 500 mg), which had been activated respectively with 3 mL of methanol and 3 mL of ultrapure water. The target compounds were eluted with 5 mL of methanol. The eluted solution was concentrated to 1 mL under a stream of nitrogen. The final solution was filtered through a Whatman filter paper (pore size: 0.2 µm) and analyzed on an LC-MS/MS instrument. Calibration curves of the native compounds were constructed in the concentration range of 0.5–200 ng/mL (R2 > 0.997). The recoveries of the surrogate standards (13C-MeP and 13C-BuP) were in the range of 85.5–105% (RSD < 9.5%) and 88.0–110% (RSD < 8.0%), respectively. The method detection limits of parabens in sediment samples ranged from 0.027 to 0.067 ng/g. The standardized method was applied to determine the distribution of parabens in sediment samples collected from To Lich River, Hanoi. Total concentrations of parabens in sediment samples ranged from 12.5 to 81.9 ng/g.