Detection of nonylphenol isomers in sewage and sludge of waste water treatment plant by GC-FID-MS combined with deans switch

Nonylphenols (NPs) are persistent endocrine-disrupting organic pollutant. Most studies focus on total NP content, with limited research on individual isomers. This study developed a method to separation and detection of 10 NP isomers using GC-FID-MS combined with Deans switch. It can effectively transfer NPs from the first gas chromatography column (DB-5MS) to the second column (CP-ChiraSil-DEXCB), achieving efficient separation of the 10 isomers. Sewage and sludge samples from wastewater treatment plants were prepared using solid-phase extraction (SPE) and solid-liquid extraction. NP isomers in sewage samples were enriched with a phenol-specific SPE column, rinsed with 10 mL methanol-water (v/v 2:8), and eluted with 3 mL methanol and 5 mL dichloromethane. NP isomers in sludge samples underwent three ultrasonic extractions with 30 mL ethyl acetate-dichloromethane (v/v 1:1). Concentrate the extract to 1 mL and then purified using an LC NH2 column, rinsed with 9 mL of ethyl acetate-n-hexane (v/v 1:9), and eluted with 10 mL of ethyl acetate-dichloromethane (v/v 1:1) .The results showed that the recovery rates for NP isomers ranged from 70.82 % to 110.12 % in sewage (LOQ: 0.09–0.31 μg/L; RSD: 1.82 %-10.12 %) and from 72.82 % to 114.12 % in sludge (LOQ: 0.15–0.47 μg/kg; RSD: 0.23 %-11.28 %), complying with the USEPA standards (70 %-130 %). Application of the method to real samples detected all 10 NP isomers, with concentrations of 0.50–5.01 μg/L in sewage and 0.13–24.91 μg/g in sludge.This method provides a reliable approach for the detection of NP isomers in complex environmental matrices.