Simultaneous determination of degradation products of nonylphenol polyethoxylates and their halogenated derivatives by solid-phase extraction and gas chromatography–tandem mass spectrometry after trimethylsilylation

An efficient method for the simultaneous determination of the degradation products of nonylphenol polyethoxylates (NPnEOs, n = number of ethoxy units), i.e., nonylphenol (NP), NPnEOs (n=1–3), nonylphenoxy carboxylic acids (NPnECs, n=1–2, number of ethoxy units plus an acetate) and their halogenated derivatives (XNP, XNP1EO and XNP1EC; X=Br or Cl), in water samples were developed. After trimethylsilylation with N,O-bis(trimethysilyl)acetamide, all the analytes were determined by gas chromatography–tandem mass spectrometry (GC–MS–MS) with electron ionization (EI). The ion peaks of [M−85]+ of the derivatives were selected as precursor ions and their product ions showing the highest intensities were used for the quantitative analysis. The instrumental detection limits were in the range from 2.1 to 11 pg. The recoveries of the analytes from the water samples were optimized by using solid-phase extraction (SPE). The deuterated reagents of octylphenol, octylphenol monoethoxylate and octylphenoxyacetic acid were used as the surrogates. The method detection limits (500 ml water sample) using C18 SPE were from 2.5 to 18 ng/l. The recoveries from spiked pure water and the environmental water samples were greater than 78%. The method was successfully applied to environmental samples. Remarkably, the concentrations of the halogenated compounds (ClNP, ClNP1EO and BrNP1EO) were detected at the hundreds of ng/l levels in the Neya river.