Urine and saliva biomonitoring by HF-LPME-LC/MS to assess dinitrophenols exposure

Abstract

In this work, the determination of 2,4-, 2,5- and 2,6-dinitrophenols and the identification of some of their metabolites in human urine and saliva is proposed. A three phase hollow fiber based liquid phase microextraction prior to ultra-high performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry allowed low detection and quantitation limits of the target analytes, as well as the investigation and tentatively identification of some metabolites by accurate mass full-spectrum measurements. The chromatographic separation was accomplished on an Acquity BEH C18 column (50 mm × 2.1 mm i.d., 1.7 µm particle size) at 25 °C using water and acetonitrile (with 0.1% (v/v) formic acid) 20:80 v/v as mobile phase, at a flow rate of 0.5 mL/min in isocratic elution mode for 5 min. Hollow fiber liquid phase microextraction was achieved at donor phase pH 2, acceptor phase pH 13 and dihexylether as supported liquid membrane. Under the optimal conditions, detection limits for 2,4-, 2,5- and 2,6-dinitrophenol, respectively, were 0.18 µg·L−1, 0.38 µg·L−1 and 0.14 µg·L−1 in urine samples and 0.32 µg·L−1, 0.67 µg·L−1 and 0.24 µg·L−1 in saliva samples. The proposed methodology was applied on urine and saliva samples from laboratory staff likely to be or not occupationally exposed to dinitrophenols, finding quantitative levels of 2,4- and 2,6-dinitrophenol and identifying some metabolites previously reported in literature.