Development and validation of a new analytical method for the determination of 1,4-dichlorobenzene in honey by gas chromatography–isotope dilution mass spectrometry after steam-distillation

A simple, fast, sensitive and robust analytical method using gas chromatography (GC)–isotope dilution mass spectrometry (MS) was developed and validated for the identification and quantification of 1,4-dichlorobenzene (p-DCB) residues in honey samples. The proposed methodology is based on steam-distillation using a Clevenger-type apparatus followed by gas chromatography–mass spectrometry (GC–MS) in the selected ion monitoring (SIM) mode employing the isotopically labeled analogue d4-1,4-dichlorobenzene (d4-p-DCB) as internal standard (IS). Validation of the method was performed in two different GC–MS systems, using quadrupole MS (QMS) and ion-trap MS (ITMS) detectors, with no statistically significant differences between two. Recoveries were better than 91% with percent relative standard deviations lower than 12%. The instrumental limits of detection were 1 μg kg−1 in the GC–ITMS system and 0.6 μg kg−1 in the GC–QMS system. The expanded uncertainty was estimated as 17% at the currently accepted “action level” of 10 μg kg−1. The method was applied to the analysis of 310 honey samples in an extensive national monitoring study. A quality control (QC) system applied during the assays has demonstrated a good performance and long-term stability over a period of more than 8 months of continuous operation.