Determination of parabens in domestic sewage by isotope-coded derivatization coupled with high performance liquid chromatography-tandem mass spectrometry

We have established an isotope labeling protocol for determining parabens in wastewater, based on a pair of isotope-coded derivatization reagents, by high performance liquid chromatography (LC) and electrospray mass spectrometry (ESI-MS). The pair of reagents used in our work were d0-10-methylacridone-2-sulfonyl chloride (d0-MASC, light form) and d3-10-methylacridone-2-sulfonyl chloride (d3-MASC, heavy form). d0-MASC and d3-MASC could easily derivatize parabens at 55 °C for 7.5 min in the mixture of bicarbonate and acetonitrile (1:1 v/v). It is shown that the derivatization offers 1-2 orders of magnitude signal enhancement over underivatized counterparts. The global isotope internal standard technology was employed for quantification analysis with d3-MASC-paraben as internal standard for corresponding d0-MASC-paraben. In addition, homologous internal standard was simultaneously used to correct derivatization processes. The obtained double internal standard calibration curves for parabens were linear over the range of 1-500 nmol L− 1 (r > 0.997). The isotope-coded derivatization based quantification method was precise and practical with RSD ≤ 3.6% and accuracy ranged 96.5 to 104.7%. The proposed method has also been successfully applied to the quantification of parabens in domestic sewage samples with precisions ≤ 5.2% and recoveries ≥ 87.9%. Five kinds of paraben including methylparaben, ethylparaben, propylparaben, butylparaben, and benzylparaben were detected in the tested samples. The quantitative results indicated that parabens were at nmol L− 1 level or lower, and ethylparaben were the most abundant, followed by methylparaben, propylparaben and butylparaben. It has been demonstrated that the isotope-coded derivatization reagents are useful for accurate quantification of analytes having target functional groups in real samples.