A rapid, accurate and sensitive method with the new stable isotopic tags based on microwave-assisted dispersive liquid-liquid microextraction and its application to the determination of hydroxyl UV filters in environmental water samples

A rapid, accurate and sensitive method, using the stable isotope labeling (SIL), microwave-assisted dispersive liquid-liquid micro extraction (MADLLME) and the ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), was developed and validated for the determination of hydroxyl UV Filters in environmental water samples. A pair of new isotopic tags D 0 -/D 3 -1-methylindole-3-acetic acid (D 0 -/D 3 -MIAA) is synthesized, with which a simple yet efficient pretreatment MADLLME-SIL is developed. Under the optimized conditions (80   ℃, 240   W, 180   s), the sample pretreatment including analyte extraction, pre-concentration and isotope labeling can be finished conveniently in only 9   min. D 0 -/D 3 -MIAA labeling improves the chromatographic retention by strengthening the hydrophobicity and enhances the MS response for 3–4 orders of magnitude. Excellent linearity is established by the H/D ratios of 1/10–10/1 with the correlation coefficients >0.9990. The quite low detection limits (0.54–1.79   ng/L) are achieved, ensuring the trace detection. This method is successfully applied to a series of environmental water samples. The recoveries (93.2%~103.5%) are significantly improved and the analysis time is largely reduced (<15   min). The excellent sensitivity, accuracy, recovery, and efficiency demonstrate this MADLLME-SIL-LC-MS/MS method a superior alternative for the analysis of UV filters in water samples.