One-step extraction prior to two-step detection by ultra high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) to determine different groups of antibacterial agents in infant disposable hygiene products

Abstract

One-step extraction prior to a two-step detection method based on UHPLC-MS/MS was developed to determine seven quaternary ammonium salts (QACs), three isothiazolinone antibacterial agents and seven phenolic antibacterial agents in infant disposable hygiene products. Samples were ultrasonically extracted by acetonitrile; the extraction solution was directly used to separate seven QACs on a hydrophilic chromatographic column (HILIC column) by isocratic elution (0.1% formic acid acetonitrile and 10 mmol L⁻¹ ammonium acetate solution as the mobile phases). QACs were then detected in multiple reaction monitoring (MRM) of MS/MS under an electro-spray ionization source in positive mode (ESI⁺). For the remaining ten analytes, the extraction solution was dried by nitrogen gas blowing and re-dissolved with acidulated methanol water solution. Then they were separated on a C18 chromatographic column with gradient elution program using methanol and water as mobile phases. Finally, ten analytes were simultaneously ionized by using a electro-spray source in positive and negative modes and acquisition was achieved in MRM. The developed methods were validated in terms of the method limit of detection and quantitation (MLOD and MLOQ), matrix effects, recovery and precision. Results indicated that favorable linear relations (r > 0.997) were obtained over the selected concentration ranges of 0.1–50 μg L⁻¹, 1.0–500 μg L⁻¹ and 50–2000 μg L⁻¹ for QACs, isothiazolinone antibacterial agents and phenolic antibacterial agents, respectively. The MLODs of the three groups of antibacterial agents were 0.8 μg kg⁻¹, 1.5–6.5 μg kg⁻¹ and 200–500 μg kg⁻¹, respectively. Recoveries were calculated at three concentration levels spiked in negative paper diaper samples and the values were found between 83.7% and 112% with relative standard deviation (RSD) values less than 13% for intra-day precision (n = 6) and less than 16% for inter-day precision (n = 5). The developed and validated methods were successfully applied to determine the concentrations of antibacterial agents in real samples and QACs and isothiazolinone antibacterial agents were detected in several samples. These methods are rapid, sensitive and suitable for the determination of antibacterial agents in infant disposable hygiene products and some other similar products.