Simultaneous Extraction and Determination of Three Quaternary Ammonium Compouds in Soil by Ultrasonic Exaction and Gas Chromatography-Mass Spectrometry / 分析化学

ABSTRACT

An analytical method was developed for the simultaneous extraction and determination of three quaternary ammonium compouds ( QACs) in soil samples using ultrasonic extraction and gas chromatography-mass spectrometry( GC-MS) . The qualitative and quantitative analysis of the three analytes dodecyltrimethyl ammonium chloride ( DTAC) , cetyltrimethyl ammonium bromide ( CTAB) and didodecyldimethyl ammonium chloride ( DDAC) were conducted by application of EI mass spectra and selected ion monioring ( SIM ) . Characteristic ions of the QACs were m/z 58 ( DTAC and CTAB) and m/z 212 ( DDAC) . To achieve optimum extraction efficiency, several impact factors including types of extractants, pH of extraction, concentration of linear alkylbenzene sulfonates ( LAS) , extraction times and content of purification column were investigated. Methanol with pH 3. 5 and 40 μg/L LAS solution were selected as extractant. Soil sample was extracted by treated methanol each 10 mL for 20 min every time. Extract of the soil sample was purified by neutral alumina column with 4 cm in length and 1cm in diameter, and then was determineted by GC-MS. Good linear relationships of all the three QACs were obtained in the range of 0. 02-2. 0 mg/L. The limits of determination (LOD, S/N=3) was 1. 2-4. 5 μg/kg. The method was used to analyse real soil samples ( paddy soil, lateritic red soil, and ore tailings) collected from a mining district in south China. Results of determination exhibited the concerntrations of the three analytes in real soil samples ranged from 0 . 24 mg/kg to 0. 41 mg/kg, and their recoveries ranged from 76% to 113% with relative standard deviations ( RSD) of 1. 1%-12. 9% in three different spiked concentrations of 0. 2, 0. 5 and 1. 0 mg/kg.