固相微萃取/气相色谱/燃烧-同位素比值质谱技术测定水体中微量苯系物单体碳同位素方法研究

Research on the Method for Determining Compound Specific Carbon Isotopes of Trace Benzenes in Water by Solid Phase Microextraction/Gas Chromatography/Combustion-Isotope Ratio Mass Spectrometry

该文建立了固相微萃取/气相色谱/燃烧-同位素比值质谱(SPME/GC/C-IRMS)技术测定水体中7种苯系物碳同位素(δ13C)的方法。实验结果表明,萃取温度30℃,萃取时间60 min条件下萃取效果最佳,萃取温度(30~60℃)和萃取时间(15~60 min)对顶空萃取(HS-SPME)过程中的碳同位素分馏无影响。最佳萃取条件下,利用HS-SPME和直接萃取(D-SPME)方法分别测试7种苯系物的δ13C值,标准偏差分别为0.08‰~0.45‰和0.05‰~0.39‰,测试误差分别为-0.16‰~0.33‰和-0.41‰~0.46‰,两种SPME方式在萃取过程中均未发生明显碳同位素分馏,HS-SPME的灵敏度比D-SPME方法高1~2个数量级。通过移动平均值算法计算苯、间/对二甲苯、异丙苯的检出限为1μg/L,甲苯、乙苯、邻二甲苯、苯乙烯的检出限为2μg/L。测得江苏某废弃农药场地下水中7种苯系物δ13C值的标准偏差为0.01‰~0.43‰。该方法样品前处理简单、灵敏度高、准确性好,适用于水体中痕量苯系物单体碳同位素的检测。

This study introduces a solid phase microextraction/gas chromatography/combustion-iso⁃tope ratio mass spectrometry(SPME/GC/C-IRMS)technology for analyzing the carbon isotopes of sev⁃en benzene series compounds in water.The pretreatment conditions for headspace solid phase micro⁃extraction(HS-SPME)were optimized.The results demonstrated that the extraction efficiency reached its maximum at an extraction temperature of 30℃and an extraction time of 60 minutes.Vari⁃ations in extraction temperature(30-60℃)and extraction time(15-60 min)did not cause carbon iso⁃tope fractionation during HS-SPME.Under the optimized extraction conditions,both HS-SPME and D-SPME methods were employed to measure theδ13C values of the seven benzene series compounds.The standard deviations ranged from 0.08‰-0.45‰and 0.05‰-0.39‰,and the test error varied from-0.16‰-0.33‰and-0.41‰-0.46‰,respectively.No obvious carbon isotope fractionation occurred during the extraction process in both SPME methods,and the sensitivity of the HS-SPME method is 1-2 orders of magnitude higher than the D-SPME method.Utilizing the moving average al⁃gorithm,the detection limits for benzene,m-/p-xylene,and isopropylbenzene were determined to be 1μg/L,while for toluene,ethylbenzene,o-xylene and styrene,the detection limits were 2μg/L.This method was applied to analyze groundwater from an abandoned pesticide factory in Jiangsu,yield⁃ingδ13C values for the seven benzene series compounds with good repeatability(standard deviation:0.01%-0.43‰).This method can be applied to detect the carbon isotope for trace benzene series com⁃pounds in water,because of the simple pretreatment procedure,high sensitivity and good accuracy.