分散固相法与气相色谱-质谱法相结合测定自来水中的土腥味物质

Determination of Earthy-musty Odorants in Tap Water by Gas Chro⁃matography-Mass Spectrometry with Dispersion Solid-phase

建立了正己烷提取、分散固相浓缩、气相色谱-质谱(GC-MS)测定自来水中土腥味物质土臭素(GSM)和2-甲基异冰片(2-MIB)的方法。通过对提取剂体积、分散固相时间、洗脱剂比例的优化,确定了最佳实验条件,即15 mL正己烷进行液液萃取,0.5 g硅胶分散固相吸附7 min,1 mL正己烷-乙酸乙酯(1∶1,体积比)进行洗脱。采用优化的GC-MS色谱条件,在选择离子监测(SIM)模式下进行测定,内标法定量。结果显示,GSM和2-MIB在0.5~500 ng/mL范围内呈良好线性关系,相关系数(r^(2))均大于0.999,检出限分别为0.8、0.4 ng/L,定量下限分别为2.5、1.5 ng/L。以自来水为空白基质,在4、8、20、80、400 ng/L加标水平下,GSM和2-MIB的平均回收率为72.7%~114%,相对标准偏差(RSD)为1.1%~7.8%。该方法操作简便,定量准确,适用于自来水中GSM和2-MIB的测定。

A gas chromatography-mass spectrometry(GC-MS)with dispersive solid-phase extrac⁃tion was developed for the analysis of earthy-musty odorants,including geosmin(GSM)and 2-methyl⁃isoborneol(2-MIB)in tap water.n-hexane liquid-liquid extraction(LLE)combined with silica disper⁃sion solid-phase(DSP)was used to isolate the analytes in tap water.The pretreatment conditions in⁃cluding the volume of extractant,time of DSP and eluent ratio were optimized.The optimal experimen⁃tal conditions were as follows:the samples were extracted with 15 mL n-hexane,then the targets in ex⁃tract solution were absorbed with 0.5 g silica for 7 min,and finally,1 mL n-hexane/ethyl acetate(1∶1,by volume)was used to elute the compounds.The chromatographic conditions for detection of GSM and 2-MIB were optimized,then the supernatant was determined by GC-MS in selected ion monitoring(SIM)mode,and quantified by the internal standard method.The results showed that there were good linearities for GSM and 2-MIB in the range of 0.5-500 ng/mL,with correlation coefficients(r^(2))great⁃er than 0.999.The limits of detection(LODs)for GSM and 2-MIB were 0.8 ng/L and 0.4 ng/L,respectively,while the limits of quantitation(LOQs)for GSM and 2-MIB were 2.5 ng/L and 1.5 ng/L,respectively.The average recoveries for GSM and 2-MIB in tap water,at five spiked levels of 4,8,20,80,400 ng/L ranged from 72.7%to 114%,with relative standard deviations(RSDs)of 1.1%-7.8%.The method is simple in operation and accurate in quantification,and it is suitable for the de⁃termination of GSM and 2-MIB in tap water.