- 學位論文
以液相層析�質譜�質譜儀分析飲用水中的含鹵乙酸
Determination of Haloacetic Acids in Drinking Water using Liquid Chromatography / Tandem Mass Spectrometry
摘要
含鹵乙酸為主要的消毒副產物之一，自來水在加氯消毒的過程中，水中的天然有機物質會與氯反應生成含鹵乙酸，而台灣地區的自來水消毒以加氯為主。動物實驗已證實含鹵乙酸具有肝毒性、生殖毒性、發展毒性、胚胎毒性、致突變性和致癌性。對於不易揮發之含鹵乙酸，食入為其主要之暴露途徑，人體會經由每日的飲水而暴露到含鹵乙酸。 含鹵乙酸因在環境中的濃度極低，且具有高極性和易解離等特性，因此在定量分析上會造成很大的挑戰。目前含鹵乙酸之標準分析方法，為美國環保署所公告之552.3方法，此氣相層析儀－電子捕捉偵測器（gas chromatography–electron capture detection, GC-ECD）分析方法雖然有很低的偵測極限，不過萃取和衍生步驟卻很耗時費力。而且針對含鹵乙酸的高極性之特性，液相層析方法會比氣相層析方法更適合於分析不易揮發之液態樣品。然而，目前之液相層析方法，管柱對含鹵乙酸的分離和滯留能力一直是個很大的問題。 本研究可不經衍生，並以BetaMax Acid管柱和HILIC UPLC管柱分離九種含氯和溴之含鹵乙酸，以及新興之消毒副產物—一碘乙酸，再以電灑游離串連式質譜儀（electrospray ionization tandem mass spectrometry, ESI-MS/MS）偵測負離子。以減壓濃縮方式濃縮自來水水樣40倍和400倍，其回收率分別為69.7－114%和86.2－102%。雖然此濃縮方式有不錯之回收率，不過卻有嚴重的基質干擾。以BetaMax Acid管柱分析含鹵乙酸的離子抑制為12.6－88.6%，HILIC UPLC管柱之含鹵乙酸離子抑制為53.4－89.2%。 含鹵乙酸之偵測極限（LOD）在BetaMax Acid管柱為0.18－71.5 pg/μL，HILIC UPLC管柱之偵測極限為0.08－2.73 pg/μL； BetaMax Acid 管柱之定量極限（LOQ）為1.03－222 pg/μL，HILIC UPLC管柱之定量極限為0.31－9.78 pg/μL。雖然含鹵乙酸在HILIC UPLC管柱之偵測極限較低，不過若使用HILIC UPLC管柱，進樣樣品需溶於90% 乙腈，由於目前還沒有適當的前處理方法能將水中之含鹵乙酸轉換至乙腈，因此，能以100%水相進樣的BetaMax Acid管柱較適合用以分析水中之含鹵乙酸。對於自來水中主要的物種二氯乙酸（dichloroacetic acid, DCAA）和三氯乙酸（trichloroacetic acid, TCAA）而言，兩者在自來水中的濃度較高，BetaMax Acid管柱已可直接用以分析水樣中的DCAA和TCAA；而二溴乙酸（dibromoacetic acid, DBAA）、一溴一氯乙酸（bromochloroacetic acid, BCAA）和一溴二氯乙酸（bromodichloroacetic acid, BDCAA）的分析則可應用在個別濃度高於1－3 pg/μL以上之自來水水樣。此研究提供了部分含鹵乙酸之直接分析方法，而不需經萃取、衍生和濃縮步驟。
並列摘要
Haloacetic acids（HAAs）are one class of disinfection byproducts（DBPs）, which are formed when chlorinated disinfectants react with natural organic matter. In Taiwan, chlorination is the main disinfection step of in drinking water treatment. Haloacetic acids have been shown to possess hepatic, reproductive and developmental toxicity, as well as embryotoxicity, mutagenicity and carcinogenicity in laboratory animals. Because HAAs are non-volatile, ingestion is the major exposure route; people usually expose to HAAs through the consumtion of drinking water. To determine low levels of HAAs is a challenge because of their hydrophilic and strong acidic characteristics. USEPA 552.3 is a standard method for determining HAAs. The method uses gas chromatography–electron capture detection（GC-ECD）for quantitation and can reach a low detection limit to analyze HAAs in aqueous samples, but needs time-consuming and labor-intensive processes of extraction and derivatization. Due to the strong polarity of HAAs, liquid chromatography（LC）technique is more suitable than GC technique for analyzing non-volatile chemicals in aqueous samples. However, how to retain and separate HAAs with LC columns is the main problem. Nine chlorinated and brominated haloacetic acids and one emerging disinfection byproduct-monoiodoacetic acid were analyzed without dervatization in this study. HAAs were separated on BetaMax Acid column and HILIC UPLC column, and detected by negative electrospray ionization-tandem mass spectrometry（ESI (-)－MS/MS）. The samples of drinking water were concentrated with vacuum for 40 or 400 times. The recovery of 40-fold preconcentration was 69.7－114%, and was 86.2－102% in that of 400-fold preconcentration. The preconcentration methods had good recoveries, but the matrix effects were high. The ion suppression of HAAs analyzed by BetaMax Acid column was between 12.6－88.6%, and was 53.4－89.2% with HILIC UPLC column. The on-column detection limit （LOD）of HAAs by BetaMax Acid column ranged from 0.18 to 71.5 pg/μL, and was in the range of 0.08－2.73 pg/μL by HILIC UPLC column. The limits of quantification（LOQ）by BetaMax Acid column and HILIC UPLC column were 1.03－222 pg/μL and 0.31－9.78 pg/μL, respectively. The LOD of HAAs is lower on HILIC UPLC column, but the sample of HAAs needed to be dissolved in 90% acetonitrile（ACN）before injection. There were no suitable methods to transfer the HAAs from water to ACN directly. So, BetaMax Acid column with 100% aqueous injection was more suitable for analyzing HAAs in drinking water. BetaMax Acid column can be applied to determine major species of HAAs, such as dichloroacetic acid（DCAA）and trichloroacetic acid（TCAA）without concentration. BetaMax Acid column can also be applied to determine dibromoacetic acid（DBAA）, bromochloroacetic acid（BCAA） and bromodichloroacetic acid（BDCAA）, when the concentrations of these HAAs are higher than 1－3 pg/μL in drinking water. This study provided a method for determination of some HAAs without extraction, derivatization and concentration.