飲用水中含鹵乙酸分析方法評估

Abstract

自來水加氯消毒會產生共九種的含鹵乙酸消毒副產物，而目前的分析方法，如美國環保署method 552.3，及台灣NIEA W533.51B是用化學衍生搭配氣相層析分析，對其中之含溴三鹵乙酸的分析有衍生不完全與高溫注射口裂解的問題。故本研究參考美國環保署method 552.3前處理方法，使用氣相層析/質譜儀分析含鹵乙酸，探討兩種替代方法：使用管柱直接系統分析及直接分析不經衍生之含溴三鹵乙酸其裂解產物含溴三鹵甲烷。 於不分流系統，當汽化管不填充玻璃棉即可大幅減少含溴三鹵乙酸甲酯的裂解。另比較不分流模式與管柱直接注射系統，結果顯示使用管柱直接注射系統分析含鹵乙酸的訊號反應優於不分流系統，但不顯著。另外，若添加濃度0.6-30 μg/L含鹵乙酸於水樣，管柱直接注射系統與不分流系統所得之方法偵測極限介於0.12-6.7 μg/L與0.2 -5.90 μg/L。添加濃度6-200 μg/的含鹵乙酸於二次水中，管柱直接注射系統與不分流系統所得的添加回收率介於92.79-115.62％與100.07-128.80％，另外相對標準偏差分別介於2.30-12.39％與1.36-19.44％。 由於含溴三鹵乙酸通過高溫注射口即轉變成含溴三鹵甲烷，故若欲直接分析水中的含溴三鹵乙酸，可能會受水中既存之三鹵甲烷所影響。因此本實驗配置濃度50 μg/L含溴三鹵甲烷與0.1 μg/L含溴三鹵乙酸於二次水中，經氮氣吹除15分鐘後萃取，不分流系統下直接分析含溴三鹵乙酸裂解為含溴三鹵甲烷，所得方法偵測極限介於0.11-0.24 μg/L。添加濃度3 μg/L所得的添加回收率介於79.06-98.16％，另外相對標準偏差分別介於6.18-17.62％。 結論，本研究建議若欲分析含鹵乙酸可使用不分流模式之注射系統搭配汽化管不填充玻璃棉，或使用管柱直接注射系統減少含溴三鹵乙酸甲酯高溫裂解。另外，可採用含溴三鹵乙酸直接分析的方式，以降低含溴三鹵乙酸甲酯於注射口高溫的裂解，增加分析時的感度。

Nine haloacetic acids (HAAs) in drinking water are disinfection by-products. The method of analyze haloacetic acids are United States Environment Protection Agency method 552.3 and Taiwan Environment Protection Agency NIEA W533.51B, which using esterification and analyzing them by gas chromatography. Because bromocontained trihaloacetic acid esters decompose at high temperature injection port and the esterification efficiency of bromocontained trihaloacetic acids are bad, the analytical methods of haloacetic acids are still not clear. Therefore, we referred to the sample preparation methods of USEPA method 552.3, and using GC/MS to analyze haloacetic acids for investigating the sensitivity of bromocontained trihaloacetic acid esters analysis by using cool on column mode injection or analyzing bromocontained trihaloacetic acids that decomposed bromocontained to methanes at high temperature injection port. In splitless mode injection, it would decrease the situation of thermal decomposition of bromocontained trihaloacetic acid esters when liner did not packed glass wool. For comparing the analysis of haloacetic acids by the two injection systems, we used cool on column mode injection to analyze haloacetic acids was better than used splitless mode injection to do so; however, it was not apparent. Besides, adding 0.6-30 μg/L concentrations of haloacetic acids into double deionized reagent water, the range of detection limit of haloacetic acids was 0.12-6.7 μg/L in cool on column mode injection, and 0.2-5.9 μg/L in splitless mode injection. And we adding 6-200 μg/L concentrations of haloacetic acids into double deionized reagent water, the range of mean recovery of haloacetic acids was 92.79-115.62％ in cool on column mode injection, and 100.07-128.80％ in splitless mode injection. The range of relative standard diversion of haloacetic acids was 6.18-17.62％ in cool on column mode injection, and 1.36-19.44％ in splitless mode injection. Due to the high injection port temperature, bromocontained trihaloacetic acids decomposed to bromocontained methanes easily, thus, analysis of bromocontained trihaloacetic acids may be interfered with the bromocontained methanes that existed in drinking water. For this reason, 50 μg/L bromocontained methanes and 0.1 μg/L bromocontained trihaloacetic acids added to double deionized reagent water. After purging bromocontained methanes 15 minutes by nitrogen gas, the range of detection limit of bromocontained trihaloacetic acids that decomposed bromocontained methanes was 0.11-0.24 μg/L. And we adding 3 μg/L concentrations of bromocontained trihaloacetic acids into double deionized reagent water, the range of mean recovery of bromocontained trihaloacetic acids that decomposed bromocontained methanes was 92.79-115.62％. The range of relative standard diversion of bromocontained trihaloacetic acids that decomposed to bromocontained methanes was 6.18-17.62％. In conclusion, we recommended that using splitless mode injection without glass wool or using cool on column mode injection that decreased the thermal decomposition of bromocontained trihaloacetic acid esters. Besides, directly analyzing bromocontained trihaloacetic acids that decomposed bromocontained to methanes to avoid the decomposition of bromocontained trihaloacetic acid esters at a high injection port temperature and increase the sensitivity of analysis.