Use of gas chromatography-mass spectrometry-olfactometry and a conventional flask test to identify off-flavor compounds generated from phenylalanine during chlorination of drinking water.
Use of gas chromatography-mass spectrometry-olfactometry and a conventional flask test to identify off-flavor compounds generated from phenylalanine during chlorination of drinking water.
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DOI：
10.1016/j.watres.2017.08.063
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发表时间：
2017-11
期刊：
影响因子：
12.8
通讯作者：
T. Matsushita;Miki Sakuma;Shiori Tazawa;Taiki Hatase;N. Shirasaki;Y. Matsui
中科院分区：
文献类型：
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作者：
T. Matsushita;Miki Sakuma;Shiori Tazawa;Taiki Hatase;N. Shirasaki;Y. Matsui
饮用水中的异味可能是由氯化过程中存在的有机化合物（如氨基酸）产生的转化产物（TP）引起的。然而，这些TP中的许多对整体异味的贡献尚未被量化，主要是因为缺乏适当的化学标准，阻止了通过常规烧瓶测试进行感官评价。在本研究中，我们使用气相色谱-质谱-嗅觉测定法（GC-MS-O），以确定负责的氨基酸苯丙氨酸的水溶液的氯化产生的异味的化合物，我们提出了一个感官评价程序的量化的贡献确定的TP的整体异味，无论可用的化学标准的TP。GC-MS-O显示，两种TP，N-氯苯基乙醛亚胺和2-氯-2-苯乙醛，其化学标准没有商业上可获得的，是导致氯化溶液异味的主要组分。通过使用的感官评价程序，涉及GC-MS-O和传统的烧瓶测试的组合，我们量化的贡献TP的整体异味的氯化溶液。约60%的异味可归因于游离氯（13%）、2-氯-2-苯乙醛（13%）、三氯胺（12%）、苯乙醛（11%）、苯乙腈（8%）和N-氯苯乙醛亚胺（2%）。用粉末活性炭（PAC）处理去除异味。氯化15 N-标记的苯丙氨酸的实验表明，PAC还原分解三氯胺成N2气体和吸附所有其他确定的TP。超细PAC（中位粒径0.7 μm）比普通PAC（中位粒径8.0 μm）去除异味更快。
Off-flavor in drinking water can be caused by transformation products (TPs) generated from organic compounds, such as amino acids, present during chlorination. However, the contributions of many of these TPs to overall off-flavor have not been quantified, mainly because the lack of appropriate chemical standards prevents sensory evaluation by means of a conventional flask test. In the present study, we used gas chromatography–mass spectrometry–olfactometry (GC-MS-O) to identify compounds responsible for the off-flavor generated by chlorination of an aqueous solution of the amino acid phenylalanine, and we propose a sensory evaluation procedure for quantification of the contributions of the identified TPs to the overall off-flavor, regardless of the availability of chemical standards of the TPs. GC-MS-O revealed that two TPs,N-chlorophenylacetaldimine and 2-chloro-2-phenylacetaldehyde, for which chemical standards are not commercially available, were the main components responsible for the off-flavor of the chlorinated solution. By using a sensory evaluation procedure involving a combination of GC-MS-O and a conventional flask test, we quantified the contributions of TPs to the overall off-flavor of the chlorinated solution. Approximately 60% of the off-flavor was attributable to free chlorine (13%), 2-chloro-2-phenylacetaldehyde (13%), trichloramine (12%) phenylacetaldehyde (11%) phenylacetonitrile (8%), andN-chlorophenylacetaldimine (2%). Treatment with powdered activated carbon (PAC) removed the off-flavor. Experiments with chlorination of15N-labeled phenylalanine suggested that PAC reductively decomposed trichloramine into N2gas and adsorbed all of the other identified TPs. Superfine PAC (median diameter, 0.7 μm) removed the off-flavor more rapidly than normal-size PAC (median diameter, 8.0 μm).