Department of Environmental Health Sciences, School of Public Health, Seoul National University, Seoul 08826, South Korea.
Institute of Health & Environment, Seoul National University, Seoul 08826, South Korea.
Chemosphere. 2017 Oct;185:1039-1047. doi: 10.1016/j.chemosphere.2017.07.104. Epub 2017 Jul 19.
The removal and degradation pathways of microcystin-LR (MC-LR, [M+H] = 995.6) in UV-B photolysis and UV-B/HO processes were examined using liquid chromatography-tandem mass spectrometry. The UV/HO process was more efficient than UV-B photolysis for MC-LR removal. Eight by-products were newly identified in the UV-B photolysis ([M+H] = 414.3, 417.3, 709.6, 428.9, 608.6, 847.5, 807.4, and 823.6), and eleven by-products were identified in the UV-B/HO process ([M+H] = 707.4, 414.7, 429.3, 445.3, 608.6, 1052.0, 313.4, 823.6, 357.3, 245.2, and 805.7). Most of the MC-LR by-products had lower [M+H] values than the MC-LR itself during both processes, except for the [M+H] value of 1052.0 during UV-B photolysis. Based on identified by-products and peak area patterns, we proposed potential degradation pathways during the two processes. Bond cleavage and intramolecular electron rearrangement by electron pair in the nitrogen atom were the major reactions during UV-B photolysis and UV-B/HO processes, and hydroxylation by OH radical and the adduct formation reaction between the produced by-products were identified as additional pathways during the UV-B/HO process. Meanwhile, the degradation by-products identified from MC-LR during UV-B/HO process can be further degraded by increasing HO dose.
采用液相色谱-串联质谱法研究了微囊藻毒素-LR（MC-LR，[M+H]+=995.6）在 UV-B 光解和 UV-B/HO 过程中的去除和降解途径。UV/HO 过程比 UV-B 光解更有效地去除 MC-LR。在 UV-B 光解中，新鉴定出 8 种产物（[M+H]+=414.3、417.3、709.6、428.9、608.6、847.5、807.4 和 823.6），在 UV-B/HO 过程中鉴定出 11 种产物（[M+H]+=707.4、414.7、429.3、445.3、608.6、1052.0、313.4、823.6、357.3、245.2 和 805.7）。在这两种过程中，除了 UV-B 光解过程中[M+H]+值为 1052.0 的产物外，大多数 MC-LR 产物的[M+H]+值均低于 MC-LR 本身。基于鉴定出的产物和峰面积模式，我们提出了这两种过程中的潜在降解途径。氮原子中的电子对发生键断裂和分子内电子重排是 UV-B 光解和 UV-B/HO 过程中的主要反应，而 OH 自由基的羟化作用和生成产物之间的加合反应被确定为 UV-B/HO 过程中的附加途径。同时，在 UV-B/HO 过程中从 MC-LR 中鉴定出的降解产物可以通过增加 HO 剂量进一步降解。
