A highly specific electrochemical reduction method has been developed that enables the trace level measurement of dimethyl sulfoxide (DMSO) concentration in natural waters. Following the sparging of native dimethyl sulfide (DMS) from the sample, DMSO is reduced to DMS using a novel electrochemical workflow that relies upon CuSO₄ as a redox mediator. The DMS produced through DMSO reduction is collected, concentrated, and detected using a previously described Purge & Trap-Atmospheric Pressure Chemical Ionization-Tandem Mass Spectrometry (P&T-APCI-MS/MS) analytical workflow. The method provides a 0.5 pM detection limit for the analysis of DMSO in 10 mL sample volumes, with a demonstrated method precision of 5.4% for the analysis of consecutive 10 nM aqueous standards. The method selectivity for DMSO was evaluated using a range of commonly observed marine organosulfur compounds, none of which were found to interfere with the analysis at a reduction potential of 4 V. Method intercomparison confirmed that the electrochemical reduction provides results that are equivalent (at the 95% confidence level) to an established TiCl₃ reduction protocol for the analysis of both freshwater and seawater samples. Relative to established methods of DMSO reduction, the electrochemical method provides excellent selectivity and reproducibility, and offers the potential for automated, high-throughput analysis. In addition, the new electrochemical method does not require expensive, difficult to procure enzymes or hazardous, corrosive chemical reagents. Depth profile measurements of DMSO, DMS, and dimethylsulfoniopropionate (DMSP) for unfiltered seawater samples collected in Saanich Inlet, a coastal fjord in British Columbia, demonstrate the effectiveness of the DMSO reduction method in an oceanographic context.

中文翻译：

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电化学还原法测定天然水中二甲亚砜

我们开发了一种高度特异性的电化学还原方法，可以对天然水中的二甲亚砜 (DMSO) 浓度进行痕量测量。从样品中喷射天然二甲硫醚 (DMS) 后，使用依赖 CuSO _{4的新型电化学工作流程将 DMSO 还原为 DMS}作为氧化还原介体。使用先前描述的吹扫捕集-大气压化学电离-串联质谱 (P&T-APCI-MS/MS) 分析工作流程收集、浓缩和检测通过 DMSO 还原产生的 DMS。该方法为 10 mL 样品体积中的 DMSO 分析提供 0.5 pM 的检测限，连续 10 nM 水性标准品分析的方法精度为 5.4%。使用一系列常见的海洋有机硫化合物评估了 DMSO 的方法选择性，没有发现这些化合物会干扰 4 V 还原电位下的分析。方法比对证实，电化学还原提供了等效的结果（在95% 置信水平）到既定的 TiCl ₃用于分析淡水和海水样品的还原协议。相对于现有的 DMSO 还原方法，电化学方法具有出色的选择性和重现性，并为自动化、高通量分析提供了潜力。此外，新的电化学方法不需要昂贵、难以采购的酶或危险的、腐蚀性的化学试剂。对在不列颠哥伦比亚省沿海峡湾 Saanich 湾采集的未过滤海水样品进行 DMSO、DMS 和二甲基磺基丙酸盐 (DMSP) 的深度剖面测量，证明了 DMSO 还原方法在海洋学背景下的有效性。