We describe a method for measuring trace concentrations of dimethyl sulfide (DMS) in seawater using a commercial tandem mass spectrometer configured for atmospheric pressure chemical ionization (PT‐APCI‐MS/MS), coupled with a custom‐built purge and trap gas extraction system. DMS was ionized through proton transfer, generating abundant [M + H]⁺ ions. The semiautomated method analyzes samples in under 6 min, and is capable of processing up to 10 samples in a single batch. A detection limit of 0.9 pmol L⁻¹ was determined for the analysis of 5 mL sample volumes, with a precision of 3.9% between replicates. Practical performance was evaluated during two oceanographic research cruises within the coastal waters around Vancouver Island, British Columbia. To demonstrate method utility, a series of DMS depth profiles were obtained along two transects extending from the west coast of Vancouver Island into deep water off the continental shelf. Additional depth profile sampling was conducted in Saanich Inlet, a coastal anoxic fjord with active chemotrophic sulfur cycling. This method enabled us to capture the deep‐water accumulation of subnanomolar DMS in the anoxic water of Saanich Inlet, providing evidence of cryptic sulfur cycling. The method was also leveraged to facilitate stable isotope rate measurement experiments, in which the consumption of isotopically labeled DMS, dimethylsulfoxide, and dimethylsulfoniopropionate tracers was monitored in the low picomolar range. These measurements enable metabolic rate determinations using low‐level tracer additions that do not perturb in situ microbial activity. Our sensitive, high throughput method helps to improve understanding of the natural marine cycling of volatile sulfur compounds.

中文翻译：

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吹扫捕集-大气压化学电离串联质谱法在海水中二甲硫的测定中的应用

我们描述了一种使用配置用于大气压化学电离的商用串联质谱仪（PT-APCI-MS / MS）结合定制的吹扫和捕集气体萃取系统来测量海水中痕量二甲基硫（DMS）的方法。DMS通过质子转移离子化，生成大量的[M + H] ⁺离子。半自动化方法可在6分钟内分析样品，并且能够在一个批次中处理多达10个样品。检出限为0.9 pmol L ^-1确定用于分析5 mL样品量的样品，重复之间的精确度为3.9％。在不列颠哥伦比亚省温哥华岛附近沿海水域的两次海洋学研究航行中，对实用性能进行了评估。为了证明该方法的实用性，沿着从温哥华岛西海岸延伸到大陆架深水的两个断面获得了一系列DMS深度剖面。另外的深度剖面采样是在萨尼奇湾（Saanich Inlet）进行的，萨尼奇湾是沿海的缺氧性峡湾，具有活跃的化学营养硫循环。这种方法使我们能够捕获Saanich Inlet缺氧水中亚纳摩尔DMS的深水积累，从而提供了隐含硫循环的证据。还利用该方法促进了稳定的同位素速率测量实验，其中在低皮摩尔范围内监测了同位素标记的DMS，二甲基亚砜和二甲基磺酸丙酸示踪剂的消耗。这些测量可使用不干扰原位微生物活性的低水平示踪剂添加量来确定代谢率。我们灵敏，高通量的方法有助于增进对挥发性硫化合物的自然海洋循环的了解。