Isoprene is a biogenic volatile organic compound (BVOC), which is predominantly emitted by terrestrial plants but also from marine systems. However, the marine contribution to isoprene emissions is less understood due to the difficulty of measuring trace concentrations in seawater. Previous methods using “purge and trap” coupled with flame ionization detection and/or chemiluminescence have been developed, although these methods have limitations including large sample sizes, excessive manipulation, and potential interference from other BVOCs. These limitations could lead to overestimations or sample loss due to the high volatility and reactivity of isoprene. Here, we present an improved method for measuring isoprene in coastal marine ecosystems with elevated isoprene concentrations using cumulative headspace injection coupled with gas chromatography–mass spectrometry (GC‐MS). Sampling technique, preservation, and analytical conditions were tested and optimized using an analytical cycle time of 13 min. The analytical precision was 2.6% (n = 7), limit of detection was 15 pM, limit of quantification was 285 pM, accuracy based on recovery was 79% ± 2.8%, and reproducibility yielded a coefficient of variation of 15%. This method provides an improved way to measure isoprene from seawater using a simple sampling technique and fast, automated analysis, reducing isoprene loss through sample manipulation, and human error. This method meets analytical requirements to accurately measure isoprene at pM concentrations, which are typical of tropical coastal marine habitats. This method can also be adapted to measure other BVOCs in seawater such as dimethyl sulfide, providing a versatile method for marine research.

中文翻译：

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气相色谱-质谱联用顶空进样技术定量分析沿海生态系统中的异戊二烯

异戊二烯是一种生物挥发性有机化合物（BVOC），主要由陆地植物排放，但也从海洋系统排放。但是，由于很难测量海水中的痕量浓度，因此对海洋对异戊二烯排放的贡献的了解很少。已经开发了使用“吹扫捕集”技术结合火焰离子化检测和/或化学发光的先前方法，尽管这些方法具有局限性，包括大样本量，过度操作以及来自其他BVOC的潜在干扰。由于异戊二烯的高挥发性和反应性，这些限制可能导致高估或样品丢失。这里，我们提出了一种改进的方法，该方法使用累积顶空进样与气相色谱-质谱联用（GC-MS）来测量异戊二烯浓度升高的沿海海洋生态系统中的异戊二烯。使用13分钟的分析循环时间测试并优化了采样技术，保存和分析条件。分析精度为2.6％（n = 7），检测限为15 pM，定量限为285 pM，基于回收率的准确度为79％±2.8％，重现性得出的变异系数为15％。该方法提供了一种改进的方法，该方法使用简单的采样技术和快速，自动的分析方法来测量海水中的异戊二烯，并通过样品处理和人为错误减少异戊二烯的损失。此方法符合分析要求，可准确测量pM浓度下的异戊二烯，这是热带沿海海洋生境的典型特征。该方法还可以适用于测量海水中的其他BVOC，例如二甲基硫，为海洋研究提供了一种通用方法。