Gas chromatograph-combustion-isotope ratio mass spectrometer (GC-C-IRMS) for enhanced compound-specific N isotope determinations

这项提议将提供必要的尖端资本，以支持多种创新方法(由OGU开发)，这些方法将提供涉及多个NERC研究主题的新的、未实现的见解，即粮食安全、气候变化、微生物、动植物生态学、古生态学和考古学。二十多年来，OGU一直致力于开发和改进有机化合物稳定氮同位素表征的分析方法。这导致了在稳定同位素生态学和考古学的新兴领域中，开发并成功地应用了一种特定化合物的方法，该方法确定了单个AAs的d15N值。测定单个氨基酸的d15N值极具挑战性，导致样品吞吐量远低于d2H和d13C测定，而OGU也具有这两种能力。这些挑战的出现有几个原因，最终导致建立时间较长和固有的分析误差，导致需要对每个样品进行多次分析。我们在开发和使用这项技术方面的长期经验使OGU成为世界上为数不多的能够自信地提供这种分析能力的实验室之一(参见O‘Connell和Collins)。2018年。J.嗯。埃沃尔。117、53-55)。化合物特定的氮同位素方法为自然丰度和15N示踪剂的测定提供了潜在无与伦比的灵敏度和特异度，这是任何其他方法无法实现的，例如散装EA-IRMS。目前，在生态学、古生态学、考古学和15N稳定同位素探测(15N-SIP)生物地球化学方面，使用这种化合物特有的稳定同位素技术的情况有一个强劲的上升轨迹，这是由OGU、大华大学内部和更广泛的国家和国际社会的其他合作者/用户开展的。食物网生态学和陆地/水生生物地球化学是NERC研究的重要领域，人们公认化合物特定同位素方法比整体稳定同位素测定具有显著优势。需求将迅速增长(见学术受益者)，因此，迫切需要增加运力，以满足这种需求的增长。最重要的是，最新一代的GC-C-IRMS仪器，即建议的资产，与其前身(&lt；1000分子/离子)相比，提供了显著增强的灵敏度。这种增强的灵敏度将使分析能够在比现有仪器更低的样品浓度和更高的吞吐量下进行。至关重要的是，这将使我们能够扩大目前的分析窗口，以包括质量较低的样本(例如，小型大型动物、来自高价值古生态和考古标本的亚样本)，从而使我们能够在国家环境研究中心的职权范围内开展更广泛的潜在研究应用。除了降低AAs(天然高摩尔比的化合物)的检测下限外，资产灵敏度的提高将使测定具有更高C：N比的化合物成为可能。这将使以前难以甚至不可能研究的N循环的某些方面能够服从15N-SIP测定，从而开启对N循环过程的基本新见解(例如，土壤中氮碱和氨基糖的d15N值为土壤细菌和真菌群落的活动和功能提供了新的见解)。这种对复杂环境系统的深入探索将有助于解决关键的全球问题，如农业中的氮素利用效率和水生系统中氮素有机物质的确切性质。

This proposal will provide the necessary state-of-the-art capital to underpin multiple innovative methodologies (developed by the OGU) that will provide new, unrealised insights into the N-cycle across multiple NERC research themes, i.e food security, climate change, microbial, plant and animal ecology, palaeoecology and archaeology. For over twenty years, the OGU has committed itself to developing and improving analytical methodologies for the stable-N isotopic characterisation of organic compounds. This has led to the development and successful application of a compound-specific approach, that determines d15N values of individual AAs, in the burgeoning field of stable isotope ecology and archaeology. Determining d15N values for individual amino acids is extremely challenging, resulting in far lower sample throughput compared with d2H and d13C determinations, capabilities the OGU also possesses. The challenges arise for several reasons, which ultimately result in long set-up times and inherent analytical errors that result in the need for multiple analyses of every sample. Our long experience in the development and use of this technique has made the OGU one of the few laboratories, worldwide that can deliver this analytical capability with confidence (see O'Connell and Collins. 2018. J. Hum. Evol. 117, 53-55.). The compound-specific N isotope approach provides potentially unrivalled sensitivity and specificity for natural abundance and 15N-tracer determinations, unachievable by any other means, e.g. bulk EA-IRMS. There is now a strong upward trajectory in the uptake in use of this compound-specific stable-isotope technique in ecology, palaeoecology, archaeology and 15N-stable isotope probing (15N-SIP) biogeochemistry being undertaken by the OGU, other collaborators/users within UoB and in the wider national and international communities. The food-web ecology and terrestrial/aquatic biogeochemistry represent significant areas of NERC research, and it is accepted that compound-specific isotope approaches have significant advantages over bulk stable isotopic determinations. Demand is set to increase rapidly (see Academic beneficiaries), therefore, there is a an immediate and acute need to increase capacity to meet this increase in demand. Critically, the latest generation of GC-C-IRMS instruments, i.e. the proposed asset, offer significantly enhanced sensitivity compared to their predecessors (<1000 molecules/ion). This enhanced sensitivity will enable analyses to be performed at much lower sample concentrations with a higher throughput than possible using existing instruments. Crucially, this would enable us to expand the current analytical window to include lower mass samples (e.g. small macrofauna, sub-samples from high-value palaeoecological and archaeological specimens) allowing us to field a greater range of potential research applications within the NERC remit. As well lowering the limit of detection for AAs (compounds with naturally high molar ratios of N), the increased sensitivity of the asset will enable compounds with higher C:N ratios to be determined. This will enable aspects of the N-cycle, previously difficult, or even impossible to study, to become amenable to 15N-SIP determinations, thereby unlocking fundamental new insights into N-cycling processes (e.g. d15N values of nitrogenous bases and amino sugars in soil providing new insights into the activity and function of the soil bacterial and fungal communities). This deeper probing of complex environmental systems will help address key global problems, such as N use efficiency in agriculture and the exact nature of N-organic matter in aquatic systems.