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

该提案将提供必要的最先进的资本，以支持多种创新方法（由OGU开发），这些方法将在多个NERC研究主题（即粮食安全、气候变化、微生物、植物和动物生态学、古生态学和考古学）中提供新的、未实现的n循环见解。二十多年来，OGU一直致力于发展和改进有机化合物稳定n同位素表征的分析方法。这导致了稳定同位素生态学和考古学新兴领域中测定单个原子吸收物d15N值的化合物特异性方法的发展和成功应用。测定单个氨基酸的d15N值极具挑战性，与测定d2H和d13C相比，样品通量要低得多，而OGU也具有这种能力。挑战的出现有几个原因，最终导致设置时间长和固有的分析错误，导致需要对每个样品进行多次分析。我们在这项技术的开发和使用方面的长期经验使OGU成为世界上为数不多的能够充满信心地提供这种分析能力的实验室之一（参见O'Connell and Collins. 2018）。j .的嗡嗡声。进化。117,53-55.)。化合物特异性N同位素方法为天然丰度和15n示踪剂测定提供了潜在的无与伦比的灵敏度和特异性，这是任何其他方法（例如批量EA-IRMS）无法实现的。现在，OGU、大华银行内的其他合作者/用户以及更广泛的国家和国际社会正在采用这种特定化合物的稳定同位素技术，用于生态学、古生态学、考古学和15n -稳定同位素探测（15N-SIP）生物地球化学。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，人们普遍认为化合物特异性同位素方法比整体稳定同位素测定具有显着优势。需求将迅速增加（见学术受益人），因此，迫切需要增加能力以满足需求的增加。重要的是，最新一代的GC-C-IRMS仪器，即提议的资产，与它们的前辈（<1000分子/离子）相比，提供了显着提高的灵敏度。这种增强的灵敏度将使分析能够在更低的样品浓度下进行，比使用现有仪器可能具有更高的吞吐量。至关重要的是，这将使我们能够扩大当前的分析窗口，包括低质量样本（例如小型大型动物，高价值古生态和考古标本的子样本），使我们能够在NERC的职责范围内开展更大范围的潜在研究应用。除了降低原子吸收剂（天然具有高N摩尔比的化合物）的检测限外，该资产的灵敏度提高将使具有较高C:N比的化合物能够被确定。这将使n循环的各个方面，以前很难，甚至不可能的研究，变得适用于15N-SIP的测定，从而解锁对n循环过程的基本新见解（例如，土壤中含氮碱基和氨基糖的d15N值为土壤细菌和真菌群落的活性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，如农业中的氮利用效率和水生系统中氮有机质的确切性质。

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.