使用氢作为气相色谱法作为载气

许多氢气应理解为气相色谱（GC）的优异载气，并且在一些应用中，其个体性能 - 快速分析，最佳效率和低成本 - 使其成为首选的气体。尽管如此，氦仍然是最受欢迎的选择。然而，这可能会改变，因为临时氦供应限制导致色谱仪重新考虑氢及其对GC的益处。

氦载气的仍然是一个可靠的选择GC however, although there are sufficient reserves for several hundreds of years, the utilisation of hydrogen is growing and GC manufacturers are developing new instruments optimised for hydrogen carrier gas. In contrast to helium, hydrogen is flammable, but its high diffusivity permits more rapid linear velocities and shorter analyses, while still offering a similar separation efficiency as helium.

To explore the effect of carrier gas on resolution and analysis time, a Supelco isothermal non-polar test mixture was tested in helium, hydrogen and nitrogen. Each carrier gas was calibrated at its optimal linear velocity at the starting temperature of the temperature ramp. There are observable differences in the retention times and resolution. The column and conditions were unchanged. Lower duration analyses allowed increased throughput and reduced costs per sample.

Figure 1.Effect of carrier gas on resolution and analysis time

Nonetheless, when using hydrogen as the mobile phase, there are potential concerns relating to reactivity in certain situations (catalytic hydrogenation of unsaturated molecules at high inlet temperature). This potential for chemical reactions in your analytical system must be considered.

The Air Products Solution – Hydrogen BIP^®

To satisfy the demand for hydrogen as a carrier gas, Air Products has now extended its unique BIP^®technology to hydrogen.Hydrogen BIP^®气瓶可提供超低的杂质规格，以前没有可从气缸或发电机源提供。（见下表）

年级	H2O	O2	THC	认证
H2BIP®圆筒	20 PPB.	100 PPB.	10 ppb	Batch
H2BIP®PLUS cylinder	20 PPB.	100 PPB.	10 ppb	Individual

THC = Total Hydrocarbons measured as Methane

独特的BIP^®气瓶manufactured by Air Products use an advanced technique to remove critical impurities as the gas is withdrawn from the cylinder. This yields a gas with superior purity levels, which is suitable for the most exacting gas chromatography functions. Every H₂BIP^®圆柱体含有超级杂质的水平，水分不超过20 ppb;100ppb氧气和10ppb的总烃。这确保了氢弯曲^®气体是最纯净的等级之一。

使氦气转换为氢气开关

When changing from helium to hydrogen, the adjustments required by the gas chromatograph correspond to the hazards of hydrogen. Hydrogen is flammable and can generate an explosive atmosphere when it gathers. The priority is to maintain safety standards and ensure there is no accretion of gas by preventing and detecting leaks, and safely venting any hydrogen outlet stream.

避免气体积聚

Contemporary gas chromatographs can identify leaks upstream in the column by observing gas pressure. This can be implemented directly for a GC operating with hydrogen. If hydrogen leaks prior to reaching the column, the GC pressure drop is minimal; hydrogen pressure cannot build up and it does not arrive at the defined set point. The GC interprets the permanent divergence between the operative and the set point pressure as a leak and safeguards the GC by restricting the hydrogen valve. Conversely, when the leak is downstream in the column, this protection is inefficient and a hydrogen sensor would need to be integrated to identify any hydrogen build-up in the oven.

图2。使用氦气或氢作为载气的0.5μl样品色谱图

Safe Venting

The second adjustment required when switching from helium to hydrogen is to safely vent the outlet stream. The relevant ports are the outlet of the septum purge and the split from the injector. This is important because when helium is utilised it can be vented from within the laboratory, but hydrogen requires the ports to carry it to the laboratory’s flammable vent line.

引入压力调节器上游的流动限制器，限制最大泄漏可能并保证实验室通风可以稀释氢泄漏。流量限制器是限制这种煤气泄漏的低成本，功能和有效的方法。一旦这些措施进行了处理，可以通过实现标准FID性能评估测试来认证新的GC配置。

Hydrogen Cylinders or Generators?

氢气发生器可能呈现替代品GC carrier在决定偏好之前，应在汽缸之前比较和燃气，以及它们的相对优点和缺点。H₂generators have two principal advantages:

• 当气缸供应受限或不存在时，它们是远程位置的固体解决方案。
• They generate H₂按需，所以很少的h₂is stockpiled.

However, H₂generators are not always the best solution, and there are often hidden disadvantages:

• 天然气规范 - 应该暗中仔细审查，因为大多数制造商只表明o₂或H.₂o杂质水平，但不是两者。
• 成本- H₂generators are typically more expensive than an H₂气缸供应。
• 可靠性和备用 - h₂generators can fail disastrously without warning, rendering back-up cylinder supply as vital.
• Specialist Equipment - Deionizer bags purify the demineralised water supply. These must be changed regularly or the generator will be seriously damaged.

Figure 4.BIP^®valve and purifier design

Figure 5.基线降噪和柱出血改善，具有同时燃料和载气从H变化₂standard to H₂BIP^®gas

Safety Systems

无论气缸或发电机是否提供载气，未检测到的气体泄漏都可以在破碎的柱或泄漏连接内实现。危险是未检测到的气体泄漏可能会在GC烤箱中产生爆炸，将实验室和操作员造成风险。因此，对于利用氢作为载气的任何实验室，它是至关重要的，以便能够安全地识别GC烘箱中的氢泄漏。

H₂所有领先的GC供应商都可以使用在GC分析中安全使用氢的传感器。H.₂sensor performs its function by continually examining the H₂在GC烘箱中浓度，并且通常达到惰性气体时，通常达到25％箱。这一重要特征可降低危险并保持安全性。

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