In my area of interest (i.e., analytical chemistry), we accurately measure hydrogen in metals. This is usually done with a mass spectrometer, high-temperature furnace, and vacuum system. Measurements are important for engineering materials that are either directly or indirectly exposed to hydrogen. The ingress of hydrogen into metals can change the mechanical behaviour of materials. Sometimes, hydrogen dissolution can be advantageous when hot-working refractory metals such as titanium by lowering flow stress through a beta-transformation or when producing porous aluminum form for lightweight applications with hydrides. In less desirable examples, hydrogen may limit the service life of a critical component, such as turbomachinery for aircraft, welds in gas pipelines for fuel distribution, and pressure tubes that support nuclear fuel channels. With the emerging hydrogen economy, these problems will become strategically important for adopting this fossil fuel alternative. In fact, hydrides are becoming increasingly important as a solid storage medium.
Trace amounts of hydrogen, on the order of parts per million by weight, can significantly change a material. Major factors related to hydrogen affect fracture toughness and elongation, among many other properties. Without knowing exactly how much hydrogen is in a material, it is often difficult to even understand how engineering metals can be impacted.
For example, copper, a material being proposed for the long-term containment of spent nuclear fuel, can absorb hydrogen and allow it to migrate through the barrier. Over long periods, that hydrogen ingress (or perhaps egress) can lead to corrosion of structural materials designed as nuclear barriers such as steels. Literature suggests that we have only studied the solubility, permeation, and diffusion of hydrogen in copper at high temperatures (approximately > 450 Celsius) because it is very difficult to measure hydrogen at ambient temperatures. Spent nuclear fuel will remain at 70 to 150 Celsius for centuries, and we have not even measured hydrogen concentrations in copper at these temperatures. All we can do is rely on extrapolations. Imagine the difficulty of accurately measuring hydrogen migration in a container that is expected to last up to 100,000 years without all the empirically measured variables. This lack of information (or a greater reliance on good assumptions) is present in most other areas involving hydrogen.
In summary, metrology is important so that scientists can compare results with others to a high level of certainty and also measure hydrogen with incredible accuracy so that we can study real-world phenomena that impact socioeconomic problems that deeply impact our civilizations. Metrology is a hidden giant that binds almost all other quantitative fields of science together. I am studying gravimetry and amperometry, which are the foundations of mass spectrometry: the mass-to-charge ratio and the relative intensity. Chemistry is simply a secondary interest to me.