A new method has been developed to measure tiny amounts of carbon in very pure iron. The method involves heating the iron in hydrogen gas to release gases like methane and carbon monoxide, which are then detected. This allows for the separate determination of carbon on the surface and within the iron. The method can accurately measure about 4 micrograms of carbon per gram of iron with a 10% margin of error. The time needed to analyze one sample is around 50 minutes. The results obtained using this method match well with those obtained using a different method.