Abstract: A diamond-like carbon coating is provided on a metal interior surface of a sample chamber of a well fluid sampling apparatus to render the sample chamber substantially impervious to the absorption of at least H2S, mercury, and/or mercaptans. The coating is a dense, amorphous, diamond-like carbon with an sp3 content greater than about 65% and is composed of about 70 percent (%) carbon, 30 percent (%) hydrogen. The coating may be applied over the surface in one or more layers by a suitable method, e.g., plasma assisted chemical vapor deposition or a PAVCD process, and is between about 10 and about 20 microns thick. One or more of the layers of the coating includes a small percentage of silicon to increase both the adherence to the metal interior surface of the sample chamber and the absorption resistance of the coating. The resulting sample chamber provides H2S, mercaptan, and mercury retention of greater than about 95% of the original concentration in samples stored up to 14 days.