A ΔE- E telescope was used in coincidence to separate the isotopes of hydrogen and to improve the sensitivity of hydrogen detection when recoiled with 3.8 MeV He +. This was achieved by recording coincident events in both detectors (corresponding to the recoil of H, D or T from the target) thereby excluding any contribution from D (or T) beam contamination to the ERDA spectrum for hydrogen and also eliminating electronic noise from the background. The analysis of standard hydrogen-bearing silicates (6–189 wt ppm H) suggested that the concentrations at the lower part of this range were resolvable. The lowest counts were accumulated on two fragments of colourless diamond and were <20% of the counts obtained for the standard bearing 6 wt ppm H. We suggest sensitivities of better than 0.0056 wt% H 2O (or 75 at. ppm H in carbon-rich matrices) are achievable with relative precisions <20% in the range 0–400 at. ppm H.