Element-selective detectors for carbon, sulfur, phosphorus, and nitrogen are used to determine methane, hydrogen sulfide, phosphine and ammonia in the effluent from a pyrolytic hydrogenator. Solid ecological field samples, e.g., forest floor litter, plant stream particulate, and insects, require no chemical pretreatment. These are pyrolyzed and the pyrolyzates pass through a catalyst bed which reduces the elements to the corresponding hydrides. Data are given for sulfur, carbon, and nitrogen.