A system for scrubbing and monitoring H2S includes: a sample inlet valve that controls an input stream of the hydrocarbon gas from the gas canister; a first scrubber that removes a first portion of H2S from the input stream and that outputs a first stream with less H2S than the input stream; a second scrubber that removes a second portion of H2S from the first stream and that outputs a second stream with less H2S than the first stream; a H2S converter that converts all remaining H2S in the second stream into a di-ketone and that outputs an output stream with a concentration of the di-ketone; an optical detector that measures the concentration of the di-ketone in the output stream; and a processor that determines a concentration of H2S in the second stream based on the concentration of the di-ketone in the output stream.