We report on a novel modus operandi in the gas-chromatographic determination of ultra small contents (from 20 ng/l) of acetylene dissolved in water by employing a flame-ionisation detector with hydrogen as a carrier gas. The method bases on the gas extraction of acetylene with a frontal variant of liquid-gas chromatography in a tube with fluro-plastic carrier and simultaneous catalytic hydrogenation of acetylene to produce ethane in the presence of platinum deposited on the sorbent surface. The method in view gives way to a 20-fold decrease in the detection limit of acetylene against extraction with no hydrogenation. A plausible application of the method is the assessment of anthropogenic impact on the environmental hydrosphere embarking from the concentration of dissolved acetylene.