A continuous flow instrument with flow regulation and automatic sensitivity range adaptation for the determination of atmospheric H2S

A set-up for continuous measurements of atmospheric H₂S concentrations in the range between 0.138 g/m³ and 17.5 g/m³ is described. All flows are regulated by flow sensors which are connected to the respective pump by a feed back circuit. The instrument is working in two sensitivity ranges. One is provided for low H₂S concentrations (lower than 1.75 g/m³) and the other for higher levels (higher than 1.75 g/m³). During continuous measurements the set-up enables an automatic adaptation of one of the sensitivity ranges to ambient H₂S concentrations. The critical step of absorption of gaseous H₂S into the liquid phase of the continuous flow system could be stabilised by the development of a new fluid level control system. After numerous test measurements under laboratory conditions the instrument was tested for the first time in June 1993 during field measurements in the tropics. These measurements took place in the environment of natural and industrial sources of H₂S in the vicinity of Salvador da Bahia in Brazil. Data are presented which prove the ability of the instrument.Dedicated to Professor D. Dieter Klockow on the occasion of his 60th birthday