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A novel sorbent tube for ambient hydrogen sulfide determination
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A novel tubular device has been developed for hydrogen sulfide determination in air. Several substrates such as commercial silica gel and alumina TLC plates, silica gel powder, alumina, CaSO4, CaCO3, BaSO4, MgO, chalk, α-cellulose and ethyl cellulose were tested as solid substrates. 30–70-mesh silica gel was finally employed in glass tubes of 4.0 mm internal diameter. Silica gel is treated with 0.5 M aqueous CdCl2 solution, dried, filled into the glass tube and sample gas is passed through the device using nitrogen as the carrier gas where 70% relative humidity is employed. The analyte reacts with the solid substrate to form a luminescent spot whose length in the tube is measured and correlated to concentration. The flow rate was 68 ml min−1. The analytical system is linear in the range of 0.2–1.3 ppm H2S for the specified conditions. The prepared devices are stable at least for 3 months prior to sampling; and after sampling, the luminescing spot is stable also at least for 3 months.