A NOVEL SORBENT TUBE FOR AMBIENT HYDROGEN-SULFIDE DETERMINATION

A novel tubular device has been developed for hydrogen sulfide determi nation in air. Several substrates such as commercial silica gel and al umina TLC plates, silica gel powder, alumina, CaSO4, CaCO3, BaSO4, MgO , chalk, alpha-cellulose and ethyl cellulose were tested as solid subs trates. 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 CdCl 2 solution, dried, filled into the glass tube and sample gas is passed through the device using nitrogen as the carrier gas where 70% relati ve humidity is employed. The analyte reacts with the solid substrate t o form a luminescent spot whose length in the tube is measured and cor related to concentration. The flow rate was 68 ml min(-1). The analyti cal 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 pri or to sampling; and after sampling, the luminescing spot is stable als o at least for 3 months. (C) 1998 Elsevier Science B.V. All rights res erved.