The homogenate
was mixed with 0.5 ml 1 M HCl to release H2S, and H2S was then
absorbed in a 1% (w/v) zinc acetate (0.5 ml) trap located at the
bottom of the test tube. After 30 min of reaction, the trapwas added
with 0.3 ml 5 mM dimethyl-p-phenylenediamine dissolved in
3.5 mM H2SO4. Afterward, 0.3 ml 50 mM ferric ammonium sulfate
in 100 mM H2SO4 was injected into the trap.