Micro GC H2S quantification
An Agilent 490 Micro GC (Agilent Technologies, Palo Alto, CA, USA)
equipped with parallel Molsieve 5A and PoraPLOT U columns and a thermal
conductivity detector was used for H2S analysis with Helium carrier gas
(15PSI). The column and injector temperatures were isothermally set to
60 °C for the duration of the 120 s run. The injector was set to split
mode with an injection time of 40 ms and a backflush time of 10 s.
H2S standards were prepared as previously
described66 where, briefly, H2S was
generated by reacting Na2S (Sigma-Aldrich, Saint Louis,
MO, USA) with excess HCl (Fisher) in a 20 ml Hungate bottle with a butyl
rubber stopped in the anaerobic chamber. Six working calibration
standards at concentrations corresponding to 25, 50, 100, 250, 750, and
1,500 ppm of H2S were prepared by diluting from a 5
µmol/ml stock. Either a 2 ml headspace of standard or the microcosm
samples was withdrawn and injected into the instrument with a gas
syringe. Standards were run in triplicate to create a calibration curve
while the biological samples were each run once.