[Microbiology] Sulfate Assay for SRB

[Matt McMahon]

Hi, I'm working with sulfate reducing bacteria (Desulfovibrio spp.) and am using a spectrophotometric assay (420 nm) to measure dissolved sulfate in my culture (Postgate C).  It's a method based on the precipitation of sulfate as BaSO4 when mixed with BaCl2.2H2O in a conditioning fluid which helps to keeps the precipitate in suspension.  I've tried methods based on the APHA and the Kolmert et al. (2000) literature but still experience lots a variation in my absorbance readings.
 
Does anyone have a quick and simple spectrophotometric method for measuring sulfate in ~1mL size culture samples or know how to reduce the variability in the standard barium chloride turbimetric method?
 
Sulfate concentrations are in the range of <100 mM most being below 30 mM.
 
Thanks, 
 
-Matt McMahon
 
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Matthew McMahon, MScE Candidate
Dept. Chemical Engineering, Queen's University 
Kingston Ontario Canada K7L 3N6 
(613) 533-6000 Ext. 75170 (Office) 75055 (Lab)
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