[ziagemini]

Hello All

I need to find out how much organic and inorganic sulfur is present in my substrate(energy crops, animal manure etc). Beside that I also want to know what forms of sulfur are present in the fermenter(sulfides, sulfates, polysulfide etc.) Could you please tell me whether this is possible to analyse?

Regards!

[Stepan]

I would analysed sample for sulfide, sulfite and sulfate first, Thann the same sample for total. Difference between Total and Inorganic would be Organic.

[ziagemini]

Hello,

Thanks for the reply. Seems to be a good solution. But how can i measure  sulfide, sulfite and sulfate etc and total sulfur? What are the methods that are available and how can i find them??

Thanks for the help.

Regards!

[ajkoer]

To test for Sulfides, Polysulfides:

Add a strong acid (like H2SO4) and pass the H2S gas (strong odor and poisonous) into aqueous NaClO (Bleach will do).

 H2S + NaClO --> NaCl + H2O + S (s)

The colloidal sulfur is a marker of the Sulfur content from sulfides. Alternate test: use an aqueous Lead salt in place of NaClO:

Pb2+(aq) + S2-(aq) => PbS(s)

To test for Sulfite, after acidifying pass the SO2 gas into a large quantity of aqueous ZnCl2:

 ZnCl2 + SO2 + H2O --> ZnSO3 (s) + 2 HCl

I am assuming that Zinc sulfite is not soluble in dilute HCl (check). Alternatively, pass the SO2 into very dilute NaClO and add Lead acetate Pb(Ac)2 at room temperature. Reactions:

 H2SO3 + 2 NaClO --> Na2SO3 + 2 HOCl

 2 HOCl + Pb(Ac)2 --> Pb(ClO)2 (s) + 2 HAc

quickly measure the amount of white Lead hypochlorite precipitate before it decomposes into the dark PbO2. Each mole of Pb(ClO)2 implies 1 mole of SO2.

[Stepan]

I am not an expert in analysis of biological samples and the test you select will require proper validation for your samples. Most likely you can test H2S via colourimetric reaction as it is done in Environmental chemistry, or with Ion selective electrode. SO3(2-) and SO4(2-) can be measured by ion chromatography or via the set of colourimetric and gravimetric reactions. Total sulfur test will require either elemental analysis - high temperature ashing and analysis of SO2/SO3 in gases, or digestion with aqua regia and analysis by ICP for sulfur.