I think that you are correct in worry about expose to oxygen. Sulfide reacts very quickly with molecular oxygen. I've done a similar analysis using a method involving the formation of copper (II) sulfide reasonably often. I've found that I get the best results by using rigorously degassed water (via boiling, sonication, vaccuum degassing, helium sparging or some combination thereof) and storing the sulfide standards in nitrogen-flushed serum bottles. I'd recommend working with (reasonably) air tight syringes if possible and working quickly if you don't have access to a glove box filled with inert gas.

While I've had good results with non-anaerobic cuvettes, I did find that using cuvettes with silicon septa that had been nitrogen flushed did improve the reproducibility of some of the lower concentration sulfide standards.

As you are interested in doing this kinetically over some time, I'd recommend doing your experiment in a small desiccator under positive pressure of nitrogen; perhaps just pull the cuvette out in time for a quick measurement before putting it back into the desiccator after a burst of nitrogen flushing. The other option would be to work with nitrogen-flushed serum bottles (or Hungate tubes) with butyl rubber septa. This way you could easily maintain anaerobic conditions and periodically sample via syringe. These bottles can be obtained from Sigma Aldrich or perhaps lent by friendly scientists.

I hope this was helpful! Good luck!

You may first flush your solution with nitrogen, then flushing the room inside the spectrophotometer with nitrogen if it is indeed necessary (maybe dissolution of oxygen into a gas tight cuvette should be negligible.

I guess that the less you handle the solution, the better. I mean, you need to develop the reaction inside the air tight cuvette (making sure that the volume takes up the whole cuvette), and close it immediately, because the head space in the cuvette is, apparently, negligible, as Titus has pointed out. 

If you have enough sample, you might compare these results with the use of nitrogen by flushing your solution, as Titus says.

Good luck, and let us know about your findings!

Hi Taher,

Is your reaction in liquid phase, or gaseous phase.

If it is in gaseous phase, you can try diffuse reflectance (UV-DRS) mode.

Hi All,

I do not know if I write here you all will be able to read my message or not.

First thanks for your comments.

What is your opinion if I use the airtight covette then connect 2 tubes to the cuvette and 2 syringes full of my solutions to the tubes. I make this set up under anerobic chamber then put them in UV-vis instrument and inject or mix the solutions inside the cuvette by injecting from syringes.  meanwhile I inject the nitrogen to the UV-VIS reaction chamber to prevent entering oxygen.

Hi Taher,

You could simply add some (only slight amounts) TCEP or DTT (which do not absorb much) to chemically prevent disulfide formation. TCEP is reactive in aqueous solvent at neutral pH, DTT can be used in organic solvent. You can test the substances in advance for UV-Vis spectrum.

Of course - this is a problem if you want to monitor disulfide formation...

To get the oxygen out, I suggest to use Argon instead of Nitrogen, because N2 is lighter then air - one moment inattentive and the oxygen is back. The beauty of Argon is that it forms a kind of cushion on the solvent surface (like e.g. CO2 or CO). Bubbling all solutions with Argon prior reaction I would recommend as well.

Time is everything, the quicker you get the measurement running, the better. Air thight reaction vessel is needed in any case during the measurement.

To your suggestion with two syringes: I doubt that the convection will be strong enough to get a homogeneous mixture of you two components without schlieren.

Hi Taher,

As long as the solutions are stable in air, this could be a good solution to your problem. Otherwise, I had bad experiences using syringes, because they might not isolate completely your solution from the atmosphere.

Greetings!

Hi Sergio,

Why did not you use the airtight (gastight) syringes?

Regards,

Hi every one

I think you can make a special cuvette for your self ! I don't know if you have ever seen septum before or not...you can design a little septum for your cuvette and close it using septum by using this you can use your simple cuvette ... I hope it be useful  

I would try using a flow-through cuvette.

Hi Taher,

I have tried using that kind of syringes, but... from my experience, the least it takes to carry out the experiment, the better.

Greetings, and thank you for your advice!

Sadhna,

why do you think all should kept be dry? Anaerobic process likely will proceed in aqueous environment.

Thanks for your valuable comments. Just to complete my question: I have been assigned to mix lead acetate and Na2S.9H2O to produce PbS that is why I want to track the PbS formation in cuvette by UV-VIS anaerobically at room temperature.

in this case there should not be the requirement of strict anaerobic environment. Precipitation and oxidation have much different kinetics. Suppose the experiment will be rather short not hours or days.

Thanks for your comments. But in some cases addition of additives to the system might make the precipitation longer (up to 10-15hours).

I think that you are correct in worry about expose to oxygen. Sulfide reacts very quickly with molecular oxygen. I've done a similar analysis using a method involving the formation of copper (II) sulfide reasonably often. I've found that I get the best results by using rigorously degassed water (via boiling, sonication, vaccuum degassing, helium sparging or some combination thereof) and storing the sulfide standards in nitrogen-flushed serum bottles. I'd recommend working with (reasonably) air tight syringes if possible and working quickly if you don't have access to a glove box filled with inert gas.

While I've had good results with non-anaerobic cuvettes, I did find that using cuvettes with silicon septa that had been nitrogen flushed did improve the reproducibility of some of the lower concentration sulfide standards.

As you are interested in doing this kinetically over some time, I'd recommend doing your experiment in a small desiccator under positive pressure of nitrogen; perhaps just pull the cuvette out in time for a quick measurement before putting it back into the desiccator after a burst of nitrogen flushing. The other option would be to work with nitrogen-flushed serum bottles (or Hungate tubes) with butyl rubber septa. This way you could easily maintain anaerobic conditions and periodically sample via syringe. These bottles can be obtained from Sigma Aldrich or perhaps lent by friendly scientists.

I hope this was helpful! Good luck!

I guess that one of the reasons you wrote that you cannot put the instrument in a glove box /oxygen free chamber is because the uv-vis is very big /the chamber is small. One of the solutions, although a little bit expensive is buying one of the new miniaturize uv-vis spectrometers for example those of ocean optics.