Hello,
My team and I are working on a method to determine the concentration of TBT in seawater. We tried to directly inject the filtered sample in seawater using 2% Formic Acid in Water and 2% Formic Acid inMethanol as A and B respectively. the problem that we're facing is that we can't get linearity with increasing concentration.
we also believe that our sample preparation are not exactly good enough. we are trying to avoid SPE method though. Can any one share their opinion on this.
Thank you. I really appreciate any help/opinion/advise
Wouldn't an ICP_MS be the best route to determine tin content in seawater? If the curve is not linear, chances are that there is a hydrolysis side reaction under your conditions. Find out more about the solution stability of TBT. A positively charged tin compound will stick to a silica phase like crazy! Long time ago a colleague used a tin compound as a catalyst in silica surface modification. Traces of tin remained on the surface forever.
This paper uses direct injection of water. You need at least 4000 Q-trap for sensitivity because Andre used dilute and shoot method.
Hi Farah,
There are a number of good methods for TBT. The problem is you are directly injecting salts into the LC/MS. The build-up of non-volatile salts on the electrospray interface will reduce your signal. I would highly recommend either Liq/Liq extraction or SPE to remove the salts. I understand your aversion to incorporating additional sample prep steps in your method, but sometimes the matrix requires it. The following U.S. EPA method has some good tips...
http://www.epa.gov/osw/hazard/testmethods/pdfs/8323.pdf
Organotins have an affinity for bonding to glass. Soak all glassware in HCl solution (pH
Dear Farah,
My opinión is that LC-MS methods for TBT determination in waters is quite challenging, as I have serious doubts that this technique can reach the detection limits required for a proper TBT monitorization.
Please be aware that the European Union Environmental Quality Standard for TBT in surface waters is 0.2 ng/L and that the recommended LOQ is 0.06 ng/L. From my experience such a low level can only be achieved by using Gas chromatograhy coupled to ICP-MS or by GC-EI-MSMS after a high preconcentration of the sample..
If you use GC you will need to apply a derivatization step which can be easily carried out with Sodium tetraethylborate and a liquid-liquid extraction. Both steps can be done simultaneiously in five minutes. Also, the application of Isotope Dilution Mass Spectrometry is highly recommended to correct for all posible sources of error.
Hope this helps
Pablo
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