Chromatography Forum

We are currently analysing Tributyltin by quad GCMS using EI and SIM analysis. Although we can achieve a level down to 5ppt we would like to better this say, down to 2ppt or lower if possible using our existing kit. Currently, our method requires derivitisation of TBTC with Sodium Tetraethylborate at pH 4.5 extraction with hexane and then concentration.

Hi

I am having problems with the derivatization of TBT , for GC/MS analysis my method is the following do you have any advice or help. My sample is just TBTCl 98% made up in methanol.

The following was added to a 1ml sample,1ml of 2molar sodium acetate buffer solution pH 4.5,1 ml of a 1% w/v sodium tetraethylborate aqueous solution. The sample is shaken for 30mins , 5mls of water is added and 1ml of hexane. The mixture is vortexed for 10s and the two phase are allowed to separate the clear upper layer is transferred to small beaker and left to evaporate. The Sample is then revived in 1ml of hexane and transferred to an autosampler vial for analysis.

Thank you

Do you evaporate to dryness? In that case you will lose your analyte, since it is very volatile. Evaporate until you have a few microliters left and then inject, then you should see your TBT.

Do you evaporate to dryness? In that case you will lose your analyte, since it is very volatile. Evaporate until you have a few microliters left and then inject, then you should see your TBT.

Hi yes i tried that originally, and all so a range of pH 4 to 5 and leaving the sample for various amounts of time. I appear to be getting a large unidentifiable peak using the NIST library and then a small peak for the TBT ethyl-derivative at a very close retention time.

Thank you for yor reply

If you have no TBT peak it is because the derivatization fails for two reasons. The first and most common one is the derivatization agent (NaBEt4). It is very unstable and degrades quite fast. Usually, I prepare 1g in 50-100 ml 0.1M NaOH and distribute it in several small glass vials which I freeze. Each time I need to do a derivatization a unfreeze a new vial and use it. The second reason is a wrong pH. Check if your pH is correct after adding the buffer solution. I use 3-4 ml at pH 5.3.