By Uberto on Wednesday, February 12, 2003 - 08:01 pm:
Dear all,
I am wondering if anyone has the previous experience in analysing boronic ester by GC. Recently I am using phenylboronic acid or methylboronic acid to derivatize some amino-alcohol drugs to form boronic esters prior to GC separation. I find that peak tailing is observed for all peaks, in particular to the late-eluting ones, using DB-5MS (0.25mmx30mx0.25um) or CP-SIL8CB column (0.15mmx25mx0.12um) and splitless injection. I have tried cutting the front end of the column; lowering the initial oven temperature while injecting the analyte; changing dissolution solvent from ethyl acetate to iso-octane; increasing the injection temperature from 250 to 300oC and all these actions have no big improvement in peak shape. Grateful if someone has experienced this before and could share it with us. Thanks.
By Anonymous on Thursday, February 13, 2003 - 05:21 am:
All peaks are tailing? What type of injector liner are you using? What is your splitless hold time?
By Anonymous on Thursday, February 13, 2003 - 12:13 pm:
If you are using the correct liner and have checked out all other hardware problems, then consider using a small split ratio (5:1). You will not lose that much sample. I have improved peak shape by doing this in a different application, but it might work for you also.
By Uberto on Thursday, February 13, 2003 - 04:34 pm:
The liner that I use is single tapered deactivated liner. The splitless hold time is 1.5 minutes.
By Anonymous on Friday, February 14, 2003 - 01:12 pm:
What is the ID of your liner? Is it packed w/glass wool? If you are running splitless you might consider a narrow 2mm ID liner, less volume will sweep the sample onto the column more quickly.
By Uberto on Saturday, February 15, 2003 - 10:17 pm:
The ID of the liner is 4mm without glass wool. A narrower 2mm ID liner is not common for splitless injection 'cos backflash may easily occur due to smaller liner volume. I usually use 2mm ID liner for volatile compounds when headspace or purge-and-trap sampling is employed.
I am wondering if someone has experience using other type of stationary phases, e.g. polar one such as DB-1701, etc which results in a better peak shape.