Contamination issue with ammonium formate -containing solven
Posted: Fri Mar 08, 2019 12:42 pm
From my collegue:
I transferred my bile acids analysis method to our new Bruker LC-QTOF system from our older Waters LC-MS/MS. I made new solvents: 0,2 % HCOOH and 10 mM ammonium acetate in A) H2O and B) MeOH, all LC-MS grade. Solvents were fresh, ammonium acetate 2 years old. Column used: Thermo Accucore polar Premium, 2,6 um, 2,1 x 150 mm + Accucore polar premium guard column
I saw a huge contamination in the blank run. I thought that I had overloaded the column in the previous instrument and the peaks were caused by our compounds, since no one else had any problems with the instrument. I tried to wash the column with methanol, iso-propanol, 95 % methanol and with following procedures that manufacturer proposed:
1. protocol:
1. 90% water / 10% acetonitrile (for buffer removal if required)
2. 50% THF / 50% acetonitrile
3. acetonitrile
4. Re-equilibrate with mobile phase
2. protocol: (reverse flushing)
1. Flush with HPLC grade water, inject 4 aliquots of 200 µL DMSO during this flush.
2. Flush with methanol
3. Flush with chloroform
4. Flush with methanol
All washing steps 40-60 column volumes.
These did not remove the contamination.
I ordered a new, similar column and saw a huge contamination in a blank run. I tried with another column (Kinetex C18 2.6 um, 2.1x 100 mm) and saw the same contamination. I made a run without buffers and without column and the blank was pure. So the contamination is not stuck into instrument lines. I also ran blanks without buffers in these columns, but contamination is stuck there.
My guess is that ammonium acetate is contaminated somehow, possibly by some wax. The m/v value of the biggest contaminant peak is 604.383 (may be protonated form or ammonium adduct of some molecule). Any ideas?
I transferred my bile acids analysis method to our new Bruker LC-QTOF system from our older Waters LC-MS/MS. I made new solvents: 0,2 % HCOOH and 10 mM ammonium acetate in A) H2O and B) MeOH, all LC-MS grade. Solvents were fresh, ammonium acetate 2 years old. Column used: Thermo Accucore polar Premium, 2,6 um, 2,1 x 150 mm + Accucore polar premium guard column
I saw a huge contamination in the blank run. I thought that I had overloaded the column in the previous instrument and the peaks were caused by our compounds, since no one else had any problems with the instrument. I tried to wash the column with methanol, iso-propanol, 95 % methanol and with following procedures that manufacturer proposed:
1. protocol:
1. 90% water / 10% acetonitrile (for buffer removal if required)
2. 50% THF / 50% acetonitrile
3. acetonitrile
4. Re-equilibrate with mobile phase
2. protocol: (reverse flushing)
1. Flush with HPLC grade water, inject 4 aliquots of 200 µL DMSO during this flush.
2. Flush with methanol
3. Flush with chloroform
4. Flush with methanol
All washing steps 40-60 column volumes.
These did not remove the contamination.
I ordered a new, similar column and saw a huge contamination in a blank run. I tried with another column (Kinetex C18 2.6 um, 2.1x 100 mm) and saw the same contamination. I made a run without buffers and without column and the blank was pure. So the contamination is not stuck into instrument lines. I also ran blanks without buffers in these columns, but contamination is stuck there.
My guess is that ammonium acetate is contaminated somehow, possibly by some wax. The m/v value of the biggest contaminant peak is 604.383 (may be protonated form or ammonium adduct of some molecule). Any ideas?