Odd Chromatography Problem... Help
Posted: Sat Jun 09, 2012 10:51 pm
Hi Everyone,
Got a perplexing problem. Working in a toxicology lab running a drugs of abuse/pharmaceuticals method detecting about 35 compounds on an Agilent 1290 LC. Mobile phase A is 0.1% formic acid. Mobile phase B is methanol. The gradient is 5%B - 85%B over 6 minutes, and I'm using a Zorbax Eclipse Plus 2.1x50x1.8 column. We run urine samples, prepared by solid phase extraction, on one instrument and oral fluid samples, again prepared by solid phase extraction, on a second instrument. All of the mobile phases and reagents are prepared in batches and shared on both systems. Been running samples this way for about 18 months, about 100 urines and 50 oral fluids a day. Now all of a sudden, in my oral fluid samples i'm getting poor peak shapes for very specific compounds, namely fentanyl, amitriptyline, nortriptyline, Imipramine, and buprenorphine. The peaks are very broad and in some instances are splitting. All of the other compounds look normal. Urine samples look great, no problems. Replaced the LC column and everything looked good again. But three days later the peak shape issues cropped up again. I've replaced all of my rotor seals/filters/capillary tubing, cleaned everything I could think of but still my LC columns are failing after only 3-4 days of use! Anyone have any suggestions or advice? I'm pulling my hair out over this one.
Thanks in Advance,
Chemboy831
Got a perplexing problem. Working in a toxicology lab running a drugs of abuse/pharmaceuticals method detecting about 35 compounds on an Agilent 1290 LC. Mobile phase A is 0.1% formic acid. Mobile phase B is methanol. The gradient is 5%B - 85%B over 6 minutes, and I'm using a Zorbax Eclipse Plus 2.1x50x1.8 column. We run urine samples, prepared by solid phase extraction, on one instrument and oral fluid samples, again prepared by solid phase extraction, on a second instrument. All of the mobile phases and reagents are prepared in batches and shared on both systems. Been running samples this way for about 18 months, about 100 urines and 50 oral fluids a day. Now all of a sudden, in my oral fluid samples i'm getting poor peak shapes for very specific compounds, namely fentanyl, amitriptyline, nortriptyline, Imipramine, and buprenorphine. The peaks are very broad and in some instances are splitting. All of the other compounds look normal. Urine samples look great, no problems. Replaced the LC column and everything looked good again. But three days later the peak shape issues cropped up again. I've replaced all of my rotor seals/filters/capillary tubing, cleaned everything I could think of but still my LC columns are failing after only 3-4 days of use! Anyone have any suggestions or advice? I'm pulling my hair out over this one.
Thanks in Advance,
Chemboy831