-
- Posts: 1
- Joined: Wed Aug 01, 2012 8:12 pm
Hello all! I have browsed the boards before and found it to be a great resource with help in diagnosing and resolving issues with an instrument in our laboratory that is quite difficult to work with, as it never seems to want to stay up and running for more than a few days before having issues! I am curious to see if anyone out here has had similar issues with a similar system and, if so, what they were able to do to diagnose/resolve the issues. Any input or widsom learned from past experience is greatly welcomed. Thanks so much!
System: Teledyne Tekmar Aquatek 70 Vial AutoSampler, Teledyne Tekmar Stratum Purge and Trap, Agilent 5975C VL MSD with Triple-Axis Detector, Agilent 7890A GC System
Method: EPA Method 8260B used for detection of Benzene (ppb level) in Wastewater samples
Standards/Trap: Pentafluorobenzene (internal standard), Bromofluorobenzene (surrogate), Vocarb 3000 Trap
Description of Issues:
Over the last 2 years, the laboratory I now work for have had numerous issues related to sudden spikes or losses in internal standard recoveries which result from random, sudden decreases in the bromofluorobenzene responses (typically, the internal standard we now use - pentafluorobenzene - does not decrease). These drops are essentially "hit or miss." That is, if you run 10 samples, you may have one or two that the bromofluorobenzene response drops just enough on to move the percent recovery out of the acceptable method limits of 86-115%. Any thoughts?
Tuning has also been an issue. I have found several good resources regarding some ways to do a modified autotune to suit the particular needs (i.e. I have learned how to change the Ion Focus, Voltages, Lens, Offset, etc. to increase/decrease abundance for different m/z that may fall out of range over time as the source gets dirty). However, it seems as though I am in a constant battle of either re-tune the instrument (typically followed by the need to re-calibrate), or take it down, clean the source, and have to waste nearly 2 days re-tuning and calibrating. I have tried many suggestions (including, time and again, the modified autotune suggested in an Agilent technical document that I have see many state works for them... but it doesn't hardly ever for us). Any suggestions?
System: Teledyne Tekmar Aquatek 70 Vial AutoSampler, Teledyne Tekmar Stratum Purge and Trap, Agilent 5975C VL MSD with Triple-Axis Detector, Agilent 7890A GC System
Method: EPA Method 8260B used for detection of Benzene (ppb level) in Wastewater samples
Standards/Trap: Pentafluorobenzene (internal standard), Bromofluorobenzene (surrogate), Vocarb 3000 Trap
Description of Issues:
Over the last 2 years, the laboratory I now work for have had numerous issues related to sudden spikes or losses in internal standard recoveries which result from random, sudden decreases in the bromofluorobenzene responses (typically, the internal standard we now use - pentafluorobenzene - does not decrease). These drops are essentially "hit or miss." That is, if you run 10 samples, you may have one or two that the bromofluorobenzene response drops just enough on to move the percent recovery out of the acceptable method limits of 86-115%. Any thoughts?
Tuning has also been an issue. I have found several good resources regarding some ways to do a modified autotune to suit the particular needs (i.e. I have learned how to change the Ion Focus, Voltages, Lens, Offset, etc. to increase/decrease abundance for different m/z that may fall out of range over time as the source gets dirty). However, it seems as though I am in a constant battle of either re-tune the instrument (typically followed by the need to re-calibrate), or take it down, clean the source, and have to waste nearly 2 days re-tuning and calibrating. I have tried many suggestions (including, time and again, the modified autotune suggested in an Agilent technical document that I have see many state works for them... but it doesn't hardly ever for us). Any suggestions?
