loss of sensitivity on Agilent 6540

Discussions about GC-MS, LC-MS, LC-FTIR, and other "coupled" analytical techniques.

8 posts Page 1 of 1
Good day!
We are working with MSD 6540 Agilent, and recently we been observing problems with signal intensity. Immediately after switching on from standby mode, when filling the calibration solution, the line intensity is very good, but after 5-6 minutes, the signal drops by 10-15 times and stabilizes at this value. After a short change of polarity (transition to negative ionization mode), the signal intensity is high again, but then it decreases rapidly again. I know that this is a sign of contamination of ion optics, the transfer capillary, but everything has been washed several times already, as recommended by the manufacturer. What else can cause such symptoms? Can it be a problem with electronics?
lav877 wrote:
Good day!
We are working with MSD 6540 Agilent, and recently we been observing problems with signal intensity. Immediately after switching on from standby mode, when filling the calibration solution, the line intensity is very good, but after 5-6 minutes, the signal drops by 10-15 times and stabilizes at this value. After a short change of polarity (transition to negative ionization mode), the signal intensity is high again, but then it decreases rapidly again. I know that this is a sign of contamination of ion optics, the transfer capillary, but everything has been washed several times already, as recommended by the manufacturer. What else can cause such symptoms? Can it be a problem with electronics?


I don't know about the Agilent system, but that sounds similar to what the engineer described to me with the Sciex instruments when the quadrupoles become dirty.
The past is there to guide us into the future, not to dwell in.
Thanks for your reply! I was afraid of that too. As far as I understand, the quadrupoles on this device are not serviced, they can not be washed.

Tell me please, instability of the parameter HEX2 RF in the collision cell can cause such symptoms?
lav877 wrote:
Thanks for your reply! I was afraid of that too. As far as I understand, the quadrupoles on this device are not serviced, they can not be washed.

Tell me please, instability of the parameter HEX2 RF in the collision cell can cause such symptoms?


I'm not certain on the Agilent, but it would seem if you have drift in the RF in the collision cell, you would have changing collision energy which would alter the amount of ions produced.
The past is there to guide us into the future, not to dwell in.
Also I just read through this older thread that might address your problem.

viewtopic.php?t=21739

Seems others had similar problem with triple quad instruments.
The past is there to guide us into the future, not to dwell in.
Thank you, I carefully read the link you suggested. I have at my disposal two capillaries resistive and non-resistive. I also tried several ways of washing, including the one described in the discussion. Unfortunately it did not bring any results. That is why I turned to a respected community, I just have no more ideas where to look for a problem.

The only problem diagnosed by the device itself is the inability to set the value of the HEX2 RF parameter in the collision cell, which is the default. This is 650V. I just set the value to 500V, I passed the autotune procedure, and the device works without giving an error message. Perhaps due to a malfunction of the electronics unit, this value is also subject to drift during operation of the device, which causes a decrease in the signal during operation. This is just the only version I have about the observed problem. But I do not know how believable it is.
lav877 wrote:
Thank you, I carefully read the link you suggested. I have at my disposal two capillaries resistive and non-resistive. I also tried several ways of washing, including the one described in the discussion. Unfortunately it did not bring any results. That is why I turned to a respected community, I just have no more ideas where to look for a problem.

The only problem diagnosed by the device itself is the inability to set the value of the HEX2 RF parameter in the collision cell, which is the default. This is 650V. I just set the value to 500V, I passed the autotune procedure, and the device works without giving an error message. Perhaps due to a malfunction of the electronics unit, this value is also subject to drift during operation of the device, which causes a decrease in the signal during operation. This is just the only version I have about the observed problem. But I do not know how believable it is.


If the voltage is drifting on the HEX RF it could be a power supply problem or a problem on the control board. I had an Agilent 7500ICPMS that had a drifting sensitivity problem, it would become twice as sensitive over night as it ran, turning off the plasma and starting over would bring it back to normal. I finally noticed that while the Electron Multiplier voltage was set to 1800v, and the setting would remain the same, the readout in diagnostics would show that after about 5 hours the voltage was actually 2200v while the setting was 1800v. Once the control board was replaced it was a very steady instrument for years.

I would have Agilent take a look at the drifting voltages just to be sure.
The past is there to guide us into the future, not to dwell in.
What you are writing about is very similar to what I observe with the intensity of the signal on my instrument. Unfortunately, the challenge of diagnosing an agilent is very expensive. I have already ordered the voltage management board for the collision cell about six months ago, I will probably test it soon.
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