LCMS Carryover

[ta068]

How can I reduce carryover from LCMS ?

[Schmitty]

What model autosampler?
What model MS?

Is it MS or MS/MS analysis?

[ta068]

Thank you for answer.

Agilent ion trap xct
lc ms/ms

Now i can reduce carry over from injection by wash outside of the needle with 0.1% acetic acid.

But now i have a new problem about the contamination.
My work is to determine risperidone in plasma, m/z 411.4 --> m/z 191.1
and extract by liquid liquid extraction.
I found risperidone peak every time when i inject plasma blank.
So I think, it contaminate from labware or it is something in plasma.
Then, I changed plasma blank and use new testtube, I saw reperidone peak but decreased in intensity.
I'm very confuse.
I plan to clean up every labware (beaker, pipette, cylinder etc.) by washing and sonication in acid condition and...
1. Used MS3 to detect that peak. (is it advantage or posiible ?)
2. I will extract plasma blank compare with water (is it advantage?)
3. Other from the kindly reply

Sorry for very poor english writting.
Thank you for every reply.

[ta068]

I have a very chronic problem about air pump/air compressor of nitrogen generator.
My lab cannot use liquid nitrogen because of its cost.
The nitrogen generator and air pump are separate and connect with tubing.
I want to know the specification of air pump which use in LC-MS/MS laboratory. (My LC-MS/MS is used five continuous days per week.)

Thanks.

[Schmitty]

Good!
I've noticed that there can be significant differences between autosamplers and carryover. Doing a needle rinse is a very good way to overcome carryover.

Cleaning glassware or using new glassware can help determine the source of contamination. Are you the only one working with the risperidone in your lab? How much smaller was the area of the risperidone peak in the different plasma test tube?

Are you currently using an ion transition in your analysis? Are you looking for 411.4 or 191.1? For maximum sensitivity you should be fragmenting the 411.4 into 191.1.

For you gas supplies, you should look up your specific instrument and determine its gas needs. These will probably be listed in liters/hour. Then you will have to find a generator that can meet that supply. The Agilent may also have a recommendation for a maker of each of the gas ganerators.

[ta068]

Thank you very much for your reply.

[Schmitty]

So...is it working?

[ta068]

Yes, I think it will work soon if the instrument work.

Now, I have same problem as past, air supplier for nitrogen generator (air compressor).
The problem is circuit breaker that control electricity to motor of this air compressor. And I can't found any shop that sell the same circuit breaker like this in my province which located in district part of my countrty.

Since my lab brought this LCMSMS from Agilent (1 1/2 years), the problem of air compressor were occured 5-6 times. Agilent changed new one for my lab and after I used it for 1 month, the problem occured again.
Every time the problem occured, it take 2 - 6 weeks to solve problem depend on how hard of the promblem. Agilent brought this air compressor from a company that import this air compressor from Taiwan.

Air compressor is
PUMA NCS 20 Silent type
1-15HP 13 AMP 1 Phase

I used 5L/min nitrogen flow in LCMSMS

No on-side service from any company. So I'm not know the true cause of all problem. No engineer can answer my question?
Service was only by phone and mail.

What is normally air compressor and nitrogen generator used in LCMSMS lab?
How should I manage this air compressor?
and How about your LCMSMS air supply?
(I'm beginner and only one work LCMSMS in my lab)

Thank you very much for your kindness.

[Peter Apps]

The problem might be with the mains electricity supply and not with the compressor.

The compressor is rated at 13 A, if it is plugged into a 15A power socket it might trip the mains circuit breaker (it is not clear whether the circuit breaker is on the compressor, or on the mains supply).

If you have surges and dips in your electrical supply they can also cause circuit breakers to trip.

Try getting an electrician to check your electical mains supply.

Peter

[Schmitty]

We have Sciex and Quattro instruments here, so we only need nitrogen and argon. The nitrogen is in a tank(s) outside, and we have some type of system to use the purest portion that is above the compressed liquid.

The argon is just regular UHP I think.

If your compressor is operating at the limits of the circuit (13A on 15A line), you may want to upgrade the wiring, breaker and outlet to 20A. If the circuit is always operating at a high level of use, if may be prone to failure sooner. Also, when a compressor is cycled on/off it will draw more than the 13A that it is rated at. Usually the circuit breaker can handle this (or cannot respond quickly enough) and everything is fine. But a lifetime of going 0A>18A>13A>0A>18A>13A will kill a breaker (faster than having a lower constant load on it.)

You could also upgrade the compressor to oversize it, and get the outlet rewired to 2 phase. But, that shouldn't be necessary if the instrument has operated successfully before.

[ta068]

now it 's work.
But I don't know when it will down
Thanks for the kindness of Schmitty and peter to help me solve every problem.

Now, I know the cause of contamination in blank chromatogram.
I evaporate only the extraction solvent in new tube and reconstitute, I found the high intensity peak compare with no peak in new solvent bottle.

Could I ask you a problem?I use ion trap LC-MSMS .
Does it appropiate to use in routine quantitative analysis?

The first objective of this LC-MSMS is to determine nitrofuran in shrim, and LOQ must down to 0.1 ppb. I try and try for a long time but LOQ cannot down to 0.1 ppb with this ion trap LCMSMS. I don't know if Triple Quad is better.

[Schmitty]

We generally use our triple quads for routine analysis and the ion traps for development work. I am not sure about robustness and sensitivity of (for example) our Sciex 4000 QQQ vs our Sciex 4000 iontrap.

[Mary Carson]

All the methods I am familiar with use triple quads. Just out of curiosity, who is enforcing a 0.1 ppb target for nitrofurans (and their protein bound metabolites)? So far as I know, EU is still using a 1 ppb minimum required performance level (MRPL).

Your background contamination isn't semicarbazide by any chance, is it?

[drhlrao]

I suggest that you incorporate a MICRO SONICATOR inside the auto-sampler, with the help of a service engineer.