ZQ tune conditions

[stanlee]

I know this will be method/compound specific but has anyone got a set of generic tune condtions for a Waters ZQ ?
Running a simple acetonitrile/water gradient with formic acid.

Ta

Stanlee

[JA]

For ESI at 1.0 ml/min

Voltages
Capillary: 3.00 kV
Cone: 20V
Extractor: 3V
RF Lens: 0.1V

Temperatures
Source: 120°C
Desolvation: 300°C

Gas Flow
Desolvation: 400 L/hr
Cone: 50 L/hr

Analyser
LM Res: 15.0*
HM Res: 15.0*
Ion Energy: 0.5V
Multiplier: 650V

* recalibration is usually required after adjusting these.

Considering downloading the Waters Micromass ZQ Detector Operator's Guide from their website.

[stanlee]

I did and thats why I was confused !
Will give these a go today as my starting conditions.
Thanks

[stanlee]

Oh, One further question, why set the multiplier voltage at 650, when the manual suggest 400 - 450V ?

Ta

[james little]

I have been optimizing my ZQ using post-column injection. I setup the instrument with a column in SIR mode, but use a very short column just to keep the flow constant. I use the built-in injector and inject 5 uL. I dissolve the sample in the same solution that I am flowing through the column. I pick a column eluent strength that matches where the compounds elutes from the column.

I make an injection (just inject water), and wait for the solvent front to elute from the column. This usually takes 0.37 min since I am using a 2 x 20 column. Then I start flow injecting the sample as I manually vary the desired parameter on the screen.

I then integate the m/z or peaks of interest and export the peaks into Excel for plotting the data. You can use a scatter chart to quickly see the optimum value.

Surprised you saw something in the manual on setting the multiplier at 400-450 volts. The 650 value has been used on even the odd Platform instrument. The instrument uses a phosphor-type detector. Electron multipliers usually start out better, but decay in response quicker. The phototype detector stays pretty much constant for years, though initially might be a little less signal than an electron multiplier.

I have occasionally set the multiplier at 700 which gives more signal, but might not really help. Would have to look at the S/N, not just the S..

I don't usually use any cone gas since I find it doesn't really keeps the instrument much cleaner and hurts my sensitivity. I also optimized the probe position for optimum signal. It tends to optimize where you hear it "whistle" (about 18 turns of the black knob starting with 0 turns as far away as the probe will go). However, I usually run between 14 and 15 turns to minimize cone cleaning. I can run about 200-300 protein-precipitated plasma samples without cleaning the cone.

All the parameters offered in a previous post look reasonable. The main one you need to optimize is the cone voltage which varies for every compound. You don't have to use the molecular ion adduct, can use a fragment. Often very useful to construct a breakdown curve of the molecular ion and all the fragment ions. If you suspect interferences, you can setup the SIR to monitor the molecular ion adduct at its maxium voltage and the fragment at its maximum cone voltage then keep an eye on the ratio to detect interferences.

I will post a link to the results of a flow injection experiment with a breakdown curve when I get to the lab.

[JA]

james, a few questions:

1. What is the relevance of the 5 uL injection of water?
2. To integrate your data are you doing an acquisition of set time? Can we not just observe the signal height in the tune page while adjusting parameters?
3. How does one set up the flow injection so that the solution we are teeing into the eluent flow closely resembles the analyte's concentration band which has passed through a column. I mean if the combination of sample concentration, injection volume and peak width meant the analyte was effectively introduced into the MS in the order of a few nmol/sec do you set up your flow injection experiment to give the same?

Thanks

[james little]

here is the file showing the results from the experiment..

http://littledomain.com/james/files/breakdown.pdf

to answer your questions:

1. I just injecting something to get the run started from the autosampler. Too lazy to change configuration to remove the autosamper. After started, I just wait for the signal to come to the baseline before changing the parameter of interest on the tune page. In the example above, was doing full scan acquisition to see how the spectrum changed as a function of the cone (skimmer) voltage.

2. I think I was doing a scan of about 10 to 475 for this particular compound every 0.3 seconds. Could just observe on tune page, but I wanted to automatically export the peaks from the chromatgram function to Excel. By making separated post column injections manually, I get distinct peaks to remind me when I changed the parameter of the value. Like to use area, better precision than height..

3. I knew at what % solvent A and solvent B my component eluted, so I dissolved it in this solvent mix and used the same solvent mix through the column. Could just do the chromatoraphy each time, but would take forever to obtain the data. I often do the injections in duplicate or triplicate and average results to get better data. I think in this case I was injecting 5 ul of 1.5 ppm solution post column. Just use the column to minimize pump pulsation. I just make sure the concentration I inject isn's so large the response is starting to saturate..

[JA]

james, thanks very interesting.

Do you just have a simple rheodyne valve plummed in-line with the eluent flow between the LC(autosampler) and the MS?

On the first page of breakdown.pdf are you doing all four SIR simultaneously? What parameters are you using in your MS file?

[james little]

I actually have a Quattro Micro, but many things about it are very similar to the ZQ. The Quattro Micro has an injector valve built-in to the mass spectrometer case. I thought the ZQ did also.

I was injecting a high enough concentration in the experiment that I could actually do a full scan, think it was m/z 10-450. I usually scan to at least twice the MW of the unknown when doing breakdown curves to also see the gas phase dimer.

I use the same process to understand all the paramters such as desolvation gas flow, desolvation gas temperature, cone gas, span, dwell times etc.

Nice to see the whole experiment graphed..