Chromatography Forum

I looked through the book, but I did not find specific refrence compounds for negative ESI tuning. Anyone can tell me about that? The LCQ from Finnigan. My target compounds MW is from 200 to 500.
thanks

I'm actually not using the LCQ, but an esquire 3000+ (brucker) trap. I tune my ms with the agilent tuning mix, both for + and - modes. It has the advantage to cover a wide range of m/z.

i use polypropylene glycol in both the positive and negative ion modes. A mix of the PPG 1000 (or lower MW depending on range) in water/acn 50/50 containing about 4 mmolar ammonium acetate. In positive, increase source voltage to get fragments at 117, 175, etc plus the fragments at M+NH4.

In negative ion weaker signal, but get adequate M+OAC signal. Turn down source voltage so I get the 59 for acetate and 119 for acetate dimer.

Do this routinely on LCT and on our Quattro Micro.

Hi Shangyer,
You must to used polytirosin (mono, tri and hexa) for your tunning. The used of low Spray voltage (3000 if you have an ion MAX source) and 30 unit for Sheat gas pressure (nitrogen) increassed your signal.

Cheers


Alejandro

I thought normal practice would be to tune using one of your compounds of interest, assuming you have access to a pure standard. This is the best solution and likely to give you optimal response. Maybe you were thinking of mass calibration, for which compounds like PEG are routinely used? But I thought this was not necessary in negative mode on the LCQ, where positive claibration is sufficient.

I move that we abolish the use of the word "tuning" in regards to mass spectrometry, because it is vaguely defined, as evidenced by this thread.