Chromatography Forum

http://www.flickr.com/photos/56860579@N02/5247320768/

as the chart in the link shows that Waters ZQ2000 signal/peak area was 1) drifting and 2) had some abnormal variation when the same solution was injected multiple times. One vial was only injected once.

this was a gradient from 75%B to 100%B in 2.5 min. A: 0.1% acetic acid, B: ACN(no acid). 0.5mL/min, Water BEH 50x2.1 1.7um column, 35 C. Diluent: ACN. Analyte is a zwitterion.

I hope some one can tell me if this is normal.If not what I can do to improve it.

Thanks in advance

for system suitability testing on our LC-MS-MS (Waters 2790-ABI/4000) we used to use a <5% acceptance criteria on peak area ratio (API/IS).

For an autosampler precision qualification test once (on an LC-MS-MS system), I put a UV detector between the LC and mass spec, injected caffeine, and monitored both responses. By UV, RSD ranged between 0.1 and 0.2%. By MS, RSD was 2 to 3.3%. Convinced me to use UV detectors to qualify autosamplers....which is not at all the same as setting system suitability parameters on an LC-MS-MS method.

You also have to ask...

How much precision does your autosampler give you????

Alp