Chromatography Forum

In my lab there was an old agilent API 2000 QQQ that wasn't being used for at least three years. I was put in charge to find out if the equipment still worked, so I cleaned the source and the interface, changed the ESI electrode and turned it on. I calibrated it with agilent's specific calibration solution (PPG) and it ran just fine in LC/MS. However, the fridge where the calibration solution was kept had a failure during the weekend, leaving the solution at room temperature for three days (the package says it must be maintained between 2°C and 8°C).When I injected the PPG, the peaks that the software uses to calibrate the equipment were with extreme low intensity and the base peaks were with some mass shift (the highest masses had at least 2 Da of difference if compared to previous values). I guessed that the calibration solution had degraded. Still, I manually calibrated with those low intensity peaks and ran some injections with known standards. Where before the calibration was a beautiful peak with the correct mass (995.6 m/z), it now had a very broad peak, with good intensity, that started at about 992 up to 996, with the highest intensity at 993. I tried to reverse the calibration to an earlier one but the peaks stood the same way. While waiting for the new calibration solution, my question is: Can this broad peak and this mass shift be explained by the lack of the correct calibration or is it something else? All suggestions are welcome. (I'll try to post some spectrograms later)

I'm guessing it's got itself into a terrible calibration, but I don't understand why this has happened. Quadrupoles are usually stable for ages.