UPLC XevoTQ-S Pesticide Residue Analysis requires increased Maintenance

Our lab is using the Waters UPLC coupled to Waters Xevo TQ-S Triple Quad MS to analyze pesticide residues in various food matrices that have been cleaned up (offline) using a modified QuEChERS approach. With this application I have found that (through many service repairs, tech calls, etc...) the Sample Cone Assembly needs to be cleaned once every week and the Ion Block AND StepWave (yes the StepWave) need to be cleaned every 3-4 months. This seems excessive to me, but if I don't maintain this kind of PM schedule, the Mass Analyzer (MS1, Coll Cell, MS2) gets contaminated after about 6 months of use and requires a FSE to thoroughly clean the entire assembly. Last time this was done, there were ion burns on both MS1 and MS2. More details about our applicationInjection Concentration = 0.25g/mL (g sample per mL extraction solvent, it used to be 4g/mL but that was too much)Injection Vol = 4uLCalibration Range = 1ppb to 1ppmAnalytes = about 142 different pesticides, all classesMRM = 2 MRM transitions per pesticideUPLC Method = 15 min separation, mobile phase is Water/MeOH w/10mM Ammonium Formate and 0.1% Formic Acid buffers, flow rate 0.45mL/min, temperature controlled column & sample manager, Column is HSS T3 1.8um 100x2.1mm Is this increased maintenance normal for my application or is my application not optimized correctly? Any thoughts, suggestions, etc... are greatly appreciated, I am banging my head on a wall over here!! Thank you!


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