Acquity H-Class wash solvent

Hi

The best way to look at this is to ask what each solvent's purpose is.

For the seal wash the solvent is removing the salts or buffers that might precipitate on the plumnger, crystalize and wear the seal suface. The solvent then needs to dissolve the salts, acids, bases, additives. It also can run at different flow rates. The compatibility is only with the solvents, but for the H-Class the ability to blend four solvents means that the mobile phase can be wide ranging. I believe that 50/50 is too high a concentration for this purpose. More aqueous, with some organic would make a better re-solvent. However, this is a risky statement as it assumes your work is 100% reversed phase, but if your methods are normal phase or HILIC or ion exchange, clearly this would be inappropriate.

The needlewash has a very different job, it is re-solvating any precipitated sample and sample diluent on the needle surface and preventing carryover. Its choice should be to dissolve the sample and be compatible with the sample diluent and therefore in this sense should be closely related to the sample diluent. Needlewashn is more specific to the sample and the actual analysis. Samples can have wide solubilities and so this should be more organic, as sample components elute across the range of a gradint analysis. If the analysis is isocratic, than a similar solvent to the mobile phase would be appopriate. It is often necessary to adjus between sample sets, but not in all cases. Clearly a sample soluble in 100% methanol and a sample soluble in 10% methanol would be better served by different needlewashes. The H-Class sample manager needlewash is in contact with the external surface of the needle and des not have to match the mobile phase, it only has to ensure the sample solubility.

For exisitng and transfered methods, what has worked in the past is a good place to start. However, in general, a good needlewash is not the same solvent mix as a good seal wash.

Hope this helps

Liz