Wash solvent guidelines

To reduce the risk of carryover, follow these wash solvent guidelines.

Wash solvents clean the sample needle between injections and remove traces of the previous sample. They are commonly stronger than an application's isocratic mobile phase and are often as strong as—or even stronger than—the final mobile phase conditions for a gradient separation. Because they are not injected onto a column, determining an appropriate wash solvent requires, for all practical purposes, no chromatographic considerations.

For best performance, follow these guidelines when selecting wash solvents. Otherwise, you can increase the risk of carryover. However, these guidelines do not prohibit all other solvent combinations, which you can run with lower performance expectations or by manipulating injection parameters.

• Important: Wash solvents must be compatible and miscible with both the application's mobile phase and the sample components. They must also be fully soluble with the mobile phase and sample and should not cause precipitation.
  Use wash solvents based on the sample and mobile phase chemistries of your application.
• Wash solvents must be strong enough to easily dissolve the sample and thereafter maintain solubility.
• For buffered aqueous, reverse-phase chromatographic conditions, wash solvent with a high concentration of organic solvent is typically used, such as 80 to 100% ACN or MeOH with the remainder water.
  Note: Titanium is subject to corrosion in anhydrous methanol, which you can avoid by adding a small amount of water (approximately 3%). Slight corrosion is possible when ammonia is >10%. If using an Alliance iS Bio HPLC system, you can alternatively remove the titanium filter sinkers (the system loses its first line of protection from particulates) or replace them with stainless steel sinkers if your analysis is unaffected by biocompatibility considerations.

Contents

• Wash solvent recommendation
  
• Optional uses for wash solvents