In a mixture of salt solutions and organic solvent the salt solution might be well dissolved in the organic solvent without showing precipitations. However in the mixing point of the gradient valve, at the boundary between the two solvents, micro precipitation is possible. Gravity forces the salt particles to fall down. Normally the A channel of the valve is used for the aqueous/salt solution and the B channel of the pump is used for the organic solvent. If used in this configuration the salt will fall back into the aqueous solution and will be dissolved. When using the pump in a different configuration (e.g., D - salt solution, A - organic solvent) the salt can fall into the port of the organic solvent and may lead to performance problems.
NOTE
When using salt solutions and organic solvents it is recommended to connect the salt solution to one of the bottom ports of the MCGV/4CGV and the organic solvent to one of the upper gradient valve ports. It is best to have the organic channel directly above the salt solution channel. Regular flushing with water of all MCGV/4CGV channels is recommended to remove all possible salt deposits in the valve ports.
NOTE
Precipitations formed during the mixing of buffers and organic solvents which do not dissolve salts may cause a loss of pump performance (flow/retention time stability), a blockage or internal leak of the pump. Avoid the use of such solvent combinations, as they can cause irreproducible chromatographic results.
The use of an G1311-60006 (Inline filter) can avoid or reduce such effects by filtering crystals and re-dissolving them over time.
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