Between samples, using 25% Bleach is the most effective media to consistently achieve carryover of <1%.
Please also note 25% bleach is not actually 25% bleach, because the active ingredient in bleach is sodium hypochlorite at a concentration of 5-9%. That makes it 25% of the 5-9% of sodium hypochlorite.
25% bleach has been observed to be effective in cleaning both bacterial, yeast, and viral samples, and at the end of such experiments on other flow cytometry and cell sorting instrumentation.
Use of Flow Clean in the absence of bleach when cleaning between samples is possible, but will not consistently achieve the same result, and may result in carryover slightly above the acceptable threshold of <1%.
Flow Clean is used for an extended period of time during the Daily Clean procedure since this is Beckman Coulter's recommended cleaning agent for this particular step. The duration of the Daily Clean step is extended due to the previously stated observation that it does not produce as consistent of a result between samples as the 25% Bleach when run for the same duration.