CHROMATOGRAPHY SYSTEM WITH GUARD COLUMNS

1 . A method for chromatographic separation of a target substance comprising the steps of:

a) loading the target substance on a main column by conveying a feed from a feed tank via a first guard column through the main column and a second guard column to a waste receptacle;

b) washing the columns by conveying a wash fluid via the first guard column through the main column and the second guard column; and

c) eluting said target substance by conveying an elution fluid via the first guard column or the second guard column through the main column to an eluate tank.

2 . The method of claim 1 , further comprising the step of:

d) loading the target substance on the main column by conveying a feed from a feed tank via the second guard column through the main column and the first guard column to a waste receptacle.

3 . The method of claim 1 , wherein step a) further comprises measuring the concentration of a target substance in the fluid exiting the main column and ending step a) when said concentration has reached a predetermined value.

4 . The method of claim 1 , wherein step a) further comprises determining a breakthrough point or a saturation point of the main column and ending step a) when said breakthrough or saturation point has been reached.

5 . The method of claim 1 , wherein step b) further comprises measuring the concentration of a target substance in the fluid exiting the main column and ending step b) when said concentration is lower than a predetermined value.

6 . The method of claim 1 , wherein said first and second guard columns comprise a chromatography resin having essentially the same selectivity as the chromatography resin in the main column.

7 . The method of claim 1 , wherein said main column and said first and second guard columns comprise a chromatography resin with Fc fragment-binding affinity ligands.

8 . The method of claim 1 , wherein said first and second guard columns comprise a chromatography resin having a volume average particle size at least 10%, such as at least 25% or 50%, higher than the volume average size of the chromatography resin in the main column.

9 . The method of claim 1 , wherein the bed volumes of the first and second guard columns are each less than about 50%, such as less than about 25% or less than about 15%, of the bed volume of the main column.

10 . A method for use with a chromatography apparatus, the method comprising:

generating, by a first detector disposed between a main column and a first guard column of the chromatography apparatus, in response to a feed stream passing through the first guard column, a first signal including a first signal's first plateau and a first signal's second plateau, the first signal being a time-varying signal and the first signal's first plateau occurring before the first signal's second plateau,

wherein the first signal is indicative of species of the feed stream binding and passing through the first column, and wherein the first signal's first plateau is indicative of non-adsorbing species breaking through the first column and the first signal's second plateau is indicative of all the substance in the feed stream;

generating, by a second detector disposed between the main column and a second guard column of the chromatography apparatus, a second signal including a second signal's plateau, wherein the second signal is indicative of all of the substances included in an effluent stream of the main column;

determining, by a programmable logic controller of the chromatography apparatus, (i) a first breakthrough point based on a first difference between the first signal and the second signal reaching a first threshold and (ii) a second breakthrough point based on a second difference between the first signal and the second signal reaching a second threshold;

wherein the determining includes conducting a first comparison between the first signal and the second signal,

wherein the first difference corresponds to the first comparison reaching the first threshold;

wherein the second difference is based on a second comparison between the first signal and the second signal,

wherein the second difference corresponds to the second comparison reaching the second threshold;

wherein the first threshold and second thresholds are each a percentage of a difference between the first signal's second plateau and the second signal's plateau; and

wherein the second threshold is different than the first threshold.

11 . The method of claim 10 , wherein generating the first and second signals, and the determining are performed when the first and second guard columns each has a bed volume of less than about 15% of a bed volume of the main column.

12 . The method of claim 10 , wherein said first and second detectors are ultraviolet absorption detectors, and generating the first and second signals are each based on an ultraviolet absorption measurements.

13 . The method of claim 10 , wherein the first signal is a feed signal representative of the composition of a feed material provided to a first end of the main column and the second signal is the effluent signal representative of an effluent from the second end of the main column.

14 . The method of claim 10 , further comprising determining a saturation point of the main column by the programmable logic controller.

15 . The method of claim 10 , wherein the first guard column is connected to one of a first feed tank and a first waste receptacle via a first valve;

wherein the second guard column is connected to one of a second feed tank and a second waste receptacle via a second valve;

wherein when the first guard column is connected to the first feed tank, the second guard column is connected to the second waste receptacle;

wherein when the first guard column is connected to the first waste receptacle, the second guard column is connected to the second feed tank;

wherein the programmable logic controller is coupled to said first and second valves;

wherein the method further comprises controlling positions of said first and second valves by the programmable logic controller.

16 . The method of claim 15 , wherein there is disposed a third valve between the main column and the first guard column, a fourth valve disposed between the main column and the second guard column, and wherein the method further includes controlling positions of said third and fourth valves by the programmable logic controller.

17 . The method of claim 10 , wherein said main column and said first and second guard columns include Fc fragment-binding affinity ligands in their respective chromatography resins.