Characteristics of Ni Sepharose®, Ni Sepharose® excel, TALON® Superflow™, and Uncharged IMAC Sepharose® Products
- Ni Sepharose® Products
- Stripping, recharging, and cleaning of Ni Sepharose® products
- Ni Sepharose® excel/His Mag Sepharose® excel products
- TALON® Superflow™ products
- Stripping, recharging, and cleaning of TALON® Superflow™ products
- Uncharged IMAC Sepharose® products
- Stripping, recharging, and cleaning of IMAC Sepharose® products
Ni Sepharose® products
Ni Sepharose® High Performance is recommended for high-resolution purification of histidine-tagged proteins, providing sharp peaks and concentrated eluate. Ni Sepharose® 6 Fast Flow is excellent for scaling up and batch purifications. Ni Sepharose® excel is designed for capture and purification of histidine-tagged proteins secreted into eukaryotic cell culture supernatants. Two magnetic bead formats are also available: His Mag Sepharose® Ni and His Mag Sepharose® excel. Table A1.1 summarizes key characteristics of bulk Ni Sepharose® High Performance and Ni Sepharose® 6 Fast Flow chromatography media, and Table A1.2 lists the stability of these media under various conditions. Tables A1.3 to A1.11 summarize the characteristics of these same media as prepacked columns, prepacked 96-well plates, and magnetic beads.
1 Dynamic binding capacity conditions:
| Sample: Column volume: Flow rate: Binding buffer: Elution buffer: |
1 mg/mL (histidine)6-tagged pure protein (Mr 43 000) in binding buffer or (histidine)6-tagged protein (Mr 28 000) bound from E. coli extract. Capacity determined at 10% breakthrough. 0.25 mL or 1 mL 0.25 mL/min or 1 mL/min, respectively 20 mM sodium phosphate, 0.5 M NaCl, 5 mM imidazole, pH 7.4 20 mM sodium phosphate, 0.5 M NaCl, 500 mM imidazole, pH 7.4 |
Note: Dynamic binding capacity is protein dependent.
2 H2O at room temperature.
3 Ni2+-stripped medium.
1 Before performing runs with sample/buffers containing reducing reagents, a blank run with binding and elution buffers excluding reducing agents is recommended (see, for example, Manual purification using HisTrap FF crude Kit with a syringe).
2 Tested for 1 wk at 40 °C.
3 The strong chelator EDTA has been used successfully in some cases, at 1 mM. Generally, chelating agents should be used with caution (and only in the sample, not in the buffer). Any metal-ion stripping may be counteracted by adding a small excess of MgCl2 before centrifugation/filtration of the sample. Note that stripping effects may vary with the applied sample volume.
1 According to ANSI/SBS 1-2004, 3-2004, and 4-2004 standards (ANSI = American National Standards Institute and SBS = Society for Biomolecular Screening).
2 Protein binding capacity is protein dependent.
3 Ni2+-stripped medium.
1 Protein binding capacity is protein dependent.
1 Dynamic binding capacity conditions:
| Sample: Column volume: Flow rate: Binding buffer: Elution buffer: |
1 mg/mL (histidine)6-tagged pure protein (Mr 43 000) in binding buffer or (histidine)6-tagged protein (Mr 28 000) bound from E. coli extract. Capacity determined at 10% breakthrough. 0.25 mL or 1 mL 0.25 mL/min or 1 mL/min, respectively 20 mM sodium phosphate, 0.5 M NaCl, 5 mM imidazole, pH 7.4 20 mM sodium phosphate, 0.5 M NaCl, 500 mM imidazole, pH 7.4 |
Note: Dynamic binding capacity is protein dependent.
2 H2O at room temperature.
3 Ni2+-stripped medium.
1 Dynamic binding capacity conditions:
| Sample: | 1 mg/mL (histidine)6-tagged pure protein (Mr 43 000) in binding buffer or (histidine)6-tagged protein (Mr 28 000) bound from E. coli extract. Capacity determined at 10% breakthrough. |
| Column volume: Flow rate: Binding buffer: Elution buffer: |
0.25 mL or 1 mL 0.25 mL/min or 1 mL/min, respectively 20 mM sodium phosphate, 0.5 M NaCl, 5 mM imidazole, pH 7.4 20 mM sodium phosphate, 0.5 M NaCl, 500 mM imidazole, pH 7.4 |
Note: Dynamic binding capacity is protein dependent.
2 H2O at room temperature.
3 Ni2+-stripped medium.
1Table A1.6 for the characteristics of HisTrap FF crude columns.
1 Protein binding capacity is protein dependent.
2 Ni2+-stripped medium.
1 d50v is the average particle size of the cumulative volume distribution.
2 Dynamic binding capacity conditions:
| Samples: | 1 mg/mL (histidine)6-tagged pure protein (Mr 43 000) in binding buffer (QB, 10% determination) or histidine)6-tagged protein (Mr 28 000) bound from E. coli extract. |
| Column volumes: Flow rates: Binding buffer: Elution buffer: |
0.25 or 1 mL 0.25 or 1 mL/min, respectively 20 mM sodium phosphate, 500 mM NaCl, 5 mM imidazole, pH 7.4 20 mM sodium phosphate, 500 mM NaCl, 500 mM imidazole, pH 7.4 |
Note: Dynamic binding capacity is protein dependent.
3 H2O at room temperature.
4 Many chromatography systems are equipped with pressure gauges to measure the pressure at a particular point in the system, usually just after the pumps. The pressure measured here is the sum of the pre-column pressure, the pressure drop over the medium bed, and the post-column pressure. It is always higher than the pressure drop over the bed alone. We recommend keeping the pressure drop over the bed below 1.5 bar. Setting the upper limit of your pressure gauge to 1.5 bar will ensure the pump shuts down before the medium is overpressured. If necessary, post-column pressure of up to 3.5 bar can be added to the limit without exceeding the column hardware limit. To determine post-column pressure, proceed as follows:
To avoid breaking the column, the post-column pressure must never exceed 3.5 bar.
- Connect a piece of tubing in place of the column.
- Run the pump at the maximum flow you intend to use for chromatography. Use a buffer with the same viscosity as you intend to use for chromatography. Note the back pressure as total pressure.
- Disconnect the tubing and run at the same flow rate used in step 2. Note this back pressure as pre-column pressure.
- Calculate the post-column pressure as total pressure minus pre-column pressure. If the post-column pressure is higher than 3.5 bar, take steps to reduce it (shorten tubing, clear clogged tubing, or change flow restrictors), and perform steps 1 to 4 again until the post-column pressure is below 3.5 bar. When the post-column pressure is satisfactory, add the post-column pressure to 1.5 bar and set this as the upper pressure limit on the chromatography system.
5 Short term pH: pH interval where the medium can be subjected to cleaning- or sanitization-in-place without significant change in function.
Long term pH: pH interval where the medium can be operated without significant change in function.
6 The strong chelator EDTA has been used successfully in some cases at 1 mM. Generally, chelating agents should be used with caution (and only in the sample, not in the buffer). Any metal-ion stripping may be counteracted by adding a small excess of MgCl2 before centrifugation/filtration of the sample. Note that stripping effects may vary with the applied sample volume.
1 Dynamic binding capacity conditions:
| Sample: | 1 mg/mL (histidine)6-tagged pure protein (Mr 43 000) in binding buffer or (histidine)6-tagged protein (Mr 28 000) bound from E. coli extract. Capacity determined at 10% breakthrough. |
| Column volume: Flow rate: Binding buffer: Elution buffer: |
0.25 mL or 1 mL 0.25 mL/min or 1 mL/min, respectively 20 mM sodium phosphate, 0.5 M NaCl, 5 mM imidazole, pH 7.4 20 mM sodium phosphate, 0.5 M NaCl, 500 mM imidazole, pH 7.4 |
Note: Dynamic binding capacity is protein dependent.
2 H2O at room temperature.
3 Ni2+-stripped medium.
1 The capacity was determined using 5 mM imidazole in sample and binding buffer. Note that binding capacity is sample dependent.
Stripping, recharging, and cleaning of Ni Sepharose® products
Stripping and Recharging
Ni Sepharose High Performance and Ni Sepharose 6 Fast Flow do not have to be stripped and recharged between each purification if the same protein is to be purified. It may be sufficient to strip and recharge it after approximately two to five purifications, depending on the specific sample, sample pretreatment, sample volume, etc.
Stripping buffer: 20 mM sodium phosphate, 500 mM NaCl, 50 mM EDTA, pH 7.4
- Strip the chromatography medium by washing with at least 5 to 10 column volumes of stripping buffer.
- Wash with at least 5 to 10 column volumes of binding buffer.
- Immediately wash with 5 to 10 column volumes of distilled water.
- Recharge the water-washed column by loading 0.5 column volumes of 0.1 M NiSO4 in distilled water onto the column.
- Wash with 5 column volumes of distilled water, and 5 column volumes of binding buffer (to adjust pH) before storage in 20% ethanol. Salts of other metals, chlorides, or sulfates may also be used.
It is important to wash with binding buffer as the last step to obtain the correct pH before storage.
Washing with buffer before applying the metal ion solution may cause unwanted precipitation.
Cleaning-in-place
When an increase in back pressure is seen, the chromatography medium should be cleaned. Before cleaning, strip off metal ions using the recommended procedure described above. The stripped medium can be cleaned by the following methods:
To remove ionically bound protein:
- Wash with several column volumes of 1.5 M NaCl.
- Immediately wash with approximately 10 column volumes of distilled water.
To remove precipitated proteins, hydrophobically bound proteins, and lipoproteins:
- Wash the column with 1 M NaOH, contact time usually 1 to 2 h (12 h or more for endotoxin removal).
- Immediately wash with approximately 10 column volumes of binding buffer, followed by 5 to 10 column volumes of distilled water.
To remove hydrophobically bound proteins, lipoproteins, and lipids:
- Wash with 5 to 10 column volumes of 30% isopropanol for about 15 to 20 min.
- Immediately wash with approximately 10 column volumes of distilled water.
2a. Alternatively, wash with 2 column volumes of detergent in a basic or acidic solution. Use, for example, 0.1 to 0.5% nonionic detergent in 0.1 M acetic acid, contact time 1 to 2 h. After treatment, always remove residual detergent by washing with at least 5 column volumes of 70% ethanol. Then wash with approximately 10 column volumes of distilled water.
Reversed flow may improve the efficiency of the cleaning-in-place procedure. After cleaning, store in 20% ethanol (wash with 5 column volumes) or recharge with Ni2+ prior to storage in ethanol.
Ni Sepharose® excel/His Mag Sepharose® excel products
Ni Sepharose® excel and His Mag Sepharose® excel are designed for capture and purification of histidine-tagged proteins secreted into eukaryotic cell culture supernatants. Nickel ions are very strongly bound to both chromatography media, enabling direct loading of large sample volumes without removing agents that normally would cause metal ion stripping. His Mag Sepharose® excel is magnetic beads designed for simple and efficient purification and screening. Ni Sepharose® excel is available for all scales of work from convenient, prepacked HisTrap excel columns to bulk quantities.
Table A1.12 summarizes key characteristics of both media, and Table A1.13 lists the stability of Ni Sepharose® excel under various conditions. Table A1.14 summarizes the characteristics of Ni Sepharose® excel prepacked as a HisTrap excel column.
1 Binding capacity is sample dependent.
2 H2O at room temperature.
3 Optimal flow velocity during binding is sample dependent. During column wash and elution, a flow velocity of 150 cm/h is recommended.
4 Working range: pH interval where the medium can be operated without significant change in function.
Cleaning-in-place: pH interval where the medium can be subjected to cleaning-in-place without significant change in function.
1 Chemical stability was tested by incubating the medium in the listed solutions at room temperature, and thereafter measuring either the nickel leakage or the protein binding capacity.
1 H2O at room temperature. Maximum flow rate will be lower when using buffers or samples with high viscosity or when performing purification at low temperature.
2 Optimal flow rate during binding is sample dependent. During column wash and elution, a flow rate of 1 mL/min and 5 mL/min is recommended for 1 mL and 5 mL columns, respectively.
Note: The maximum pressure the packed bed can withstand depends on the chromatography medium characteristics and sample/liquid viscosity. The value measured on the chromatography system used also depends on the tubing used to connect the column.
TALON® Superflow™ products
TALON® Superflow™ is a cobalt-based immobilized metal ion affinity chromatography medium (IMAC) offering enhanced selectivity for histidine-tagged proteins compared with nickel-charged chromatography media. TALON® Superflow™ is available for all scales of work from 96-well plates to convenient, prepacked columns to bulk quantities, enabling different throughput and scales from screening in low microgram scale to milligram preparative purification of histidine-tagged proteins.
Table A1.15 summarizes key characteristics of bulk TALON® Superflow™ medium, and Table A1.16 lists the stability of the medium under various conditions. Tables A1.17 to A1.18 summarize the characteristics of these same media as prepacked columns and as prepacked 96-well plates.
1 The binding capacity for individual proteins may vary.
2 H2O in a 0.75 × 10 cm (i.d. × H) column.
3 Co2+-stripped medium.
4 Below pH 4, metal ions will be stripped off the medium, and therefore neutral to slightly alkaline pH (pH 7 to 8) is recommended.
1 Data provided by Clontech Laboratories, Inc.
2 EDTA and other chelators, such as EGTA, will strip Co2+ ions from the medium; EDTA may be used, but must be removed prior to sample application. Strong reducing agents should also be avoided (e.g., DTT, DTE, and TCEP) because they interfere with Co2+ ions binding to the medium.
3 Use TALON® Superflow™ immediately after equilibrating with buffers containing β-mercaptoethanol, otherwise the medium will change color. Do not store the medium in buffers containing β-mercaptoethanol.
4 Ionic detergents like CHAPS, SDS, and sarcosyl are compatible up to 1%. However, due to their charged nature, you should anticipate interference with binding.
5 Ethanol may precipitate proteins, causing low yields and column clogging.
6 Imidazole at concentrations higher than 5 to 10 mM may cause lower yields of histidine-tagged proteins because it competes with the histidine side chains (imidazole groups) for binding to the immobilized metal ions.
7 Tris coordinates weakly with metal ions, causing a decrease in capacity.
1 The binding capacity for individual proteins may vary.
1 H2O at room temperature.
2 The pressure over the packed bed varies depending on a range of parameters such as the characteristics of the chromatography medium and the column tubing used.
Stripping, recharging, and cleaning of TALON® Superflow™ products
TALON® Superflow™ and HiTrap TALON® crude do not have to be stripped and recharged between each purification if the same protein is to be purified. It may be sufficient to strip and recharge it after approximately two to five purifications, depending on the specific sample, sample pretreatment, sample volume, etc.
Purification of histidine-tagged proteins using imidazole gradients will cause TALON® Superflow™ to take on a dark purplish color. Washing the medium with 5 to 10 bed/column volumes of 20 mM MES Buffer (pH 5.0) will restore the normal pink color and bring the absorbance at 280 nm back to the original baseline level. After equilibrating with binding buffer (50 mM sodium phosphate, 300 mM NaCl, pH 7.4), the medium/column is ready for reuse.
Stripping and recharging
Stripping buffer: 200 mM EDTA, pH 7.0
- Strip the TALON® Superflow™/HiTrap TALON® crude of cobalt ions by washing with 10 bed/column volumes of stripping buffer.
- Wash excess EDTA from the medium with an additional 10 bed/column volumes of distilled water.
- Charge the chromatography medium with 10 bed/column volumes of 50 mM CoCl2 solution.
- Wash with 7 bed/column volumes of distilled water followed by 3 bed/column volumes of 300 mM NaCl and by 3 bed/column volumes of distilled water to remove excess cobalt metal ions.
- Equilibrate with 10 bed/column volumes of binding buffer.
It is important to wash with binding buffer as the last step to obtain the correct pH before storage.
Uncharged IMAC Sepharose® products
IMAC Sepharose® High Performance is recommended for high-resolution purifications, providing sharp peaks and concentrated eluate. IMAC Sepharose® 6 Fast Flow is excellent for scaling up.
Table A1.19 summarizes key characteristics of IMAC Sepharose® media, and Table A1.20 lists the stability of the media under various conditions. Tables A1.21 to A1.23 summarize the characteristics of the media as prepacked columns.
1 Conditions for determining dynamic binding capacity:
| Samples: | (Histidine)6-tagged proteins: Capacity data were obtained for a protein (Mr 28 000) bound from an E. coli extract, and a pure protein (Mr 43 000) applied at 1 mg/mL in binding buffer; capacity at 10% breakthrough. Untagged protein (IMAC Sepharose® 6 Fast Flow only): Capacities determined at 10% breakthrough for human apotransferrin applied at 1 mg/mL in binding buffer. |
| Column volume: | 0.25 mL or 1 mL |
Flow rate: |
0.25 mL/min or 1 mL/min, respectively 20 mM sodium phosphate, 0.5 M NaCl, 5 mM imidazole (1 mM for untagged protein, IMAC Sepharose® 6 Fast Flow only), pH 7.4 20 mM sodium phosphate, 0.5 M NaCl, 500 mM imidazole (50 mM for untagged protein, IMAC Sepharose® 6 Fast Flow only), pH 7.4 |
Note: Dynamic binding capacity is metal ion and protein dependent.
2 H2O at room temperature.
3 Uncharged medium only. See Table A1.20 for more information.
1 Before performing runs with sample/buffers containing reducing reagents, a blank run with binding and elution buffers excluding reducing agents is recommended (see, for example, Blank run in Purification using IMAC Sepharose® High Performance, Chapter 3).
2 Tested for 1 wk at 40 °C.
3 The strong chelator EDTA has been used successfully in some cases, at 1 mM. Generally, chelating agents should be used with caution (and only in the sample, not the buffer). Any metal-ion stripping may be counteracted by adding a small excess of MgCl2 before centrifugation/filtration of the sample. Note that stripping effects may vary with the applied sample volume.
1 Conditions for determining dynamic binding capacity:
| Samples: | (Histidine)6-tagged proteins: Capacity data were obtained for a protein (Mr 28 000) bound from an E. coli extract, and a pure protein (Mr 43 000) applied at 1 mg/mL in binding buffer; capacity at 10% breakthrough. Untagged protein (IMAC Sepharose® 6 Fast Flow only): Capacities determined at 10% breakthrough for human apotransferrin applied at 1 mg/mL in binding buffer. |
| Column volume: | 0.25 mL or 1 mL |
| Flow rate: Binding buffer: Elution buffer: |
0.25 mL/min or 1 mL/min, respectively 20 mM sodium phosphate, 0.5 M NaCl, 5 mM imidazole (1 mM for untagged protein, IMAC Sepharose® 6 Fast Flow only), pH 7.4 20 mM sodium phosphate, 0.5 M NaCl, 500 mM imidazole (50 mM for untagged protein,IMAC Sepharose® 6 Fast Flow only), pH 7.4. |
Note: Dynamic binding capacity is metal ion and protein dependent.
2 H2O at room temperature.
3 Uncharged medium only. See Table A1.20 for more information.
1 d50v is the average particle size of the cumulative volume distribution.
2 Dynamic binding capacity conditions:
| Samples: | 1 mg/mL (histidine)6-tagged pure protein (Mr 43 000) in binding buffer (QB, 10% determination) or histidine)6-tagged protein (Mr 28 000) bound from E. coli extract. |
| Column volumes: | 0.25 or 1 mL |
| Flow rates: Binding buffer: Elution buffer: |
0.25 or 1 mL/min, respectively 20 mM sodium phosphate, 500 mM NaCl, 5 mM imidazole, pH 7.4 20 mM sodium phosphate, 500 mM NaCl, 500 mM imidazole, pH 7.4 |
Note: Dynamic binding capacity is protein dependent.
3 Water at room temperature.
4 Many chromatography systems are equipped with pressure gauges to measure the pressure at a particular point in the system, usually just after the pumps. The pressure measured here is the sum of the pre-column pressure, the pressure drop over the medium bed, and the post-column pressure. It is always higher than the pressure drop over the bed alone. We recommend keeping the pressure drop over the bed below 1.5 bar. Setting the upper limit of your pressure gauge to 1.5 bar will ensure the pump shuts down before the medium is overpressured. If necessary, post-column pressure of up to 3.5 bar can be added to the limit without exceeding the column hardware limit. To determine post-column pressure, proceed as follows:
To avoid breaking the column, the post-column pressure must never exceed 3.5 bar.
- Connect a piece of tubing in place of the column.
- Run the pump at the maximum flow you intend to use for chromatography. Use a buffer with the same viscosity as you intend to use for chromatography. Note the back pressure as total pressure.
- Disconnect the tubing and run at the same flow rate used in step 2. Note this back pressure as pre-column pressure.
- Calculate the post-column pressure as total pressure minus pre-column pressure. If the post-column pressure is higher than 3.5 bar, take steps to reduce it (shorten tubing, clear clogged tubing, or change flow restrictors), and perform steps 1 to 4 again until the post-column pressure is below 3.5 bar. When the post-column pressure is satisfactory, add the post-column pressure to 1.5 bar and set this as the upper pressure limit on the chromatography system.
5 Short term pH: pH interval where the medium can be subjected to cleaning- or sanitization-in-place without significant change in function.
Long term pH: pH interval where the medium can be operated without significant change in function.
6 The strong chelator EDTA has been used successfully in some cases at 1 mM. Generally, chelating agents should be used with caution (and only in the sample, not in the buffer). Any metal-ion stripping may be counteracted by adding a small excess of MgCl2 before centrifugation/filtration of the sample. Note that stripping effects may vary with the applied sample volume.
1 Conditions for determining dynamic binding capacity:
| Samples: | (Histidine)6-tagged proteins: Capacity data were obtained for a protein (Mr 28 000) bound from an E. coli extract, and a pure protein (Mr 43 000) applied at 1 mg/mL in binding buffer; capacity at 10% breakthrough. Untagged protein: Capacities determined at 10% breakthrough for human apotransferrin applied at 1 mg/mL in binding buffer. |
| Column volume: | 0.25 or 1 mL |
| Flow rate: Binding buffer: Elution buffer: |
0.25 or 1 mL/min, respectively 20 mM sodium phosphate, 500 mM NaCl, 5 mM imidazole, (1 mM for untagged protein) pH 7.4 20 mM sodium phosphate, 500 mM NaCl, 500 mM imidazole, (50 mM for untagged protein) pH 7.4 |
Note: Dynamic binding capacity is metal ion and protein dependent.
2 H2O at room temperature.
3 Uncharged medium only. See Table A1.20 for more information.
Stripping, recharging, and cleaning of IMAC Sepharose® products
IMAC Sepharose High Performance and IMAC Sepharose 6 Fast Flow do not have to be stripped and recharged between each purification if the same protein is to be purified. It may be sufficient to strip and recharge medium after approximately two to five purifications, depending on the specific sample, sample pretreatment, sample volume, etc.
Stripping and recharging
Stripping buffer: 20 mM sodium phosphate, 500 mM NaCl, 50 mM EDTA, pH 7.4
- Strip the chromatography medium by washing with at least 5 to 10 column volumes of stripping buffer.
- Wash with at least 5 to 10 column volumes of binding buffer; see Blank run in Purification using IMAC Sepharose High Performance, Chapter 3 (link to your Google Drive).
- Immediately wash with 5 to 10 column volumes of distilled water.
- Prepare a 0.1 M solution of the chosen metal ion in distilled water. Salts of chlorides, sulfates, etc., can be used: e.g., 0.1 M CuSO4 or 0.1 M NiSO4.
- Recharge the water-washed column by loading at least 0.5 column volume of 0.1 M metal ion/salt solution.
- Wash with 5 column volumes of distilled water, and 5 column volumes of binding buffer (to adjust pH) before storing column in 20% ethanol.
It is important to wash with binding buffer as the last step to obtain the correct pH before storage.
Washing with buffer before applying the metal ion solution may cause unwanted precipitation.
Cleaning-in-place
When an increase in back pressure is seen, the chromatography medium should be cleaned. Before cleaning, strip off metal ions using the recommended procedure described above. The stripped medium can be cleaned by the following methods:
To remove ionically bound protein:
- Wash with several column volumes of 1.5 to 2.0 M NaCl.
- Immediately wash with approximately 3 to 10 column volumes of distilled water.
To remove precipitated proteins, hydrophobically bound proteins, and lipoproteins:
- Wash with several column volumes of 1.5 to 2.0 M NaCl.
- Immediately wash with approximately 3 to 10 column volumes of distilled water.
To remove precipitated proteins, hydrophobically bound proteins, and lipoproteins:
- Wash the column with 1 M NaOH, contact time usually 1 to 2 h (12 h or more for endotoxin removal).
- Immediately wash with approximately 10 column volumes of binding buffer, followed by 5 to 10 column volumes of distilled water.
To remove hydrophobically bound proteins, lipoproteins, and lipids:
- Wash with 5 to 10 column volumes of 30% isopropanol for about 15 to 20 min.
- Immediately wash with approximately 10 column volumes of distilled water.
2a. Alternatively, wash with 2 column volumes of detergent in a basic or acidic solution. Use, for example, 0.1 to 0.5% nonionic detergent in 0.1 M acetic acid, contact time 1 to 2 h. After treatment, always remove residual detergent by washing with at least 5 column volumes of 70% ethanol. Then wash with approximately 10 column volumes of distilled water.
Reversed flow may improve the efficiency of the cleaning-in-place procedure. After cleaning, store column in 20% ethanol (wash with 5 column volumes) or recharge with metal ions prior to storing in ethanol.
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