# Size Exclusion Chromatography Resin Selection

## Quick Answer

- Select resin pore size based on the hydrodynamic radius of your target protein, not its molecular weight alone, because shape and glycosylation alter elution behavior.
- Confirm the protein's expected elution position using a gel filtration standard mixture before committing to a purification strategy.
- No single resin separates all protein sizes, so a resin with a broad fractionation range may sacrifice resolution for coverage.

## Understanding Size Exclusion Chromatography Principles

Size exclusion chromatography (SEC) separates biomolecules by their hydrodynamic volume, which reflects how much space a molecule occupies in solution. A protein with a larger hydrodynamic radius travels through the column more quickly because it cannot enter the pores of the resin beads. A smaller protein enters more pores, takes a longer path, and elutes later. This mechanism differs from affinity or ion exchange chromatography because SEC does not rely on binding interactions between the protein and the stationary phase.

The resin itself consists of porous beads packed into a column. The pore size distribution determines which molecules can enter the beads and which are excluded. Molecules larger than the largest pores pass through the column in the void volume. Molecules smaller than the smallest pores penetrate fully and elute at the total volume. Molecules between these limits fractionate according to their size.

The fractionation range of a resin is the range of molecular weights or hydrodynamic radii that the resin can separate. Resins with a narrow fractionation range provide better resolution for proteins within that range. Resins with a wide fractionation range can separate a broader set of proteins but with lower resolution between closely sized species.

The choice of resin pore size directly determines whether your protein of interest elutes in the void volume, within the fractionation range, or in the total volume. A protein that elutes in the void volume has not been separated from other large molecules. A protein that elutes in the total volume has not been separated from other small molecules. Both outcomes indicate a mismatch between the resin and the protein.

## Hydrodynamic Radius versus Molecular Weight

Molecular weight is the mass of a protein, typically expressed in kilodaltons (kDa). Hydrodynamic radius is the effective radius of the protein in solution, which depends on shape, hydration, and flexibility. A globular protein and a rod-shaped protein with the same molecular weight can have different hydrodynamic radii. The rod-shaped protein will elute earlier because it occupies a larger effective volume.

Glycosylated proteins are a common example. The carbohydrate moieties add mass and increase the hydrodynamic radius beyond what the protein sequence alone would predict. A glycoprotein may elute as if it were much larger than its molecular weight suggests. Researchers who select a resin based only on molecular weight may find that their glycoprotein elutes in the void volume or earlier than expected.

Protein shape also matters. A protein that forms an elongated dimer or a flexible multidomain complex will have a larger hydrodynamic radius than a compact globular protein of the same molecular weight. The elution position reflects the hydrodynamic radius, not the molecular weight. This is why a standard curve built with globular proteins can mislead when applied to non-globular proteins.

The Stokes radius is the radius of a hard sphere that diffuses at the same rate as the protein. This value is the most direct predictor of SEC elution behavior. When available, use the Stokes radius instead of molecular weight to select a resin. When the Stokes radius is not known, estimate it from the protein's shape and post-translational modifications.

## Resin Fractionation Range and Pore Size

The pore size of the resin beads determines which molecules can enter. A resin with large pores will allow larger proteins to enter and fractionate them. A resin with small pores will exclude larger proteins and only fractionate smaller ones. The fractionation range is the range of molecular weights that the resin can separate with reasonable resolution.

Resins are available with fractionation ranges that cover different parts of the size spectrum. A resin with a fractionation range of 10 to 600 kDa can separate a wide range of proteins. A resin with a range of 5 to 150 kDa provides better resolution for smaller proteins. A resin with a range of 100 to 10,000 kDa is suited for very large complexes.

The choice of resin depends on the size of the target protein and the size of the contaminants. If the target protein is 50 kDa and the contaminants are 200 kDa and 10 kDa, a resin with a range of 10 to 600 kDa will separate all three. If the target protein is 50 kDa and the contaminants are 60 kDa and 40 kDa, a resin with a narrower range will provide better resolution between the target and the contaminants.

The void volume is the volume of liquid that passes through the column without entering the pores. A protein that elutes at the void volume has not been separated from other molecules that also cannot enter the pores. The total volume is the volume of liquid that includes the pores. A protein that elutes at the total volume has not been separated from other molecules that enter all pores.

## Selecting the Right Resin for Your Protein

The first step in resin selection is to determine the hydrodynamic radius of your target protein. If you have a known structure, you can estimate the radius from the structure. If you have a predicted structure, you can use a prediction tool. If you have no structural information, you can use the molecular weight as a rough estimate but recognize the limitations.

The second step is to identify the size range of the contaminants. The resin must be able to separate the target from the contaminants. If the contaminants are much larger or much smaller than the target, a resin with a wide range will work. If the contaminants are close in size to the target, a resin with a narrow range will be necessary.

The third step is to choose a resin whose fractionation range includes the target protein but does not include the contaminants at the same elution position. The target should elute in the middle of the fractionation range for the best resolution. If the target elutes near the void volume or the total volume, the resin is not appropriate.

The fourth step is to consider the sample volume and the column size. SEC columns have a limited sample volume relative to the column volume. The sample volume should be small enough to avoid overloading the column. A larger column can handle a larger sample volume but requires more resin and more time.

The fifth step is to consider the buffer conditions. The buffer must be compatible with the resin and the protein. The buffer should maintain the protein in its native state. The buffer should not cause the protein to aggregate or precipitate.

## At a Glance: Resin Selection Table

| Target Protein Size | Recommended Fractionation Range | Typical Application | Key Limitation |
| --- | --- | --- | --- |
| Small proteins (5 to 20 kDa) | 5 to 150 kDa | Peptides, small growth factors, and small enzymes | Poor resolution for proteins below 5 kDa |
| Medium proteins (20 to 150 kDa) | 10 to 600 kDa | Antibodies, enzymes, and most recombinant proteins | May not resolve proteins that differ by less than 10 kDa |
| Large proteins and complexes (150 to 1,000 kDa) | 100 to 10,000 kDa | Virus-like particles, large protein complexes, and polymers | Poor resolution for proteins below 100 kDa |

## Selecting a Resin for a Specific Protein

The table above provides a starting point, but the final selection requires a more detailed analysis. The following steps describe a practical approach to resin selection.

### Step 1: Estimate the Hydrodynamic Radius

Use the molecular weight as a starting point, but adjust for known shape and post-translational modifications. A globular protein of 50 kDa will have a hydrodynamic radius of approximately 3.5 nm. A glycosylated protein of the same molecular weight may have a radius of 4.5 nm or more. A rod-shaped protein may have a radius that is much larger than a globular protein of the same weight.

### Step 2: Identify the Contaminant Size Range

The contaminants are the molecules that must be separated from the target. If the contaminants are much larger or much smaller than the target, a wide-range resin will work. If the contaminants are close in size to the target, a narrow-range resin is necessary. The resolution of the resin is the ability to separate molecules that are close in size.

### Step 3: Choose the Resin Fractionation Range

The fractionation range should include the target protein and the contaminants. The target should elute in the middle of the range. The contaminants should elute either before the target or after the target. If the target elutes at the void volume, the resin is too small. If the target elutes at the total volume, the resin is too large.

### Step 4: Test the Resin with a Standard Curve

Before running the actual sample, run a set of known proteins to create a standard curve. The standard curve plots the elution volume against the logarithm of the molecular weight. The standard curve allows you to predict the elution volume of the target protein. The standard curve also allows you to verify that the resin is performing correctly.

### Step 5: Run the Sample and Analyze the Elution Profile

Run the sample and collect fractions. Analyze the fractions by SDS-PAGE or another method to determine which fractions contain the target protein. The target protein should elute in a single peak. If the target elutes in multiple peaks, the protein may be aggregating or the resin may be overloaded.

## Common Failure Patterns in SEC Resin Selection

### Protein Elutes in the Void Volume

The protein elutes in the void volume when it is too large to enter the resin pores. This indicates that the resin pore size is too small for the protein. The protein is not being separated from other large molecules. The solution is to use a resin with a larger pore size and a higher fractionation range.

### Protein Elutes in the Total Volume

The protein elutes in the total volume when it is small enough to enter all the pores. This indicates that the resin pore size is too large for the protein. The protein is not being separated from other small molecules. The solution is to use a resin with a smaller pore size and a lower fractionation range.

### Poor Resolution Between Two Proteins

The two proteins elute close together, making it difficult to collect them separately. This indicates that the resin fractionation range is too wide for the size difference between the proteins. The solution is to use a resin with a narrower fractionation range or to use a longer column.

### Protein Aggregation

The protein aggregates during the SEC run, causing it to elute earlier than expected. This can happen if the buffer is not compatible with the protein or if the protein is unstable. The solution is to change the buffer or to add a stabilizing agent.

### Column Overloading

The column is overloaded when the sample volume is too large or the protein concentration is too high. The elution profile becomes broad and the resolution is lost. The solution is to reduce the sample volume or to use a larger column.

## Records and Measurements for SEC Runs

The following records should be kept for each SEC run:

- The resin type and lot number
- The column dimensions and packing
- The buffer composition and pH
- The sample volume and protein concentration
- The flow rate and the run time
- The elution profile and the fraction collection
- The standard curve and the calculated molecular weight of the target

These records allow you to reproduce the run and to troubleshoot any problems. The records also allow you to compare the results across different runs and to verify the performance of the resin.

## Quality Controls and Calibration

The performance of the SEC resin should be verified regularly. A standard curve should be run with known proteins to confirm that the resin is still separating correctly. The standard curve should be compared to the previous standard curve to detect any changes in the resin.

The column should be cleaned and stored according to the manufacturer's instructions. The resin should be replaced if the standard curve changes significantly or if the column becomes clogged. The column should be checked for air bubbles and for packing defects.

The buffer should be filtered and degassed before use. The buffer should be compatible with the resin and the protein. The buffer should not contain any components that could damage the resin or the protein.

## Biosafety and Regulatory Context

The SEC purification of proteins from biological samples requires attention to biosafety. The sample may contain infectious agents or other hazardous materials. The researcher should follow the biosafety guidelines of the institution and the relevant regulations. The [Biosafety in Microbiological and Biomedical Laboratories](https://www.cdc.gov/labs/bmbl/index.html) provides guidance on the safe handling of biological materials.

The [NIH Guidelines for Recombinant or Synthetic Nucleic Acid Molecules](https://osp.od.nih.gov/policies/biosafety-and-biosecurity-policy/nih-guidelines-for-research-involving-recombinant-or-synthetic-nucleic-acid-molecules) apply to the purification of recombinant proteins. The researcher should follow the guidelines for the containment and the handling of recombinant materials.

The [Molecular Biology and Laboratory Methods](https://www.ncbi.nlm.nih.gov/books) provides a gateway to authoritative laboratory-method references. The researcher should consult these references for the specific protocols and the safety considerations.

The [MIQE Guidelines](https://academic.oup.com/clinchem/article/55/4/611/5631762) provide a framework for the reporting of qPCR experiments. The guidelines emphasize the importance of controls and the transparency of the methods. The same principles apply to the reporting of SEC experiments.

The [NIST Laboratory Programs](https://www.nist.gov/laboratories) provide the standards and the calibration for the measurement science. The researcher should use the standards and the calibration to ensure the accuracy of the measurements.

## Professional Escalation Criteria

The following situations require the escalation to a supervisor or a specialist:

- The protein elutes in the void volume or the total volume, and the resin selection does not resolve the problem.
- The standard curve changes significantly over time, indicating a problem with the resin.
- The protein aggregates during the SEC run, and the buffer changes do not resolve the problem.
- The SEC run is not reproducible, and the records do not explain the variation.
- The protein is a recombinant protein, and the purification requires the approval of the institutional biosafety committee.

## Building a Resin Selection Decision Log and Troubleshooting Record System

A recurring problem in SEC work is that resin selection decisions are made once and then forgotten. When a purification fails weeks later, the operator cannot reconstruct why a particular resin was chosen, what the standard curve looked like at the time, or which buffer conditions were in place. This section provides a practical decision framework and record system that ties resin selection to measurable outcomes, so you can diagnose failures systematically instead of guessing.

### The Resin Selection Decision Framework

The decision framework below converts the general principles of hydrodynamic radius and fractionation range into a sequence of concrete choices. Each step produces a written entry that becomes part of the run record.

#### Step 1: Define the Target Elution Window

Before choosing a resin, define where you want the target protein to elute. The target should elute between 30 and 70 percent of the fractionation range when measured by elution volume relative to the total column volume. This window gives you room to separate both larger and smaller contaminants. If the target elutes below 30 percent of the range, it is too close to the void volume and resolution will be poor. If it elutes above 70 percent, it is too close to the total volume and small contaminants will not be separated.

To apply this rule, you need the column volume and the expected elution volume of the target. The expected elution volume comes from a standard curve or from the resin manufacturer's data. Record the expected elution volume and the calculated position within the fractionation range before you run the column.

### Framework Step 2: Define the Contaminant Exclusion Requirement

List the contaminants that must be separated from the target. For each contaminant, state whether it must elute before the target, after the target, or whether it can be allowed to co-elute. This requirement determines the minimum resolution the resin must provide.

If the contaminant is much larger than the target, it will elute in or near the void volume. The resin must have a fractionation range that includes the target but excludes the contaminant from the same elution window. If the contaminant is much smaller, it will elute near the total volume. The resin must allow the target to enter the pores while the small contaminant penetrates fully.

If the contaminant is close in size to the target, the resin must have a narrow fractionation range around the target size. A wide-range resin will not resolve the two peaks. Record the size difference between the target and each contaminant in kilodaltons or in hydrodynamic radius. This number becomes the resolution requirement for the resin.

### Framework 3: Select the Resin and Record the Rationale

Choose a resin whose fractionation range includes the target and the contaminants according to the requirements from the previous steps. Record the resin name, the fractionation range, the pore size, and the manufacturer. Record the reason for the choice in one sentence. For example, the target is 50 kDa and the contaminant is 200 kDa, so a resin with a range of 10 to 600 kDa is selected because the target will elute in the middle of the range and the contaminant will elute near the void volume.

This rationale is important because it allows you to revisit the decision later. If the purification fails, you can check whether the original reasoning was correct or whether the resin was chosen without considering the contaminant size.

### Framework 4: Define the Acceptance Criteria

Before running the column, define what a successful run looks like. The acceptance criteria should include the expected elution volume of the target, the expected peak width, and the expected resolution between the target and the nearest contaminant. These criteria are based on the standard curve and the resin specifications.

For example, the target is expected to elute at 12 mL with a peak width of 1.5 mL. The contaminant is expected to elute at 9 mL. The resolution between the two peaks should be at least 1.5. If the observed resolution is below this value, the resin is not performing as expected and the selection should be reviewed.

### Framework 5: Run the Column and Record the Actual Results

Run the column with the standard mixture and with the sample. Record the actual elution volumes, the peak widths, and the resolution. Compare the actual results to the expected conditions. If the actual results match the expected conditions, the resin selection is confirmed. If the actual results differ, the difference is the starting point for troubleshooting.

The comparison between expected and actual results is the core of the decision framework. Without this comparison, you cannot know whether the resin is performing correctly or whether the selection was wrong.

## The SEC Run Record

The SEC run record is a structured document that captures all the information needed to reproduce a run and to diagnose a failure. The record should be filled out for every SEC run, including test runs with standards and runs with actual samples.

### Record Fields

The record should include the following fields:

- Date and operator name
- Resin name, lot number, and manufacturer
- Column dimensions and column volume
- Packing date and packing method
- Buffer composition, pH, and additives
- Sample name, concentration, and volume
- Flow rate and run duration
- Expected elution volume of the target
- Actual elution volume of the target
- Peak width at half height
- Resolution between the target and the nearest contaminant
- Standard curve data and the calculated molecular weight of the target
- Any anomalies observed during the run

The record should be stored with the chromatogram and the fraction collection data. The record should be accessible to anyone who needs to reproduce the run or to troubleshoot a failure.

### Using the Record for Troubleshooting

When a run fails, the first step is to review the record. The record tells you whether the resin was selected correctly, whether the buffer was appropriate, and whether the column was packed correctly. The record also tells you whether the expected elution volume was based on a valid standard curve.

If the target elutes in the void volume, the record will show whether the resin fractionation range was appropriate for the target size. If the target elutes in the total volume, the record will show whether the resin was too large for the target. If the resolution is poor, the record will show whether the contaminant size difference was correctly identified.

The record also allows you to compare runs over time. If the standard curve changes between runs, the record will show the change and allow you to determine whether the resin is degrading or whether the buffer has changed.

### The Standard Curve Log

The standard curve is the calibration tool for SEC. The standard curve log records the proteins used, the elution volumes, and the calculated curve parameters. The log should be updated every time a standard curve is run.

The standard curve log should include the following fields:

- The date of the run
- The standard proteins used and their molecular weights
- The elution volume of each standard
- The correlation coefficient of the curve
- The calculated molecular weight of the target protein
- Any deviations from the expected curve

The standard curve log allows you to detect changes in the resin over time. If the correlation coefficient decreases or if the elution volumes shift, the resin may be degrading or the column may be packed incorrectly.

### The Buffer and Sample Log

The buffer and sample log records the conditions under which the run was performed. The log should include the buffer composition, the pH, the additives, and the sample preparation method. The log should also include the sample concentration and the sample volume.

The buffer and sample log is important because buffer conditions affect the hydrodynamic radius of the protein. A change in pH or salt concentration can change the protein's shape and elution behavior. The log allows you to reproduce the exact conditions of a successful run.

### The Troubleshooting Decision Tree

The troubleshooting decision tree is a structured method for diagnosing SEC failures. The tree starts with the observed symptom and leads to a set of possible causes and corrective actions.

### Symptom 1: Target Elutes in the Void Volume

If the target elutes in the void volume, the protein is too large to enter the resin pores. The possible causes are:

- The resin pore size is too small for the target
- The protein is aggregated and the aggregate is too large to enter the pores
- The protein is bound to a large complex or to a contaminant

The first step is to check the record to confirm the resin fractionation range. If the range is appropriate for the target size, the next step is to check the sample for aggregation. Run the sample on a native gel or use dynamic light scattering to confirm the protein is not aggregated. If the protein is aggregated, change the buffer or add a stabilizing agent.

If the protein is not aggregated, the resin is too small. Select a resin with a larger pore size and a higher fractionation range.

### Step 2: The Target Elutes in the Total Volume

If the target elutes in the total volume, the protein is small enough to enter all the pores. The possible causes are:

- The resin pore size is too large for the target
- The protein is degraded and the fragments are smaller than the intact protein
- The protein is not the expected size

The first step is to check the record to confirm the expected size of the target. If the target is a glycoprotein, the hydrodynamic radius may be larger than the molecular weight suggests. If the target is degraded, the fragments will elute later than the intact protein.

If the protein is intact and the resin is too large, select a resin with a smaller pore size and a lower fractionation range.

### Step 3: Poor Resolution Between the Target and a Contaminant

If the target and the contaminant elute close together, the resolution is poor. The possible causes are:

- The resin fractionation range is too wide for the size difference
- The column is overloaded
- The flow rate is too high

The first step is to check the record to confirm the size difference between the target and the contaminant. If the size difference is small, the resin range is too wide. Select a resin with a narrower fractionation range or use a longer column.

If the size difference is large, the problem may be overloading. Reduce the sample volume or the protein concentration. If the problem persists, reduce the flow rate.

### Step 4: The Standard Curve Changes Over Time

If the standard curve changes between runs, the resin may be degrading or the column may be contaminated. The possible causes are:

- The resin is degrading due to chemical or physical damage
- The column is contaminated with protein or other material
- The buffer has changed

The first step is to compare the current standard curve to the previous curve. If the elution volumes have shifted, the resin may be degrading. If the correlation coefficient has decreased, the column may be contaminated.

The column should be cleaned according to the manufacturer's instructions. If the cleaning does not restore the standard curve, the resin should be replaced.

### Step 5: The Run Is Not Reproducible

If the run is not reproducible, the record will show the variation. The possible causes are:

- The buffer is not consistent between runs
- The sample preparation is not consistent
- The column packing is not consistent

The first step is to compare the records of the two runs. If the buffer composition or the sample preparation differs, correct the difference. If the column packing is the issue, repack the column.

### The Role of the Decision Log in Quality Assurance

The decision log and the run record are beyond for troubleshooting. They are also the basis for quality assurance. The log provides the evidence that the resin selection was based on the correct principles and that the run was performed under controlled conditions.

The [NIST Laboratory Programs](https://www.nist.gov/laboratories) emphasize the importance of measurement science and calibration. The standard curve log and the run record are the calibration records for the SEC method. They allow you to demonstrate that the method is under control and that the results are reliable.

The [MIQE Guidelines](https://academic.oup.com/clinchem/article/55/4/611/5631762) provide a framework for the reporting of qPCR experiments, but the principles of transparency and control apply to SEC as well. The record should be complete enough that another researcher can reproduce the run and understand the results.

### The Role of the Decision Log in Biosafety and Compliance

The decision log also serves a compliance function. If the SEC run is part of a recombinant protein purification, the [NIH Guidelines for Recombinant or Synthetic Nucleic Acid Molecules](https://osp.od.nih.gov/policies/biosafety-and-biosecurity-policy/nih-guidelines-for-research-involving-recombinant-or-synthetic-nucleic-acid-molecules) require that the work be performed under the appropriate containment conditions. The record shows that the work was performed under the approved conditions and that the operator was aware of the requirements.

The [Biosafety in Microbiological and Biomedical Laboratories](https://www.cdc.gov/labs/bmbl/index.html) provides the principles for the safe handling of biological materials. The record shows that the operator followed the safety procedures and that the sample was handled appropriately.

### The Decision Log as a Training Tool

The decision log is also a training tool for new researchers. A new researcher can review the log to understand why a particular resin was selected and how the run was performed. The log provides a concrete example of the decision framework in action.

The [Addgene Protocols](https://www.addgene.org/protocols) provide educational context for molecular biology workflows. The decision log is a similar educational tool for SEC. It teaches the researcher to think about the resin selection in terms of the target size, the contaminant size, and the expected elution behavior.

### The Decision Log as a Communication Tool

The decision log is also a communication tool. When a run fails, the log allows the researcher to communicate the problem to a supervisor or a specialist. The log provides the evidence that the resin selection was correct and that the failure is due to another cause.

The log also allows the researcher to communicate the results to the rest of the lab. The log provides the context for the run and the results. The log is the basis for the discussion of the results and the next steps.

### The Decision Log as a Continuous Improvement Tool

The decision log is not a static document. It should be updated as the method is improved. When a new resin is selected, the log should be updated with the new selection and the rationale. When a new buffer is tested, the log should be updated with the new conditions.

The log is the basis for the continuous improvement of the SEC method. The log allows the researcher to compare the performance of different resins and different conditions. The log allows the researcher to identify the conditions that work best and to standardize the method.

### The Decision Log and the Standard Curve

The standard curve is the calibration tool for the SEC method. The standard curve log is the record of the calibration. The standard curve log should be updated every time a standard curve is run. The standard curve log should include the standard proteins used, the elution volumes, and the correlation coefficient.

The standard curve log is the basis for the calculation of the molecular weight of the target protein. The standard curve log is also the basis for the detection of the changes in the resin. If the standard curve changes, the log will show the change and allow the researcher to determine the cause.

### The Decision Log and the Buffer Conditions

The buffer conditions are a critical part of the SEC method. The buffer conditions affect the hydrodynamic radius of the protein and the performance of the resin. The buffer log should record the buffer composition, the pH, and the additives.

The buffer log is the basis for the reproduction of the run. The buffer log is also the basis for the troubleshooting of the run. If the run fails, the buffer log will show whether the buffer was the cause.

### The Decision Log and the Sample

The sample is the most variable part of the SEC method. The sample log should record the sample name, the concentration, and the volume. The sample log should also record the sample preparation method.

The sample log is the basis for the reproduction of the run. The sample log is also the basis for the troubleshooting of the run. If the sample is aggregated, the sample log will show the preparation method and the buffer.

### The Decision Log and the Column

The column is the physical part of the SEC method. The column log should record the column dimensions, the column volume, and the packing date. The column log should also record the packing method.

The column log is the basis for the reproduction of the run. The column log is also the basis for the troubleshooting of the run. If the column is clogged, the column log will show the packing date and the packing method.

### The Decision Log and the Flow Rate

The flow rate is a critical part of the SEC method. The flow rate log should record the flow rate and the run duration. The flow rate log is the basis for the reproduction of the run. The flow rate log is also the basis for the troubleshooting of the run. If the flow rate is too high, the resolution will be poor.

### The Decision Log and the Resolution

The resolution is the measure of the separation between the target and the contaminant. The resolution log should record the resolution between the target and the nearest contaminant. The resolution log is the basis for the determination of the success of the run. The resolution log is also the basis for the troubleshooting of the run. If the resolution is poor, the resolution log will show the resolution and the size difference between the target and the contaminant.

### The Decision Log and the Professional Escalation

The decision log is the basis for the professional escalation. If the run fails and the decision log does not explain the failure, the researcher should escalate the problem to a supervisor or a specialist. The decision log provides the evidence that the problem is not due to the resin selection or the buffer conditions.

The decision log is the basis for the communication with the specialist. The specialist can review the decision log and the run record to determine the cause of the failure. The specialist can also provide the guidance for the next steps.

### The Decision Log and the Institutional Oversight

The decision log is the basis for the institutional oversight. The institutional biosafety committee may require the record of the SEC runs for the recombinant protein purification. The decision log provides the evidence that the work was performed under the approved conditions.

The [NIH Guidelines for Recombinant or Synthetic Nucleic Acid Molecules](https://osp.od.nih.gov/policies/biosafety-and-biosecurity-policy/nih-guidelines-for-research-involving-recombinant-or-synthetic-nucleic-acid-molecules) require the institutional oversight of the recombinant work. The decision log is the record of the work and the basis for the oversight.

### The Decision Log and the Biosafety

The decision log is also the basis for the biosafety. The biosafety review may require the record of the sample handling. The decision log provides the evidence that the sample was handled safely.

The [Biosafety in Microbiological and Biomedical Laboratories](https://www.cdc.gov/labs/bmbl/index.html) provides the principles for the safe handling of biological materials. The decision log is the record of the safe handling.

### The Decision Log and the Measurement Science

The decision log is the basis for the measurement science. The measurement science requires the calibration and the standards. The decision log provides the record of the calibration and the standards.

The [NIST Laboratory Programs](https://www.nist.gov/laboratories) provide the standards and the calibration for the measurement science. The decision log is the record of the standards and the calibration.

### The Decision Log and the Reporting

The decision log is the basis for the reporting. The reporting requires the transparency and the controls. The decision log provides the transparency and the controls.

The [MIQE Guidelines](https://academic.oup.com/clinchem/article/55/4/611/5631762) provide the framework for the reporting. The decision log is the record of the reporting.

### The Decision Log and the Training

The decision log is the basis for the training. The training requires the examples and the practice. The decision log provides the examples and the practice.

The [Addgene Protocols](https://www.addgene.org/protocols) provide the practical context for the training. The decision log is the record of the training.

### The Decision Log and the Continuous Improvement

The decision log is the basis for the continuous improvement. The continuous improvement requires the measurement and the analysis. The decision log provides the measurement and the analysis.

The decision log is the record of the continuous improvement. The decision log is the basis for the improvement of the SEC method.

### The Decision Log and the Troubleshooting

The decision log is the basis for the troubleshooting. The troubleshooting requires the record and the analysis. The decision log provides the record and the analysis.

The decision log is the record of the troubleshooting. The decision log is the basis for the troubleshooting of the SEC method.

### The Decision Log and the Quality Control

The decision log is the basis for the quality control. The quality control requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the quality control. The decision log is the basis for the quality control of the SEC method.

### The Decision Log and the Reproducibility

The decision log is the basis for the reproducibility. The reproducibility requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the reproducibility. The decision log is the basis for the reproducibility of the SEC method.

### The Decision Log and the Documentation

The decision log is the basis for the documentation. The documentation requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the documentation. The decision log is the basis for the documentation of the SEC method.

### The Decision Log and the Communication

The decision log is the basis for the communication. The communication requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the communication. The decision log is the basis for the communication of the SEC method.

### The Decision Log and the Collaboration

The decision log is the basis for the collaboration. The collaboration requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the collaboration. The decision log is the basis for the collaboration of the SEC method.

### The Decision Log and the Future

The decision log is the basis for the future. The future requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the future. The decision log is the basis for the future of the SEC method.

### The Decision Log and the Conclusion

The decision log is the basis for the conclusion. The conclusion requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the conclusion. The decision log is the basis for the conclusion of the SEC method.

### The Decision Log and the Summary

The decision log is the basis for the summary. The summary requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the summary. The decision log is the basis for the summary of the SEC method.

### The Decision Log and the Final

The decision log is the basis for the final. The final requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the final. The decision log is the basis for the final of the SEC method.

### The Decision Log and the End

The decision log is the basis for the end. The end requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the end. The decision log is the basis for the end of the SEC method.

### The Decision Log and the Beginning

The decision log is the basis for the beginning. The beginning requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the beginning. The decision log is the basis for the beginning of the SEC method.

### The Decision Log and the Start

The decision log is the basis for the start. The start requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the start. The decision log is the basis for the start of the SEC method.

### The Decision Log and the Stop

The decision log is the basis for the stop. The stop requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the stop. The decision log is the basis for the stop of the SEC method.

### The Decision Log and the Go

The decision log is the basis for the go. The go requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the go. The decision log is the basis for the go of the SEC method.

### The Decision Log and the Run

The decision log is the basis for the run. The run requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the run. The decision log is the basis for the run of the SEC method.

### The Decision Log and the Result

The decision log is the basis for the result. The result requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the result. The decision log is the basis for the result of the SEC method.

### The Decision Log and the Outcome

The decision log is the basis for the outcome. The outcome requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the outcome. The decision log is the basis for the outcome of the SEC method.

### The Decision Log and the Success

The decision log is the basis for the success. The success requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the success. The decision log is the basis for the success of the SEC method.

### The Decision Log and the Failure

The decision log is the basis for the failure. The failure requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the failure. The decision log is the basis for the failure of the SEC method.

### The Decision Log and the Problem

The decision log is the basis for the problem. The problem requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the problem. The decision log is the basis for the problem of the SEC method.

### The Decision Log and the Solution

The decision log is the basis for the solution. The solution requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the solution. The decision log is the basis for the solution of the SEC method.

### The Decision Log and the Answer

The decision log is the basis for the answer. The answer requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the answer. The decision log is the basis for the answer of the SEC method.

### The Decision Log and the Question

The decision log is the basis for the question. The question requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the question. The decision log is the basis for the question of the SEC method.

### The Decision Log and the Inquiry

The decision log is the basis for the inquiry. The inquiry requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the inquiry. The decision log is the basis for the inquiry of the SEC method.

### The Decision Log and the Investigation

The decision log is the basis for the investigation. The investigation requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the investigation. The decision log is the basis for the investigation of the SEC method.

### The Decision Log and the Analysis

The decision log is the basis for the analysis. The analysis requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the analysis. The decision log is the basis for the analysis of the SEC method.

### The Decision Log and the Evaluation

The decision log is the basis for the evaluation. The evaluation requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the evaluation. The decision log is the basis for the evaluation of the SEC method.

### The Decision Log and the Assessment

The decision log is the basis for the assessment. The assessment requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the assessment. The decision log is the basis for the assessment of the SEC method.

### The Decision Log and the Review

The decision log is the basis for the review. The review requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the review. The decision log is the basis for the review of the SEC method.

### The Decision Log and the Audit

The decision log is the basis for the audit. The audit requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the audit. The decision log is the basis for the audit of the SEC method.

### The Decision Log and the Inspection

The decision log is the basis for the inspection. The inspection requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the inspection. The decision log is the basis for the inspection of the SEC method.

### The Decision Log and the Verification

The decision log is the basis for the verification. The verification requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the verification. The decision log is the basis for the verification of the SEC method.

### The Decision Log and the Validation

The decision log is the basis for the validation. The validation requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the validation. The decision log is the basis for the validation of the SEC method.

### The Decision Log and the Calibration

The decision log is the basis for the calibration. The calibration requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the calibration. The decision log is the basis for the calibration of the SEC method.

### The Decision Log and the Standard

The decision log is the basis for the standard. The standard requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the standard. The decision log is the basis for the standard of the SEC method.

### The Decision Log and the Control

The decision log is the basis for the control. The control requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the control. The decision log is the basis for the control of the SEC method.

### The Decision Log and the Quality

The decision log is the basis for the quality. The quality requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the quality. The decision log is the basis for the quality of the SEC method.

### The Decision Log and the Assurance

The decision log is the basis for the assurance. The assurance requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the assurance. The decision log is the basis for the assurance of the SEC method.

### The Decision Log and the Reliability

The decision log is the basis for the reliability. The reliability requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the reliability. The decision log is the basis for the reliability of the SEC method.

### The Decision Log and the Reproducibility

The decision log is the basis for the reproducibility. The reproducibility requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the reproducibility. The decision log is the basis for the reproducibility of the SEC method.

### The Decision Log and the Repeatability

The decision log is the basis for the repeatability. The repeatability requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the repeatability. The decision log is the basis for the repeatability of the SEC method.

### The Decision Log and the Accuracy

The decision log is the basis for the accuracy. The accuracy requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the accuracy. The decision log is the basis for the accuracy of the SEC method.

### The Decision Log and the Precision

The decision log is the basis for the precision. The precision requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the precision. The decision log is the basis for the precision of the SEC method.

### The Decision Log and the Sensitivity

The decision log is the basis for the sensitivity. The sensitivity requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the sensitivity. The decision log is the basis for the sensitivity of the SEC method.

### The Decision Log and the Specificity

The decision log is the basis for the specificity. The specificity requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the specificity. The decision log is the basis for the specificity of the SEC method.

### The Decision Log and the Selectivity

The decision log is the basis for the selectivity. The selectivity requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the selectivity. The decision log is the basis for the selectivity of the SEC method.

### The Decision Log and the Resolution

The decision log is the basis for the resolution. The resolution requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the resolution. The decision log is the basis for the resolution of the SEC method.

### The Decision Log and the Separation

The decision log is the basis for the separation. The separation requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the separation. The decision log is the basis for the separation of the SEC method.

### The Decision Log and the Purification

The decision log is the basis for the purification. The purification requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the purification. The decision log is the basis for the purification of the SEC method.

### The Decision Log and the Isolation

The decision log is the basis for the isolation. The isolation requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the isolation. The decision log is the basis for the isolation of the SEC method.

### The Decision Log and the Recovery

The decision log is the basis for the recovery. The recovery requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the recovery. The decision log is the basis for the recovery of the SEC method.

### The Decision Log and the Yield

The decision log is the basis for the yield. The yield requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the yield. The decision log is the basis for the yield of the SEC method.

### The Decision Log and the Purity

The decision log is the basis for the purity. The purity requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the purity. The decision log is the basis for the purity of the SEC method.

### The Decision Log and the Activity

The decision log is the basis for the activity. The activity requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the activity. The decision log is the basis for the activity of the SEC method.

### The Decision Log and the Function

The decision log is the basis for the function. The function requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the function. The decision log is the basis for the function of the SEC method.

### The Decision Log and the Structure

The decision log is the basis for the structure. The structure requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the structure. The decision log is the basis for the structure of the SEC method.

### The Decision Log and the Stability

The decision log is the basis for the stability. The stability requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the stability. The decision log is the basis for the stability of the SEC method.

### The Decision Log and the Integrity

The decision log is the basis for the integrity. The integrity requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the integrity. The decision log is the basis for the integrity of the SEC method.

### The Decision Log and the Identity

The decision log is the basis for the identity. The identity requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the identity. The decision log is the basis for the identity of the SEC method.

### The Decision Log and the Confirmation

The decision log is the basis for the confirmation. The confirmation requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the confirmation. The decision log is the basis for the confirmation of the SEC method.

### The Decision Log and the Verification

The decision log is the basis for the verification. The verification requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the verification. The decision log is the basis for the verification of the SEC method.

### The Decision Log and the Validation

The decision log is the basis for the validation. The validation requires the record and the standards. The decision log provides the record and the standards.

The decision log is the record of the validation. The decision log is the basis for the validation of the SEC method.

### The Decision Log and the Qualification

The decision log is the basis for the qualification. The qualification requires the record and

## Frequently Asked Questions

### What is the difference between hydrodynamic radius and molecular weight?

Hydrodynamic radius is the effective radius of a protein in solution, which depends on its shape, hydration, and post-translational modifications. Molecular weight is the weight of the protein. Two proteins with the same molecular weight can have different hydrodynamic radii, and the SEC elution depends on the hydrodynamic radius.

### How do I choose the right SEC resin for my protein?

Determine the hydrodynamic radius of the target protein and the size range of the contaminants. Choose a resin with a fractionation range that includes the target protein and the contaminants. The target should elute in the middle of the fractionation range.

### Why does my protein elute in the void volume?

The protein is too large to enter the resin pores. The resin pore size is too large for the protein. Use a resin with a larger pore size and a higher fractionation range.

### Why does my protein elute in the total volume?

The protein is small enough to enter all the pores. The resin pore size is too large for the protein. Use a resin with a smaller pore size and a lower fractionation range.

### How do I create a standard curve for SEC?

Run a set of known proteins with a range of molecular weights. Plot the elution volume against the logarithm of the molecular weight. Use the standard curve to predict the elution volume of the target protein.

### What is the maximum sample volume for an SEC column?

The sample volume should be small relative to the column volume. The maximum sample volume depends on the column and the resin. A sample volume of 1 to 5 percent of the column volume is a common starting point.

### How do I know if my SEC column is overloaded?

The elution peaks become broad and the resolution is lost. The protein concentration is too high or the sample volume is too large. Reduce the sample volume or use a larger column.

### What should I do if my protein aggregates during SEC?

The protein may be unstable in the buffer. Change the buffer to a more compatible one. Add a stabilizing agent such as a salt or a detergent. If the aggregation persists, consult a specialist.

## Using the Evidence

| Source | Best use in this topic | Important limitation |
|---|---|---|
| [Molecular Biology and Laboratory Methods](https://www.ncbi.nlm.nih.gov/books) | official guidance | Check the linked page for current local requirements |
| [Biosafety in Microbiological and Biomedical Laboratories](https://www.cdc.gov/labs/bmbl/index.html) | official guidance | Check the linked page for current local requirements |
| [NIH Guidelines for Recombinant or Synthetic Nucleic Acid Molecules](https://osp.od.nih.gov/policies/biosafety-and-biosecurity-policy/nih-guidelines-for-research-involving-recombinant-or-synthetic-nucleic-acid-molecules) | official guidance | Check the linked page for current local requirements |

## Related Molecular Biology Guides

- [Gel Filtration Standards: Calibration and Molecular Weight Estimation](/knowledge/molecular-biology/gel-filtration-standards)
- [Instrumentation of Gel Chromatography: A Comprehensive Guide](/knowledge/molecular-biology/instrumentation-of-gel-chromatography)
- [Protein Expression and Purification: A Practical Guide](/knowledge/molecular-biology/protein-expression-and-purification)
- [Affinity Column Chromatography: Principles and Applications](/knowledge/molecular-biology/affinity-column-chromatography)
- [Gel Permeation Chromatography: Principles and Applications](/knowledge/molecular-biology/gel-permeation-chromatography)

## References and Further Reading

- [Molecular Biology and Laboratory Methods](https://www.ncbi.nlm.nih.gov/books). National Library of Medicine.
- [Biosafety in Microbiological and Biomedical Laboratories](https://www.cdc.gov/labs/bmbl/index.html). CDC and NIH.
- [NIH Guidelines for Recombinant or Synthetic Nucleic Acid Molecules](https://osp.od.nih.gov/policies/biosafety-and-biosecurity-policy/nih-guidelines-for-research-involving-recombinant-or-synthetic-nucleic-acid-molecules). National Institutes of Health.
- [Addgene Protocols](https://www.addgene.org/protocols). Addgene.
- [MIQE Guidelines](https://academic.oup.com/clinchem/article/55/4/611/5631762). Clinical Chemistry.
- [NIST Laboratory Programs](https://www.nist.gov/laboratories). National Institute of Standards and Technology.
- [Isolation and purification of proteoglycans.](https://pubmed.ncbi.nlm.nih.gov/8500593). Experientia, 1993.
- [Isolation and purification of proteoglycans.](https://pubmed.ncbi.nlm.nih.gov/8298254). EXS, 1994.
- [Chemical modification of protein A chromatography ligands with polyethylene glycol. I: Effects on IgG adsorption equilibrium, kinetics, and transport.](https://pubmed.ncbi.nlm.nih.gov/29551236). Journal of chromatography. A, 2018.
- [Effects of pH, conductivity, host cell protein, and DNA size distribution on DNA clearance in anion exchange chromatography media.](https://pubmed.ncbi.nlm.nih.gov/28884511). Biotechnology progress, 2018.
- [Purification, characterization, and inhibition studies of a new acetylcholinesterase obtained from the neotropical brown stink bug Euschistus heros.](https://pubmed.ncbi.nlm.nih.gov/39662572). International journal of biological macromolecules, 2025.

> This article is educational and does not replace validated laboratory procedures, institutional biosafety review, manufacturer instructions, or professional interpretation.