| Process analytical technology (PAT) requires | | | | volume to control the collection of the product of |
| continuous monitoring of quality and this in turn | | | | interest as it elutes from the process |
| requires a model able to predict product qualities | | | | chromatography column. |
| that can be measured in real-time from the | | | | The issue with this approach is that it is totally |
| values of real-time process measurements. | | | | dependent on the reproducibility of the column |
| Process scale chromatography plays an important | | | | elution profile which is impacted by column loading, |
| role in the purification of pharmaceutical products. | | | | purity of the starting material, column packing, and |
| Adjusting the eluent collection points allows the | | | | column gradient generation. |
| process to compensate for the chromatography | | | | 2. Collection of product based on column eluent |
| variability rather than increased variability in the | | | | volume and optical density. |
| product purity. In addition to reducing product | | | | In this approach, an in-line UV sensor set to 280 |
| variability, using on-line HPLC also increases | | | | nm is used to measure the absorbance from the |
| product yield, enables the use of increased levels | | | | product’s peptide bonds. Since this is a non |
| of automation and reduces overall cycle time. | | | | product specific measurement, the OD |
| Determining where the product elution occurs, | | | | sensor’s output is examined in combination |
| generally involves collecting the column eluent | | | | with the in-line flow meter to gain an additional |
| stream in small volumes that are sampled and | | | | level of resolution. That is, the product is only |
| analyzed in the laboratory utilizing higher resolution | | | | collected when the OD at 280 nm exceeds the |
| chromatographic techniques such as | | | | OD set point and falls within the volume set point |
| reversed-phase chromatography. This process of | | | | window. This imparts greater selectivity than using |
| eluent fractionation and off-line chromatographic | | | | the eluent volume approach alone, but is still |
| analysis is performed in process development | | | | dependent on the reproducibility of the |
| area in order to generate sufficient process | | | | column’s elution profile. |
| understanding to enable when the product elutes | | | | Although the variability is less with this approach, |
| from the process scale chromatography column. | | | | the lack of a high level of selectivity still leads to |
| Fractionation of the column eluent has several | | | | conservative collection set points that negatively |
| negative issues associated with it including: | | | | impact product yields. |
| - Degradation of product caused by the delays | | | | 3. Measurement of product purity by on-line HPLC. |
| - Difficulty automating processing due to manual | | | | The critical quality attribute of the product is its |
| handling of fractions | | | | purity. Meeting a specified purity value is the |
| - Increased process cycle time caused by time to | | | | criterion that determines if the process |
| obtain off-line assays | | | | chromatography step has been successful and if |
| - Labor intensive | | | | the in-process material is suitable for forward |
| - Error may occur | | | | processing. By transferring the specificity of HPLC |
| - Reduced production capacity due to long cycle | | | | to an on-line analyzer, it is possible to directly |
| times | | | | measure the critical quality attribute in near real |
| - Opportunities for product contamination | | | | time, thus allowing the process decision (i.e., when |
| - Storage required for “Work in Process” | | | | to start and stop collection of the product eluting |
| (the column fractions) | | | | from the process chromatography column) to be |
| Due to the many negative issues associated with | | | | based on the critical quality attribute rather than |
| column fractionation, companies strive to eliminate | | | | being based on a surrogate measurement that is |
| this process operation as quickly as possible. | | | | impacted by the process variability. |
| Options to eliminate fractionation include: | | | | The increased emphasis on cost reduction and |
| 1. Collection of product based on column eluent | | | | improving production efficiency needs real-time |
| volume. | | | | process information. Product safety methodologies |
| In this approach, the eluent volume where the | | | | result in an increased need to track product |
| product of sufficient purity is expected to elute is | | | | quality throughout the manufacturing process. So |
| determined from historical data and the start | | | | this on-line HPLC helps to give advanced process |
| collection and stop collection set points are set. An | | | | control and real-time product release. |
| in-line flow meter is used to measure the eluent | | | | |