I Want to know what is the most effective method for taking swab samples from filters of fluid bed dryer for performing cleaning validation
Dear Sameh06,
as to my knowledge there is no way to take swab samples from the filters of a fluid bed dryer with an acceptable recovery. If the filter is of the bag type, there is even no way of getting it really clean and the filter bags should be dedicated. This is one of the few parts that can only be sampled by rinsing with an appropriate solvent (other examples are wire mesh screens, the mesh bottom of the product pan of the fluid bed dryer, hammer mill screens, etc.). The sampling method by rinsing (not rinse sampling!) requires a separate validation to fix the rinsing volume, revalidate the analytical method because of the potential interference of the sampling solvent and the higher dilution of the samples, to determine the recovery rate, and so on. Not everything is bad: Sampling by rinsing has normally higher recovery rates and reproducibility, and less dependance from sampling technician skills.
Best regards
Alfred
[quote=Alfred]Dear Sameh06,
as to my knowledge there is no way to take swab samples from the filters of a fluid bed dryer with an acceptable recovery. If the filter is of the bag type, there is even no way of getting it really clean and the filter bags should be dedicated. This is one of the few parts that can only be sampled by rinsing with an appropriate solvent (other examples are wire mesh screens, the mesh bottom of the product pan of the fluid bed dryer, hammer mill screens, etc.). The sampling method by rinsing (not rinse sampling!) requires a separate validation to fix the rinsing volume, revalidate the analytical method because of the potential interference of the sampling solvent and the higher dilution of the samples, to determine the recovery rate, and so on. Not everything is bad: Sampling by rinsing has normally higher recovery rates and reproducibility, and less dependance from sampling technician skills.
Best regards
Alfred[/quote]
Dear Alfred
Thank You for your reply
Can you tell me how to do this exactly
Sameh
Dear Sameh06,
as stated above, cleaning validation of filter bags is close to impossible. For filter cartridges (which is our case, we have a Glatt 120 FBD with 6 filter cartridges made of a sandwich assembly of coarse wire mesh, fine wire mesh, and an outer lining of a sheet made of sintered stainless steel), the steps are as follows:
- Measure and calculate the product contact surface of the FBD and the cartridge(s) exactly.
- Determine the worst case location of the cartridges. This is usually the lower portion of the cartridge because it is the last part to drain and dry, and thus the residues concentrate there. Define the sampled area (the classical 100 cm² portion, or a portion that takes into account the symmetry of the cartridge. Take into account that you will need to reach the sampled area from inside the cartridge with a pipette, because it is nearly impossible to rinse a portion of the outer surface without covering a far bigger portion because of solvent spreading. Thus, the sampled area is usually a compromise between the accessibility and the worst case location. It is wise to run a blank try, to get together all the utensils (pipette, something to support the cartridge while sampling, a huge funnel and a big flask to collect the rinse, etc.)
- Decide where to carry out the recovery test. To rinse stainless steel coupons is not representative of the actual rinsing of a complex structure as the above described, where solvent (and contamination) is occluded between the wires and retained by the sintered shets. The two options are to spike and recover directly in the equipment, or to get samples of the cartridge material from the manufacturer. The first option has the limitation that the amount spiked cannot go above the maximum allowed contamination (you don´t want to get your equipment contaminated above limit on purpose), thus not allowing bracketing the target concentration. The advantage is that this is more “real life” because comfortably sampling at the laboratory workbench is clearly not the same as sampling in the equipment. The second option depends on the goodwill of the manufacturer of the FBD. In our case it took us 16 months to get a sample, but this approach is highly recommendable, because after the fifth try of a recovery test blocking the equipment your life is at peril by hands of the production people.
- Choose the sampling solvent. If you follow a worst case approach, your target analyte most probably is the most insoluble contamination possible, thus eliminating water as sampling solvent. The sampling solvent should dissolve the target analyte readily, not interfere with the analysis, be non toxic, non flammable, volatile but not too much, etc.,etc. In most cases ethanol is a fairly good choice.
- Determine the needed solvent amount. This is try and error, spiking and sampling with different quantities of solvent. Usually quantities between 0,5 - 1 ml/cm² sampled surface is a good starting point. At this stage you will develop the sampling procedure, covering the sampled surface entirely with a steady flow of solvent from a pipette, and collecting the rinse. Take into account that some solvent will be lost and that you will have to adjust the final volume in the collecting flask with fresh solvent in order to make it reproducible.
- With the solvent amount and the maximum allowed contamination, calculate the target concentration of analyte in the sample, and revalidate your analytical method for a range of 50% - 150 % of that concentration, and including the solvent. Concentrating the sample by solvent evaporation is a possibility but very often the traces of analyte present will degrade, react, evaporate, or otherwise dissapear.
- Once revalidated the analytical method, repeat the recovery test (now with the accurately validated method), and determine the recovery factor.
At this stage you have developed the whole standardized procedure, and all you have to do is to carry it out after cleaning the equipment.
Best regards, and good luck
Alfred
[quote=Alfred]Dear Sameh06,
as stated above, cleaning validation of filter bags is close to impossible. For filter cartridges (which is our case, we have a Glatt 120 FBD with 6 filter cartridges made of a sandwich assembly of coarse wire mesh, fine wire mesh, and an outer lining of a sheet made of sintered stainless steel), the steps are as follows:
- Measure and calculate the product contact surface of the FBD and the cartridge(s) exactly.
- Determine the worst case location of the cartridges. This is usually the lower portion of the cartridge because it is the last part to drain and dry, and thus the residues concentrate there. Define the sampled area (the classical 100 cm² portion, or a portion that takes into account the symmetry of the cartridge. Take into account that you will need to reach the sampled area from inside the cartridge with a pipette, because it is nearly impossible to rinse a portion of the outer surface without covering a far bigger portion because of solvent spreading. Thus, the sampled area is usually a compromise between the accessibility and the worst case location. It is wise to run a blank try, to get together all the utensils (pipette, something to support the cartridge while sampling, a huge funnel and a big flask to collect the rinse, etc.)
- Decide where to carry out the recovery test. To rinse stainless steel coupons is not representative of the actual rinsing of a complex structure as the above described, where solvent (and contamination) is occluded between the wires and retained by the sintered shets. The two options are to spike and recover directly in the equipment, or to get samples of the cartridge material from the manufacturer. The first option has the limitation that the amount spiked cannot go above the maximum allowed contamination (you don´t want to get your equipment contaminated above limit on purpose), thus not allowing bracketing the target concentration. The advantage is that this is more “real life” because comfortably sampling at the laboratory workbench is clearly not the same as sampling in the equipment. The second option depends on the goodwill of the manufacturer of the FBD. In our case it took us 16 months to get a sample, but this approach is highly recommendable, because after the fifth try of a recovery test blocking the equipment your life is at peril by hands of the production people.
- Choose the sampling solvent. If you follow a worst case approach, your target analyte most probably is the most insoluble contamination possible, thus eliminating water as sampling solvent. The sampling solvent should dissolve the target analyte readily, not interfere with the analysis, be non toxic, non flammable, volatile but not too much, etc.,etc. In most cases ethanol is a fairly good choice.
- Determine the needed solvent amount. This is try and error, spiking and sampling with different quantities of solvent. Usually quantities between 0,5 - 1 ml/cm² sampled surface is a good starting point. At this stage you will develop the sampling procedure, covering the sampled surface entirely with a steady flow of solvent from a pipette, and collecting the rinse. Take into account that some solvent will be lost and that you will have to adjust the final volume in the collecting flask with fresh solvent in order to make it reproducible.
- With the solvent amount and the maximum allowed contamination, calculate the target concentration of analyte in the sample, and revalidate your analytical method for a range of 50% - 150 % of that concentration, and including the solvent. Concentrating the sample by solvent evaporation is a possibility but very often the traces of analyte present will degrade, react, evaporate, or otherwise dissapear.
- Once revalidated the analytical method, repeat the recovery test (now with the accurately validated method), and determine the recovery factor.
At this stage you have developed the whole standardized procedure, and all you have to do is to carry it out after cleaning the equipment.
Best regards, and good luck
Alfred[/quote]
Dear Alfred
Thank you very much for your advise. and I w’ll try that
Best regards
Sameh