Some variability in filter times is normal.  Default filter time settings encompass much of this variability.  Default settings for IDF/SDF filtration are as follows: IDF after release of bar B (5.0 min), IDF after water rinses (1.0 min), IDF after EtOH rinses (1.0 min), SDF after release of bar D (10.0 min), SDF after EtOH rinses 3.0 min).  The following are several factors that may contribute to slow filtration (taking longer than the default settings).

Lower air pressure
Make sure that the low-pressure regulator is set properly.  Our recommended setting for the low-pressure regulator is 4.0 PSI (static).  Do not adjust the regulator during filtration.  If your regulator is set lower than this, adjust the regulator and run the instrument again.  It should also be noted that during filtration, time may be added if slow filtration is observed.  As filtration is occurring, a button will appear on screen that states, "Filter Time +".  Each time this is pressed, 1 minute will be added to the filtration time.

Sample type
The IDF and SDF filter bags have a significantly greater filter surface area than is found in the Gooch filter-crucible. However, regardless of filter surface area, some sample types can be difficult to filter. Samples that become quite gelatinous in an aqueous solution (such as psyllium and chia seeds) can be difficult to filter.  To accommodate these types of samples in the ANKOMTDF Dietary Fiber Analyzer we recommend the following options:

Add filter time before the assay begins
At the beginning of a run, a series of user prompts appear on screen. One of these prompts states, “Filter Minutes OK? (for an IDF/SDF run) or “SDF Filter minutes OK?” for a TDF run.  From this screen, you can add filter time if you are working with samples that require more filter time.  Familiarity with a particular sample may dictate 10 minutes of IDF filter time, for example. Be aware that any time changes will be stored to memory and will be there for the next run.  However, you will be able to change this back to the default or another setting at the beginning of each run.

Add more filter time during the filtering process
During IDF or SDF filtration and during the water or alcohol rinses (when filtering is occurring) one can press the “Filter Time +” button to add one additional minute at a time, up to 50 additional minutes.  The user will need to be present at the time of filtering to take advantage of this option.

Use a smaller sample size
Reduce the sample size to 0.1 g to minimize the filter clogging effect of gelatinous sample types.

Use Diatomaceous Earth (DE) in the IDF bags 
Pre-weigh 1 g of DE for each IDF bag.  When starting the run, select YES for the screen that states, “Check pH manually?”. Select YES whether you plan to perform a manual pH check or not.  When the instrument pauses for the pH check (and after any pH check/adjustment is complete) add 1 g of DE to each bag.  Press the “Continue” button once DE is added. The DE will be mixed in during the AMG digestion.  Adding the DE at this point, rather than at the beginning of the run, minimizes the risk of bag wear during mixing by having abrasive DE in a hot bag.  Be sure that the DE in the IDF bags is factored into your blank values.  Use of this technique helps increase filter capacity.

Wrinkles in the Filter Bags at clamp bar A or C
There is always some air leakage from the filter bags during filtration at clamp bars A and C.  Larger wrinkles may exacerbate this to the point of needing to add time to the filtration.  If one filter bag is taking longer than the others to filter, time may be added using the "Filter Time +" button that will be available on screen during each filtration.  When setting up IDF and SDF filter bags try to keep them lying flat against the rear clamp bar before starting the run.

Clogged Spray Tip
If slow filtration is observed consistently at one individual station, inspect the spray tip at this station.  The white spray tip is friction fit onto a stainless-steel tube.  Remove the spray tip at the IDF or SDF station and inspect under magnification. The TDF45 Illuminated Magnifier (10x) is recommended for this. There are six small orifices (holes) around the side of the spray tip.  Check to make sure they are clear and not clogged with debris.  This can be cleaned with a TDF94 0.020 inch or 0.5 mm drill bit and pressurized air.  You could also replace it with one of the extra spray tips that was sent with the instrument originally.  After the spray tip has been cleaned or replaced turn on nitrogen to the spray tips.  Using the "Diagnostics" screen, select "Valve Test" and then either "IDF N2" or "SDF N2" to turn the nitrogen on through the six spray tips.  Hold a beaker of water up to each of the six spray tips to make sure nitrogen is bubbling equally at all positions.  Spare spray tips can be ordered as part TDF44. 

Black rubber gasket on front clamp bar A or C may be dented
Inspect the black gasket seal area at the position in question on front clamp bar A or C.  See if there are any dents or low spots.  The best way to check this is to lay the gasket from the front of the clamp bars against a very flat (machined) surface and see if light shows through at the position in question.  If you can visually see a significant low spot or dent in the gasket at the position in question, this will contribute to a poor seal and slow filtration. 

If you have a second TDF instrument, perform the following test: Switch the suspect clamp bar with the second instrument. Install filter bags at all six positions (either IDF or SDF) and close the upper and lower clamp bars keeping the bags as flat as possible to minimize leaks.  Using the "Diagnostics" screen, select "Valve Test" and either "IDF N2" or "SDF N2" to inflate the bags.  If the position in question now inflates its filter bag as quickly as the rest, the problem points to a dent or low spot on the original front clamp bar.  Contact ANKOM Technology at https://www.ankom.com/contact/technical-services or 1-315-986-8090 for assistance.  A replacement Front Clamp Bar A-position can be ordered as part TDF73; a replacement Front Clamp Bar C-position can be ordered as part TDF75.