How do I handle samples that are difficult to filter?

Some sample types can be difficult to filter, even though the IDF and SDF filter bags have a significantly greater filter surface area than the Gooch crucible. Some samples become gelatinous in an aqueous solution (such as psyllium, chia seeds, or milled beans) and can be difficult to filter. To accommodate these types of samples, we recommend the following options: 

(1) Add filter time before the assay begins 
At the beginning of a run, a series of user prompts appear on the screen, one of which 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 ten minutes of IDF filter time, for example. Be aware that any time changes will be stored in memory and will be there for the next run. You will, however, be able to change this back to the default or another setting at the beginning of each run. 

(2) 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 fifty additional minutes. The user will need to be present at the time of filtering to take advantage of this option. 

(3) Use a smaller sample size 
Reduce the sample size to 0.1 g to minimize the filter-clogging effect of gelatinous sample types. NOTE: Remember, the TDF values will be greatly influenced by variability in protein and ash values - of a small sample size. 

(4) Use Diatomaceous Earth (DE) in the IDF bags  
The use of this technique helps increase filtering capacity. Pre-weigh 0.5-1 g of DE for each IDF bag. About 2 minutes before the end of AMG digestion, open Clamp Bar A by pressing Clamp Bar A, add the DE quantitatively, and then close Clamp Bar A by pressing Clamp Bar A again. The DE will be mixed in during the end of the AMG digestion. Adding DE at this point, rather than at the beginning of the run, minimizes the risk of bag wear from abrasive DE in a hot/agitated bag. Be sure that the DE in the IDF bags is factored into your blank values. We recommend running a blank position when implementing this technique to account for DE loss from the IDF bag if there is any.