TDF Analyzer

IDF filter bags have a shorter length of clear polypropylene material and a taller filter at the bottom of the bag.

SDF filter bags have a longer length of clear polypropylene material and a shorter, wider filter at the bottom of the bag.

Refer to the TDF Operator's Manual, sections "IDF/SDF Analysis" and "TDF Analysis."

Refer to the TDF Operator's Manual, sections "IDF/SDF Analysis" and "TDF Analysis."

Follow the steps in this instructional video to perform a pH adjustment: TDF Manually Measuring pH in the IDF Digestion

Note: Measure within the appropriate pH range for your specific testing method.

The MoistureStop Desiccant Pouch is a small, airtight zipper bag, utilized for desiccating all of the Filter Bags that are used with ANKOM instrumentation. A single pouch can hold a full run of F57, F58 or XT4 bags at one time.  When folded, 6 IDF or SDF bags can also be placed into a MoistureStop Desiccant Pouch. Each time a bag has been removed from the desiccant pouch, the air can and should be pushed out. The "zipper" does not have to be used with every bag removal but some action should be taken to keep the air from entering the pouch while the just removed Filter Bag is being weighed. For example, air can be pushed out of the bag by laying it on a firm surface while compressing or flattening the air out of the pouch with your hand.

Many instruments in the marketplace have the capacity to run 6 samples at a time.  After being dried, the beakers, flasks or crucibles are placed into a counter top or cabinet desiccator.  Once cooled, they are then removed one at a time and weighed. Each time the desiccator is opened to remove sample, moist ambient air is introduced inside the desiccator. However, because the lid or door of the desiccator is opened just 6 times, the samples that remain in the desiccator after each item is removed are affected very little by ambient moisture that may be introduced.

However, with Filter Bag Technology, generally larger numbers of Filter Bags are extracted at a time. As with the beakers, flasks and crucibles mentioned above, if the bags are placed in a desiccator after drying, each time the lid or door is opened to remove a bag, moist, ambient air is introduced. Because the desiccator is opened up to 24 times, the moisture can more readily affect the remaining bags. If a collapsible, ANKOM desiccant pouch is utilized, the air can be pushed out of the pouch each time a Filter Bag is removed. This will eliminate a build up of moisture on the remaining Filter Bags and allow for a more accurate and precise result. Every month it is possible to place the small desiccant packets into the oven at 100° - 105°C for a few hours to insure that the desiccant is renewed. In addition, to ensure the integrity of the zip lock bag, regular replacement should be considered.

Static electricity during the weighting process:  The largest contributor to poor results is the effect of static electricity on the weighing process. Because plastic gloves can contribute to static electricity, only use anti-static gloves. To eliminate static electricity while the bag is being weighed, you MUST use the Bag Weigh Holder (TDF52) during the weighing process.

Moisture control: Moisture Stop desiccant pouches (X45) should be used to minimize the effect of moisture on the weighing process. Verify that the desiccant pouches are in good condition (no holes and the zipper is functioning) and the packets within the desiccant pouches are still working (they should be a blue color).

BLANK values: BLANK values are used in the IDF, SDF, and TDF calculations. If you're not using the BLANK values provided by ANKOM, try using them in your calculation.

Chemicals: Because the MES-TRIS buffer can degrade in performance due to bacteria growth, making this solution daily is important. Clean all containers daily and refill with fresh solutions. Make sure that each container is securely connected to the appropriate supply tube on the instrument.

Protein and Ash Determinations: Because protein and ash values are part of the IDF, SDF, and TDF calculations, verify that your protein and ash systems are working properly and providing expected results.

Protein and Ash preparation: See the procedures detailed in the TDF Operator's Manual (Protein and Ash Determination sections) for preparing the bags for protein and ash.

Drying: Bags must be dried at 105^° C to constant weight (90 minutes).

Acetone rinses: See the procedure detailed in the TDF Operator's Manual (IDF/SDF Analysis section) for performing the acetone rinses.

Sample size: Using sample sizes larger than the recommended size of 0.5 (+/- 0.05g) can cause higher results.

Digestion times: For demonstration and diagnostic purposes, you can set the digestion times to non-standard values through the Touch Screen Display. Results will be inaccurate if the instrument is run using non-standard digestion times.

Technician variability: Confirm that all technicians are following the procedures detailed in the TDF Operator's Manual to avoid any variation in results associated with different operators.

pH: Typically the pH reading should be between 3.5 and 6 before correction. If the pH reading is outside of these values check the acid and buffer solutions, and check that tubing is connected to the proper containers.

Enzyme delivery: View the enzyme containers while the enzymes are being delivered. The fluid level should go down. If the enzymes are not being delivered properly, contact ANKOM at [email protected].

Temperature control: To verify that the temperature is being properly controlled, follow the procedure detailed in the TDF Operator's Manual (QC / Calibration section).

Mixing: To verify that the mixing is being properly controlled, follow the procedure detailed in the TDF Operator's Manual (QC / Calibration section).

Sample with bound fat: It is possible you have a sample which has been highly processed and has bound the fat to the extent the fat is not available to the solvent before the TDF process. In this case, after running the TDF instrument, remove the bags, place them on the rinse stand and perform the 2 standard acetone rinses. Immediately after the rinses (no air drying) remove the bags from the stand and soak the filters in fresh pet ether for 10 minutes. Place the bags back on the rinse stand and immediately perform 2 pet ether rinses (just like the acetone rinses). When the solvent has evaporated, seal the bags and dry them normally.

Static electricity during the weighting process:  The largest contributor to poor results is the effect of static electricity on the weighing process. Because plastic gloves can contribute to static electricity, only use anti-static gloves. To eliminate static electricity while the bag is being weighed, you MUST use the Bag Weigh Holder (TDF52) during the weighing process.

Sample sticking to the IDF Flow-thru bags: When running a TDF assay, particles can stick to the IDF Flow-thru bag and not get rinsed down into the SDF filter. The weight of the sample stuck to the IDF Flow-thru bag is not accounted for in the TDF calculation. To avoid this problem, after the digestion processes are complete, use 78% EtOH to manually rinse any sticky particles down from the IDF Flow-thru bag into the SDF bag. If necessary, a laboratory spatula can be used to help loosen particles that are stuck to the bag.

BLANK values: BLANK values are used in the IDF, SDF, and TDF calculations. If you're not using the BLANK values provided by ANKOM, try using them in your calculation.

Chemicals: Because the MES-TRIS buffer can degrade in performance due to bacteria growth, making this solution daily is important. Clean all containers daily and refill with fresh solutions. Make sure that each container is securely connected to the appropriate supply tube on the instrument.

Protein and Ash Determinations: Because protein and ash values are part of the IDF, SDF, and TDF calculations, verify that your protein and ash systems are working properly and providing expected results.

Protein and Ash preparation: See the procedures detailed in the TDF Operator's Manual (Protein and Ash Determination sections) for preparing the bags for protein and ash.

Drying: Bags must be dried at 105^°C to constant weight (90 minutes).

Acetone rinses: See the procedure detailed in the (IDF/SDF Analysis section) for performing the acetone rinses. TDF Operator's Manual

Sample loss: If any sample is spilled or left in a weigh tin during transfer to the IDF bag, the assay will produce lower values.

Filtrate transfer from IDF to SDF bag: If any liquid does not quantitatively transfer from the IDF bag to the SDF bag, SDF results will be low. Make sure that the bottom of the IDF bags remain inside the top of the SDF bags during the IDF filter process.

Diatomaceous Earth (DE) loss: If any DE is spilled or left in a weigh tin during transfer to the SDF bag, the assay will produce lower values.

Digestion times: For demonstration and diagnostic purposes, you can set the digestion times to non-standard values through the Touch Screen Display. Results will be inaccurate if the instrument is run using non-standard digestion times.

Technician variability: Confirm that all technicians are following the procedures detailed in the TDF Operator's Manual to avoid any variation in results associated with different operators.

pH: Typically the pH reading should be between 3.5 and 6 before correction. If the pH reading is outside of these values check the acid and buffer solutions, and check that tubing is connected to the proper containers.

In order to properly prepare the IDF & SDF bags for Kjeldahl and Ashing procedures, view the documents below or watch the following video: Kjeldahl & Ashing Bag Preparation.

We have found that it is best to slowly ramp up the digestion temperatures so that foaming in the digestion tubes is minimized. As a result we would suggest the following times and temperatures: 15 minutes at 150°C followed by 15 minutes at 250°C followed by 15 minutes at 350°C and finally 40 minutes at 420°C.

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:

Add filter time before the assay begins
At the beginning of a run a series of user prompts appear on 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 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.  You will, however, 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. NOTE: Remember, the TDF values will be greatly influenced by variability in protein and ash values - of a small sample size.

Use Diatomaceous Earth (DE) in the IDF bags 
Use of this technique helps increase filtering capacity. Pre-weigh 0.5-1 g of DE for each IDF bag.  About 2 min 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 are any.

AOAC 991.43 calls for filtration via a fritted crucible of 40-60 microns with diatomaceous earth, or equivalent.  Particle retention per the method is accomplished by the addition of diatomaceous earth contained in a fritted crucible.  The fine filtration and particle retention of the ANKOM SDF bags is also accomplished with diatomaceous earth contained in the filter bag.  The IDF filtration may or may not use the diatomaceous earth but produces the correct particle retention in a water medium.  Therefore, the filtration used in the ANKOM TDF is equivalent to the approved AOAC 991.43 Method.

Utilize a transfer pipette to handle this and follow the procedure below:

1. Weigh the pipette and tare the weight.
2. Fill the pipette with a liquid sample.
3. Place the pipette on the balance and record the weight.
4. Pipette out the liquid into the IDF Bag.
5. Weigh the pipette and subtract that weight from the weight with a sample. This supplies us with the actual sample weight that went into the bag.

If you do the de-fat procedure using ANKOM XT4 filter bags, after you complete the Kjeldahl digestion, there will be a white substance on top of the resulting liquid. This substance is the PTFE coating on the XT4 filter bags. This substance will NOT impact your results.

In the past we recommended to customers to defat in XT4 bag. When the defat process was completed, the XT4 bags were cut up and placed in the IDF bag. Unfortunately, if the XT4 bag is cut into very small pieces, the sharp edges of the cut pieces can penetrate the clear polypropylene IDF bag, potentially causing leaks. We no longer recommend defatting in XT4 bags. We recommend that you refer to official methods that describes the defatting process, such as AOAC 985.29.