ANKOM Hydrolysis Systems HCL/RD

To determine how much DE to use with various sample types, see the Hydrolysis Procedure subsection titled Sample Categorization of the ANKOM HCl Hydrolysis System Operator's Manual. 

To understand how to mix DE with various sample types, view the How to mix DE with samples video.

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.

When samples are dried for three hours after hydrolysis, they should be placed in a desiccant pouch (ANKOM part # X45) with a strip of pH paper. When the bags are fully dry the pH paper will NOT show the presence of acid.

If a Mojonnier mixture (pet ether, ethyl ether, ethanol) is utilized, a blank value as high as 0.003g is normal. If pet ether only is used, a blank value as high as 0.001g is normal.

During the hydrolysis phase, fat migration may occur with samples that have fat with low melting points such as triacylglycerides or emulsifiers. Fat loss can be detected by placing a blank bag next to suspect samples in the holder and performing the hydrolysis.  If a blank bag loses too much weight during the extraction, this is an indication of fat loss from the neighboring high fat sample during the hydrolysis. We would recommend a greater amount of diatomaceous earth and reduced sample size with any sample that shows this indication of fat loss.

Research with high fat samples has given us the following understandings:

Some samples with fats that have low melting point triacylglycerides or emulsifiers may encounter fat migration during hydrolysis.

To improve fat retention, increase the level of diatomaceous earth (DE) to sample ratio. A ratio of up to 7:1 can be used by reducing the amount of sample and increasing the amount of DE. No more than 1.5g of DE and sample should be placed in each bag.

The increased volume of DE inside the bags will limit the number of samples processed in the Hydrolysis chamber to ten.

Reducing the hydrolysis temperature and time may also improve fat retention.

If, after increasing the DE-to-sample ratio, fat continues to migrate from the bag then a crude fat extraction prior to the hydrolysis may be necessary. By running a crude fat extraction first, the readily available fats are removed before the hydrolysis, but are accounted for. The challenge with this technique is the additional time the process takes.

Fat migration can be detected by placing a blank bag next to suspect samples. Place blank bags next to high fat samples in the holder, and perform the hydrolysis. If a blank bag looses more than 0.0025g of weight during the extraction, this is an indication of fat loss from the neighboring high fat sample during the hydrolysis. Blank bags should always contain at least 0.5g of DE.

You can see unexpected High Values when hydrolizing fat samples if the samples are not adequately dried after the hydrolysis step.

Possible reasons for insufficient drying include:

1) Dryer is not working properly
       - Filter needs to be replaced
       - Dryer is not heating up to the correct temperature (the dryer controller should be set at 110°C)

2) Samples are not being dried for a long enough time
       - All samples should be dried for 3 hours

3) Contaminated rinse water
       - The water used for rinsing the sample must be free of contaminants (e.g., salt)

You should place a strip of litmus paper in the desiccant pouch (as noted in the procedure). If the paper shows the presence of acid when the dried XT4 bags are placed inside the pouch, dry the samples for an additional 30 minutes. Repeat this procedure until the acid is gone.

Possible Causes:

The dial on the heat sealer is not be turned up high enough. In order to seal the F57 Filter Bag, the dial must be set at approximately "4." In order to seal the XT4 Filter Bag the dial must be set to approximately "6." Different lab conditions may effect the proper setting. Experiment with a bag to "dial in" the correct setting.

The heating element is broken. On the sides of the Teflon cover on the heater sealer are two shiny metal strips that keep the cover in place. Loosen the screws that keep the strips tight to the base of the heat sealer and remove the Teflon cover. Check to see if there is a break in the heating element. If there is, take the extra heating element that comes with the heat sealer and replace the defective element. Additional elements can be ordered from ANKOM Technology (SKU: 1917).

The Insulator is not properly installed. The insulator should be installed to ensure that the heating element does not touch any of the metal on the base of the heat sealer.

Possible Causes:

The vent tube or drain tube is blocked- The blockage is caused by water trapped in the line. It is very important that the vent and drain tubes are running downhill, and are not submerged in water. If the vent tube is blocked, a vacuum is created and the vessel cannot drain.

There is a faulty drain valve- If tubes are functioning properly contact ANKOM for instruction in testing the drain valve.

Due to a combination of acidity and heat, the bag holders occasionally need repair or replacement. If a leg is broken, it can be solvent welded together using dichloromethane. Follow proper safety handling procedures when handling any solvent.

The overtemp message happens when the ANKOM HCl Instrument is heating but there is no solution in the vessel. The quartz heaters will heat the vessel and the ETS (Emergency Temperature Switches) will trip.

Possible Causes:

Instrument was not properly filled- make sure the acid was put in the instrument and that the water supply is on.

There is a filling or draining problem-To investigate, run the following test:

1. Add 500ml of water to the vessel and run a 60 minute hydrolysis.
2. Check the water level every 5 minutes during the hydrolysis to make sure that the water has not boiled away or that the water has not drained from the may have a leak.
3. After the hydrolysis, make sure the solution completely drains and the heat is off.
4. During the first rinse step, make sure the vessel has been automatically filled with water. If this does not occur, the water valve may not be functioning. Contact ANKOM for assistance.
5. Check the water level during the rinses and make sure the water only drains during the "Drain Cycle"
6. If this test does not provide answers, contact ANKOM Tech Support with your results.

To best assist you, it is helpful to know the following:

• Does this fault occur every time?
• When does the fault occur?
• How many minutes into the hydrolysis?
• How many minutes into the rinse?

Replacement of the dryer completely depends upon how often it is used to dry hydrolysis samples.The best method for determining filter capability is to cut out a 3" X 6" piece of cardboard and then cut out a 1" diameter circle in the middle of the cardboard.Turn on the dryer with the filter in place. Lay the cardboard directly on top of the filter. Then lay a mini thermo-anemometer (part # 45118 airflow meter from www.extech.com) over the hole. The air speed should be in excess of 9 mph. When the air speed is less than 9 mph, it is time to replace it. Refer to HCL Service Procedure 011.

Another sure sign that it is time to change filters is when the filter bags do not dry sufficiently after Hydrolysis at 110°C in 3 hours (pH paper in the desiccant pouch shows acid presence).

When the lid is raised, some residual acid may flow onto the hinges and the handle. Over time corrosion will occur if this is allowed to happen. When lifting the lid after a run, it is recommended that the lid be wiped off with a paper towel to prevent dripping onto the hinges and handle.

When using the ANKOM Rapid Dryer to dry acid hydrolysis samples, the air flow through the special hydrolysis filter (ANKOM part # RD2) will eventually become too limited and the filter will need to be changed.

To check the air filter for proper air flow, follow HCL Service Procedure 011.

View the HCL Periodic Maintenance video.

In the development of our hydrolysis process, we did extensive research into both acid and base hydrolysis.  We found that while the acid performed well, the base hydrolysis constantly produced much lower than expected results.  Fortunately, we found that the acid did a very good job with products normally hydrolyzed in a base solution, i.e. dairy products.  As a result of our findings, our only procedure utilizes HCl and no base solutions.

ANKOM's Total Fat/Oil Analysis Technology includes a range of products and instrumentation designed to support accurate and efficient analysis of total fat and oil in various sample matrices, including the ANKOM Hydrolysis Systems. These systems are used to hydrolyze fat and oil from samples, providing a more complete extraction and analysis of the total fat content. ANKOM's technology is compatible with a range of ANKOM instruments and other commonly used methods in the industry, and our team provides technical support and training to ensure optimal use of our products and systems.