With the lignin procedure, there are two common errors that will create false high values.
The first error is placing the F57 Filter Bags into the 72% sulfuric acid when there is moisture in the bags and samples. To avoid this situation, after the ADF procedure is complete and the Filter Bags have been dried and weighed, place the Filter Bags back into the oven at 100o to 105° C for 30 to 60 minutes. When the bags have been dried, place them into a desiccant pouch and allow them to cool to room temperature. Once they have been cooled, immediately place them into the 72% sulfuric acid and begin the procedure.
The second error occurs in the rinsing of the bags after the three-hour soaking in 72% sulfuric acid. It is vital that all of the acid is rinsed out of the bags before the F57’s are placed into the oven for drying. The rinsing process uses copious amounts of fresh water. After several minutes of rinsing, touch several bags with litmus paper. If the litmus paper shows the presence of acid in any of the bags, continue the rinsing for several more minutes and test again. Continue to test the bags with litmus paper until no bags show the presence of acid. Place the bags into a beaker, pour enough acetone to cover the bags and soak for 3 to 5 minutes. When the soaking is complete, pour off the acetone, lay them on a clean surface, and allow the acetone to evaporate from the bags. Place the filter bags into the oven at 100° to 105° C for at least two hours. When the bags have been dried, place them into a desiccant pouch and allow them to cool to room temperature. Once they have been cooled, weigh the bags one final time.
The first error is placing the F57 Filter Bags into the 72% sulfuric acid when there is moisture in the bags and samples. To avoid this situation, after the ADF procedure is complete and the Filter Bags have been dried and weighed, place the Filter Bags back into the oven at 100o to 105° C for 30 to 60 minutes. When the bags have been dried, place them into a desiccant pouch and allow them to cool to room temperature. Once they have been cooled, immediately place them into the 72% sulfuric acid and begin the procedure.
The second error occurs in the rinsing of the bags after the three-hour soaking in 72% sulfuric acid. It is vital that all of the acid is rinsed out of the bags before the F57’s are placed into the oven for drying. The rinsing process uses copious amounts of fresh water. After several minutes of rinsing, touch several bags with litmus paper. If the litmus paper shows the presence of acid in any of the bags, continue the rinsing for several more minutes and test again. Continue to test the bags with litmus paper until no bags show the presence of acid. Place the bags into a beaker, pour enough acetone to cover the bags and soak for 3 to 5 minutes. When the soaking is complete, pour off the acetone, lay them on a clean surface, and allow the acetone to evaporate from the bags. Place the filter bags into the oven at 100° to 105° C for at least two hours. When the bags have been dried, place them into a desiccant pouch and allow them to cool to room temperature. Once they have been cooled, weigh the bags one final time.
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