Subscribe to our Newsletter

For Updates on Biomass Analysis Techniques and Biomass Composition



Email added to list. If you don't receive a confirmation email check your spam folder and add Celignis as a trusted sender.

This website is using cookies
We use cookies to ensure that we give you the best experience on our website. If you continue using the site, we'll assume that you are happy to receive all cookies on this website.

  • Facebook
  • Facebook
  • Facebook
  • YouTube
  • Facebook
Lignin (Acid Soluble)

Acid Soluble Lignin (ASL) is the fraction of lignin that is soluble in 72% sulphuric acid. It is typically present in relatively small amounts in most biomass samples, with Klason Lignin contributing towards the majority of the total lignin content.

Click here to place an order for determining Lignin (Acid Soluble).

Analysis Packages for Lignin (Acid Soluble)

The Celignis Analysis Package(s) that determine this constituent are listed below:

P8     Lignin Content
Lignin (Klason), Lignin (Acid Soluble), Acid Insoluble Residue, Ash (Acid Insoluble)

Further Details

P9     Lignocellulosic Sugars and Lignin
Total Sugars, Glucose, Xylose, Mannose, Arabinose, Galactose, Rhamnose, Lignin (Klason), Lignin (Acid Soluble), Acid Insoluble Residue, Ash (Acid Insoluble)

Further Details

P10   Sugars, Lignin, Extractives, and Ash
Total Sugars, Glucose, Xylose, Mannose, Arabinose, Galactose, Rhamnose, Lignin (Klason), Lignin (Acid Soluble), Acid Insoluble Residue, Extractives (Ethanol-Soluble), Extractives (Water-Soluble), Extractives (Exhaustive - Water then Ethanol), Extractives (Water-Insoluble, Ethanol Soluble) , Ash, Ash (Acid Insoluble)

Further Details

P11   NIR Prediction Package
Total Sugars, Glucose, Xylose, Mannose, Arabinose, Galactose, Rhamnose, Lignin (Klason), Lignin (Acid Soluble), Acid Insoluble Residue, Extractives (Ethanol-Soluble), Ash, Ash (Acid Insoluble)

Further Details

Analytical Procedure for Lignin (Acid Soluble)

Step 1: Acid Hydrolysis of the Sample
When this Method is the first step in the Analysis Package, the acid hydrolysis takes place on the biomass sample with no prior extraction carried out at Celignis. If previous Steps involving the extraction of the sample have take place then the extracted material is used for the acid hydrolysis.

In the case where three different types of extracted material exist (water-extracted, ethanol-extracted, and water- then ethanol-extracted) then the sample that has undergone both water and ethanol extraction is typically used for acid hydrolysis, unless otherwise requested by the customer.

The following steps are involved in the acid hydrolysis of a sample.

1.  The moisture content of the sample is determined, in duplicate.

2.  Approximately 300 mg (with the exact weight noted) of the sample is added to a pressure tube.

3.  3.00 mL of 72% H2SO4 is added by means of an automatic titrator, the weight of the acid added is noted.

4.  The sample is mixed thoroughly with the acid using a glass rod, care is taken that no sample stays adherent to the sides of the tube, but instead stays in contact with the acid.

5.  The tube is transferred to a water bath that is maintained at 30 degrees celcius.

6.  Steps 2-5 are repeated for the duplicate sample.

7.  Every 10 minutes the glass rod for each pressure tube is stirred so that the acid reaches all parts of the sample and complete hydrolysis occurs. This is a crucial step.

8.  Exactly one hour after it is placed in the water bath the pressure tube is removed and placed on a scales and 84 mL of water added (with the weight of the added water recorded). Any acid/sample on the rod is removed from the rod at this point using this water.

9.  A lid is screwed on the tube and the tube is inverted several times to ensure thorough mixing of the acid.

10. Two sugar recovery solution (SRS) pressure tubes are prepared in order to monitor the sugar-loss associated with the second-stage-hydrolysis. This involves the following steps:

(a) 348 microlitres of 72% H2SO4 is added to a test tube containing a solution containing a known weight (approximately 10 g) of a sugar standard. This standard should be of a similar sugar composition to that expected of the samples being analysed. The acid and sugar solution are thoroughly mixed.
(b) The sugar-acid mixture is transferred to a pressure tube which is then sealed.

11. All SRS and sample pressure tubes are placed in an autoclave which is run at 121 degrees celcius for 60 minutes.

12. After the temperature in the autoclave drops to under 80C the tubes are removed and are left (closed) in the lab until they reach room temperature.

13. The hydrolysates are then filtered (using vacuum suction) through filter crucibles of known weight and the resulting filtrate is stored.

14. Any residual solids are washed out from the tube using deionised water until all the Acid Insoluble Residue resides on the filter crucible.

Step 2: Determination of ASL Using UV-Vis Spectroscopy
The following steps are involved in the determination of the Acid Soluble Lignin (ASL) content:

1. The hydrolysate (filtrate) from the Acid Hydrolysis Stage, is quantitatively transferred using a pipette to a 1 cm path-length (3 mL volume) quartz cuvette.

2. The UV-Visible (190-520nm) transmission spectrum of the sample is then obtained using the HP 8452A diode-array spectrophotometer.

3. If the absorbance at a given wavelength is outside of the linear region (considered to be between 0.7 and 1.0 absorbance units) then the sample is diluted with water until the value falls within this region.

3. This dilution and UV-Visible analysis is carried out twice for each hydrolysate, meaning that each sample will have four spectra collected (two spectra for each of the duplicate hydrolysates). 4. The Acid Soluble Lignin content is then calculated based on the absorbance value at 205nm, the dilution factor, and a given absorptivity constant.

Equipment Used for Lignin (Acid Soluble) Analysis

NIR Model

Acid-Soluble Lignin Global 1

This model has been built from a global dataset comprising a wide variety of biomass samples. Click here for a list of the types of samples that were used to build this model.

The samples were air-dried and then ground-down to a particle size of less than 850 microns prior to NIR analysis.

Model Statistics

Min. Value (%) 0.53
Max. Value (%) 7.74
Calibration Samples 350
Validation Samples 119
R2 (Validation) 0.899
RMSEP (%) 0.338
Bias (%) 0.02
SEP (%) 0.339
RPD 3.081
RER 14.886
Regression Plot
(Independent Validation Set)

Acid-Soluble Lignin Global 1

Additional Material

We can determine the Lignin (Acid Soluble) content of biomass, click here to learn more about our various biomass analysis methods.