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Determination of Starch in Solid 

Biomass Samples by HPLC 

Laboratory Analytical Procedure (LAP) 

Issue Date: 07/17/2005 

A. Sluiter and J. Sluiter 

Technical Report 

NREL/TP-510-42624 

January 2008 

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Contract No. DE-AC36-99-GO10337

Technical Report 

NREL/TP-510-42624 

January 2008 

Determination of Starch in Solid 

Biomass Samples by HPLC 

Laboratory Analytical Procedure (LAP) 

Issue Date: 07/17/2005 

A. Sluiter and J. Sluiter 
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Procedure Title: Determination of Starch in Solid Biomass 

Samples by HPLC 

Laboratory Analytical Procedure 

1. Introduction 

1.1 Carbohydrates make up a major portion of biomass samples. These carbohydrates are 

polysaccharides constructed primarily of glucose, xylose, arabinose, galactose, and 

mannose monomeric subunits. One such polysaccharide is starch, which is present in 

certain types of biomass. Starch will contribute to the overall glucose measurement when 

it breaks into the component sugar glucose. Starch is often a more readily accessible 

source of glucose than structurally bound glucose polymers. Due to the increased 

accessibility, it is often advantageous to determine the amount of starch present. 

1.2 The amount of starch present in a solids biomass sample is determined by this procedure. 

This procedure is based on the Megazyme Total Starch Assay Procedure 

(amyloglucosidase / α-amylase method). The Megazyme procedure is also listed as AOAC 

Method 996.11, AACC Method 76.13, and ICC Standard method No. 168. 

2. Scope 

2.1 This procedure is used to measure the starch content in solid biomass samples. 

2.2 This procedure is appropriate for solid biomass samples containing starch. 

2.3 All analyses should be performed in accordance with an appropriate laboratory specific 

Quality Assurance Plan (QAP). 

3. Terminology 

3.1 None 

4. Significance and Use 

4.1 This procedure is used to determine the starch content of solid biomass samples. Other 

optional procedures can be used in conjunction with this procedure, to determine whole 

biomass composition. 

4.2 This procedure is used, in conjunction with other procedures, to determine the chemical 

composition of biomass samples, see LAP “Summative Mass Closure for Biomass 

Samples”. (Note: The amount of glucan determined in the sample will include a 

contribution of glucose from starch. The starch measurement should not be included as a 

separate category unless the starch contribution is first removed from the glucan value.) 

5. Interferences 

5.1 Samples containing galacturonic acid, which elutes at the same time as glucose on the 

Aminex HPX-87H column, may have artificially high glucose peaks. 

6. Apparatus 

6.1 Analytical balance, accurate to 0.1mg 

6.2 Automatic moisture analyzer or 105o

C drying oven 

 1
6.3 pH meter 

6.4 Water bath, capable of maintaining boiling water and 50oC. 

6.5 Vortex mixer 

6.6 Centrifuge, capable of 3,000 rpm, with 15 ml centrifuge vial slots 

6.7 HPLC system equipped with refractive index detector and the following columns: 

6.7.1 Biorad Aminex HPX-87H column (or equivalent) with corresponding guard column 

7. Reagents and materials 

7.1 Reagents 

7.1.1 High purity D-(+)glucose standard 

7.1.2 Second sample of high purity D-(+)glucose standard, as listed above, from a 

different source (manufacturer or lot), to be used to prepare calibration verification 

standards (CVS) 

7.1.3 190 proof ethanol, reagent grade 

7.1.4 Dimethyl sulfoxide (DMSO), reagent grade 

7.1.5 Thermostable α-amylase, available from Megazyme 

7.1.6 Amyloglucosidase, available from Megazyme 

7.1.7 MOPS buffer 

7.1.7.1 MOPS (sodium salt, 11.55g: Sigma Chemical Co.; cat. Number M9381) 

7.1.7.2 1M (10%) Hydrochloric acid 

7.1.7.3 Calcium chloride dihydrate 

7.1.7.4 Sodium azide (optional) 

7.1.8 Sodium acetate buffer 

7.1.8.1 Glacial acetic acid 

7.1.8.2 1M sodium hydroxide solution 

7.1.8.3 Sodium azide (optional, see ES&H Considerations and Hazards, section 8.2) 

7.1.9 Water, HPLC grade, 0.2 μm filtered 

7.1.10 Starch, chemical quality 

7.1.11 0.01N sulfuric acid, or appropriate HPLC mobile phase 

7.2 Materials 

7.2.1 Volumetric flasks (2), 1 L 

7.2.2 Autosampler vials with crimp top seals to fit and crimper 

7.2.3 15 ml plastic tubes with tightly fitting screw caps 

7.2.4 Disposable syringes, 3 mL, fitted with 0.2 μm syringe filters 

7.2.5 Volumetric pipets, class A, of appropriate sizes or corresponding pipettors 

7.2.6 Volumetric flasks, class A, of appropriate sizes for standard and CVS dilution 

7.2.7 Adjustable pipettors, covering ranges of 10 μl to 10 ml 

8. ES&H Considerations and Hazards 

8.1 Sulfuric acid, hydrochloric acid, and glacial acetic acid are corrosive and should be 

handled with care 

8.2 Sodium azide is highly toxic and explodes when heated. It releases a poisonous gas when 

acidified. It is added to the buffers only as a preservative. The use of sodium azide can be 

avoided if the buffers are stored at 4o

C.

8.3 Follow all applicable NREL chemical handling procedures 

 2
9. Sampling, Test Specimens and Test Units 

9.1 Follow LAP “Preparation of Biomass for Compositional Analysis” prior to analysis. 

9.2 Care must be taken to ensure a representative sample is taken for analysis at each step. 

When measuring volumes for analysis, the liquid should be at room temperature. 

10. Procedure 

10.1 Prepare the buffers. 

10.1.1 MOPS buffer. 

10.1.1.1 In a 1 L volumetric flask, add 11.55 g MOPS, sodium salt, to 900 ml of 

deionized water. Adjust the solution to pH7.0 using 1M (10%) HCl. 

Approximately 17 ml of 1M HCl will be required. 

10.1.1.2 Add 0.74g calcium chloride dihydrate. If desired, add 0.2g sodium azide. The 

sodium azide can be omitted if the buffer is stored in the refrigerator. As sodium 

azide is highly toxic, omission is recommended. Bring the volume to 1 L with 

deionized water. 

10.1.2 Soduim acetate buffer 

10.1.2.1 In a 1 L volumetric flask, add 11.8 ml glacial acetic acid to 900 ml of deionized 

water. Adjust the solution to pH 4.5 using a 1M (4g/100 ml) sodium hydroxide 

solution. Approximately 60 ml of 1M sodium hydroxide solution will be 

required. 

10.1.2.2 If desired, add 0.2g sodium azide. The sodium azide can be omitted if the buffer 

is stored in the refrigerator. As sodium azide is highly toxic, omission is 

recommended. Bring the volume to 1 L with deionized water. 

10.2 Prepare the sample for HPLC analysis. 

10.2.1 Add 100 mg (+ 10mg) of sample to a tared 15 ml plastic centrifuge tube with a 

tightly fitting screw cap. Record the weight to the nearest 0.1 mg. LAP 

“Determination of Total Solids in Biomass” should be performed at the same time, to 

accurately measure the percent solids for correction. Each sample should be 

analyzed in duplicate, at minimum. 

10.2.2 Repeat step 10.1.1 for a starch sample of known purity. The starch sample should be 

included throughout the analysis and treated as a sample. 

10.2.3 Add 0.2 ml 190 proof ethanol and vortex vigorously. This will aid in sample 

dispersion. 

10.2.4 Immediately add 2 ml of dimethyl solfoxide (DMSO) and vortex vigorously. 

10.2.5 Tightly cap the tube and place it in a briskly boiling water bath for five minutes. Use 

caution when removing the tubes, as they will be hot. 

10.2.6 Immediately add 2.9 ml MOPS buffer and 0.1 ml thermostable α-amylase (or 300 

Units). Tightly cap the tube. Vortex vigorously. Incubate the tube in a boiling 

water bath for 6 minutes, vortex mixing every two minutes. 

10.2.7 Place the tube in a 50o

C water bath. Add 4 ml of the sodium acetate buffer, followed 

by 0.1 ml (20 units) amyloglucosidase. Vortex and incubate for 30 minutes at 50o

C. 

10.2.8 Remove the samples from the water bath and centrifuge the tubes for 10 minutes at 

3,000 rpm. 

10.2.9 If the sample has been capped tightly throughout the analysis, the solvent volume is 

 3
constant, and the volume of the solvent can be assumed to be 9.3 ml. Filter an 

aliquot through a 0.2 μm filter into an autosampler vial, seal and label. Prepare each 

sample in duplicate if desired. 

10.3 Analyze the sample for glucose on an HPLC 

10.3.1 Prepare 0.01 N sulfuric acid for use as a HPLC mobile phase. In a 2L volumetric 

flask, add 2.00 mL of 10 N sulfuric acid and bring to volume with HPLC grade 

water. Alternatively, add 278 μl concentrated sulfuric acid to a 1L volumetric flask 

and bring to volume with HPLC grade water. Filter through a 0.2 μm filter and 

degas before use. 

10.3.2 Prepare a series of calibration standards containing D(+)-glucose. Suggested 

concentration range is 0.2 mg/ml to 15 mg/ml. Use a four point calibration. Filter 

the standard solutions through 0.2 μm filters into autosampler vials. Seal and label 

the vials. 

10.3.3 Prepare an independent calibration verification standard (CVS) for each set of 

calibration standards. Use a reagent from a source or lot other than that used in 

preparing the calibration standards. Prepare the CVS at a concentration that falls in 

the middle of the validated range of the calibration curve, but is not equal to the 

concentration of any of the standards. The CVS should be analyzed on the HPLC 

after each calibration set and at regular intervals throughout the sequence, bracketing 

groups of samples. The CVS is used to verify the quality and stability of the 

calibration curve(s) throughout the run. 

10.3.3.1 A fresh set of standards is not required for every analysis. A large batch of 

standards may be produced, filtered through 0.2 μm filters into autosampler vials, 

sealed and labeled. The standards and CVS samples must be stored in a freezer 

and removed when needed. Thaw and vortex frozen standards prior to use. 

During every use, standards and CVS samples should be observed for unusual 

concentration behavior. Unusual concentrations may mean that the samples are 

compromised or components have been lost. Assuming sufficient volume, 

standards and CVS samples should not have more than 12 injections drawn from 

a single vial. In a chilled autosampler chamber, the lifetime of standards and 

CVS samples is approximately seven days. 

10.3.4 Analyze the calibration standards, CVS, and samples by HPLC using a Biorad 

Aminex HPX-87H column. 

HPLC conditions: 

Sample volume: 10 - 25 μL, dependent on sample concentration and detector 

limits 

Mobile phase: 0.01 N sulfuric acid, 0.2 μm filtered and degassed 

Flow rate: 0.6 mL / minute 

Column temperature: 55 – 65 °C 

Detector temperature: as close to column temperature as possible 

Detector: refractive index 

Run time: 50 minutes, or shorter if peak resolution is adequate 

Note: The retention time of DMSO should be verified prior to reducing the run 

time. 

10.3.5 Calculate the amount of starch present in the sample. Correct for any starch loss 

 4
using the high purity starch sample as a reference. Use calculations 11.5. 

11. Calculations 

11.1 Calculate the oven dry weight (ODW) of the sample, using the average total solids 

content as determined by the LAP “Standard Method for the Determination of Total 

Solids in Biomass”. 

100

 solidsTotal % x Weight = ODW sampledryair

11.2 Create a calibration curve for each analyte to be quantified using linear regression. From 

these curves, determine the concentration in mg/mL of each component present in the 

samples analyzed by HPLC, correcting for dilution if required. 

11.3 Calculate and record the amount of each calibration verification standard (CVS) 

recovered following HPLC analysis. 

% CVS recovery = conc. detected by HPLC, mg/mL

known conc. of standard, mg/mL

 x 100

11.4 For the reagent starch samples, calculate the amount of starch recovered after analysis. 

Average any replicate (%Rstarch) values obtained for each individual starch sample and 

report %Ravg, starch. 

100 x 

known mg/mL analysis, before starchof weight

mg/mL HPLC,by detected conc. % R = starch

11.5 Calculate the % starch for each sample. 

100

11.1 %

,.

% ×

⎟

⎟

⎟

⎟

⎠

⎞

⎜

⎜

⎜

⎜

⎝

⎛

×

⎟

⎠

⎞ ⎜

⎝

⎛

R

ODW

mlsolutionVol

C x 

 = Starch

starch

HPLC

Where: CHPLC = conc. of glucose as determined by HPLC, mg/mL. 

Vol. Solution = 9.3 ml, total volume of liquid added to solids 

ODW = Oven dry weight of the sample, mg, as calculated in step 

11.1. 

“1.11” is the glucose to starch oligomer correction factor 

%Rstarch is the starch recovery as calculated in step 11.4 

11.6 To report or calculate the relative percent difference (RPD) between two samples, use the 

following calculation 

RPD = 1 (X − X2)

X mean

⎛

⎝ ⎜ ⎞⎠ ⎟ × 100

Where: 

X1 and X2 = measured values 

Xmean = the mean of X1 and X2 

 5
11.7 To report or calculate the root mean square deviation (RMS deviation) or the standard 

deviation (st dev) of the samples, use the following calculations. 

First find the root mean square (RMS), of the sample using 

RMS = x m = mean = 

x

1

n

∑

 n 

⎛ 

⎝ 

⎜ 

⎜ 

⎜ 

⎜ ⎜ 

⎞ 

⎠ 

⎟ 

⎟ 

⎟ 

⎟ ⎟ 

2

Then find the root mean square deviation, or standard deviation, using 

RMSdeviation = σ = stdev =

xi − x ( ) m

2

1

n

∑

n

Where: 

xm=the root mean square of all x values in the set 

n=number of samples in set 

xi=a measured value from the set 

12. Report Format 

12.1 Report concentrations, in weight percent, of analytes of interest. RPD and RMS deviation 

may also be reported. 

13. Precision and Bias 

13.1 Determined by data quality objectives and laboratory specific Quality Assurance Plan. 

14. Quality Control 

14.1 Reported Significant Figures or Decimal Places: Determined by data quality objectives 

and laboratory specific Quality Assurance Plan. 

14.2 Replicates: All analyses may be run in duplicate if desired. 

14.3 Blank: An optional instrument blank may be run, using HPLC grade water analyzed by 

HPLC in the same manner as a sample. 

14.4 Relative percent difference criteria: Determined by data quality objectives and laboratory 

specific Quality Assurance Plan. 

14.5 Calibration verification standard: Calibration verification standards should be 

independently prepared and analyzed as described in the procedure section. 

14.6 Sample size: 1.2 g minimum 

14.7 Sample storage: Liquid samples and buffers should be stored in the refrigerator. 

14.8 Standard storage: The standards should be stored in a freezer and removed when needed. 

Thaw and vortex frozen standards prior to use. 

14.9 Standard preparation: Standards should be prepared as described in the procedure. 

 6
14.10 Definition of a batch: Any number of samples which are analyzed and recorded together. 

Samples within a batch should be of the same matrix. The maximum size of a batch will 

be limited by equipment constraints. 

14.11 Control charts: All CVS and SRS recoveries should be control charted. 

15. Appendices 

15.1 See Appendix 1 at the end of the document for a quick reference sheet for calculation 11.3. 

16. References 

16.1 Megazyme “Total Starch Assay Prodecure (Amyloglucosidase / α-amylase method)” 

AA/AMG 11/01, AOAC Method 996.11, AACC Method 76.13, ICC Standard Method 

No. 168 

16.2 NREL Laboratory Analytical Procedure, “Determination of Sugars, Byproducts, and 

Degradation Products in Liquid Fraction of Process Samples”. 

 7