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Determination of Total Solids in 

Biomass and Total Dissolved 

Solids in Liquid Process 

Samples 

Laboratory Analytical Procedure (LAP) 

Issue Date: 3/31/2008 

A. Sluiter, B. Hames, D. Hyman, C. Payne, 

R. Ruiz, C. Scarlata, J. Sluiter, D. Templeton, 

and J. Wolfe 

Technical Report 

NREL/TP-510-42621 

Revised March 2008 

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Contract No. DE-AC36-99-GO10337

Technical Report 

NREL/TP-510-42621 

Revised March 2008 

Biomass and Total Dissolved 

Solids in Liquid Process 

Samples 

Laboratory Analytical Procedure (LAP) 

Issue Date: 3/31/2008 

A. Sluiter, B. Hames, D. Hyman, C. Payne, 

R. Ruiz, C. Scarlata, J. Sluiter, D. Templeton, 

and J. Wolfe 
DISCLAIMER 

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Procedure Title: Determination of Total Solids in Biomass and Total 

Dissolved Solids in Liquid Process Samples 

Laboratory Analytical Procedure 

1. Introduction 

1.1 Biomass samples can contain large and varying amounts of moisture, which can change 

quickly when exposed to air. To be meaningful, the results of chemical analyses of biomass 

are typically reported on a dry weight basis. 

1.2 Portions of this procedure are similar to ASTM E1756-01 and T412 om-02 

1.3 The following procedure describes the methods used to determine the amount of solids or 

moisture present in a solid or slurry biomass sample. It also covers the determination of 

dissolved solids in a liquor sample. A traditional convection oven drying procedure is 

covered as well as solids determination using an automatic infrared moisture analyzer. The 

convection oven method is recommended for liquor samples. 

2. Scope 

2.1 This procedure is intended to determine the amount of total solids remaining after 105oC 

drying of a biomass sample. 

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

Quality Assurance Plan (QAP). 

3. Terminology 

3.1 Oven dry weight (ODW)- the weight of biomass mathematically corrected for the amount of 

moisture present in the sample at the time of weighing 

3.2 Total solids- the amount of solids remaining after heating the sample at 105oC to constant 

weight. Conversely, the moisture content is a measure of the amount of water (and other 

components volatilized at 105o

C) present in such a sample 

3.3 Total dissolved solids- the amount of residue remaining from a 0.2 μm filtered liquor sample 

after heating the sample at 105oC to constant weight. 

3.4 Prepared biomass- biomass prepared according to LAP “Preparation of Samples for 

Biomass Compositional Analysis”. 

3.5 Pretreated biomass- biomass that has been chemically or thermally altered, possibly 

changing the structural composition 

3.6 Slurry- the combined liquid and solid material resulting from biomass pretreatment 

3.7 Liquor- the liquid fraction of a biomass slurry 

4. Significance and Use 

4.1 The results of the chemical analyses of biomass samples are typically reported on a 105o

C 

dry weight basis. The total solids content of a sample is used to convert the analytical 

results obtained on an as-received basis to that of an oven dry weight basis. 

 1
5. Interferences 

5.1 This procedure is not suitable for biomass samples that chemically change upon heating, 

such as acidic or alkaline biomass samples. 

6. Apparatus 

6.1 Apparatus required for oven drying method: 

6.1.1 Convection drying oven, with temperature control of 105 ± 3oC 

6.1.2 Analytical balance, accurate to 0.1 mg 

6.1.3 Desiccator containing dessicant 

6.2 Apparatus required for moisture analyzer method: 

6.2.1 Automated infrared moisture analyzer 

6.2.2 Convection drying oven, with temperature control of 105 ± 3oC, optional 

7. Reagents and materials 

7.1 Reagents 

7.1.1 None 

7.2 Materials 

7.2.1 Aluminum pans, made to fit infrared moisture analyzer if necessary 

7.2.2 Glass fiber pads for liquor samples, optional 

7.2.3 0.2 μm pore size filters, either large syringe filters with syringes or 50 mm filter 

units, for liquor samples only 

8. ES&H Considerations and Hazards 

8.1 Follow all applicable NREL chemical handling procedures. 

8.2 This standard does not purport to address all of the safety concerns, if any, associated with 

its use. It is the responsibility of the user of this standard to establish appropriate safety and 

health practices and determine the applicability of regulatory limitations prior to use. 

9. Sampling, Test Specimens and Test Units 

9.1 Test specimens suitable for analysis by this procedure are as-received, air dried, milled, or 

extractive-free biomass solids and the solid fraction of process samples. Slurry and 

separated liquor samples are also suitable. 

9.2 The test specimen size will be dependent on the type of material and shall be obtained in 

such a manner as to ensure that it is representative of the entire lot of material being 

tested. 

9.3 This procedure is not suitable for biomass samples that chemically change upon heating, 

such as acidic or alkaline biomass samples. 

10. Procedure 

Note: Solid samples usually require 0.5 to 2 grams, slurry samples require 2-5 grams, and 

liquor samples require 10 ml, per duplicate. Liquor samples should be filtered through a 0.2 

μm pore size filter prior to analysis. Convection oven method is recommended for liquor 

samples. 

 2
10.1 Convection oven method (use either 10.1 or 10.2) 

10.1.1 Pre-dry aluminum weighing dishes by placing them in a 105 ± 3oC drying oven for a 

minimum of four hours. Cool the dishes in a desiccator. Using gloves or tweezers to 

handle the dishes, weigh a pre-dried dish to the nearest 0.1 mg. (It may be helpful to 

place a dry glass fiber pad in the bottom of each pan for liquor samples. Include the 

weight of the pad with the weight of the pan.) Record this weight. 

10.1.2 Thoroughly mix the sample and then weigh out an appropriate amount to the nearest 

0.1 mg, into the weighing dish. Liquor samples should be passed through a 0.2 μm 

filter prior to analysis. Record the weight of the sample plus weighing dish. Analyze 

each sample in duplicate, at minimum. 

10.1.3 Place the sample into a convection oven at 105 ± 3oC for a minimum of four hours. 

Remove the sample from the oven and allow it to cool to room temperature in a 

desiccator. Weigh the dish containing the oven-dried sample to the nearest 0.1mg and 

record this weight. 

10.1.4 Place the sample back into a convection oven at 105 ± 3oC and dry to constant weight. 

Constant weight is defined as ± 0.1% change in the weight percent solids upon one 

hour of re-heating the sample. Overnight drying is usually required for very wet or 

liquid samples. 

10.2 Automatic infrared moisture analyzer method (use either 10.1 or 10.2) 

10.2.1 Program the automated moisture analyzer for a standby temperature of 70oC, an 

analysis temperature of 105o

C, and an end point of less than 0.05% solids change in one 

minute. 

10.2.2 Turn on the infrared heating elements and allow them to warm up for approximately 20 

minutes. Run the instruments once with an unimportant, disposable sample to bring the 

heating elements to temperature, if necessary. 

10.2.3 Pre-dry aluminum weighing dishes by placing them in a 105 ± 3oC drying oven for a 

minimum of four hours or running them through the moisture analyzer once without a 

sample. If pans are dried in the oven, cool them in a desiccator. Using gloves or 

tweezers, place an aluminum weighing dish on the balance pan, and tare the balance if 

necessary. 

10.2.4 Quickly transfer desired amount of the thoroughly mixed sample to the weighing dish. 

Spread the sample evenly over the surface of the weighing dish. Analyze each sample 

induplicate, at minimum. 

10.2.5 As soon as the instrument balance stabilizes, shut the hood of the instrument and 

proceed with the analysis, following the instructions in the instrument operation 

manual. 

10.2.6 Once the sample has been dried to constant weight, as determined by the programmed 

analysis parameters, the analysis will automatically be terminated. Record the percent 

solids or percent moisture. 

11. Calculations 

11.1 Calculate the percent total solids, or percent dissolved solids for a liquor sample, on a 

105o

C dry weight basis as follows (the automated moisture analyzer will provide the 

calculated value as part of the instrument printout). 

 3
% ×100

receivedassample

sampledry plus pandry pandry

weight

 (Weight ) Weight - = SolidsTotal

% ×100

receivedasliquor

liquordry plus pandry pandry

weight

 (Weight ) Weight - Dissolved = Solids

11.2 If desired, the percent moisture can also be calculated 

⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

% 100 − ×100

receivedassample

sampledry plus pandry pandry

weight

 (Weight ) Weight - = Moisture

11.3 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 

11.4 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 

 4
12. Report Format 

12.1 Report the result as the percent total solids (or percent moisture), and cite the basis used 

in the calculations. 

12.2 For replicate analyses of the same sample, report the average, standard deviation, and 

%RPD. 

13. Precision and Bias 

13.1 An inherent error in any moisture determination involving drying of the sample is that 

volatile substances other than water may be removed from the sample during drying. 

14. Quality Control 

14.1 Reported Significant Figures or decimal places: Determined by data quality objectives 

and laboratory specific Quality Assurance Plan, see LAP “Rounding and Significant 

Figures”. 

14.2 Replicates: Run all samples and method verification standards, if applicable, in duplicate, 

at minimum. 

14.3 Blank: This gravimetric analysis utilizes a balance blank with every batch of samples, 

consisting of a weighing dish passed through all steps of the procedure. The difference in 

weight must be less than the equivalent of a 0.5% error. 

14.4 Relative percent difference criteria: Each sample must reproduce total solids content + 

0.5 wt %. 

14.5 Method verification standard (MVS): A MVS may be run in duplicate with every batch. 

Sodium tartrate is a suitable material for use as a MVS, since the moisture content of this 

material is not greatly affected by its storage conditions. The published moisture loss on 

drying for sodium tartrate is 15.62% (84.38% total solids). 

14.6 Sample size: Determined by sample matrix. 

14.7 Sample storage: Samples should be stored in an airtight container. Process samples and 

high-moisture-content feedstock samples must be refrigerated or frozen until ready for 

use. 

14.8 Standard storage: Not applicable 

14.9 Standard preparation: Not applicable 

14.10Definition of a batch: Any number of samples analyzed and recorded together. The 

maximum size of a batch will be limited by equipment constraints 

14.11Control charts: MVS or a QA/QC material should be control charted to verify 

reproducibility 

14.12Others: Biomass can rapidly gain or lose moisture when in contact with air. During the 

weighing steps, minimize the amount of time the sample is exposed to the air. 

15. Appendices 

15.1 None 

 5
16. References 

16.1 NREL Laboratory Analytical Procedure, "Determination of Moisture, Total Solids, and 

Total Dissolved Solids in Biomass Slurry and Liquid Process Samples." 

16.2 NREL BAT Team Laboratory Analytical Procedure #001, "Standard Test Method for 

Determination of Total Solids in Corn Stover." 

16.3 TAPPI Method T412 om-02. 2002. "Moisture in Pulp, Paper and Paperboard." Test 

methods of the Technical Association of the Pulp and Paper Industry 2002-2003. 

16.4 Vinzant, T.B., L. Ponfick, N.J. Nagle, C.I. Ehrman, J.B. Reynolds, and M.E. Himmel. 

1994. "SSF Comparison of Selected Woods From Southern Sawmills." Appl. Biochem. 

Biotechnol. 45/46:611-626. 

16.5 Moore, W., and D. Johnson. 1967. Procedures for the Chemical Analysis of Wood and 

Wood Products. Madison, WI: U.S. Forest Products Laboratory, U.S. Department of 

Agriculture.

16.6 Milne, T. A.; Chum, H. L.; Agblevor, F. A.; Johnson, D. K. (1992). “Standardized 

Analytical Methods” Biomass & Bioenergy. Proceedings of International Energy Agency 

Bioenergy Agreement Seminar”, 2-3 April 1992, Edinburgh, U.K.. Vol. 2(1-6), 1992; pp. 

341-366 

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