Method SM 2540G

Total, Fixed, and Volatile Solids in Solid and Semisolid Samples

This method is for the determination of total solids and its fixed and volatile fractions in such solid and semi-solid samples as river and lake sediments, sludges separated from water and wastewater treatment processes, and sludge cakes from vacuum filtration, centrifugation, or other sludge dewatering processes.   A portion of the sample is weighed then ashed for an hour at 550°C ± 50°C and the weight difference represents the percent moisture.  The percent solids can be calculated by subtracting the percent moisture from 100.

‘‘Total solids’’ is the term applied to the material residue left in the vessel after evaporation of a sample and its subsequent drying in an oven at a defined temperature.  Total solids includes ‘‘total suspended solids,’’ the portion of total solids retained by a filter, and ‘‘total dissolved solids,’’ the portion that passes through the filter. ‘‘Fixed solids’’ is the term applied to the residue of total, suspended, or dissolved solids after heating to dryness for a specified time at a specified temperature.  The weight loss on ignition is called ‘‘volatile solids.’’   All weighings should be made as soon as possible as wet samples tend to lose weight by evaporation.  After drying or ignition, residues often are very hygroscopic and rapidly absorb moisture from the air. 

Bring samples to room temperature before analysis.

(Standard Methods)


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Method Data

Hold Times, Preservatives, Preps, Collection, Analytical & Documentation
Holding Time:   Analyze samples within 24 hours if possible. The maximum holding time is 7 days from collection to analysis.
Preservatives:   Refrigerate samples at 4°C from sampling to analysis to minimize microbiological decomposition of solids.
Required Preps:   Use resistant-glass or plastic bottles, provided that the material in suspension does not adhere to container walls.
Collection Method:   Grab sampling
Analytical Methodology:   Gravimetric

Analyte List*

Analyte Formula CAS Number Detection Limit
Fixed Solids
Total Solids
Volatile Solids

* The analytes and detection limits listed for each method represent the typical detection limits and analytes reported for that particular method. Keep in mind that analyte lists may vary from laboratory to laboratory. Detection limits may also vary from lab to lab and are dependent upon the sample size, matrix, and any interferences that may be present in the sample.