Should I use cellulose or glass fibre extraction thimbles?

Use cellulose for standard fat and oil determination with solvents such as petroleum ether, hexane or diethyl ether, because it is inexpensive, holds fine powders well and fits most Soxhlet bodies. Use glass fibre when the solvent is hot and aggressive, when the sample must be extracted at elevated temperature, or when cellulose blank values would interfere with a low-level result. Quartz thimbles are for trace analysis and for methods that require pre-firing at high temperature.

Do extraction thimbles need to be pre-extracted?

Yes for any gravimetric result near the detection limit. Cellulose thimbles carry a small extractable fraction, typically 0.1 to 1 percent by mass, which is measured as fat if you skip the step. Pre-extract with the same solvent for the same cycle count, dry, condition in a desiccator and weigh. For routine fat determination on samples with several percent fat, a documented blank run alongside each batch is often enough.

Why is my fat result low or variable between replicates?

Check four things in order: the thimble is not overloaded, so solvent cannot circulate through the sample; the sample was dried and ground fine enough to expose the fat; the extraction cycle count is sufficient, usually 20 to 30 siphon cycles or 4 to 6 hours; and the flask was dried to constant weight. Thimble fit matters too, because a thimble taller than the Soxhlet body holds the sample above the solvent level and extracts only partly.

Does JWRESEARCH supply extraction thimbles in Singapore?

Yes. JWRESEARCH supplies cellulose, glass fibre and quartz extraction thimbles in diameters from 22 to 43 millimetres and heights from 80 to 123 millimetres, together with Soxhlet extractors, extraction flasks, condensers and heating mantles, delivered across Singapore.

Extraction Thimbles and Soxhlet Supplies Singapore

Published: {{NEW_ARTICLE_DATE}} | By JWRESEARCH | Category: Laboratory Consumables

The extraction thimble is the cheapest part of a Soxhlet setup and the one most likely to ruin the result. It has to hold a fine powder without letting it through, pass solvent freely, survive hours of boiling solvent cycling, and contribute almost nothing to the mass you weigh at the end. Get the material or the fit wrong and the fat value drifts by a few tenths of a percent in a way that is hard to trace.

At JW RESEARCH SUPPLY, we supply cellulose, glass fibre and quartz extraction thimbles, plus Soxhlet extractors, flasks, condensers and heating mantles, to food, feed, environmental and polymer laboratories across Singapore. This guide covers material selection, sizing and the handling rules that keep blank values low.

Thimble Materials Compared

Material	Max Temperature	Extractable Blank	Typical Use
Cellulose	About 120 °C	0.1 – 1.0 % by mass	Fat and oil in food and feed, standard methods
Glass fibre	About 500 °C	Very low, under 0.05 %	Hot solvents, fast cycling, low-level gravimetry
Quartz	About 1000 °C	Negligible	Trace analysis, pre-fired blanks, high-temperature methods
Paper, hardened	About 120 °C	0.5 – 1.5 % by mass	Teaching, coarse screening, non-critical work

Specification Reference

Parameter	Typical Value	What It Affects
Internal diameter	22, 25, 26, 28, 33, 43 mm	Must clear the Soxhlet body and sit below the siphon arm
Height	80, 100, 118, 123 mm	Thimble must stay below the top of the extractor
Wall thickness	1.0 – 1.5 mm	Mechanical strength versus solvent flow
Retention	1 – 3 µm nominal	Whether fine powder escapes into the flask
Capacity	10 – 100 mL of sample	Load should fill about two thirds of the height
Max temperature	120 °C cellulose, 500 °C glass fibre	Drying and pre-firing limits
Pack size	25 or 100 per box	Consumption planning and lot traceability
Shelf life	3 – 5 years dry	Moisture pickup changes tare mass

Choosing the Size

Size the thimble to the extractor, not to the sample. A thimble that is too tall sits with its rim above the solvent level, so the upper part of the sample never sees fresh solvent and the result comes out low. A thimble that is too narrow will not clear the body, and one that is too wide blocks the vapour path.

Load the sample to about two thirds of the thimble height. Overfilling compresses the powder into a plug that solvent cannot percolate through, and the extraction becomes a surface wash. For fatty or sticky samples, mix with anhydrous sodium sulfate or sand to keep the bed open, and cap the top with a small plug of defatted cotton wool so fine particles do not float out.

Pre-Extraction and Blanks

Cellulose thimbles are not mass-free. Depending on grade and lot, a thimble can release 0.1 to 1.0 percent of its own mass into the solvent, and in a 2 g sample that is a serious bias. For any method with a low specification limit, pre-extract the batch of thimbles with the same solvent for the same number of cycles, dry them, condition them in a desiccator and store them in a closed container.

Where the sample fat content is high and the method allows it, run one blank thimble per batch and subtract. Record the lot number on the worksheet: blank values move between lots, and a supplier change mid-project is a common cause of an unexplained shift in results.

Solvent and Safety Notes

Petroleum ether, hexane and diethyl ether are the usual solvents, and all of them are flammable with low flash points. Run extractions in a fume hood, use a heating mantle or water bath rather than an open flame, and never let a flask boil dry. Diethyl ether forms peroxides on storage, so keep stock in small amber bottles with the date opened and test or discard old stock.

Check the condenser flow before heating and keep the cooling water on until the flask is cool. A Soxhlet that siphons dry and then overheats can crack, and hot solvent on a bench is a serious fire risk.

Drying and Weighing

Dry the extraction flask at 100 to 105 °C, cool in a desiccator and weigh to constant mass.
Use the same desiccator time for every replicate; glass holds a moisture film that changes with cooling time.
Handle flasks with tongs or lint-free gloves, never bare fingers.
Dry cellulose thimbles at or below 105 °C; higher temperatures embrittle them and add to the blank.
For glass fibre, pre-fire at 500 °C if the method requires a true zero blank.

Ordering Checklist

Extractor body size and the thimble diameter that clears it
Thimble height that stays below the solvent level
Material: cellulose for routine fat, glass fibre for hot or low-level work
Retention needed for the sample fineness
Whether the method requires pre-extracted or pre-fired thimbles
Box quantity and a record of the lot number

Tell us your extractor model, the sample type and the method limit, and we will match a thimble specification and pack size, delivered across Singapore.

Contact JWRESEARCH

JW RESEARCH SUPPLY — laboratory equipment and consumables, Singapore.
Telephone / WhatsApp: +65 8039 3660
Email: SINGAPORE@JWSHY.COM
Website: www.jwresearch.cn