The purpose of the document is to establish a general and uniform method for determination of moisture content by dean & stark method.
2.0 SCOPE
This standard testing procedure is suitable for determination of moisture content by dean & stark method in sample.
3.0 RESPONSIBILITY
The expert and trained chemist are responsible for following this procedure. The technical manager is responsible for implementing this procedure.
4.0 REQUIREMENTS
4.1 Apparatus
4.1.1 Moisture Distillation Apparatus: dean stark apparatus
4.1.2 Heating mantle
4.1.3 Copper wire (This should be long enough to extend throughout the condenser with one end twised into a spiral. The diameter of the spiral should be such that it fits snugly within the graduated portion of the receiver and yet can be moved up and down)
4.2 Glassware
4.2.1 Round bottom and short-neck flask with standard joint
4.3 Reagent
Toluene - Saturate the toluene by shaking with a small quantity of water and distill.
5.0 PROCEDURE
5.1 Clean the entire apparatus with chromic acid (cleaning solution) to minimize the adherence of water droplets to the sides of the condenser and the receiver.
5.2 The amount of water is determined by first distilling the material with an organic liquid not miscible with water and then collecting the distillate in a graduated tube.
5.3 Weigh, to the nearest 0·0 I g of about 20 to 40 g of the prepared sample such that the quantity of water measured does not exceed 4.5 ml and not less than 1.5ml.
5.4 Transfer quantitatively the test portion to the distillation flask with toluene; add sufficient toluene (about 75 ml in all) to cover the sample completely and swirl to mix.
5.5 Assemble the apparatus and fill the receiver with toluene by pouring it through the condenser until it begins to overflow into the distillation flask.
5.6 If necessary, insert a loose cotton plug at the top of the condenser to prevent condensation of atmospheric moisture within the condenser tube.
5.7 Heat the flask so that the distillation rate is about 100 drops per minute. Pumice stone pieces may be added to avoid bumping.
5.8 When the greater part of the water has distilled over, increase the distillation rate to about 200 droplets per minute and continue until no more water is collected.
5.9 Purge the reflux condenser occasionally during the distillation with 5 ml portions of toluene to wash down any moisture adhering to the walls of the condenser.
5.10 The water in the receiver may be made to separate from the toluene by occasionally moving a spiral copper wire up and down in the condenser and receiver thus causing the water to settle at the bottom of the receiver.
5.11 Reflux until the water level in the receiver remains unchanged for 30 minutes and then shut off the source of heat.
5.12 Flush the condenser with toluene as required by making use of a spiral copper wire to discharge any moisture droplets.
5.13 Let the receiver stay untouched until the toluene layer is clear and then read the volume of water.
100xV
Moisture content, %
by mass (H) = --------------
M
Where,
V =
volume in ml of water collected; and
M= mass in g of the test
portion.
7.0 REVISION/CHANGE HISTORY: NA
8.0ATTACHMENTS
Appendix-1: FLOW CHART FOR MOISTURE CONTENT BY DEAN & STARK METHOD
9.0 REFERENCES
· IS 1797-1985(Reaff.2009)
· AOAC 20th Edn:2016 43.1.04/986.21/p.1
· FSSAI Lab Manual for Spice and condiments-2016 – Sr. No 3.0
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1. List of All SOPs and Documents for the Chemistry Laboratory
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3. List of All SOPs and Documents For Quality Assurance Dept.
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