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Preparation and Standardization of 0.1 M Tetrabutylammonium Hydroxide

Preparation and standardisation of 0.1 M Tetrabutylammonium Hydroxide using Benzoic acid and Thymol blue as indicator used for pharmaceuticals analysis.

Tetrabutylammonium Hydroxide Solution Preparation:

•  Dissolve 40 g of tetrabutylammonium iodide in 90 ml of dehydrated methanol in a glass-stoppered flask. • •  Place in an ice-bath, add 20 g of powdered silver oxide, insert the stopper and agitate vigorously for 1 hour. 
•  Centrifuge a few ml, and test the supernatant liquid for iodides. If the test is positive, add an additional 2 g of silver oxide and continue to stand for 30 minutes with intermittent agitation. 
•  When all of the iodide has reacted, filter through fine sintered-glass filter. Rinse the flask and filter with three quantities, each of 50 ml, of anhydrous toluene. Add the washings of the filtrate and dilute to 1000 ml with anhydrous toluene. Flush the solution for 10 minutes with dry, carbon dioxide-free nitrogen. 
•  Store protected from carbon dioxide and moisture, and discard after 60 days.
•  Alternatively, prepare the solution by diluting a suitable volume of commercially available tetrabutylammonium hydroxide solution in methanol with a mixture of four volumes of anhydrous toluene and 1 volume of dehydrated methanol.
•  Standardise the solution in the following manner immediately before use.

Tetrabutylammonium Hydroxide Solution Standardization:

•  Weigh accurately about 0.4 g of benzoic acid, dissolve in 80 ml of dimethylformamide.
•  Add a few drops of a 1% w/v solution of thymol blue in dimethylformamide and titrate with the tetrabutylammonium hydroxide solution to a blue end-point. 
•  Protect the solution from atmospheric carbon dioxide throughout the titration. Perform a blank determination and make any necessary correction.
•  1 ml of 0.1 M tetrabutylammonium hydroxide is equivalent to 0.01221 g of C7H6O2.

                                                                                         W  x  0.1
Molarity of 0.1 M Tetrabutylammonium hydroxide =  ----------------------
                                                                                       BR  x 12.21

Also see: Determination of Shelf Life of Solutions in Laboratory

Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of Pharmaceutical Guidelines, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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