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  • dilution question.

    Diazepam tabs contain 92.5 to 107.5% of the stated amount of diazepam.

    Twenty, 10mg diazepam tablets, weighing a total of 1..5426g were powdered and allowed to stand for 15 minutes. 140ml of 0.5%w/v solution of sulfuric acid in methanol was added, shaken for 15 minutes and sufficient methanolic sulfuric acid to produce 200ml was added. Following filtration, 10ml of the filtrate was diluted to 50ml with the same solvent. A . Taking the value of A (1%,1cm) as 450, calculate weight of C10H13CLN20 in 1 tablet and comment on the result.
    Last edited by Msocpharm; 29, January 2009, 10:01 PM.

  • #2
    Re: dilution question.

    Originally posted by Msocpharm View Post
    Diazepam tabs contain 92.5 to 107.5% of the stated amount of diazepam.

    Twenty, 10mg diazepam tablets, weighing a total of 1..5426g were powdered and allowed to stand for 15 minutes. 140ml of 0.5%w/v solution of sulfuric acid in methanol was added, shaken for 15 minutes and sufficient methanolic sulfuric acid to produce 200ml was added. Following filtration, 10ml of the filtrate was diluted to 50ml with the same solvent. A subsequent dilution was carried out by diluting 15ml of the resulting solution to 100ml again using methanolic sulfuric acid.
    Absorbance of 1cm layer of the solution was 0.792 at the max 284nm. Taking the value of A (1%,1cm) as 450, calculate weight of C10H13CLN20 in 1 tablet and comment on the result.
    Beer Lambert's law states absorbence is directly proportional to concentration and some how proportional to the length (here a constant 1cm) at a given wavelegth usuually the maximum (here 284nm). The constant is A so you can find a formula or make one to and solve it to find the percentage concentration of the methanolic solution.

    As I mentioned last time, learn the Beer-Lambert law and equation and when you see the word Absorbance think Paul2008.

    Have a good weekend.
    Real stupidity beats artificial intelligence every time.
    (T. Pratchett)

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