Guest guest Posted July 19, 2006 Report Share Posted July 19, 2006 , First thing - you need to know that a ratio is expressing the relationship of drug to volume (concentration) measured as G: mL, so this means 1:1000 = 1 G / 1000 mL 1 G = 1000 mg so: 1:1000 = 1000 mg/1000 mL = 1 mg/mL Now that you have the concentration of the stock solution (1 mg/mL) you need to determine the amount of drug you need the final product. 1:4000 = 1 G/4000 mL = 1000 mg / 4000 mL = 1 mg/4 mL you desire 100 mL 1 mg/4 mL = X mg/100 mL cross multiply: X = (100 mL x 1 mg) / 4 mL = 25 mg You now need to determine the amount of stock solution needed: 1 mg/mL = 25 mg/ X X = 25 mL Hope this helped taking it step by step. This could also be solved as a dilution or using alligation. Anne LaVance TEXpert Quote Link to comment Share on other sites More sharing options...
Guest guest Posted July 19, 2006 Report Share Posted July 19, 2006 Use Jeanetta's formula: C1V1=C2V2 The concentration of the stock solution is 1 -------- x 100 = 0.1% 1000 the concentration of required solution is 1 ------- x 100 = 0.025% 4000 Plug in the concentrations in to the formula ... C1 V1 = C2 V2 (0.1%) (V1) = (0.025%) (V2) You already know you need to prepare 1000ml of 0.025% solution, so you replace V2 with 1000ml hence ... (0.1%) (V1) = (0.025%) (1000ml) solve for V1 4 (V1) = 1000 V1 = 250 ml Hope it helped, and wait for Jeanetta to verify it too before you go ahead with the solution. Tingting P.S. I like the C1V1 = C2V2 formula, it is so much easier. =) help on calculation the question goes like this: how much 1:1000 stock solution is required to prepare a 1000ml of a 1:4000 solution? any help you can give me would be much appreciated. -Reyn Quote Link to comment Share on other sites More sharing options...
Guest guest Posted July 19, 2006 Report Share Posted July 19, 2006 Anne, Got it. thanks for the clear explanation. > > , > First thing - you need to know that a ratio is expressing the relationship > of drug to volume (concentration) measured as G: mL, so this means > 1:1000 = 1 G / 1000 mL > 1 G = 1000 mg > so: 1:1000 = 1000 mg/1000 mL = 1 mg/mL > > Now that you have the concentration of the stock solution (1 mg/mL) you need > to determine the amount of drug you need the final product. > > 1:4000 = 1 G/4000 mL = 1000 mg / 4000 mL = 1 mg/4 mL > you desire 100 mL > 1 mg/4 mL = X mg/100 mL > cross multiply: X = (100 mL x 1 mg) / 4 mL = 25 mg > > You now need to determine the amount of stock solution needed: > 1 mg/mL = 25 mg/ X > X = 25 mL > > Hope this helped taking it step by step. This could also be solved as a > dilution or using alligation. > > Anne LaVance > TEXpert > > > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted July 20, 2006 Report Share Posted July 20, 2006 Dear Anne, TEXPERT I do believe you may have misread the math problem or you used a typo/transcription error. Please correct me if I am wrong. The problem calls for 1000 ml NOT 100 ml. Therefore I concur with Tingting Gao that the answer is 250 ml not 25 ml. Please check the original problem and your math and mine to see which one of us is correct. There is either a decimal error in your answer or mine. I did this problem three different ways and got 250 ml. Please get back to us. Thanks Jeanetta > > , > First thing - you need to know that a ratio is expressing the relationship > of drug to volume (concentration) measured as G: mL, so this means > 1:1000 = 1 G / 1000 mL > 1 G = 1000 mg > so: 1:1000 = 1000 mg/1000 mL = 1 mg/mL > > Now that you have the concentration of the stock solution (1 mg/mL) you need > to determine the amount of drug you need the final product. > > 1:4000 = 1 G/4000 mL = 1000 mg / 4000 mL = 1 mg/4 mL > you desire 100 mL > 1 mg/4 mL = X mg/100 mL > cross multiply: X = (100 mL x 1 mg) / 4 mL = 25 mg > > You now need to determine the amount of stock solution needed: > 1 mg/mL = 25 mg/ X > X = 25 mL > > Hope this helped taking it step by step. This could also be solved as a > dilution or using alligation. > > Anne LaVance > TEXpert > > > Quote Link to comment Share on other sites More sharing options...
Guest guest Posted July 20, 2006 Report Share Posted July 20, 2006 Good job Tingting Gao! You got the right answer using this formula and it will work. However I would explain it differently in terms of parts of the whole and percentage. But it works. This formula (C1V1 =C2V2) is typically used in the determination of the Base Solutions of Amino Acids and Dextrose for TPN's, WHEN the exact strength ordered is less than what is in stock. Please see my explanation of how to solve this problem one of three ways. In the C1xV1 = C2 x V2 method I show how to use it without converting but using it 'as is'. If you liked the method you problably love this short cut. Jeanetta > > Use Jeanetta's formula: > > C1V1=C2V2 > > The concentration of the stock solution is > > 1 > -------- x 100 = 0.1% > 1000 > > the concentration of required solution is > > 1 > ------- x 100 = 0.025% > 4000 > > Plug in the concentrations in to the formula ... > > C1 V1 = C2 V2 > (0.1%) (V1) = (0.025%) (V2) > > You already know you need to prepare 1000ml of 0.025% solution, so you replace V2 with 1000ml > hence ... > > (0.1%) (V1) = (0.025%) (1000ml) > > solve for V1 > > 4 (V1) = 1000 > V1 = 250 ml > > Hope it helped, and wait for Jeanetta to verify it too before you go ahead with the solution. > > Tingting > > P.S. I like the C1V1 = C2V2 formula, it is so much easier. =) > > help on calculation > > > the question goes like this: > > how much 1:1000 stock solution is required to prepare a 1000ml of a > 1:4000 solution? > > any help you can give me would be much appreciated. > > -Reyn > > > > > Quote Link to comment Share on other sites More sharing options...
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