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- Posts: 24
- Joined: Fri Sep 24, 2004 2:37 pm
Hi,
I know this isn't the right forum, but I couldn't find a forum especially for titrations.
We have to do an assay on cloxacilline benzathine as stated in the British Pharmacopea (Veterinary).
But we have some discussion about the calculation of the result.
When you perform the titration on the 12mg substance, it looks like it doesn't matter if you weigh 10 mg or 14 mg. You titrate with the same volume of thiosulphate. Do we have to take this weight into account?
Our fomula now looks like:
(V1sample-V2sample)*Wref1*Wref2*%
(V1ref-V2ref)*Wsample1*Wsample2
Where V1 are the volumes thiosulphate titrated with the 12 mg sample,
V2 are the volumes thiosulphate titrated with the 60 mg sample,
W are the weights and % is the declared content of the BPCRS.
How would you calculate this?
Best regards
For the ones who don't have the BP VET at hand:
Assay cloxacilline benzathine (BP Vet 2004, p 44-45):
To 60 ml add 40 ml methanol, shake to dissolve, add 25 ml of 1M sodium hydroxide and allow to stand for 30 minutes. Add 27.5 ml of 1M hydrochloric acid and sufficient water to produce 100 ml, mix, transfer 20 ml of the solution to a stoppered flaskm add 30 ml of 0.01M iodine VS, close the flask with a wet stopper and allow to stand for 15 minutes, protected from light. Titrate the excess of iodine with 0.02M sodium thiosulphate VS, using stach mucilage, added towards the end of the titration as indicator. Add a further 12 mg of the substance to be ecamined to 10 ml of water, swirl to dispersem add 30 ml of 0.01M iodine VS and titrate immediately with 0.02M sodium thiosulphate VS, using stach mucilage, added towards the end of the titration as indicator. The difference between the titrations represents the volume of 0.01M iodine VS, equivalent to the total penicillins present. Calculate the content of C16H20N2,(C19H18ClN3O5S)2 from the difference obtained by carrying out the assay simultaneously using cloxacilline benzathine BPCRS and from the declared content of C16H20N2,(C19H18ClN3O5S)2 in cloxacilline benzathine BPCRS.
I know this isn't the right forum, but I couldn't find a forum especially for titrations.
We have to do an assay on cloxacilline benzathine as stated in the British Pharmacopea (Veterinary).
But we have some discussion about the calculation of the result.
When you perform the titration on the 12mg substance, it looks like it doesn't matter if you weigh 10 mg or 14 mg. You titrate with the same volume of thiosulphate. Do we have to take this weight into account?
Our fomula now looks like:
(V1sample-V2sample)*Wref1*Wref2*%
(V1ref-V2ref)*Wsample1*Wsample2
Where V1 are the volumes thiosulphate titrated with the 12 mg sample,
V2 are the volumes thiosulphate titrated with the 60 mg sample,
W are the weights and % is the declared content of the BPCRS.
How would you calculate this?
Best regards
For the ones who don't have the BP VET at hand:
Assay cloxacilline benzathine (BP Vet 2004, p 44-45):
To 60 ml add 40 ml methanol, shake to dissolve, add 25 ml of 1M sodium hydroxide and allow to stand for 30 minutes. Add 27.5 ml of 1M hydrochloric acid and sufficient water to produce 100 ml, mix, transfer 20 ml of the solution to a stoppered flaskm add 30 ml of 0.01M iodine VS, close the flask with a wet stopper and allow to stand for 15 minutes, protected from light. Titrate the excess of iodine with 0.02M sodium thiosulphate VS, using stach mucilage, added towards the end of the titration as indicator. Add a further 12 mg of the substance to be ecamined to 10 ml of water, swirl to dispersem add 30 ml of 0.01M iodine VS and titrate immediately with 0.02M sodium thiosulphate VS, using stach mucilage, added towards the end of the titration as indicator. The difference between the titrations represents the volume of 0.01M iodine VS, equivalent to the total penicillins present. Calculate the content of C16H20N2,(C19H18ClN3O5S)2 from the difference obtained by carrying out the assay simultaneously using cloxacilline benzathine BPCRS and from the declared content of C16H20N2,(C19H18ClN3O5S)2 in cloxacilline benzathine BPCRS.
