# Urgent help for concentration calculations watch

1. Hey guys,

I have to make a 200 microgram (ug) per mL solution of Insulin in 10 mL buffer. How would I approach it ?

I am given 100 % pure Insulin in powder form, so my first step would be in finding out the amount to weigh. But my teacher tells me to take 50-100 mg and start from there.
2. Sometimes writing it out like you're speaking helps so here goes.

So we're wanting 200ug in every ml of the solution. If I read right, the solution will be a total of 10ml. Now since there is 200ug in every ml, there will be x10 that in the total of 10ml. That means you'll need 2000ug (2mg) of the powdered insulin in to 10ml of buffer.

I do think you've written your question slightly wrong though if your teacher is talking about 50-100mg. To me it sounds like they're wanting you to maybe create a more concentrated version and dilute it down successively maybe?
3. (Original post by TraineeBMS)
Sometimes writing it out like you're speaking helps so here goes.

So we're wanting 200ug in every ml of the solution. If I read right, the solution will be a total of 10ml. Now since there is 200ug in every ml, there will be x10 that in the total of 10ml. That means you'll need 2000ug (2mg) of the powdered insulin in to 10ml of buffer.

I do think you've written your question slightly wrong though if your teacher is talking about 50-100mg. To me it sounds like they're wanting you to maybe create a more concentrated version and dilute it down successively maybe?
Yes because 2 mg would be hard to weigh in.

So here is what I can do:

I can weigh 100 mg of Insulin and then dissolve it in 2 mL 1 M HCl since Insulin is very insoluble. I can then neutralize the solution with 1 M NaOH, after which I can add the dissolved insulin in 10 mL buffer to give me 10 mg/ml HBSS + Insulin solution.

I can then successively dilute it to 200 ug/ml in 10 or 20 ml HBSS.

C1 * V1 = C2 * V2
10 mg/ml (10,000 ug/ml) * V1 = 200 ug/ml * 10 ml

V1 = (200 ug/ml * 10 ml) / 10000 ug/ml
V1 = 0.2 ml or 200 uL

So I can take out 200 ul from the stock and add 9.8 mL of fresh buffer.

Does this sound correct ?

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