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Author: Subject: Drug concentration in blood (calculation)

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[*] posted on 2-2-2017 at 09:53
Drug concentration in blood (calculation)

Apologies for a stupid question. I need to determine the concentration of drug that is reconstituted for GC-MS. Here how the prep work goes:

50 uL of 10 ug/mL of a drug is used to spike 0.5 g of blood. So the concentration in blood is 1 ug/g. But then blood is diluted with water by half which means the concentration of drug is halved i.e. 0.5 ug/g. The drug is extracted and then 75 uL is used to reconstitute the analyte. I am having problem how can I go from ug/g to whatever ug or ng is in 75 uL. should I assume density of water and blood is the same? so is it 0.5 ug in 1 mL or 1000 uL ( 1 g of water = 1 mL ). Hence 0.5 ug *75/1000 = 0.0375 ug in 75 uL so the concentration is 0.0375 ug/0.075 mL = 0.5 ug/mL or 500 ng/mL

I know, I know - a stupid question but I think I am missing something here. Please, don't be too mean :P

[Edited on 2-2-2017 by amateur23]
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