What is the concentration of my extracted sample?

Situational problem:

I have a sample made from powdered ciku slices. The powder is dissolved in ethanol (95%), filtered and evaporated. The problem is, although I begin with a standard sample weight (300g powdered ciku), I ended up with different amount of concentrated extract for every single batch. Some is as small as a few mL. Some could fill up the bottom of a 300mL flask!

What is the concentration of my extracted sample and how do I make it standardized?

Answer:


Well, we look at it this way. Concentration is measured as mg/mL, so in each bottle there is 300000mg per mL of ethanol 95% (even though it might not look like it). So, we can determine the concentration by measuring the volume inside the bottle. If there’s 5 ml inside the bottle, it’ll become 300g/5ml = 60 000 mg/mL.

Since we have so many bottles, it’s better to standardize everything to ease later dilutions. For example, fill up every bottle until 30mL mark with the same solvent. So 300g in 30mL is 10 000 mg/mL. After this we can dilute it to 1000 mg/mL, 100 mg/mL or anything we wish.

Easy eh? Why haven’t I figured this out earlier.