# Fatty Acid Methyl Esters (FAMES) - converting % by weight to µg/mL

8 Apr 2014The first time I was asked by a customer about how to convert % by weight of one of our FAME reference standards to µg/mL, I needed to ask for some help. Because we (tech service) occasionally get asked this question, I thought I would show the calculation in a post.

Let’s take Restek catalog number 35077 as an example. The overall concentration of this Food Industry FAME Mix is 30mg/mL. Individual compound concentrations range from 2 to 6% by weight. So what are the individual compound concentrations in µg/mL? I’m not going to list them all, but rather show you how to perform this calculation.

We list the first compound as C4:0 and at 4% by weight. Since the total concentration of 35077 is 30mg/mL, to determine the concentration of C4:0 in µg/mL:

4/100 x 30mg/mL = 0.04 x 30mg/mL = 1.2mg/mL

To convert to µg/mL: 1.2mg/mL x 1000µg/mg = 1200µg/mL

If you purchase a neat standard like 35066, then there will be one extra step to obtaining the final answer.

This catalog number contains approximately 100mg. For the sake of simplicity, let’s say you remove exactly 100mg and dissolve this material into 10mL of methylene chloride. This will produce a solution with a concentration of 10mg/mL. Once again, I will use the first listed compound (C14:0 in this case) for an example calculation.

C14:0 is in the neat material at 6% by weight. Since the total concentration of the solution you prepared is at 10mg/mL:

6/100 x 10mg/mL = 0.06 x 10mg/mL = 0.6mg/mL

To convert to µg/mL: 0.6mg/mL x 1000µg/mg = 600µg/mL

I hope you have found these examples helpful the next time you need to perform similar calculations.

Thanks for reading.