# Thread: am I using the right units?

1. ## am I using the right units?

Hello,

Probably a really simple question for any mathematician, but not so easy for the confused biochemist needing help.

I'm looking at the concentration of a compound produced by a microbial culture that is measured in ng L -1. I want to express the concentration of this compound relative to the dry weight of this culture (DW) which I have measured in mg L-1. Does this mean my units will be ng L-1 mg L-1 DW? Or can it be simplified to ng mg L-1 DW?

Any help would be much appreciated! Thanks

2. ## Re: am I using the right units?

Hey blue00.

If you are expressing one thing relative to another you usually are looking [a]/[b] where [a] is the units for a and [b] is the units for b.

So a relative to b unit wise is [a]/[b] = m/n or mn^(-1). If m can be written as a function of n (or vice-versa) then this can be simplified.

3. ## Re: am I using the right units?

yes i also want to say the same thing.

thanks
packersm

4. ## Re: am I using the right units?

very nice information. thanks a lot for this.

thanks
99th