Converting ng/ml to uM

I need to convert 31.8 ng/ml to uM. The molecular weight of the item in question is 261.11572.

As a simple journalist rather than a scientist, but one word comes to my mind in the present circumstances - HELP!

Thank you.

[JohnS]

Originally Posted by A simple journalist

I need to convert 31.8 ng/ml to uM. The molecular weight of the item in question is 261.11572.

As a simple journalist rather than a scientist, but one word comes to my mind in the present circumstances - HELP!

Thank you.

Molarity (M) is shorthand for concentration in moles per liter. To convert between moles and mass, you need to know the molar mass which is numerically equal to the molecular weight, 261.11572 g/mol, in this case.

The concentration 31.8 ng/mL is also 31.8 µg/L. Dividing by the molar mass
31.8 µg x 1 mol/261.11572 g = 0.1218 µmol/L or 0.1218 µM.

(It might be better expressed as 121.8 nmol/L, and based on the precision of the initial number, rounded to 122 nmol/L.)

Thank you.

One point though, the ng/ml I provided was listed as just that "ml", not "mL". Does this affect the equation? Also, in terms of comparing bioactive properties of two substances' "IC50" levels denoted in 'uM', am I correct in assuming that the larger the uM found, the less potent the substance is?

[JohnS]

Originally Posted by a simple journalist

Thank you.

One point though, the ng/ml I provided was listed as just that "ml", not "mL". Does this affect the equation? Also, in terms of comparing bioactive properties of two substances' "IC50" levels denoted in 'uM', am I correct in assuming that the larger the uM found, the less potent the substance is?

The liter (spelled litre in much of the world) is the only metric unit with two symbols, l or L. At least in the US, L is preferred because in many fonts the lower case l looks too much like the number 1 or a capital I. Either is allowed, but I try to consistently use L.

I'm not sure I understand your 2nd question. A higher reading in µM denotes a higher concentration of substance. However, for two similar substances that have the same level of bioactivity (such as International Units of vitamins), if one requires more substance for the same bioactivity level, then it is weaker.

Please give me the conversion factor for the above:

[JohnS]

Originally Posted by John paciorek

Please give me the conversion factor for the above:

Without the molecular weight of the solute, no conversion is possible. With it, follow the example above, with correct MW for your case.

On autospy person had 940nanograms of morphine. How much morphine did
this person take?