millimolaarina

Millimolar (mM) is a unit of concentration used in chemistry and biology to express how many millimoles of a solute are present in one liter of solution. It is a submultiple of molarity (M), where 1 M equals 1 mole per liter; therefore 1 mM equals 1 × 10^-3 mol/L. In practice, millimolar can also be written as mmol/L, which is equivalent to mM.

In laboratory practice, concentrations are often reported in mM because many biochemical reactions and assays operate in the millimolar range. Common examples include substrates, cofactors, buffers, and ionic reagents. To convert between millimolar and molarity, multiply or divide by 1000: 2 mM = 2 × 10^-3 M, 0.5 mM = 5 × 10^-4 M.

Millimolar is especially convenient for expressing concentrations in aqueous solutions, where volumes are manageable and the molarity scale aligns with typical reagent preparations. When working from a stock solution, scientists frequently describe the final working concentration in mM rather than the stock’s higher molarity, even though the preparation steps may require conversions.

Limitations: millimolar denotes concentration, not activity. At higher ionic strengths, activity coefficients can cause effective concentrations to deviate from nominal mM values, which can be relevant for precise quantitative work. Nevertheless, millimolar remains a standard, widely used unit for expressing concentrations in chemistry, biology, and related fields.