Enter the value in parts per billion (ppb) and select the sample type or density to determine the equivalent concentration in nanograms per milliliter (ng/mL).
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ppb to ng/mL Formula
The following formula is used to convert a concentration in parts per billion (ppb) to nanograms per milliliter (ng/mL) for a liquid sample.
ng/mL = ppb \times \rho
Variables:
- ng/mL is the concentration in nanograms per milliliter
- ppb is the concentration in parts per billion
- ρ is the sample density in kilograms per liter (kg/L)
For water-like liquids with a density close to 1.00 kg/L, the numeric value in ppb is approximately the same as the value in ng/mL.
What is ppb to ng/mL Conversion?
This conversion changes a concentration expressed as mass per mass into a concentration expressed as mass per volume. By definition, 1 ppb is 1 microgram of analyte per kilogram of sample. To convert that value into ng/mL, you multiply by the liquid density in kg/L. For water and similar liquids, the density is close enough to 1 kg/L that ppb and ng/mL are often numerically equal.
When the liquid is denser or lighter than water, the ng/mL value changes in direct proportion to the density. For example, 10 ppb in water is about 10 ng/mL, while 10 ppb in blood plasma is about 10.2 ng/mL and 10 ppb in a light organic solvent is about 8.0 ng/mL.
How to Convert ppb to ng/mL?
The following steps outline how to convert ppb to ng/mL.
- First, determine the concentration in ppb.
- Next, determine the density of the liquid sample in kg/L.
- Multiply the ppb value by the density using the formula ng/mL = ppb × ρ.
- If the sample is water-like with density near 1.00 kg/L, the ppb and ng/mL values will be nearly the same.
- Check your answer with the calculator above.
Example Problem:
Use the following variables as an example problem to test your knowledge.
ppb = 10
Density (ρ) = 1.00 kg/L
ng/mL = 10 × 1.00 = 10 ng/mL
ppb to ng/mL Conversion Table
The table below lists example conversions for a 10 ppb concentration in several common liquids using the relationship ng/mL = ppb × ρ.
| Medium | Approx. Density ρ (kg/L) | 10 ppb in ng/mL |
|---|---|---|
| Pure Water | 1.00 | 10.00 ng/mL |
| Blood Plasma | 1.02 | 10.20 ng/mL |
| Seawater | 1.025 | 10.25 ng/mL |
| Light Organic Solvent | 0.80 | 8.00 ng/mL |
| Sugar Solution (Concentrated) | 1.15 | 11.50 ng/mL |
| Salt Brine (Concentrated) | 1.20 | 12.00 ng/mL |
| Glycerol-Rich Mixture | 1.25 | 12.50 ng/mL |
In laboratory practice, ppb and ng/mL are often treated as interchangeable for water-based samples, but accounting for density provides a more accurate conversion for other matrices.