What is the unit for ppm simplified?

What is the unit for ppm simplified?

• A. gram analyte/liter solution
• B. mg analyte/liter solution
• C. micrograms analyte/liter solution
• D. nanograms analyte/liter solution

Answer: (B)

Parts per million is a ratio of 1 part solute to 1,000,000 parts solution. In dilute aqueous solutions, this is usually expressed as milligrams of solute per liter of solution. The reason is simple: 1 liter of water has a mass of about 1,000,000 mg, so 1 mg of solute in 1 liter of solution corresponds to 1 part in 1,000,000 by mass, i.e., 1 ppm. Therefore the simplified unit for ppm in such solutions is mg analyte per liter solution. If you used other units, you’d be off by factors of 1,000 or 1,000,000. For example, micrograms per liter would correspond to 0.001 mg/L (a much smaller value for the same ppm), while nanograms per liter would be even smaller by a factor of 1,000,000. Expressing in grams per liter would make the value 1000 times larger than the same ppm value.

Parts per million is a ratio of 1 part solute to 1,000,000 parts solution. In dilute aqueous solutions, this is usually expressed as milligrams of solute per liter of solution. The reason is simple: 1 liter of water has a mass of about 1,000,000 mg, so 1 mg of solute in 1 liter of solution corresponds to 1 part in 1,000,000 by mass, i.e., 1 ppm. Therefore the simplified unit for ppm in such solutions is mg analyte per liter solution.

If you used other units, you’d be off by factors of 1,000 or 1,000,000. For example, micrograms per liter would correspond to 0.001 mg/L (a much smaller value for the same ppm), while nanograms per liter would be even smaller by a factor of 1,000,000. Expressing in grams per liter would make the value 1000 times larger than the same ppm value.