ppmppb
ppmppb is not an official unit. It appears in some data sets and discussions as a shorthand to refer to concentrations expressed in either ppm or ppb, or to indicate that a value may be reported in either scale and needs conversion. It is not itself a strictly defined measurement unit.
Parts per million (ppm) and parts per billion (ppb) are dimensionless ratios used to express very small
Conversions between the scales are simple on the same basis: 1 ppm equals 1000 ppb, and 1
In practice, when encountering a value labeled ppmppb, it is important to determine the context and the
Limitations should also be noted: non-ideal conditions, significant density differences, and variations in molecular weight can