m/z Th MS mass-to-charge ratio thomson Three-character symbol m/z is used to denote the quantity formed by dividing the mass of an ion in unified atomic mass units by its charge number (regardless of sign). The symbol is written in italicized lower case letters with no spaces. Note 1: The term mass-to-charge-ratio is deprecated. Mass-to-charge ratio has been used for the abscissa of a mass spectrum, although the quantity measured is not the quotient of the ion's mass to its electric charge. The three-character symbol m/z is recommended for the quantity that is the independent variable in a mass spectrum Note 2: The proposed unit thomson (Th) is deprecated. MS:1000040 unit