Mzvärde

Mzvärde is a Swedish term used to describe the mass-to-charge ratio (m/z) value of an ion detected by a mass spectrometer. It is the primary coordinate on the spectrum plot and represents the ratio between the ion’s mass (M) and its charge (z). In practice, mzvärde is reported as an m/z value, and the distribution of these values across a spectrum encodes information about the ions present in a sample.

The ionization process creates ions with various charge states, so the m/z value reflects the charge state. For a bare ion, m/z is approximately M divided by z, with small shifts due to isotopes and any adducts. Multiply charged ions appear at lower m/z values than their neutral mass would suggest, which influences how large molecules are detected and analyzed.

Interpreting mzvärde involves matching observed m/z values to theoretical masses in databases, while accounting for possible adducts, chemical modifications, charge states, and isotopic distributions. This approach underpins identification and, in many workflows, quantification in fields such as proteomics and metabolomics. The precision of mzvärde measurements depends on the instrument’s resolution and mass accuracy.

Instrument performance is a key factor: high-resolution analyzers like Orbitraps, FT-ICR, and advanced time-of-flight systems can resolve very close mzvärden, enabling more confident identifications. Calibration and reporting of mass accuracy in ppm are important for reliable interpretation. Common challenges include calibration drift, incorrect charge-state assignment, isotope overlap, and unanticipated adduct formation.

See also: mass spectrometry, mass-to-charge ratio, isotopic pattern, charge state, adducts.