The signal-to-noise ratio as a measure of HA oligomer concentration: a MALDI-TOF MS study

MALDI-TOF MS (matrix-assisted laser desorption and ionization time-of-flight mass spectrometry) was used to determine ng amounts of defined hyaluronan (HA) oligomers obtained by enzymatic digestion of high molecular weight HA with testicular hyaluronate lyase. The signal-to-noise (S/N) ratio of the positive and negative ion spectra represents a reliable concentration measure: Amounts of HA down to about 40 fmol could be determined and there is a linear correlation between the S/N ratio and the HA amount between about 0.8 pmol and 40 fmol. However, the detection limits depend considerably on the size of the HA oligomer with larger oligomers being less sensitively detectable. The advantages and drawbacks of the S/N ratio as concentration measure are discussed.