Ion analysis using image-charge/current analysis

An ion analyser apparatus configured for generating an image-charge/current signal representative of ions of a given charge state (Q) undergoing oscillatory motion of a respective oscillation frequency (w) within an ion analyser apparatus, the apparatus comprising:

• an ion analysis chamber configured for receiving said one or more ions and for generating said image charge/current signal in response to said oscillatory motion;
• a signal recording unit configured for recording the image charge/current signal as a recorded signal in the time domain;
• a signal processing unit for processing the recorded signal to:
• acquire a data set comprising a first measured signal frequency (ω1) associated with a first part of a measured image-charge/current signal of an ion and a second measured signal frequency (ω2) associated with a subsequent second part of the measured image-charge/current signal of the ion;
• estimate a charge state (Q) of the ion undergoing oscillatory motion of said first measured signal frequency (ω1) and subsequently of said second measured signal frequency (ω2) such that the value of a mass change quantifiable as:
• Δ
• ⁢
• m
• =
• Q
• [
• (
• α
• ω
• 1
• )
• 2
• -
• (
• α
• ω
• 2
• )
• 2
• ]
• substantially matches a reference mass corresponding to a mass of one or more neutral losses where α is a pre-set calibration constant;
• and,
• estimate the mass (M) of a deprotonated molecule forming a part of the ion according to the estimated charge state (Q) of the ion, the first measured signal frequency (ω1), the quantified mass change value Δm, and the mass-to-charge ratio (mp/e) of a protonating proton, according to the relation:
• M
• =
• Q
• [
• (
• α
• ω
• 1
• )
• 2
• -
• (
• m
• p
• e
• )
• ]
• -
• Δ
• ⁢
• m
• .